Abstract:
Method and apparatus for limiting absorption of food products in specific parts of the digestive system is presented. A gastrointestinal implant device is anchored in the stomach and extends beyond the ligament of Treitz. All food exiting the stomach is funneled through the device. The gastrointestinal device includes an anchor for anchoring the device to the stomach and a flexible sleeve. When implanted within the intestine, the sleeve can limit the absorption of nutrients, delay the mixing of chyme with digestive enzymes, altering hormonal triggers, providing negative feedback, and combinations thereof. The anchor is collapsible for endoscopic delivery and removal.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/401,258, filed on Feb. 21, 2012, which is a continuation of U.S. application Ser. No. 12/454,915, now U.S. Pat. No. 8,162,871, filed on May 26, 2009, which is a continuation of U.S. application Ser. No. 11/302,944, now U.S. Pat. No. 7,608,114, filed Dec. 13, 2005, which is a continuation-in-part of U.S. application Ser. No. 11/000,099, now U.S. Pat. No. 7,267,694, filed Nov. 30, 2004, which is a divisional of U.S. application Ser. No. 10/339,786, now U.S. Pat. No. 7,025,791, filed Jan. 9, 2003, which claims the benefit of U.S. Provisional Application No. 60/430,321, filed on Dec. 2, 2002. The entire teachings of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     According to the Center for Disease Control (CDC), over sixty percent of the United States population is overweight, and almost twenty percent are obese. This translates into 38.8 million adults in the United States with a Body Mass Index (BMI) of 30 or above. The BMI is defined as a person&#39;s weight (in kilograms) divided by height (in meters), squared. To be considered clinically, morbidly obese, one must meet one of three criteria: BMI over 35, 100 lbs. overweight or 100% above ideal body weight. There is also a category for the super-obese for those weighing over 350 lbs. 
     Obesity is an overwhelming health problem. Because of the enormous strain associated with carrying this excess weight, organs are affected, as are the nervous and circulatory systems. In 2000, the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) estimated that there were 280,000 deaths directly related to obesity. The NIDDK further estimated that the direct cost of healthcare in the US associated with obesity is $51 billion. In addition, Americans spend $33 billion per year on weight loss products. In spite of this economic cost and consumer commitment, the prevalence of obesity continues to rise at alarming rates. From 1991 to 2000, obesity in the US grew by 61%. Not exclusively a US problem, worldwide obesity ranges are also increasing dramatically. 
     One of the principle costs to the healthcare system stems from the co-morbidities associated with obesity. Type-2 diabetes has climbed to 7.3% of the population. Of those persons with Type-2 diabetes, almost half are clinically obese, and two thirds are approaching obese. Other co-morbidities include hypertension, coronary artery disease, hypercholesteremia, sleep apnea and pulmonary hypertension. 
     Although the physiology and psychology of obesity are complex, the medical consensus is that the cause is quite simple—an over intake of calories combined with a reduction in energy expenditures seen in modern society. While the treatment seems quite intuitive, the institution of a cure is a complex issue that has so far vexed the best efforts of medical science. Dieting is not an adequate long-term solution for most people. Once an individual has slipped past the BMI of 30, significant changes in lifestyle are the only solution. 
     There have been many attempts in the past to surgically modify patients&#39; anatomies to attack the consumption problem by reducing the desire to eat. Stomach saplings, or gastroplasties, to reduce the volumetric size of the stomach, therein achieving faster satiety, were performed in the 1980&#39;s and early 1990&#39;s. Although able to achieve early weight loss, sustained reduction was not obtained. The reasons are not all known, but are believed related to several factors. One of which is that the stomach stretches over time increasing volume while psychological drivers motivate patients to find creative approaches to literally eat around the smaller pouch. 
     There are currently two surgical procedures that successfully produce long-term weight loss; the Roux-en-Y gastric bypass and the biliopancreatic diversion with duodenal switch (BPD). Both procedures reduce the size of the stomach plus shorten the effective-length of intestine available for nutrient absorption. Reduction of the stomach size reduces stomach capacity and the ability of the patient to take in food. Bypassing the duodenum makes it more difficult to digest fats, high sugar and carbohydrate rich foods. One objective of the surgery is to provide feedback to the patient by producing a dumping syndrome if they do eat these food products. Dumping occurs when carbohydrates directly enter the jejunum without being first conditioned in the duodenum. The result is that a large quantity of fluid is discharged into the food from the intestinal lining. The total effect makes the patient feel light-headed and results in severe diarrhea. For reasons that have not been determined the procedure also has an immediate therapeutic effect on diabetes. 
     Although the physiology seems simple, the exact mechanism of action in these procedures is not understood. Current theory is that negative feedback is provided from both regurgitation into the esophagus and dumping when large volumes of the wrong foods are eaten. Eventually, patients learn that to avoid both these issues they must be compliant with the dietary restrictions imposed by their modified anatomy. In the BPD procedure, large lengths of jejunum are bypassed resulting in malabsorption and therefore, reduced caloric uptake. In fact, the stomach is not reduced in size as much in the BPD procedure so that the patient is able to consume sufficient quantities of food to compensate for the reduced absorption. This procedure is reserved for the most morbidly obese as there are several serious side effects of prolonged malabsorption. 
     Unfortunately, these procedures carry a heavy toll. The morbidity rate for surgical procedures is alarmingly high with 11% requiring surgical intervention for correction. Early small bowel obstruction occurs at a rate of between 2-6% in these surgeries and mortality rates are reported to be approximately 0.5-1.5%. While surgery seems to be an effective answer, the current invasive procedures are not acceptable with these complication rates. Laparoscopic techniques applied to these surgeries provide fewer surgical complications but continue to expose these very ill patients to high operative risk in addition to requiring an enormous level of skill by the surgeon. Devices to reduce absorption in the small intestines have been proposed (See U.S. Pat. No. 5,820,584 (Crabb), U.S. Pat. No. 5,306,300 (Berry) and U.S. Pat. No. 4,315,509 (Smit)). However, these devices have not been successfully implemented. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for the application of a removable implant device within the gastrointestinal tract of an animal to induce a desired result. The gastrointestinal implant device includes a hollow sleeve and a sleeve anchor coupled to a proximal portion of the sleeve and adapted to removably fasten the proximal portion of the sleeve to a predetermined location within the gastrointestinal tract. 
     The hollow sleeve is open at both ends, and adapted to extend into the duodenum. The sleeve, or liner, is positioned such that partially digested food, or chyme, moving through the digestive tract passes through the interior of the sleeve. Depending on its placement, the sleeve allows enzymes secreted in the duodenum to pass through the duodenum outside the sleeve. The desired result using the implanted sleeve can include one or more of: limiting the absorption of nutrients; delaying the mixing of chyme with digestive enzymes; providing negative feedback; reducing hormone triggers; and treating diseases, such as diabetes. The sleeve is generally flexible and can be thin and floppy and may be of a length that chyme exiting the stomach funneled through the proximal end of the sleeve exits the sleeve through the distal end below the ligament of Treitz. The distal end of the sleeve may also be directionally textured. 
     The sleeve material is preferably thin-walled and floppy so as not to interfere with natural peristalsis. The sleeve material also provides a low coefficient of friction (e.g., not more than about 0.2) to promote passage of chyme within the sleeve subjected to natural peristaltic forces. These properties can be found in a sleeve formed from a fluoropolymer, such as expanded polytetrafluoroethylene (ePTFE), or from a combination with another material. For example, one such combination includes an ePTFE layer of material combined with a different fluoropolymer layer, such as fluorinated ethylene-propylene (FEP). The combination of the FEP with ePTFE provides a low coefficient of friction while also being substantially non-permeable. In some embodiments, another material such as PTFE is applied to an ePTFE substrate using vapor deposition. Alternatively or in addition, the sleeve is formed using polyolefin films, such as low density polyethylene (LDPE), high density polyethylene (HDPE), and polypropylene. 
     Other materials include cast polytetrafluoroethylene (e.g., TEFLON), cast PTFE with FEP or perfluoroalkoxy (PFA) coating on a PTFE to minimize pin holes, extruded FEP and extruded PFA. These materials are solid and substantially non-porous in contrast to ePTFE, which is generally porous. These materials are also considered to be fluoropolymers. In some embodiments, the wall thickness of the sleeve is less than about 0.0025 mm (i.e., about 0.001 inches). 
     The sleeve anchor is preferably collapsible and adapted to be retained within the digestive system. In some applications, the sleeve anchor includes a stent formed from a network of struts. In other applications, sleeve anchors include a hollow radial spring, referred to herein as a wave anchor. A wave anchor can be formed using a resilient member, such as a wire, formed into a longitudinal oscillation at a radial distance about a longitudinal axis. For example, the wave anchor can be formed using a number of substantially straight segments, each segment alternately joined at one end to a first adjacent segment and at another end to a different adjacent segment, adjacent segments being non-parallel with the two end-most segments being joined together to form the hollow wave anchor. 
     The device may be anchored in the stomach; in the pyloric region between the stomach and the duodenum; and/or distal to the pylorus. In some embodiments, the sleeve anchor is fastened within the proximal duodenum. Preferably, the sleeve anchor is placed in a superior section of the duodenum referred to as the duodenal bulb, or bulbous duodenum that begins just distal to the pyloric sphincter and extends for about 25 to about 38 mm (i.e., 1 to 1.5 inches) in an adult human. The duodenal bulb is located between the pyloric sphincter and the hepatopancreatic ampulla, also referred to as the ampulla of Vater. 
     Placement of the sleeve anchor in this region offers certain advantages. First, the interior diameter of the duodenal bulb, as the name suggests, is slightly larger than the interior diameters of the proximal and distal regions, thereby promoting axial stability. The interior of the duodenal bulb is also relatively smooth in appearance being absent of folds and experiencing less movement compared to post bulbar duodenum. Notably, the motion is substantially limited to radial contractions without having a significant axial component, further promoting stable anchoring of the sleeve. 
     The device may include barbs, sutures, and/or other devices to further contribute to stable anchoring of the sleeve. For example, one or more barbs are attached to an exterior surface of the sleeve anchor protruding at an acute angle from the surface and sized to engage the surrounding tissue. Preferably, the one or more barbs extend through a mucosal layer and into muscular tissue. In some embodiments, the barbs include two tines: one oriented to prevent longitudinal movement of the device in a first direction and another oriented to prevent longitudinal movement of the device in a second direction substantially opposite to the first direction. In some embodiments, the barbs are placed towards the proximal end of the sleeve anchor. Such placement of the barbs is particularly well suited for a sleeve anchor implanted within the duodenal bulb as the proximal portion of the bulb is thicker than distal portions of the duodenum thereby providing a more suitable location for the placement of barbs. 
     In some embodiments, the sleeve includes an anti-buckling feature that provides linear stiffness to the sleeve, while allowing it to maintain flexibility. For example, an anti-buckling device is coupled to the sleeve extending distally from below the sleeve anchor to reduce buckling of the sleeve. The anti-buckling feature inhibits eversion of the sleeve, aiding in keeping the sleeve distally extended even in the presence of retrograde pressures. 
     The gastrointestinal implant device can be inserted endoscopically in combination with a delivery catheter and can be repositioned and/or removed endoscopically in combination with a repositioning/removal device. 
     The delivery system may comprise a gastrointestinal device that includes an anchor and a sleeve that extends from the anchor. The anchor may be stored in an outer sheath and an inner shaft within the outer sheath extends it distally beyond the outer sheath. A sleeve release mechanism may releasably retain the sleeve near a distal end of the inner shaft, and an anchor release mechanism they release the anchor from the outer sheath. 
     An atraumatic element, specifically a spherical ball, may be coupled to a distal tip of the inner shaft. 
     The sleeve may be retained on the inner shaft by a retention wire that extends through the inner shaft and out of the shaft about the sleeve. The retention wire may extend through the sleeve and back into the inner shaft with the sleeve being released by pulling the retention wire back from the sleeve. In that case, the retention wire may extend through a first hole in the inner shaft, through the sleeve, and back through a second hole in the inner shaft. Alternatively, the retention wire may be a snare wire that forms a loop around a portion of the sleeve, and the sleeve is released by pushing the retention wire distally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1  is a sectional view of a portion of the digestive tract in a body; 
         FIG. 2  is a perspective view of a gastrointestinal implant device according to the principles of the present invention; 
         FIG. 3A  is a plan view of the proximal portion of the gastrointestinal implant device shown in  FIG. 2 ; 
         FIG. 3B  is a cross-sectional view as taken along line A-A of  FIG. 3A  showing the stent and first inner layer and second outer layer of the sleeve shown in  FIG. 2 ; 
         FIG. 4  is a perspective view of the gastrointestinal implant device with the second outer layer of the sleeve removed; 
         FIG. 5A  is a sectional view of a body showing one embodiment of the gastrointestinal implant device implanted in the digestive system; 
         FIG. 5B  is a sectional view of a body showing an alternative embodiment of the gastrointestinal implant device implanted in the digestive system; 
         FIG. 6  is a perspective view of a collapsible self-expanding stent in the gastrointestinal implant device; 
         FIG. 7  is a perspective view of the stent shown in  FIG. 6  when compressed; 
         FIG. 8  is a perspective view of another embodiment of a stent when compressed; 
         FIG. 9  is a perspective view of the stent shown in  FIG. 8  with the strut ends bent to provide opposed barbs; 
         FIG. 10  is a perspective view of the stent shown in  FIG. 8  when expanded; 
         FIG. 11  illustrates the gastrointestinal device shown in  FIG. 1  including an anti-buckling mechanism; 
         FIG. 12  is a perspective view of a catheter system for delivery of the gastrointestinal implant device; 
         FIG. 13  is a cross-sectional view of the inner shaft taken along line E-E of  FIG. 12 ; 
         FIG. 14A  is an expanded perspective view of the dead-bolt mechanism shown in  FIG. 12 ; 
         FIG. 14B  is a sectional view of the dead-bolt mechanism shown in  FIG. 13A  illustrating the sleeve retention wire threaded through the sleeve; 
         FIG. 15  is sectional view of a portion of the catheter system illustrating the collapsed stent stored inside the outer sheath; 
         FIG. 16A  is a plan view of the catheter system illustrating the collapsed stent stored inside the outer sheath of the gastrointestinal implant device; 
         FIG. 16B  is a plan view of the catheter system illustrating the gastrointestinal implant device after release of the stent from the outer sheath; 
         FIG. 16C  is a plan view of the catheter system illustrating the expanded gastrointestinal implant device after the sleeve retention wire has been released; 
         FIG. 17  is a perspective view of another embodiment of the catheter system shown in  FIG. 12 ; 
         FIG. 18  is a sectional view of an everting catheter system for delivery of a longer length sleeve; 
         FIG. 19  is a perspective view of a retrieval device for removing the gastrointestinal implant device from the digestive tract; 
         FIG. 20  is a perspective view of the removal device engaged with the stent; 
         FIG. 21  is a perspective view of another embodiment of a gastrointestinal implant device; 
         FIG. 22  is a perspective view of the anchoring ring shown in  FIG. 21 ; 
         FIG. 23  is a perspective view of the anchoring ring shown in  FIG. 21  in a collapsed position for insertion and removal; 
         FIG. 24  is a perspective view of an anchor for anchoring the collapsible ring shown in  FIG. 23  to the muscular tissue of the pyloric section of the stomach; 
         FIG. 25A  is a perspective view of a delivery system for delivering the anchor after the gastrointestinal implant device has been placed in the stomach; 
         FIG. 25B  is a plan view of the delivery system shown in  FIG. 25A ; 
         FIG. 25C  is a cross-sectional view of the distal end of the catheter as taken along line B-B of  FIG. 25A ; 
         FIG. 25D  is a perspective view of the gastrointestinal implant device illustrating the anchor engaged with the tissue; 
         FIG. 25E  is a perspective view illustrating the barb engaging the tissue after delivery; 
         FIG. 26A  is a plan view of the delivery system including a snare wire for holding the distal end of the sleeve in position; 
         FIG. 26B  is a cross-sectional view taken along line CC of  FIG. 26A  through the inner sheath; 
         FIG. 26C  is a cross-sectional view taken along line DD of  FIG. 26A  through the outer sheath showing the inner sheath within the outer sheath; 
         FIG. 26D  is a cross-sectional view through the distal portion of the catheter showing the snare capturing the distal end of the sleeve; 
         FIG. 26E  is a sectional view through the distal portion of the catheter showing the snare locking mechanism; 
         FIG. 27  is a perspective view of the distal portion of the gastrointestinal implant device including texturing at the distal end; and 
         FIG. 28  is a plan view of an alternative embodiment of the gastrointestinal implant device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A description of preferred embodiments of the invention follows. 
       FIG. 1  is a sectional view of a portion of the digestive tract in a body. Food to be digested enters the stomach  102  through the cardiac orifice  110  from the esophagus. Chyme, a semi-fluid, homogeneous creamy or gruel-like material produced by gastric digestion in the stomach exits the stomach through the pyloric orifice (pylorus)  108  and enters the small intestine  112 . The pylorus  108  is a distal aperture of the stomach  102  surrounded by a strong band of circular muscle. The small intestine, about nine feet in length, is a convoluted tube, extending from the pylorus to the ileo-caecal valve where it terminates in the large intestine. The small intestine has three sections, the duodenum  104 , jejunum  106  and the ileum (not shown). The first eight to ten inch section of the small intestine, the duodenum, is the shortest, widest and most fixed part of the small intestine. 
     The duodenum has four sections: superior, descending, transverse and ascending which typically form a U-shape. The superior section is about two inches long and ends at the neck of the gall bladder. The descending section is about three to four inches long and includes a nipple shaped structure (papilla of vater)  114  through which pancreatic juice from the pancreas and bile produced by the liver and stored by the gall bladder enter the duodenum from the pancreatic duct. The pancreatic juice contains enzymes essential to protein digestion and bile dissolves the products of fat digestion. The ascending section is about two inches long and forms the duodenal-jejunal flexure  116  where it joins the jejunum  106 , the next section of the small intestine. The duodenal-jejunal flexure  116  is fixed to the ligament of Treitz  118  (musculus supensionus duodeni). The juices secreted in the duodenum break the partially digested food down into particles small enough to be absorbed by the body. The digestive system is described in Gray&#39;s Anatomy (“Anatomy of the Human Body”, by Henry Gray) and “Human Physiology”, Vander, 3 rd  Ed, McGraw Hill, 1980, the contents of which are incorporated herein by reference in their entirety. 
       FIG. 2  is a perspective view of a gastrointestinal implant device  200  according to the principles of the present invention. The gastrointestinal implant device  200  includes an elongated open-ended flexible sleeve or tube  202  having a first proximal opening  204  and a second distal opening  206 . Within the sleeve  202  is a passageway that extends from the first proximal opening  204  to the second distal opening  206  for transporting the chyme exiting the stomach  102  ( FIG. 1 ). The surface of the passageway (the interior surface of the implant device  200 ) is smooth to enable the chyme to easily pass through. The exterior surface of the implant device  200  is smooth to prevent tissue in-growth and to be non-irritating to the bowel. 
     Within the implant device  200  at the proximal end including the first proximal opening  204  is a collapsible self-expanding stent  208 . The stent  208  includes a plurality of opposed barbs  210  for anchoring the implant device  200  to the muscular pylorus in the stomach  102 . The diameter of the stent  208  is dependent on the diameter of the pyloric orifice  108  ( FIG. 1 ) about 0.8″ to 1.1″ based on human anatomy variations. In one embodiment, the length  1  of the stent  208  is selected to extend through the pylorus  108  and keep the pylorus  108  permanently open to induce “dumping syndrome.” In an alternate embodiment, a stent with a shorter length  1  allows the pylorus  108  to open and close normally. 
     The sleeve material is thin and conformable so that it collapses in the intestine to a small volume to minimize bowel irritability. It has a low coefficient of friction (&lt;0.20) so that chyme slides easily through it and the bowel slides easily around it. It is of low permeability to fluids so that the chyme does not touch the bowel wall and the digestive enzymes do not significantly breakdown the chyme. It is biologically inert and non-irritating to the tissues. One such material is expanded polytetrafluoroethylene (ePTFE), a fluoropolymer, with a wall thickness of about 0.006″ and an internodal distance of 20 microns. This material is hydrophobic but is slightly porous. However, these very small pores may plug over time. The porosity may be reduced by coating the material on the inside, outside or in the pores with dilute solutions of silicone or polyurethane. Another material is polyethylene with a wall thickness of less than 0.001″. Rubber-like materials typically have friction coefficients of 1-4, significantly stickier than these materials. However, in alternate embodiments other materials having similar characteristics can be used. 
     The sleeve  202  includes two layers of material at least at the proximal end. A first outer layer covers the exterior of the stent. The second inner layer covers the interior surface of the stent  208 . The barbs  210  protrude from the exterior surface of the stent  208  through the first outer layer of the sleeve  208 . The holes in the first outer layer through which the barbs  210  protrude are filled with an impervious material such as silicone or urethane to limit mixing of digestive juices with the chyme flowing through the passageway. The diameter of the sleeve  208  is selected such that the first outer layer of the sleeve  208  fits over the stent  208 . 
     The sleeve length  212  ranges from about one foot to about five feet. The typical length of the sleeve  208  is about 1.5 feet from the anchor (barbs  210 ) in the pyloric region of the stomach to below the ligament of Treitz  118  ( FIG. 1 ). The length  212  of the sleeve  202  is selected to bypass the duodenum  104  ( FIG. 1 ) and a portion of the jejunum. The length is increased to further decrease absorption by bypassing a longer section of the jejunum  106  ( FIG. 1 ). The length  212  of the sleeve  202  is variable and dependent on the patient&#39;s Body Mass Index (BMI). The procedure is a less invasive alternative to surgery for the treatment of obesity and morbid obesity and also provides a new treatment approach for type 2 diabetes. 
     The covered stent  208  can be collapsed into a sheath having a diameter less than ¼ inches to enable endoscopic delivery. Covering the exterior surface of the stent  208  with the first outer layer of the sleeve  202  permits endoscopic removal of the implant device  200  by preventing tissue in-growth on the exterior surface of the stent  208 . 
     Markings can be added to the exterior surface of the sleeve  202  to detect the position and orientation of the sleeve on a fluoroscopic image and whether the sleeve is twisted. For example, a stripe can be painted down the length of the device  200  using tantalum impregnated ink, or tantalum bands can be bonded to the exterior surface of the device. If the sleeve  202  is twisted, the sleeve  202  can be untwisted by inserting a balloon into the proximal end of the device thereby sealing it, and then injecting water into the sleeve at low pressure. 
       FIG. 3A  is a plan view of the proximal portion of the gastrointestinal implant device shown in  FIG. 2 .  FIG. 3B  is a cross-sectional view as taken along line AA of  FIG. 3A  showing the stent  208  and the first outer layer  300  and the second inner layer  302  of the sleeve  202  shown in  FIG. 2 . As described in conjunction with  FIG. 2 , the sleeve  202  includes a first outer layer  300  and a second inner layer  302 . The first outer layer  300  is bonded to the second inner layer  300  at positions  306  below the distal end of the stent  208  and at positions  308 , above the proximal end of the stent  208 . A passageway  304  inside the second inner layer  302  of the sleeve  202  allows passage of chyme through the sleeve  202 . The stent  208  is sandwiched between the first outer layer  300  and the second inner layer  302  at the proximal end of the sleeve  202  and is free to move at the distal end within the first outer layer  300  and the second inner layer  302  of the sleeve  202 . The covered exterior surface of the stent  208  prevents tissue growth to allow removal of the implant device  200 . The covered interior surface of the stent  208  provides a smooth passageway for chyme to bypass the duodenum  104 . 
       FIG. 4  is a perspective view of the gastrointestinal implant device  200  with the first outer layer  300  of the sleeve  202  removed. The interconnecting struts which form the mesh (a network of struts) with diamond spaced openings are sufficiently flexible to allow the stent to be collapsed inside a delivery catheter and have sufficient elasticity to hold the pylorus open once the catheter is withdrawn. The force needed to hold the pylorus open is about 1-2 lbs. of radial force outward when the stent is compressed from its full diameter by 25%. 
       FIG. 5A  is a sectional view of a body showing one embodiment of the gastrointestinal implant device  200  implanted in the digestive system. The first proximal end  204  of the implant device  200  is anchored to muscle in the pyloric portion of the stomach  102 . The barbs  210  grip onto the muscle to anchor the implant device  200  in place so that the implant device  200  can not be dragged into the stomach or down into the intestines with movement of the stomach and the intestines.  FIG. 5B  is a sectional view of a body showing an alternative embodiment of the gastrointestinal implant device  200 ′ implanted distal to the pylorus  108 . 
     The sleeve  202  extends over the ligament of Treitz  118  beyond the proximal jejunum. Extending the sleeve below the ligament of Treitz reduces the likelihood that the sleeve will move back through the duodenum  104  toward the stomach  102 . 
     After the gastrointestinal implant device  200  has been placed in the body and anchored in either the pyloric portion of the stomach or distal to the pylorus  108 , chyme leaving the stomach passes through passageway  304  ( FIG. 3B ) inside the sleeve  202  and bypasses the duodenum  104  and proximal jejunum  106 . By directing the chyme through the sleeve  202  the digestion and the absorption process in the duodenum  104  is interrupted. By interrupting mixing of the chyme with juices in the duodenum  104 , partially digested food material is not broken down into particles small enough to be absorbed by the body. Further, there is no mixing of bile with the chyme until the chyme reaches the jejunum  106 . The absorption of fats and carbohydrates is reduced by delaying the mixing of bile with the chyme. 
     The pyloric valve opens periodically to allow chyme to exit the stomach  102  to the duodenum  104 . In one embodiment of the invention the length of the stent  208  is selected to keep the pyloric valve permanently open to induce “dumping syndrome.” By keeping the pylorus  108  open, the chyme empties rapidly into the sleeve  202  and passes down through the sleeve  202  and into the jejunum  106  with minimal digestion. This results in a “dumping syndrome” which is a reaction to excessive rapid dumping of chyme into the jejunum  106  causing the patient to feel ill, dizzy and nauseated. This syndrome is particularly enhanced when sugars and carbohydrates are eaten and passed directly into the jejunum  106 . 
     To hold the pyloric valve open, the length of the stent  208  should be at least 1.5 inches so that the stent  208  extends from the anchoring position in the pyloric portion of the stomach through the pyloric orifice  108  (the opening from the stomach while the pyloric valve is open). The length of the stent is selected so that the distal end of the stent is above the papilla of Vater  114  ( FIG. 1 ). As shown, the stent  208  extends through the pyloric orifice  108  to hold the pyloric valve permanently open. In an alternative embodiment, the length of the stent  208  is selected such that the stent  208  ends at the stomach side of the pyloric orifice  108  allowing the pyloric valve to operate normally. 
     The sleeve  202  provides weight loss mechanisms by providing negative feedback, reduced fat digestion and reduced desire for food. The reduced fat digestion occurs because the sleeve  202  delays the mixing of bile and pancreatic juices with chyme from the stomach until after the chyme leaves the sleeve. The reduced desire for food may occur because the sleeve  202  blocks hormonal release from the duodenum. 
     After the chyme from the stomach has passed through the sleeve, the sleeve becomes extremely thin and floppy, permitting the sleeve to contour to the inner walls of the intestine. The sleeve is non-compliant and drapes away from the intestinal walls thereby permitting the pancreatic juice to flow unimpeded into the duodenum through the papilla of vater. The normal peristalsis of the bowel is used to propel the chyme through the intestines. 
       FIG. 6  is a perspective view of a collapsible self-expanding stent  600  in the gastrointestinal implant device  200  shown in  FIG. 2  when expanded. The stent  600  is non-woven, collapsible and self-expanding, allowing endoscopic insertion and removal of the implant device  200 . The stent  600  includes a plurality of flat struts  602  forming an open space pattern to ease collapsing while ensuring self-expansion. The open space pattern allows for collapsing into a catheter for endoscopic delivery and removal. The struts  602  may be manufactured from heat-treated spring steel, or from an alloy such as a nickel-titanium, a shape-memory alloy commonly referred to as nitinol. Other alloys include nickel-cobalt-chromium-molybdenum alloys possessing a unique combination of ultrahigh tensile strength, such as MP35N, available from Asahi Intecc Co., Ltd. of Newport Beach, Calif. 
     In the embodiment shown, the stent has a length L of about 1.5 inches and has a diameter D of about 1 inch. The struts  602  are flat, about 0.010 inches wide and about 0.004 to 0.010 inches thick. The stent can be formed from a tube of material by laser cutting followed by expansion and heat setting, or other methods well known to those skilled in the art. 
     In an alternate embodiment, the struts  602  can be formed separately and the strut intersections can be welded or attached by other means well known to those skilled in the art. Visually the struts form sections  604  around the circumference of the stent. Each section has a series of triangles with each triangle defined by one distal strut connection  606  and two proximal strut connections  608 ,  610 . The ratio of the collapsed diameter to the expanded diameter of the stent is roughly 1:4. 
     When expanded, the angle α between divergent strut sections is about 45-50 degrees and the diameter of the stent is about one inch. When compressed, the angle β between divergent strut sections is about 5-6 degrees to reduce the diameter of the stent to about 0.21 inch for endoscopic delivery and removal. The elasticity of the struts permits this compression. When the radial compression is released, the elasticity of the struts causes the stent to expand to diameter D. The stent assumes its desired diameter as the elastic restoring forces seek their minimum stress. 
     The ends of the struts at the proximal end of the stent  600  are elongated and shaped to provide barbs  612  to anchor to the muscle in the pyloric portion of the stomach  102 . 
       FIG. 7  is a perspective view of the stent  600  shown in  FIG. 6  when compressed. The stent  600  is compressed until the angle between divergent strut sections is about 5-6 degrees to reduce the diameter D of the stent  600  to about 0.21 inch for endoscopic delivery and removal. The barbs  704  at the proximal end of the stent are elongated. The barbs  704  can be shaped to anchor the stent to the muscular pylorus. 
       FIG. 8  is a perspective view of another embodiment of a stent  800  when compressed. Pairs of barbs  802  at the proximal end of the stent  800  are elongated and can be shaped to provide opposed barbs to anchor the stent  800  in the muscle of the pylorus. 
       FIG. 9  is a perspective view of the compressed stent  800  shown in  FIG. 8  with the strut ends  902 ,  900  bent to provide opposed barbs  904 ,  906 . The barbs  904 , 906  engage the muscle of the pylorus to anchor the gastrointestinal implant device in the pylorus portion of the stomach. As shown in  FIG. 2 , the strut ends  900 ,  902  protrude outward from the outer surface of the stent  800  in opposite directions. They may be perpendicular to each other. The barbs  904 ,  906  at the ends of the respective opposed strut ends  900 ,  902  dig into the pylorus muscle to anchor the stent. The barbs  904 ,  906  at the end of the protruding opposed strut ends  900 ,  902  prevent movement of the stent  800  in either direction; that is, they prevent movement of the stent  800  into the stomach and prevent movement of the stent  800  down through the duodenum. 
       FIG. 10  is a perspective view of the stent  800  shown in  FIG. 8  when expanded. As discussed in conjunction with  FIG. 9 , the barbs  904 ,  906  engage the muscle of the pylorus while the stent  800  is expanded. In the engaged position, the barbs  904 ,  906  spread radially outward from the longitudinal axis of the stent  800  such that the tips of the barbs come into contact and engage the tissue. 
       FIG. 11  illustrates the gastrointestinal device  1100  shown in  FIG. 1  including an anti-buckling mechanism  1102 . A flexible, anti-rotation, anti-buckling mechanism  1102  is attached to the sleeve  202  and extends from below the distal end of the stent along the length L of the sleeve to the distal end of the sleeve  202 . In the embodiment shown, the anti-buckling mechanism  1102  is a guidewire device attached to the exterior surface of the outer layer of the flexible sleeve. Guidewire devices are well known to those skilled in the art. A first proximal end of the guidewire device  1104  is attached below the stent and a second distal end of the guidewire device  1106  is attached to the distal end of the flexible sleeve. The diameter of the guidewire ranges from about 0.010″ to about 0.016″. 
     The length of the sleeve  202  can be sized to just pass over the ligament of Treitz thereby bypassing only the duodenum and proximal jejunum  106 . By doing this, it may not be necessary to provide any anti-buckling mechanisms in the sleeve  202  since the duodenum  104  is not very mobile compared to the jejunum  106 . Typically, an anti-buckling mechanism  1102  is added to the exterior surface of a sleeve  202  having a length exceeding the length of the duodenum  104  and proximal jejunum  106 . 
     The gastrointestinal implant device  200  is designed for endoscopic placement.  FIG. 12  is a perspective view of a portion of a catheter system  1200  for delivery of the gastrointestinal implant device. The catheter system follows a guide wire  1212  through the esophagus and the stomach to the pylorus portion of the stomach. The guide wire  1212  enters a first inner lumen at the proximal end  1208  of the catheter system  1200  and exits the first inner lumen at the distal end  1222  of the catheter system  1200 . 
     The catheter system  1200  includes an outer sheath  1202  for storing the stent  208  in collapsed form, a flange  1216  to pull back the outer sheath  1202  and a sleeve retention wire mechanism  1214  for releasing a sleeve retention wire  1210  from the proximal end of the flexible sleeve  202  after the stent has been released from the outer sheath  1202 . 
     As described in conjunction with  FIG. 2 , the distal portion of the gastrointestinal implant device includes a flexible sleeve  202  which can negotiate the duodenum and the jejunum. A sleeve retention wire  1210  travels through a second inner lumen and exits the second inner lumen to secure the distal end of the sleeve  202  to an inner sheath  1226 . The sleeve retention wire  1210  is coupled to the sleeve retention wire release mechanism  1214  for releasing the sleeve retention wire  1210  after the gastrointestinal implant device has been positioned in the pyloric section of the stomach. The release mechanism  1214  will be described later in conjunction with  FIG. 16B . 
     The sleeve  202  is secured temporarily outside the inner sheath  1226  allowing for proper positioning of the gastrointestinal implant device and then for release. As shown, the sleeve  202  is secured by the sleeve retention wire  1210  using a dead-bolt mechanism  1206 . Non-stick coatings such as Teflon on the sleeve retention wire  1210  are preferred to make release easier to accommodate tortuous anatomical pathways. The sleeve retention wire  1210  extends through the second inner lumen from the release mechanism  1214  of the catheter system  1200  to the dead-bolt mechanism  1206 . The dead-bolt mechanism  1206  is described later in conjunction with  FIG. 13A . 
     The sleeve retention wire  1210  holds the sleeve in position. The distal end of the folded sleeve is released by the release mechanism  1214  by pulling the sleeve retention wire  1210  backward from the proximal end  1208  of the catheter. 
     As described in conjunction with  FIG. 1 , the proximal portion of the gastrointestinal device includes a covered stent. The covered stent does not enter the duodenum and thus is stiffer than the sleeve because it remains in the pylorus of the stomach. The stent in the gastrointestinal implant device is collapsed and stored in the outer lumen within the outer sheath  1202  between the flange  1216  and the distal end of the outer sheath  1202 . The stent is supported in a collapsed form by the outer sheath  1202 . The catheter  1200  is inserted into the digestive system through the esophagus to the pyloric section of the stomach. The proximal end of the outer sheath  1202  is positioned in the stomach, in the pylorus through the use of positioning ring  1224 . After the outer sheath  1202  has been positioned, the stent is retracted from the outer lumen of the catheter by pulling flange  1216  toward the proximal end of the catheter system  1200 . Upon release, the stent self-expands by its own elastic restoring force to engage the anchor portion with the stomach muscle at the pyloric section of the stomach. 
       FIG. 13  is a cross-sectional view of the inner shaft  1226  taken along line E-E of  FIG. 12 . The sleeve retention wire  1210  passes through a second inner lumen  1314  in the inner sheath  1226 . The sleeve retention wire  1210  exits the second inner lumen  1314  and is threaded through folds of the sleeve  202  at  1302  in  FIG. 14A . The sleeve retention wire  1210  re-enters the second inner lumen  1314  at  1302  ( FIG. 14A ). The guidewire  1212  passes through the first inner lumen  1310 . 
       FIG. 14A  is an expanded perspective view of the dead-bolt mechanism  1206  shown in  FIG. 12 . The sleeve  202  has been folded for delivery. The sleeve is wrapped around the inner sheath  1226  and bunched above the inner sheath  1226 . The sleeve is held in folded position around the inner sheath  1226  by threading the sleeve retention wire  1210  through the folds of the sleeve  202 . The sleeve retention wire  1210  exits the second inner lumen  1314  through an opening  1306  and pierces through folds of the sleeve  202  at  1304 . Threading the sleeve retention wire  1210  through the folds of the sleeve  202  results in a plurality of small holes at the distal end of the sleeve  202 . The holes are reinforced with silicone or urethane to avoid tears in the material. The sleeve retention wire  1210  re-enters the second inner lumen through a second hole  1302  and advances a sufficient distance within the second inner lumen toward the distal end of the second inner lumen to resist pulling out of the second inner lumen. 
       FIG. 14B  is a sectional view of the dead-bolt mechanism  1206  shown in  FIG. 14A  illustrating the sleeve retention wire  1210  threaded through the sleeve. The sleeve retention wire  1210  exits the second inner lumen  1314  at  1306  and pierces through folds in the sleeve  202  at  1304 . The sleeve retention wire  1210  re-enters the second inner lumen  1314  at  1302 . 
       FIG. 15  is a sectional view of a portion of the catheter system shown in  FIG. 12  illustrating the collapsed stent  208  stored inside the outer sheath  1202 . The stent  208  is pre-compressed and held in a collapsed form inside the outer sheath  1202  of the catheter. The outer sheath  1202  is pulled back by the flange  1216  toward the proximal end of the catheter system  1200  to release the self-expanding stent  208 . The stent radially expands under its own elastic restoring force. The guidewire  1212  is directed through the first inner lumen  1310  and the sleeve retention wire  1210  is directed through the second inner lumen in the inner sheath  1226 . The inner sheath includes a first lumen through which the guidewire passes and a second lumen through which the sleeve retention wire passes. 
       FIGS. 16A-C  illustrate a method for delivery of the gastrointestinal implant device.  FIG. 16A  is a plan view of the catheter system illustrating the collapsed stent stored inside the outer sheath  1202  of the gastrointestinal implant device. As described in conjunction with  FIG. 12 , the stent  208  is stored inside the outer sheath and the distal end of the sleeve  202  is secured outside the inner sheath  1226  by a sleeve retention wire  1210 . 
       FIG. 16B  is a plan view of the catheter system  1200  illustrating the gastrointestinal implant device after release of the stent  208  from the outer sheath  1202 . The flange  1216  has been pulled back toward the proximal end of the catheter system  1200  to pull back the outer sheath  1202  from the stent and the stent  208  has self-expanded. The sleeve retention wire  1210  holds the distal end of the sleeve  202 . 
     Once in place, the sleeve retention wire  1210  can be removed. As described previously in conjunction with  FIG. 12 , the sleeve retention wire  1210  is coupled to locking mechanism  1224 . Handle  1600  in the locking mechanism  1214  acts as a pivot device to pull the sleeve retention wire  1210  from the dead-bolt mechanism  1206 . The distal end of the gastrointestinal implant device is released by moving handle  1600  in a clockwise direction  1604 . As the handle  1600  is moved in direction  1604 , the sleeve retention wire  1210  threaded through the folds of the sleeve is pulled back through the second inner lumen  1314  and disengages from the sleeve at the distal end of the gastrointestinal implant device. The sleeve retention wire  1210  extends from the distal end of the gastrointestinal implant device through the second inner lumen  1314 . The wire is connected to the handle  1600  at the proximal end of the catheter. 
       FIG. 16C  is a plan view of the catheter system illustrating the expanded gastrointestinal implant device after the sleeve retention wire has been released. The handle  1600  has been moved in a clockwise direction and the sleeve retention wire  1210  has been pulled back through the second inner lumen  1314  to release the distal end of the sleeve  202 . 
       FIG. 17  is a perspective view of another embodiment of the catheter system shown in  FIG. 16 . The catheter includes a ball  1800  coupled to the distal end  1222  of the inner sheath  1226  for guiding the catheter through the alimentary canal (e.g., to the pyloric portion of the stomach). The ball  1800  is small enough so that it can be pulled back through the gastrointestinal implant device after the gastrointestinal device has been delivered, the stent expanded and the sleeve retention wire  1210  has been released. The sleeve is shown uniformly folded  1204 . However, the sleeve may not necessarily be uniformly folded. 
       FIG. 18  is a cross-section of an everting catheter system  1900  for delivery of a longer flexible sleeve. The gastrointestinal implant device  200  is shown with the stent sleeve anchor  1901  and the attached sleeve  1902  shown as delivered into the anatomy. The delivery catheter previously described is then removed. A balloon catheter  1906  is introduced into the stent sleeve anchor  1901  and the balloon  1908  inflated to seal the lumen of the stent  1901 . The sleeve  1902  is folded inside itself and an elastic band  1912  is used to seal the end of the sleeve. Fluid is then injected through the balloon catheter shaft  1906  into the sleeve lumen  1910 , filling the lumen and pressurizing it. The pressure of the fluid is used to push the inner sleeve distally towards  1904 . When the sleeve  1902  has fully deployed distally, the elastic band  1912  falls off of the closed end of the sleeve  1902  and passes distally in the intestine until it is excreted. This mechanism permits deployment of a sleeve that is double the length of the delivered device. This may be needed as it is difficult to access the distal parts of the intestine with guidewires. This everting catheter system enables delivery of longer sleeves than are possible using only the delivery catheter described in conjunction with  FIG. 12 . 
       FIG. 19  is a perspective view of a retrieval device  2000  for removing the gastrointestinal implant device  200  from the digestive tract. As already described, the exterior surface of the stent  208  is covered with a material that prevents cellular in-growth allowing the stent  208  to be easily removed. The retrieval device  2000  includes an inner sheath  2004  and an outer sheath  2006 . A plurality of fingers  2002  extend from the proximal end of the inner sheath  2004 . The fingers  2002  engage the exterior surface of the gastrointestinal device. As the inner sheath  2004  is moved down over the fingers, the fingers  2002  pull radially inward to reduce the proximal stent diameter and pull the collapsed device into the outer sheath  2006 . 
       FIG. 20  is a perspective view of the retrieval device  2000  engaged with the stent  208 . The fingers  2002  of the retrieval device are positioned around the stent  208 . As the inner sheath  2004  is pushed over the fingers  2002 , the fingers pull radially inward on the proximal end of the stent  208  and the proximal end of the stent  208  is collapsed. After the stent  208  has been collapsed sufficiently such that the proximal stent diameter is less than the diameter of the outer sheath  2006 , the stent is drawn into the outer sheath  2006 . The entire gastrointestinal implant device can then easily be removed from the patient by pulling retrieval device  2000  through the stomach and the esophagus. 
       FIG. 21  is a perspective view of another embodiment of a gastrointestinal implant device  2200 . The gastrointestinal implant device  2200  includes a sleeve  202  and an anchoring ring  2204 . The distal end of the anchoring ring  2204  is bonded to the proximal end of the sleeve  202 . A plurality of eyelets  2206  are distributed around the circumference of the proximal end of the ring for anchoring the device to the pyloric muscle using anchors shown in  FIG. 24 . The anchoring ring  2204  is made from a flexible material such as silicone allowing the ring  2204  to be collapsed for endoscopic insertion and removal. 
     The anchoring ring  2204  does not hold the pylorus open. However, in an alternate embodiment, the anchoring ring  2204  can be bonded to a stent with sufficient length and diameter to hold the pylorus open as described in conjunction with  FIG. 2 . The anchoring ring  2204  anchors the device and the stent holds the pylorus open. 
       FIG. 22  is a perspective view of the anchoring ring  2204  shown in  FIG. 21  in the expanded position. The sleeve is bonded to the outer surface  2300  of the proximal end of the anchoring ring whose diameter is 0.8″ or about the same as the diameter of the sleeve. The anchoring ring  2204  includes at least four eyelets to anchor the device in place. The outer most diameter of the ring is about one inch. In an alternate embodiment there can be more than four eyelets. 
       FIG. 23  is a perspective view of the anchoring ring  2204  shown in  FIG. 21  in a collapsed position for insertion and removal. The circular ring  2204  shown in  FIG. 21  has been compressed to an oval shape allowing the anchoring ring to be inserted into the lumen of a catheter for delivery. 
       FIG. 24  is a perspective view of an anchor  2500  for anchoring the collapsible ring shown in  FIG. 23  to the muscular tissue of the pyloric orifice. The anchor  2500  includes an anchor pin  2504  coupled to a second pin  2506  by a flexible shaft  2502 . The anchor pin  2504  includes a shaped barb  2508  for locking the anchor  2500  into the tissue. The anchor  2500  is delivered after the collapsible ring has been positioned in the pyloric orifice. The anchor is guided so that the anchor pin  2504  is directed through a respective eyelet with the barbed portion of the anchor pin  2504  guided toward the tissue. After the barb  2508  has been locked into the tissue, the second pin  2506  sits inside the gastrointestinal implant device while the barbed portion  2508  of the anchor pin  2504  sits inside the pylorus muscle tissue. For removal of the gastrointestinal implant device from the body, the flexible shaft  2502  of the anchor  2500  is cut. 
       FIG. 25A  is a perspective view of a delivery system  2600  for delivering the anchor  2500  after the gastrointestinal implant device has been placed in the pyloric orifice. The anchor  2500  is loaded in the distal end of a catheter having a single lumen tube  2600 . The hollow, distal end of the delivery device is a sharp needle made to penetrate the pylorus muscle. In an alternate embodiment, the distal end of the delivery device can be formed in an arc to improve access to the eyelets  2206  through an endoscopic approach. The catheter  2600  includes a pusher  2604  for releasing the anchor  2500 . The pusher  2604  is moved in a longitudinal direction  2602  to release the anchor  2500  from the lumen. 
       FIG. 25B  is a plan view of the delivery system  2600  shown in  FIG. 25A .  FIG. 25C  is a cross-sectional view of the distal end of the catheter  2600  as taken along line B-B of  FIG. 25B . As described in conjunction with  FIG. 24 , the anchor  2500  includes pins  2504 ,  2506  coupled by a flexible shaft  2502 . The anchor  2500  is loaded in the lumen at the distal end of the catheter  2600 . The anchor pin  2504  is placed in the distal end of the tube  2600  and the second pin  2506  in the proximal end. The barb  2508  on the anchor pin  2504  is pointed toward the proximal end of the tube  2506  to engage with the tissue upon release in the muscle tissue. The catheter is advanced to the center of the ring positioned in the pyloric orifice. The sharp end  2510  is then pushed through an eyelet and into the muscle tissue. The pusher  2506  is pushed in longitudinal direction  2602  to release the distal anchor  2506 . Once the distal anchor is released, the delivery system is pulled back, dragging the proximal part of the anchor out of the delivery device with the flexible shaft going through the eyelet, and the proximal anchor portion resting on the inside of the device. In the embodiment of the ring shown in  FIG. 22 , four anchors  2506  are delivered to anchor the gastrointestinal implant device through the four eyelets. 
       FIG. 25D  is a perspective view illustrating the sharp end  2510  of the needle inserted through an eyelet  2206  for delivery of the anchor  2500  to the tissue  2512 . The distal end of the catheter is formed in an arc  2520  to improve access the eyelets  2206 . The sharp end  2510  of the catheter is inserted through the eyelet  2206  into the tissue  2516 . The anchor pin  2504  of the anchor has been pushed out from the lumen into the tissue  2512 . 
       FIG. 25E  is a perspective view illustrating the barb  2508  engaging the tissue  2512  after delivery. The catheter has been removed from the eyelet  2206  leaving the anchor pin  2504  engaging the tissue  2512 . 
       FIGS. 26A-E  illustrate an alternative embodiment of a locking mechanism for holding the distal end of the sleeve  202  in position during delivery of the gastrointestinal implant device. A snare wire  2656  is passed through one of the lumens of a catheter  2650  to the distal end. At the distal end, the end of the snare wire  2650  is looped back and attached to or anchored inside the catheter  2650 . The folds of the sleeve  202  are advanced through this snare loop. The snare handle  2664  pulls and releases the snare wire  2656  to lock and release the distal end of the sleeve  202 . The delivery system includes a pull tap  2666  for releasing a drawstring holding the stent in a collapsed position. 
       FIG. 26B  is cross-sectional view taken along line C-C of  FIG. 26A  through the inner sheath  2650 . The inner sheath has two lumens  2654 ,  2662  and has a diameter of about 0.078 inches. The first inner lumen  2564  is for passing a guidewire through the inner sheath and is about 0.04 inches in diameter. The second inner lumen  2662  is for passing the snare wire through the inner sheath and is about 0.02 inches in diameter. The end of the snare wire  2658  is anchored inside the inner sheath  2650 . 
       FIG. 26C  is a cross-sectional view taken along line DD of  FIG. 26A  through the outer sheath  2600  showing the inner sheath  2650  within the outer sheath  2600 . The outer sheath has an inner diameter of about 0.1 inches and an outer diameter of about 0.143 inches. The open space inside the outer sheath can be used for passing a drawstring through the outer sheath. 
       FIG. 26D  is a cross-sectional view through the distal portion of the catheter  2650  showing the snare capturing the distal end of the sleeve  202 . The distal end of the sleeve  202  is captured by the snare wire  2656  by pulling the distal end of the sleeve through a loop formed by the snare wire  2656 . 
       FIG. 26E  is a sectional view through the distal portion of the catheter showing the snare locking mechanism. The distal end of the sleeve is locked by pulling the snare wire  2656  in a longitudinal direction  2664  toward the proximal end of the delivery system to capture the sleeve folds against the inner shaft. After the gastrointestinal implant device is properly positioned in the body, the snare wire is advanced in a longitudinal direction  2662  toward the distal end of the delivery system. This opens the snare wire  2656  and releases the sleeve  202 . 
       FIG. 27  is a perspective view of the distal portion of the gastrointestinal implant device including texturing  2700 . Texturing of the distal end of the sleeve can be added to ensure that the actions of peristalsis do not advance the sleeve proximally, towards the stomach, but keep the sleeve pulled taught in the intestine. At the distal end of the sleeve, texturing  2700  is added with a directional aspect to it. The texturing  2700  can be molded into the sleeve material or added by adhesive or thermal bonding methods. The texturing material contains includes fibril shapes that are directed proximally so that any peristaltic waves that travel proximally, will have less force on the sleeve than distal peristaltic waves. 
     The gastrointestinal implant device offers a new alternative where other means of weight loss and efforts at behavior modification have failed. Because the gastrointestinal implant device is endoscopically introduced, there is a reduced risk at insertion compared to surgery. The procedure is also completely reversible, making this approach an ideal solution for patients who are desperate to reverse behavioral patterns that have lead to weight gain. 
     When inserted in the body, the gastrointestinal implant device mimics the duodenal bypass of the Roux-en-Y procedure. The implanted device reduces caloric absorption by delaying enzyme mixing with food and provides the feedback produced by the Roux-en-Y procedure by producing dumping syndrome when high sugar meals are ingested. Rapid stomach emptying is encouraged by inserting a stent in the pylorus to hold the pylorus open and all food bypasses the duodenum and passes rapidly into the jejunum. The implant device is an improvement on the Roux-en-Y procedure because it is minimally invasive and reversible. In the treatment of the super-obese where aggressive weight loss is not achieved, the length of the implant device below the stent can be further increased to drive the patient close to the point of malabsorption. 
     The gastrointestinal implant device can be used to reduce Type 2 diabetes symptoms by bypassing the duodenum. Following gastric bypass surgery, patients commonly experience complete reversal of Type 2 diabetes. While the exact mechanism of this remarkable effect is not understood, the clinical result is reported in a high percentage of cases. Reversal of Type 2 diabetes after gastric bypass is described in “Potential of Surgery for Curing Type 2 Diabetes Mellitus” by Rubino et al. incorporated herein by reference in its entirety. Since the gastrointestinal implant device provides equivalent blockage of duodenal processes, a similar effect is elicited but without the trauma of surgery. In patients who are not obese but suffer Type 2 diabetes, a modified gastrointestinal implant device is inserted. This gastrointestinal implant device provides the necessary effect to hinder pancreatic processes and receptors without blocking absorption. 
     In the embodiment of the gastrointestinal implant device for treating diabetes, the length of the stent is selected to allow the pylorus to operate normally. The length of the sleeve is also reduced to mimic the duodenum bypass. The sleeve extends to just below the ligament of Treitz but does not extend further into the jejunum, thus allowing absorption to occur in the jejunum. 
       FIG. 28  is a perspective view of a gastrointestinal implant device with another embodiment of a collapsible self-expanding anchoring device. The gastrointestinal implant device  2800  includes a sleeve  202  and an anchoring device, or sleeve anchor, for anchoring the gastrointestinal implant  2800  device within the gastrointestinal tract. In some embodiments, the implant device  2800  includes a wave anchor  2810  coupled to a proximal portion of the sleeve  202 . Wave anchors are described in more detail in co-pending U.S. patent application Ser. Nos. 10/858,851 and 10/858,852, both filed on Jun. 1, 2004, both claiming priority to U.S. Provisional Application No. 60/528,084 filed on Dec. 9, 2003 and U.S. Provisional Application No. 60/544,527 filed on Dec. 13, 2003; U.S. patent application Ser. No. 11/229,352, filed on Sep. 16, 2005, which claims priority to U.S. Provisional Application No. 60/611,038, filed on Sep. 17, 2004; and U.S. patent application Ser. No. 11/147,992, filed on Jun. 8, 2005, all incorporated herein by reference in their entirety. 
     The wave anchor  2810  includes a compliant, radial spring  2900  shaped into an annular oscillating pattern. For example, the pattern is a wave pattern, such as a sinusoidal pattern formed about a central axis. The anchor provides an outward radial force, while allowing substantial flexure about its perimeter. Such flexure is advantageous as it allows for minimally-invasive delivery and ensures that the device will substantially conform to the surrounding anatomical structure when implanted. 
     The annular wave element  2900  can be formed from one or more elongated resilient members radially-disposed about a longitudinal axis and joined together defining a lumen along its central axis formed between two open ends. When implanted, the central axis  2815  of the anchor is substantially aligned with the central axis of the lumen  2820  (e.g., duodenum  104 ), allowing chyme to pass through the interior of the device  2800 . Additionally, the compliant wave anchor  2810  minimizes trauma to the tissue by providing sufficient flexibility and compliance, while minimizing the likelihood of tissue erosion and providing a solid anchoring point to the tissue. 
     In some embodiments, the wave anchor is adapted for placement within a region of the proximal duodenum referred to as the duodenal bulb  500  ( FIG. 5B ). For these applications, the axial extent of the anchor is preferably less than the distance between the pyloric sphincter and the ampulla of Vater. Exemplary relaxed lengths can range from about 20 to 50 mm (i.e., from less than 1 to about 2 inches). The diameter of the wave anchor  2900  can have an initial installed diameter within the range of about 20-40 millimeters (i.e., between about 1 and 1¾ inches). 
     The compliance of the anchor  2900 , allows it to flex radially over a wide range according to natural contractions and expansions of the duodenum  104  (i.e., between about 25 and 45 mm). In some embodiments, the relaxed diameter of the wave anchor 2900 can be about 50 mm (i.e., about 2 inches). In other embodiments, the relaxed diameter can exceed 50 mm, being up to 60 mm (i.e., 2.5 inches) or even more. In either case, the wave anchor  2900  can be temporarily collapsed to about 12 mm (i.e., about 0.5 inches) for endoscopic placement. 
     In some embodiments, the implant device includes a retrieval/repositioning feature. For example, the implant device  2800  includes a drawstring  2825 . The drawstring  2825  can be selectively woven around the perimeter of the anchor  2900  through openings of opportunity in the anchor  2900 . Alternatively or in addition, the drawstring  2825  can be selectively woven through dedicated openings, such as eyelets provided on the anchor  2900  or in the proximal sleeve  202 . In operation, the drawstring  2825 , when pulled, contracts about the perimeter of the anchor  2900  to reduce the diameter of the anchor  2900 . Collapsing the anchor  2900  in this manner before removing or repositioning the anchor  2900  is advantageous in avoiding tissue damage, particularly when the implant device  2800  includes barbs. 
     In some embodiments, the gastrointestinal implant device  2800  can be inserted endoscopically in combination with a delivery catheter, such as any of the delivery catheters described herein ( FIGS. 12 and 17 ) or any of the delivery catheters described in U.S. patent application Ser. No. 10/999,846, filed on Nov. 30, 2004, which is a divisional of U.S. patent application Ser. No. 10/339,786, filed on Jan. 9, 2003, which claims the benefit of U.S. Provisional Application No. 60/430,321 filed on Dec. 2, 2003; any of the delivery catheters described in U.S. patent application Ser. No. 10/726,011, filed on Dec. 2, 2003, which claims the benefit of U.S. Provisional Application No. 60/512,145, filed on Oct. 17, 2003; or any of the delivery catheters described in U.S. patent application Ser. No. 11/057,861, filed on Feb. 14, 2005, which claims the benefit of U.S. Provisional Application No. 60/586,521, filed on Jul. 9, 2004 and U.S. Provisional Application No. 60/610,614, filed on Sep. 19, 2004, all incorporated herein by reference in their entirety. 
     In some embodiments, the gastrointestinal implant device can be repositioned and/or removed endoscopically in combination with a repositioning/removal device, such as any of the repositioning/removal devices described herein ( FIG. 19 ) or any of the repositioning/removal devices described in U.S. patent application Ser. No. 11/001,812, filed on Nov. 30, 2004, which is a divisional of U.S. patent application Ser. No. 10/339,786, filed on Jan. 9, 2003, which claims the benefit of U.S. Provisional Application No. 60/430,321 filed on Dec. 2, 2003; or any of the repositioning/removal devices described in U.S. Provisional Application No. 60/645,287, filed on Jan. 19, 2005, all incorporated herein by reference in their entirety. 
     Various embodiments of the gastrointestinal implant device have been described herein. These embodiments are given by way of example and are not intended to limit the scope of the present invention. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 
     The appended claims are of a scope that covers the embodiments disclosed in priority application U.S. patent application Ser. No. 10/858,852 referenced herein, and thus have the benefit of priority of that filing date. The claims are also of a sufficient scope to cover more recent embodiments, including those described above and those disclosed in U.S. patent application Ser. Nos. 11/229,352 and 11/147,992, also referenced herein.