Abstract:
The various embodiments of the present invention provide implantable occlusion devices and methods of using the occlusion devices. In an embodiment, the occlusion devices include an openable channel to facilitate reversible female contraception.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention relate to the field of minimally invasive surgical medical devices and medical procedures. More specifically, embodiments of the present invention relate to devices and methods used for transcervical gynecological procedures. 
         [0003]    2. Discussion of Related Art 
         [0004]    Female contraception and sterilization may be enabled by transcervically introduced fallopian tube inserts. Devices, systems and methods for contraceptive approaches have been described in various patents and patent applications assigned to the present assignee. For example, U.S. Pat. No. 6,526,979, U.S. Pat. No. 6,634,361, and U.S. patent application Ser. No. 12/605,304 published as U.S. Publication No. 2011/0094519, describe transcervically introducing an insert (also referred to as implant and device) through an ostium of a fallopian tube and mechanically anchoring the insert within the fallopian tube. One example of such an assembly is known as “Essure”®, manufactured by Conceptus, Inc. of Mountain View, Calif. Tissue in-growth into the Essure® insert induces long-term contraception and/or permanent sterilization. 
         [0005]    Referring to  FIG. 1 , an insert may access an ostium  106  of a fallopian tube through a cervix  102 . A delivery system may be used to carry the insert through cervix  102  into a uterus  104  toward ostium  106 . The insert may be a contraceptive implant held within a delivery catheter of the delivery system. For example, the delivery catheter may include an outer catheter sheathing the implant prior to deployment. From within uterus  104 , the delivery system may be advanced until the insert is located beyond ostium  106  in an intramural portion  108  of the fallopian tube. Intramural portion  108  leads into an isthmus segment  110  of the fallopian tube. The intramural portion  108  and isthmus segment  110  generally have a combined length of about 3-4 cm. Furthermore, intramural portion  108  and isthmus segment  110  generally have an inner diameter of about 0.5-2 mm along their length. As a result, intramural portion  108  and isthmus segment  110  provide a suitable landing for delivery of the insert into the fallopian tube. Alternatively, the insert may be delivered into an ampulla segment  112 , but given that the ampulla segment  112  inner diameter can vary to be up to about 1 cm at a distal end, securing an insert in that region is difficult. Furthermore, delivering an insert into the ampulla segment  112  may be accompanied by increased health risks such as an increase in the risk of an ectopic pregnancy. 
         [0006]    An endoscope may be used to facilitate transcervical passage of the delivery system into a patient and to view placement of the delivery system through ostium  106 . Once a physician has positioned the delivery system within the fallopian tube the insert may be deployed from the delivery catheter into the fallopian tube. The insert anchors within intramural portion  108  and/or isthmus segment  110  to occlude the fallopian tube and to prevent the passage of an ovum from ampulla  112  to uterus  104 . 
       SUMMARY OF THE DESCRIPTION 
       [0007]    An occlusion device having a hollow body, a plurality of caps, and an expandable layer is disclosed. In an embodiment, the hollow body includes an outer surface and a passage with a proximal and distal end. The hollow body can be of any shape, e.g., ellipsoidal, cylindrical, spherical, etc. The plurality of caps may cover the passage ends to enclose the passage within the hollow body. The expandable layer may be coupled with the outer surface. 
         [0008]    In an embodiment, one or more expandable anchors may also be coupled with the outer surface. For example, an anchor may include an expandable coil having an end coupled with the outer surface and another unattached end that expands radially apart from the coupled end when the expandable coil is unconstrained. 
         [0009]    In an embodiment, the outer surface may be shaped in a convex, cylindrical, or concave manner. The expandable layer on the outer surface may include a non-slip surface to facilitate anchoring. For example, the expandable layer may include a hydrogel to promote tissue in-growth and adhesion. Alternatively, the expandable layer may include a shape memory polymer (SMP) or chemical foam structure with shape memory to facilitate anchoring and promote tissue in-growth and adhesion. Furthermore, the hydrogel or shape memory foam/polymer structure may be bioresorbable. In an embodiment, the occlusion device length may be between about 2 and 35 mm. 
         [0010]    In an embodiment, the plurality of caps may be integrally formed with the hollow body or separately formed. Integrally formed caps may include a penetrable wall configured to be pierced by a guidewire. For example, the penetrable wall may be thinner than an adjacent wall of the hollow body or may include penetrable features, such as depressions or perforations. In an embodiment, the plurality of caps may be interconnected by a connector member. 
         [0011]    An elongated flexible tail may be coupled with one of the plurality of caps. For example, the flexible tail may trail away from a proximal cap when the occlusion device is implanted in a fallopian tube. To aid visualization of the occlusion device, the enclosed passage may be filled with contrast agent. 
         [0012]    A method of using the occlusion device includes delivering the occlusion device into a fallopian tube and expanding the expandable layer until it contacts and occludes the fallopian tube. The plurality of caps prevents migration of ova through the passage. The anchors may further secure the occlusion device to the fallopian tube. Thus, contraception may be achieved after deployment of the occlusion device. The method may further include opening the plurality of caps, for example, by dislodging or piercing one or more of the caps, to open the passage to the surrounding fallopian tube. Thus, ova are allowed to migrate through the passage to the uterus, and contraception can be reversed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar, but not necessarily identical, elements. 
           [0014]      FIG. 1  is a pictorial illustration of a human female reproductive system; 
           [0015]      FIG. 2  is a side view illustration of an occlusion device having an ellipsoid hollow body in accordance with an embodiment of the invention; 
           [0016]      FIG. 3  is a cross-sectional view, taken about line A-A of  FIG. 2 , illustrating an occlusion device in accordance with an embodiment of the invention; 
           [0017]      FIG. 4  is a side view illustration of an occlusion device having an expanded expandable layer in accordance with an embodiment of the invention; 
           [0018]      FIG. 5  is a side view illustration of an occlusion device having a cylindrical hollow body in accordance with an embodiment of the invention; 
           [0019]      FIG. 6  is a cross-sectional view, taken about line B-B of  FIG. 5 , illustrating an occlusion device in accordance with an embodiment of the invention; 
           [0020]      FIG. 7  is a side view illustration of an occlusion device having an anchor feature in accordance with an embodiment of the invention; 
           [0021]      FIG. 8A  is a side view illustration of an occlusion device having an expanded expandable layer and expanded coil anchor features in accordance with an embodiment of the invention; 
           [0022]      FIG. 8B  is a side view illustration of an occlusion device having an expanded expandable layer and expanded spider member and stent-like anchor features in accordance with an embodiment of the invention; 
           [0023]      FIG. 9  is a side view illustration of an occlusion device having an opened proximal cap in accordance with an embodiment of the invention; 
           [0024]      FIG. 10  is a side view illustration of an occlusion device having an opened distal cap in accordance with an embodiment of the invention; 
           [0025]      FIG. 11  is a side view illustration of an occlusion device having an opened passage in accordance with an embodiment of the invention; 
           [0026]      FIGS. 12A-12E  are various views of cap portions of an occlusion device in accordance with an embodiment of the invention; 
           [0027]      FIGS. 13A-13C  are various views of tail portions of an occlusion device in accordance with an embodiment of the invention; 
           [0028]      FIG. 14  is a pictorial illustration of an endoscope accessing an ostium of a fallopian tube in accordance with an embodiment of the invention; 
           [0029]      FIGS. 15A-15D  are pictorial illustrations of delivery of an occlusion device to occlude a fallopian tube and to effect contraception in accordance with an embodiment of the invention; and 
           [0030]      FIGS. 16A-16C  are pictorial illustrations of unblocking of the fallopian tube to reverse contraception in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Various embodiments and aspects of the invention will be described with reference to details discussed below, and the accompanying drawings will illustrate the various embodiments. The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of various embodiments of the invention. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present invention. 
         [0032]    Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment. Although the processes are described below in terms of some sequential operations, it should be appreciated that some of the operations described may be performed in a different order. Moreover, some operations may be performed simultaneously rather than sequentially. 
         [0033]    It is to be understood that embodiments of the current invention may be used in gynecological, as well as non-gynecological, target anatomies. For example, many target anatomies may benefit from procedures using the current invention, including gynecological anatomies such as the fallopian tubes, and non-gynecological target anatomies, such as the vas deferens, e.g., during a male sterilization procedure, or arteries, e.g., during a vascular intervention. Thus, while the current invention is applicable to surgeries that employ endoscopes, such as angioscopy, arthroscopy, bronchoscopy, and hysteroscopy, to name a few, it is equally applicable to surgeries that employ other delivery systems, such as vascular intervention procedures. 
         [0034]    In an aspect, an occlusion device facilitates contraception by occluding a target anatomy, such as a fallopian tube, to prevent the passage of reproductive cells, such as ova, across the occlusion device. In an embodiment, an expandable layer fills a space between a fallopian tube wall and a hollow body to prevent passage of an ovum around the hollow body. Furthermore, the hollow body may include one or more caps that enclose a passage within the hollow body and prevent the ovum from traveling through the hollow body. Thus, migration of the ovum from the ampulla to the uterus is impeded to effect contraception. 
         [0035]    In another aspect, the occlusion device facilitates reversible contraception by reopening the occluded target anatomy to allow the passage of reproductive cells. In an embodiment, the one or more caps of the hollow body may be removed, pierced, or otherwise opened to uncover and disclose the passage. Thus, the fallopian tube may become unblocked and migration of the ovum from the ampulla through the hollow body into the uterus is enabled to reverse contraception. 
         [0036]    In another aspect, the occlusion device that facilitates reversible contraception anchors within the target anatomy. In an embodiment, the occlusion device may include one or more anchors that expand within the fallopian tube to secure the hollow body to the fallopian tube. Anchoring may be achieved through non-slip surface features of the expandable layer. Alternatively, anchoring may be achieved through expanding structures and/or coatings that provide acute and long-term adherence to the fallopian tube. Thus, the anchored occlusion device may remain intact within the fallopian tube to ensure contraception is maintained until reversal of contraception is intended. 
         [0037]    Referring to  FIG. 2 , a side view of an occlusion device having an ellipsoid hollow body is shown in accordance with an embodiment of the invention. In an embodiment, occlusion device  200  includes a centrally located hollow body  202  having a shell configuration. For example, hollow body  202  may be formed as a shell capsule with a thin wall, such that a cavity or passage is located within hollow body  202 . 
         [0038]    Hollow body  202  may be configured to facilitate placement within a fallopian tube. For example, hollow body  202  may be formed from a material that is able to conform to arcuate fallopian tube anatomies and to accommodate motion of the fallopian tubes that occur during normal patient movement. Thus, in an embodiment, hollow body  202  may be formed from a flexible and resilient material, such as a copolymer of ethylene and polypropylene. Alternatively, portions of hollow body  202  may incorporate polyurethane, silicone, butyl rubber, or other elastomeric materials. 
         [0039]    In addition to being flexible, hollow body  202  may have sufficient radial strength to resist radial collapse under loads applied by the fallopian tube. More specifically, normal patient movement may result in bending and compressive loads applied to hollow body  202 , but hollow body  202  may be formed with sufficient radial strength and/or resilience to either not collapse or to not permanently deform under such loads. 
         [0040]    Although hollow body  202  may be formed from biostable materials, such as those listed above, in an alternative embodiment, hollow body  202  may be bioabsorbable or bioresorbable. For example, in an embodiment, hollow body  202  may be formulated to degrade within a fallopian tube over a set period of time such that hollow body  202  initially occludes the fallopian tube but is eventually resorbed by the fallopian tube. Following resorption, hollow body  202  may no longer impede migration of ova. As an example, hollow body  202  may be formed from a biodegradable plastic, such as a polymer containing polyglycolic acid or polylactic acid configured to degrade either by bulk erosion or surface erosion. Hollow body  202  may be tuned to reopen through this erosion within a predetermined time frame, e.g., approximately two to three years after implantation. Thus, occlusion device  200  will effect contraception over a period of about three years, but following that time, degradation of occlusion device  200  will reverse contraception. 
         [0041]    Hollow body  202  may also be sized to facilitate placement within a fallopian tube. For example, hollow body  202  may have a diameter that conforms closely to the average diameter of intramural portion  108  or isthmus segment  110 . Accordingly, hollow body  202  may have a maximum diameter between about 0.5 to 2 mm. Furthermore, the length of hollow body  202  may be chosen to prevent hollow body  202  from upending within the fallopian tube. Hollow body  202  length may be chosen to be at least as long as is needed to mitigate the risk that collateral channels will carry an ovum around implanted occlusion device  200  and thereby negate the occlusion device-induced contraception. Accordingly, in an embodiment, hollow body  202  may have a length between about 2 to 35 mm. More specifically, hollow body  202  may have a length from a proximal end to a distal end of about 10 mm. 
         [0042]    In an embodiment, an expandable layer  210  may be located on an outer surface  204  of hollow body  202 . Expandable layer  210  may be formed from a material that swells upon introduction into a physiological environment, such as the fallopian tube. For example, in an embodiment, expandable layer  210  may be formed from a hydrogel material. Hydrogels can be formed from covalently or non-covalently cross-linked materials, and can be non-degradable (“biostable”) in a physiological environment or broken down by natural processes within the body (“biodegradable”, “bioabsorbable”, or “bioresorbable”). Accordingly, in several embodiments, expandable layer  210  may be a polyacrylamide, polyethylene glycol (PEG), or polyvinylpyrrolidone (PVP) based hydrogel. Thus, a hydrogel expandable layer  210  may have a substantially unswollen state as well as a swollen state. Expandable layer  210  may be maintained in the substantially unswollen state during delivery to the fallopian tube, but after delivery, expandable layer  210  may swell against the fallopian tube wall. Alternatively, expandable layer  210  may be formed from a shape memory polymer (SMP) material such as polyurethane-based shape memory polymers or polymer foams that have excellent biocompatibility and tunable glass transition temperatures for shape restoration/self-deployment when inserted in the human body. 
         [0043]    A hydrogel used in expandable layer  210  may, in one embodiment, be made to be radiopaque by incorporating a radiopaque filler, such as iodine or heavy metals and heavy metal compounds, e.g., barium sulfate, platinum, tungsten, gold, or iridium-based contrast material, into the hydrogel. Increasing hydrogel radiopacity promotes visibility of the implanted occlusion device  200  under fluoroscopy. Similarly, visibility of the implanted occlusion device  200  may be modified to accommodate other imaging modalities. For example, visibility of the hydrogel and occlusion device  200  under ultrasound imaging may be improved by incorporating microbubbles within the hydrogel. 
         [0044]    Expandable layer  210  may be coupled with outer surface  204  to stabilize hollow body  202  within the fallopian tube when expandable layer  210  expands therein. In an embodiment, expandable layer  210  may be spray coated or dip coated over outer surface  204 . Alternatively, expandable layer  210  may be separately formed and then coupled with hollow body  202  using an adhesive layer between outer surface  204  and expandable layer  210 . For example, expandable layer  210  may be cross-linked separately or injection molded separately before being coupled with hollow body  202 . Thus, after expandable layer  210  is coupled with outer surface  204 , it may be securely attached to hollow body  202 . 
         [0045]    Occlusion device  200  may include one or more caps, such as distal cap  206  and proximal cap  208 , which are located at either end of hollow body  202 . The caps may be integrally formed with hollow body  202 , or formed separately and then coupled with hollow body  202 . In  FIG. 2 , for example, distal cap  206  is integrally formed with hollow body  202  and provides a distal end of hollow body  202 . By contrast, proximal cap  208  is formed separately from hollow body  202  and is coupled with hollow body  202 . Although distal cap  206  may be a portion of hollow body  202  while proximal cap  208  may be separate from hollow body  202 , in either case, distal cap  206  and proximal cap  208  cover an end of hollow body  202  and therefore enclose the cavity that is located within hollow body  202 . Thus, while distal cap  206  and proximal cap  208  are coupled with hollow body  202  and enclose the cavity, an ovum is prevented from passing through hollow body  202  from one end to another end. 
         [0046]    In an embodiment, occlusion device  200  may include a tail  212  trailing from proximal cap  208  or hollow body  202 . For example, tail  212  may be a flexible suture having a distal end attached to proximal cap  208  and a proximal end trailing freely away from the hollow body  202 . Tail  212  may be sized and configured to allow for it to trail into uterus  104  while hollow body  202  is located within a fallopian tube. For example, tail  212  may have a diameter less than the average diameter of intramural portion  108  and a length greater than an average length of intramural portion  108 . In an embodiment, tail  212  may have a diameter of less than about 1 mm and a length of at least about 1 cm. Tail  212  may include a flexible suture, which may be a braided or monofilament type suture, for example. Thus, the size and structure of tail  212  provides for a flexible, and in some cases limp, elongated marker that conforms to the fallopian tube and hangs from ostium  106  into uterus  104 . Accordingly, tail  212  can be visually identified by an endoscope inserted within uterus  104 . 
         [0047]    Several features may be incorporated to promote the visibility of tail  212  under both optical and x-ray imaging modalities. For example, tail  212  may be colored to visually contrast with tissue, e.g., by a surface treatment that is itself visible when illuminated and viewed employing a hysteroscope. For example, tail  212  may be coated with a dye-loaded hydrophilic coating that liquefies when it contacts the tissue surface and stains the tissue. Preferred non-toxic dyes for staining the tissue of the ostium  106  or for coloring sutures include methylene blue dye (a benign chemical often used in conjunction with hysteroscopic fertility tests), FD&amp;C BLUE dyes 3 and 6, eosin, and indocyanine green. Green or blue dyes substantially contrast with the uterine wall tissue color. In another embodiment, tail  212  may include a radiopaque ink or dye either painted on an outer surface  204  or incorporated within tail  212 . Suitable radiopaque inks include inks containing barium sulfate, gold, or other dense materials that are visible under fluoroscopy. 
         [0048]    Referring to  FIG. 3 , a cross-sectional view, taken about line A-A of  FIG. 2 , illustrates an occlusion device in accordance with an embodiment of the invention. A distal end  320  of tail  212  may be coupled with proximal cap  208  by placing tail  212  through a bore formed through proximal cap  208 . In an embodiment, tail  212  may be secured in the bore using an adhesive. In an alternative embodiment, a distal end  320  of tail  212  may be stamped to cause a localized increase in the tail  212  outer diameter and thereby prevent tail  212  from being pulled out through the bore in proximal cap  208 . 
         [0049]    Passage  306  may be defined by the cavity within hollow body  202 . More specifically, an inner surface  302  of hollow body  202  may be a closed surface that defines a space through which passage  306  is located. Thus, in an embodiment, passage  306  may have a volume that substantially conforms with the volume of hollow body  202 . For example, hollow body  202  may be a thin-walled shell with a body wall  304  between outer surface  204  and inner surface  302 . In an embodiment, body wall  304  may have a uniform thickness of about 0.1 to 0.25 mm. Accordingly, the cavity within hollow body  202  may be substantially similar to a volume within inner surface  302 , and passage  306  may be considered to encompass the entire cavity. In other embodiments, body wall  304  may not have a uniform thickness or may include additional features, such as ribbing, and therefore the volume of the cavity may be reduced. However, even in these alternative embodiments, passage  306  may be defined as passing along a path from a distal end  308  to a proximal end  310 . In an embodiment, passage  306  has an opening at distal end  308  and an opening at proximal end  310 . As shown in  FIG. 3 , distal cap  206  and proximal cap  208  may cover those openings, thereby enclosing passage  306  relative to the surrounding environment. 
         [0050]    In an embodiment, distal cap  206  may be integrally formed with hollow body  202 , and more specifically, may include material that is contiguous with body wall  304 . However, distal cap  206  may be formed such that it is more susceptible to puncture as compared to body wall  304 . For example, distal cap  206  may be thinner than adjacent body wall  304 . As an example, whereas body wall  304  may have a uniform thickness of about 0.1 to 0.25 mm, distal cap  206  may have a thickness of about 0.05 mm to 0.15 mm. Thus, distal cap  206  covers an opening of passage  306  at distal end  308 , but also provides a structure that can be preferentially punctured to expose passage  306  to the surrounding environment. 
         [0051]    In an embodiment, proximal cap  208  may be separately formed from hollow body  202 , and more specifically, may be separately formed and then coupled with body wall  304 . However, proximal cap  208  may be formed such that it is removable from hollow body  202 . For example, proximal cap  208  may include a bulge  312  that fits within a detent  314  formed in body wall  304 . Bulge  312  and detent  314  may be sized to mate with each other such that proximal cap  208  can be snapped into, and retained against, hollow body  202  until a sufficient load is applied to disengage bulge  312  from detent  314 . For example, tail  212  may be pulled to disengage bulge  312  from detent  314  and remove proximal cap  208  from hollow body  202 . Thus, proximal cap  208  covers an opening of passage  306  at proximal end  310 , but also provides a structure that can be manipulated to expose passage  306  to the surrounding environment. 
         [0052]    Referring to  FIG. 4 , a side view of an occlusion device having an expanded expandable layer is shown in accordance with an embodiment of the invention. As described above, expandable layer  210  may include a hydrogel that swells upon delivery into a physiological environment. Thus, upon delivery into a fallopian tube, expandable layer  210  can increase in volume and fill a space between hollow body  202  and the fallopian tube. However, in addition to swelling and occluding fallopian tube, expandable layer  210  may also include a non-slip surface  402  that encourages anchoring of the occlusion device  200  within the fallopian tube. For example, a hydrogel material in expandable layer  210  may facilitate tissue in-growth and epithelialization. Such in-growth results in adhesion between expandable layer  210  and the fallopian tube. 
         [0053]    In an embodiment, non-slip surface  402  of expandable layer  210  may also include one or more structural features that encourage anchoring. For example, expandable layer  210  may include one or more corrugation  404  defined by an area of increased diameter adjacent to areas of decreased diameter, e.g., an undulating, wavy, or jagged surface. Corrugation  404  facilitates gripping of the fallopian tube wall. Given that the fallopian tube wall is generally formed of a multi-layered resilient muscular structure, the fallopian tube will conform to the peaks and valleys of the non-slip surface  402  and thereby resist axial motion of the expandable layer  210 . In addition to a corrugated surface, non-slip surface  402  may have one or more other anchor features, such as barbs, protrusions, ribs, etc., that facilitate the same gripping effect described above. 
         [0054]    In an embodiment, non-slip surface  402  may include one or more surface treatments to encourage anchoring. For example, in addition to tissue in-growth within a hydrogel, further surface treatment may be used to promote tissue adhesions. For example, expandable layer  210  may be coated with a biocompatible adhesive to facilitate adhesion between the hydrogel of expandable layer  210  and tissue of the fallopian tube. A wide range of bioadhesives may be used for this purpose, but as an example, bioadhesives such as chitosan, which have found applications for wound treatment, may be used. 
         [0055]    In an embodiment, non-slip surface  402  may include structural features separate from the native expandable layer  210  material or surface treatment thereof. For example, in addition to a corrugated or surface treated hydrogel surface, additional components may be coupled with expandable layer  210  to promote tissue ingrowth and adhesion to the fallopian tube. In an embodiment, a meshlike material such as polyester fibers or other fibers or furs which are designed to promote tissue ingrowth may be incorporated into or around expandable layer  210 . Such meshlike materials may promote tissue ingrowth and corresponding adhesion between occlusion device  200  and the fallopian tube. In another embodiment, a thin wire may be wrapped around expandable layer  210  in a coil fashion to facilitate epithelialization surrounding expandable layer  210 , and to secure occlusion device  200  within the fallopian tube. 
         [0056]    In an embodiment, a frame  406  may be incorporated within expandable layer  210  to provide structural support. For example, frame  406  may be a coil or mesh member, such as a thin metallic wire, inserted or deposited within expandable layer  210 . Frame  406  may be able to expand as expandable layer  210  swells or self-deploys (shape memory behavior), but will also provide a scaffold for expandable layer  210  to bind with. Thus, swellable materials like hydrogel or self-expanding memory material/structure incorporated in expandable layer  210  are scaffolded to better resist decomposition over time. 
         [0057]    Referring to  FIG. 5 , a side view of an occlusion device having a cylindrical hollow body is shown in accordance with an embodiment of the invention. Thus, hollow body  202  is not limited to an ellipsoid configuration. On the contrary, hollow body  202  may be shaped with a convex shape, such as an ellipsoid, or it may have numerous other shapes, such as cylindrical or concave. A concave shape may include diameters at the ends of hollow body  202  that are greater than a medial diameter. In one embodiment, hollow body  202  may be spherical, with an outer diameter of about 0.5 to 2 mm. In another embodiment, hollow body  202  may be cylindrical with diameter and length dimensions similar to those described for the ellipsoid configuration above. Regardless of the shape of hollow body  202 , occlusion device  200  may include similar components, i.e., hollow body  202 , expandable layer  210 , distal cap  206 , proximal cap  208 , and tail  212 . 
         [0058]    Referring to  FIG. 6 , a cross-sectional view, taken about line B-B of  FIG. 5 , illustrates an occlusion device in accordance with an embodiment of the invention. Regardless of the shape of hollow body  202 , occlusion device  200  may include a channel such as passage  306 . However, the shape of hollow body  202  defines the cavity volume through which passage  306  extends, and thus, a cylindrical hollow body  202  with a uniform diameter over its length will have a larger passage  306  volume than an ellipsoid hollow member of equivalent diameter and length. 
         [0059]    Distal cap  206  and proximal cap  208  may engage the cavity within hollow body  202  to plug passage  306 . In an embodiment, both distal cap  206  and proximal cap  208  are formed separately from hollow body  202  and cover openings in hollow body  202  to enclose passage  306 . Distal cap  206  and proximal cap  208  may be linked by a connector  602 . For example, connector  602  may be a braided or monofilament cord attached at either end to a different cap. Alternatively, connector  602  may be contiguously formed with tail  212 , and thus may be an extension of tail  212  that runs through proximal cap  208  to distal cap  206 . In either case, as proximal cap  208  is pulled away from hollow body  202 , a tensile load will be applied to connector  602 , which then pulls distal cap  206 . 
         [0060]    In an embodiment, as proximal cap  208  and distal cap  206  are pulled by tail  212  and/or connector  602 , a tensile load may be distributed through their masses to cause them to stretch and unseal from passage  306 . Stretching of the caps may be facilitated by forming the caps from an elastomeric material, such as a silicone. Thus, as tail  212  is pulled, proximal cap  208  may disengage and be removed from passage  306  and distal cap  206  may be pulled through passage  306  until it is finally removed from hollow body  202 . Accordingly, a single pulling force applied to tail  212  may result in dislodgement of both proximal cap  208  and distal cap  206  and exposure of passage  306  to the surrounding environment. 
         [0061]    Referring to  FIG. 7 , a side view of an occlusion device having an anchor feature is shown in accordance with an embodiment of the invention. In an embodiment, occlusion device  200  includes one or more anchors to further facilitate securement of occlusion device  200  to a fallopian tube. Occlusion device  200  may include a distal anchor  702  and/or a proximal anchor  704  on either side of expandable layer  210 . In an embodiment, anchors  702 ,  704  may actually be proximal and distal portions of the same structure. For example, a single coil may wrap around hollow body  202  and be sandwiched against outer surface  204  by expandable layer  210 . 
         [0062]    In a first configuration to facilitate delivery of occlusion device  200 , the anchors may be in a low profile configuration, i.e., a small diameter. For example, proximal anchor  704  and distal anchor  702  may be formed from coil structures that are wound down to conform closely to outer surface  204  of hollow body  202  in the delivery configuration. Anchors  702 ,  704  may be retained in the low profile configuration either through internal material structure, e.g., in a martensitic phase, or by an external constraint, e.g., a sheath or catheter placed around the anchors. 
         [0063]    In an embodiment, additional features may be incorporated with the anchor structures to encourage anchoring. For example, a meshlike material such as polyester fibers or other fibers or furs which are designed to promote tissue ingrowth may be incorporated into or around proximal anchor  704  and/or distal anchor  702  to promote tissue ingrowth and adhesion between occlusion device  200  and the fallopian tube. Additionally or alternatively, adhesion-promoting coatings may be incorporated into or over proximal anchor  704  and/or distal anchor  702  to promote tissue ingrowth and adhesion. For example, proximal anchor  704  and/or distal anchor  702  may be coated with a biocompatible adhesive to facilitate adhesion. 
         [0064]    Referring to  FIG. 8A , a side view of an occlusion device  200  having an expanded expandable layer and expanded coil anchor features is shown in accordance with an embodiment of the invention. Distal anchor  702  and proximal anchor  704  may include an expandable coil  802  constructed of a thin wire that unwinds upon deployment to increase in diameter and contact fallopian tube. Accordingly, expandable coil  802  may have an attached end  804  that is coupled with outer surface  204  and an unattached end  806  that extends freely away from attached end  804 . As expandable coil  802  unwinds, unattached end  806  may become radially offset from attached end  804 , relative to a central axis passing through hollow body  202 . In addition, unattached end  806  and at least a portion of expandable coil  802  may increase to a diameter greater than a swollen diameter of expandable layer  210 , to create a mechanical gripping force against a fallopian tube, which contributes to the adhesion between expandable layer  210  and the fallopian tube. 
         [0065]    Expandable coil  802  may be formed from conventional metals and polymers, such as stainless steel, cobalt-chrome, polyethylene, etc., and sized and configured to prevent material yield when wound against hollow body  202 . As a result, upon release of expandable coil  802 , the coil unwinds and springs outward. Alternatively, expandable coil  802  may be formed from a shape memory material, such as nickel-titanium, and configured to expand under physiological conditions to a larger, unwound configuration due to a material phase transformation. In an embodiment, expandable coil  802  formed from nickel-titanium may be encapsulated or sheathed within a biocompatible, biostable polymer, e.g., by co-extrusion, dip coating, or placing a tubular sheath over expandable coil  802 . Some data suggests an incidence of nickel hypersensitivity in patients, and thus, encapsulation may avoid expandable coil  802  contacting and adversely affecting patient tissue. 
         [0066]    Referring to  FIG. 8B , a side view of an occlusion device having an expanded expandable layer and expanded spider member and stent-like anchor features is shown in accordance with an embodiment of the invention. Stent-like anchors  812  or spider members  808  provide alternative anchor structures. Examples of spider members  808  which may be used are shown in co-assigned U.S. Pat. No. 8,235,047. Each spider member  808  may include at least two spider arms  810 . Spider arms  810  are generally made up of two members that are folded against each other in a non-expanded state. Fibers may also be interwoven between and diametrically across spider arms  810  to promote tissue ingrowth as described above. Stent-like anchors  812  may be used that have a scaffold structure that is expandable from a low profile to an expanded profile. Spider members  808  and stent-like anchors  812  may be formed from the same materials and configured to expand in a fashion similar to that described for expandable coil  802  above. Although in  FIG. 8B  occlusion device  200  is shown including one spider member  808  and one stent-like anchor  812 , occlusion device  200  may have any combination of distal and proximal anchors, including only one distal anchor or proximal anchor, or a distal anchor and proximal anchor of the same type, e.g., two spider members  808 . 
         [0067]    Referring to  FIG. 9 , a side view of an occlusion device having an opened proximal cap is shown in accordance with an embodiment of the invention. Proximal cap  208  may be removed from hollow body  202  to expose passage  306  to the surrounding environment. For example, a pulling force  902  may be applied to tail  212  to exert a removal load on proximal cap  208 . As proximal cap  208  is removed, proximal end  310  of passage  306  will be opened. Thus, when occlusion device  200  is deployed within a fallopian tube, removal of proximal cap  208  will open passage  306  to a proximal portion of the fallopian tube. 
         [0068]    Referring to  FIG. 10 , a side view of an occlusion device having an opened distal cap is shown in accordance with an embodiment of the invention. Distal cap  206  may be opened, for example, by pushing a cannulation member  1002  through distal cap  206  until distal cap  206  tears or breaks open. For example, cannulation member  1002  may be a guidewire, cannula, or a catheter device that is inserted through proximal end  310  of passage  306  until it contacts distal cap  206  at distal end  308  of passage  306 . As cannulation member  1002  is pushed further, distal cap  206  eventually yields to open passage  306  to the surrounding environment. For example, when occlusion device  200  is deployed within a fallopian tube, pushing on distal cap  206  will open passage  306  to a distal portion of fallopian tube. 
         [0069]    Opening distal cap  206  may also occur in a multi-stage process. For example, a guidewire may first be advanced through passage  306  to pierce distal cap  206  and then a catheter device may be delivered over the guidewire through distal cap  206  to widen the pierced opening. Guidewires are generally maneuverable, have small diameters, and can be formed with good column strength, which makes them well suited for accessing and passing through passage  306 , and piercing distal cap  206 . Furthermore, catheters are generally flexible, include blunted or atraumatic tips, and can be formed with an outer diameter that conforms closely to an inner diameter of hollow body  202 , which makes them well suited for delivering over a guidewire to pass through hollow body  202  and to enlarge the openings at either end of the occlusion device  200 . In an embodiment, an additional stage may include accessing opened passage  306  with a balloon catheter or stent delivery catheter and inflating a balloon within passage  306  to expand and/or scaffold hollow body  202 , and to widen passage  306  even further. Thus, a multi-stage process for opening distal cap  206  may be performed with readily available medical equipment. 
         [0070]    In an alternative embodiment, cannulation member  1002 , or devices used to follow cannulation member  1002  in a multi-stage process, may include an atherectomy catheter or excimer laser ablation catheter. Such devices include a distal working end used to open blockages in body vessels and may be advanced through passage  306  and used to open distal cap  206 . Furthermore, a guidewire or catheter device having an ultrasonic probe located in a distal tip may be used to apply ultrasonic energy and rapid vibration to pierce, puncture, crack, or otherwise open distal cap  206 . For example, an ultrasonic probe may be particularly useful in opening a hard or rigid distal cap  206 , e.g., where distal cap  206  is formed from a ceramic. 
         [0071]    Referring to  FIG. 11 , a side view of an occlusion device having an opened passage is shown in accordance with an embodiment of the invention. In an embodiment, after deploying occlusion member in fallopian tube and securing occlusion member to fallopian tube with proximal anchor  704 , distal anchor  702 , and/or expandable layer  210 , passage  306  is exposed to the surrounding environment by opening proximal cap  208  and distal cap  206 . Thus, a passage axis  1102  is created through proximal end  310  and distal end  308  of passage  306 , providing a pathway for an ovum to pass through hollow body  202  from a distal fallopian tube anatomy to a proximal fallopian tube anatomy. Passage axis  1102  need not be linear. For example, in an embodiment, passage  306  may follow a curved path corresponding to a curved fallopian tube or occlusion device  200 , and in such case, passage axis  1102  may be curved as well. 
         [0072]      FIGS. 12A-12E  provide various views of cap portions of an occlusion device in accordance with an embodiment of the invention. Although the various views are oriented to correspond to either proximal cap  208  or distal cap  206 , the cap configurations may be used for either. Additionally, the various configurations are intended to be illustrative, and not exhaustive, of the numerous cap designs that may be used. 
         [0073]    Referring to  FIG. 12A , a proximal cap  208 , distal cap  206  configuration having a flared retainer is shown in accordance with an embodiment of the invention. Hollow body  202  may include an inner surface  302  that tapers downward. For example, a thin-walled ellipsoid shell may have a tapering inner surface  302  near either end. In an embodiment, proximal cap  208  includes a flared portion that fits within passage  306  and flares outward to resist pulling the cap away from hollow body  202 . Flare  1202  may be a revolved body, symmetric about a central axis, or it may be a non-symmetric body with one or more flaring elements. For example, flare  1202  may exhibit an increasing diameter along its axis, but it may have an X-shaped cross section as opposed to a circular cross section. In an embodiment, proximal cap  208  may also have a cap portion  1204  extending away from a neck  1206  of flare  1202 , and cap portion  1204  may be sized and configured to seal or block an opening in hollow body  202  and passage  306 . 
         [0074]    Referring to  FIG. 12B , a proximal cap  208 , distal cap  206  configuration having a snap  1208  retainer is shown in accordance with an embodiment of the invention. In an embodiment, cap portion  1204  may include a snap  1208  that tapers inward and is intended to be press fit over a snap detent  1210  formed in hollow body  202 . Due to the press fit, snap  1208  is retained over snap detent  1210 , but upon pulling cap portion  1204  away from hollow body  202 , snap  1208  and snap detent  1210  deflect outward and inward, respectively, to disengage and expose passage  306  to the surrounding environment. 
         [0075]    Referring to  FIG. 12C , a proximal cap  208 , distal cap  206  configuration having a plug  1212  retainer is shown in accordance with an embodiment of the invention. In an embodiment, inner surface  302  defining passage  306  may be substantially cylindrical. For example, hollow body  202  may be a thin-walled cylinder, or inner surface  302  may not conform to the shape of outer surface  204 , e.g., outer surface  204  may be ellipsoidal and inner surface  302  may be cylindrical. Proximal cap  208  may include a plug  1212  to insert and be retained within passage  306 . For example, plug  1212  may be sized to provide a press fit against inner surface  302 . Alternatively, length and/or material of plug  1212  may be sufficient to generate friction against inner surface  302  that retains plug  1212 . In an embodiment, proximal cap  208  may also have a cap portion  1204  extending away from a neck  1206  of plug  1212 , and cap portion  1204  may be sized and configured to seal or block an opening in hollow body  202  and passage  306 . 
         [0076]    Referring to  FIG. 12D , a proximal cap  208 , distal cap  206  configuration having a hollow body  202  with an integrally formed cap is shown in accordance with an embodiment of the invention. In an embodiment, cap portion  1204  may include a cap wall  1214  that is contiguously formed with body wall  304  and shares a common outer surface  204 . More specifically, cap wall  1214  may have a complementary shape, e.g., provide an end region of an ellipsoid shape, relative to body wall  304 . Furthermore, cap wall  1214  may be thinner than body wall  304 , making it more susceptible to piercing by cannulation member  1002 . 
         [0077]    In another embodiment, rather than continuing along the surface path defined by body wall  304 , cap wall  1214  may change angles substantially. For example, while outer surface  204  may be ellipsoidal about a central axis, cap wall  1214  may occupy a plane that is perpendicular to that axis. Alternatively, rather than continuing to extend in the same direction as outer surface  204 , cap wall  1214  may reverse directions, i.e., may be concave relative to outer surface  204  rather than convex as shown in  FIG. 12D . 
         [0078]    Referring to  FIG. 12E , a proximal cap  208 , distal cap  206  configuration having an integrally formed cap with puncture promoting features is shown in accordance with an embodiment of the invention. Cap portion  1204  may be weakened in one or more locations to locally promote puncture by cannulation member  1002 . For example, cap portion  1204  may have one or more depression  1216  that creates local thinning of cap wall  1214  and therefore weakens cap wall  1214  to allow cannulation member  1002  to penetrate through cap portion  1204  more easily. Depression  1216  may be formed by drilling, stamping, ablating, or any other method that provides for localized thinning of material. Furthermore, depression  1216  may extend entirely through cap wall  1214 , i.e., may be a perforation, and have a diameter that does not allow an ovum to pass. For example, a perforation may have a diameter less than about 0.1 mm. 
         [0079]    Depressions or perforations may be formed in a pattern that facilitates predictable puncturing of cap portion  1204 . For example, one or more depression  1216  may be formed in a crossing pattern with a center near a distal tip  1218  of cap portion  1204 . Thus, upon puncturing of cap portion  1204  by cannulation member  1002 , cap portion  1204  tears outward in a substantially uniform manner along the seams defined by the pattern. As a result, in an embodiment, an opening in cap portion  1204  that exposes passage  306  would have a maximum diameter centered about distal tip  1218 , which may also to approximately coincide with a central axis of the fallopian tube. 
         [0080]      FIGS. 13A-13C  provide various views of tail portions of an occlusion device in accordance with an embodiment of the invention. The various configurations are intended to be illustrative, and not exhaustive, of the numerous tail designs that may be used. 
         [0081]    Referring to  FIG. 13A , an occlusion device  200  having a tail  212  with a generally elongated shape is shown in accordance with an embodiment of the invention. Tail  212  may extend from proximal cap  208  to trail away from hollow body  202 . More specifically, tail  212  may extend from a distal end  320  coupled with proximal cap  208  to a proximal end  1302 . Tail  212  may have a generally elongated body between distal end  320  and proximal end  1302 . For example, although tail  212  may be flexible and compliant, the elongated body of tail  212  may follow an arcuate path that does not cross back on itself. That is, tail  212  may be without a loop feature. 
         [0082]    Referring to  FIG. 13B , an occlusion device  200  having a tail  212  with a generally elongated body having a loop feature is shown in accordance with an embodiment of the invention. Tail  212  may extend from proximal cap  208  to trail away from hollow body  202 . More specifically, tail  212  may extend from a distal end  320  coupled with proximal cap  208  to a proximal end  1302 . In addition to having an elongated body portion  1304 , tail  212  may also include a loop portion  1306 . As in  FIG. 13A , the elongated body portion may follow a path that is generally straight or arcuate but does not reverse on itself. However, loop portion  1306  may instead include an inflection point at proximal end  1302  in which tail  212  curves into a loop. Thus, loop portion  1306  may be contiguous with proximal end  1302 , i.e., proximal end  1302  may be along the path of loop portion  1306 . The loop may be secured at a securement point  1308 , which forms a transition between elongated body portion  1304  and loop portion  1306 . Securement point  1308  may be formed in several manners, including by tying, bonding, or otherwise securing tail  212  to itself at securement point  1308 . Alternatively, elongated body portion  1304  and loop portion  1306  may be separately formed parts that are coupled with each other at securement point  1308 . 
         [0083]    Referring to  FIG. 13C , an occlusion device  200  having a tail  212  with a generally elongated body having a loop feature is shown in accordance with an embodiment of the invention. Tail  212  may extend from proximal cap  208  to trail away from hollow body  202 . More specifically, tail  212  may extend from a distal end  320  coupled with proximal cap  208  to a proximal end  1302 . Tail  212  may include a loop portion  1306  between distal end  320  and proximal end  1302 . As in  FIG. 13B , the loop portion  1306  may reverse on itself at the inflection point contiguous with proximal end  1302 . However, loop portion  1306  may extend over the entire length between proximal cap  208  and proximal end  1302 . That is, both sides of the loop may meet and/or be coupled with proximal cap  208  rather than being joined at securement point  1308 . More specifically, tail  212  may be coupled with proximal cap  208  at distal end  320  using any of the manners described above, including by stamping tail  212  ends to prevent loop portion  212  from being pulled out of proximal cap  208 , or by adhesively bonding tail  212  inside of a bore within proximal cap  208 . 
         [0084]    Occlusion device  200  components may be formed using various well known manufacturing processes. For example, hollow body  202  may be formed using molding, e.g., injection molding, or casting processes. Alternatively, other components, such as tissue ingrowth fibers or expandable layer  210  may be formed by electrospinning onto a target having a desired shape. In addition to bulk formation of components using, e.g., casting, multiple components can be assembled and coupled together after formation. For example, expandable layer  210  may be formed separately from hollow body  202  and then bonded to hollow body  202  using a biocompatible adhesive, such as a biocompatible cyanoacrylate adhesive. Similarly, distal anchor  702  and/or proximal anchor  704  may be separately formed by casting, stamping, bending and heat treating, etc., before being attached to hollow body  202  at attached end  804 . Attachment of attached end  804  to hollow body  202  may be made in numerous manners, including by adhesive or thermal weld, tying, press fitting, etc. For example, in an embodiment, shrink tubing may be used to wrap around and sandwich attached end  804  against hollow body  202 . 
         [0085]    Referring to  FIG. 14 , an endoscope accessing an ostium of a fallopian tube is shown in accordance with an embodiment of the invention. An endoscope  1402  is introduced through cervix  102  into uterus  104  under optical direction. The physician directs the distal end of endoscope  1402  toward ostium  106  of the fallopian tube. Uterus  104  may be irrigated and/or distended. Once ostium  106  is located and endoscope  1402  is oriented toward ostium  106 , a delivery system is advanced distally from endoscope  1402  into ostium  106 . 
         [0086]      FIGS. 15A-15D  show a delivery of an occlusion device to occlude a fallopian tube in accordance with an embodiment of the invention. Referring to  FIG. 15A , in one embodiment, the delivery system includes a delivery catheter  1402  that encompasses at least a portion of occlusion device  200 . For example, distal cap  206  may extend outward from delivery catheter  1402  to provide an atraumatic tip that promotes tracking, while proximal cap  208  may be retained within a lumen of delivery catheter  1402 . Delivery catheter  1402  may be a microcatheter having a uniform inner diameter that conform to, and constrains, occlusion device  200  during delivery. 
         [0087]    To further aid navigation, in an embodiment, passage  306  may be filled with a contrast agent to allow for visualization under different imaging modalities. For example, passage  306  may be filled with a radiopaque contrast agent, e.g., iodinated contrast medium, to facilitate imaging under fluoroscopy. Alternatively, passage  306  may be filled with a magnetic resonance signal enhancing substance, e.g., gadolinium, or an ultrasound scattering substance, e.g., microbubble contrast agent. The contrast agent-filled hollow body  202  promotes navigation and visualization of occlusion device  200  through the fallopian tube. Furthermore, the contrast agent may be biocompatible, given that contrast agent will leak into the fallopian tube following the opening of passage  306  to the surrounding environment. 
         [0088]    In an embodiment, delivery catheter  1402  includes a visual marker which can be seen from the scope of a hysteroscope. The marker is preferably positioned partially within ostium  106  and partially within uterus  104  to indicate that occlusion device  200  is disposed at the target position. In an embodiment, the target position is within, or proximal to, isthmus segment  110 . For example, the target position may be about 3-4 cm from ostium  106 . 
         [0089]    Referring to  FIG. 15B , the positioned occlusion device  200  is deployed within the fallopian tube. In an embodiment, delivery catheter  1402  is withdrawn over occlusion device  200 , causing hollow body  202  to become exposed to the surrounding environment and distal anchor  702  to expand outward into contact with the fallopian tube wall  1404 . A pushing rod may be used within delivery catheter  1402  to press against a proximal end of occlusion device  200  while delivery catheter  1402  is withdrawn. Alternatively, the pushing rod may be used to push and deploy occlusion device  200  from delivery catheter  1402 . Thus, distal anchor  702  resiliently expands through spring action or material phase transformation and secures occlusion device  200  to the fallopian tube. As delivery catheter  1402  is withdrawn further from occlusion device  200 , expandable layer  210 , e.g., hydrogel layer, begins to swell and to occlude the fallopian tube. 
         [0090]    Referring to  FIG. 15C , the hydrogel of expandable layer  210  may expand to fill areas of the fallopian tube to block the ovarian pathway. Furthermore, as delivery catheter  1402  is withdrawn even further, proximal anchor  704  may resiliently expand to contact and secure hollow member to the fallopian tube wall  1404 . Thus, occlusion device  200  may become secured within fallopian tube by proximal anchor  704 , distal anchor  702 , and/or expandable layer  210 . 
         [0091]    Referring to  FIG. 15D , further withdrawal of delivery catheter  1402  releases occlusion device  200  entirely, including tail  212  that trails proximally from proximal cap  208 . In an embodiment, tail  212  extends limply from proximal cap  208  within, e.g., intramural portion  108  of the fallopian tube, into uterus  104 . Furthermore, in the deployed state, the fallopian tube may be occluded by the expandable layer  210  as it swells outward, as well as by proximal cap  208  and distal cap  206  that enclose passage  306  and prevent an ovum from traveling therethrough. Thus, following deployment of occlusion device  200  into the fallopian tube, long-term contraception is achieved. 
         [0092]      FIGS. 16A-16C  show an unblocking of the fallopian tube to reverse contraception in accordance with an embodiment of the invention. Referring to  FIG. 16A , tail  212  may act as a marker to be visualized by an endoscope  1402  inserted transcervically into uterus  104 . For example, endoscope  1402  may be able to visualize a proximal tip of tail  212 . Tail  212  may be visible as a result of its color, which may appear bright or contrast with uterus  104  tissue. Alternatively, tail  212  may be radiopaque to enable external visualization using non-optical imaging modalities, e.g., fluoroscopy. To enhance the radiopacity of tail  212 , radiopaque fillers such as iodine and heavy metal compositions described above may be incorporated within tail  212  body. After identifying tail  212 , a retrieval device  1602  may be extended from endoscope  1402  to grip tail  212 . For example, retrieval device  1602  may include biopsy forceps to clamp tail  212  under vision provided by endoscope  1402 . 
         [0093]    After gripping tail  212 , proximal cap  208  may be opened by pulling tail  212  to dislodge proximal cap  208  from hollow body  202  and retrieve proximal cap  208  through endoscope  1402 . Following removal of proximal cap  208 , proximal end  310  of passage  306  is openly exposed to the proximal region of the fallopian tube. In an embodiment as described above, removal of proximal cap  208  may also dislodge and retrieve distal cap  206  through passage  306  due to connector  602  between proximal cap  208  and distal cap  206 . 
         [0094]    In an alternative embodiment, retrieval device  1602  may include a hook or snare to capture a loop feature of tail  212 , such as loop portion  1306  shown in  FIGS. 13B-13C . Thus, rather than clamping tail  212 , a hook may be placed through loop portion  1306  and pulled to grasp tail  212  at proximal end  1302 . Sufficient force may be applied through the hook or snare to dislodge proximal cap  208  from hollow body  202  and retrieve proximal cap  208  through endoscope  1402 . 
         [0095]    Referring to  FIG. 16B , in an embodiment in which proximal cap  208  and distal cap  206  are not coupled with each other, distal cap  206  may be opened by introducing cannulation member  1002  through endoscope  1402 . Cannulation member  1002  may be a guidewire, cannula, or a catheter device having an outer diameter that fits through passage  306 . In an embodiment, cannulation member  1002  may access passage  306  through a microcatheter. For example, a microcatheter may be introduced over tail  212  to a proximal end of occlusion device  200  before removing proximal cap  208 . After removing proximal cap  208  by pulling it through the microcatheter, a guidewire may then be introduced through the microcatheter directly to the proximal end with minimal steering. 
         [0096]    Following access, cannulation member  1002  may be advanced further through passage  306  to contact and pierce distal cap  206  and to expose distal end  308  of passage  306  to a distal region of the fallopian tube. As described above, cannulation of distal cap  206  may be performed in a multi-stage process, in which a guidewire is first advanced through distal cap  206  and then used as a rail to deliver a catheter through hollow body  202 , which widens the opening in distal cap  206 . 
         [0097]    Referring to  FIG. 16C , after opening both proximal cap  208  and distal cap  206 , passage  306  is no longer enclosed and passage axis  1102  provides a pathway for an ovum to travel from the distal region of the fallopian tube to the proximal region of the fallopian tube. Accordingly, contraception is reversed to allow the patient to conceive. 
         [0098]    In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will be evident that various modifications may be made to these embodiments without departing from the broader spirit and scope of the invention, as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.