Method and device for thermal ablation of hollow body organs

Hollow body organs, such as the gallbladder, may be ablated by introducing a substantially unheated thermally conductive medium to the interior of the organ. The thermally conductive medium is then heated to a temperature sufficient to necrose the endothelial lining or mucous membrane of the organ. After the lining or membrane has necrosed, the interior of the organ will fibrose over time and the organ will eventually be resorbed by the body. A catheter useful in performing the ablation method comprises an elongate member having a heating element at its distal tip. The catheter will include at least oen lumen for delivering the thermally conductive medium to the interior of the hollow body organ, and the heating means is used to raise the temperature of the thermally conductive medium after it has been delivered. Optionally, the catheter may include one or more inflatable balloons which facilitate sealing of the hollow body organ to inhibit leakage of the thermally conductive medium during the treatment process.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to methods and apparatus for the 
thermal ablation of hollow body organs, such as the gallbladder. In 
particular, the present invention relates to a catheter structure having a 
heating element at its distal end, where the catheter may be used to 
introduce an unheated thermally-conductive medium to the hollow body 
organ, and the heating element used to heat the medium in situ in order to 
destroy the endothelial lining or mucous membrane of the organ. 
Heretofore, it has frequently been necessary to perform open surgery in 
order to remove diseased body organs, such as gallbladders, appendixes, 
and the like. For example, the current treatment for cholecystolithiasis 
(gallstone disease) involves the surgical removal of the gallbladder, 
referred to as a cholecystectomy. As with all major surgical procedures, 
the patient is exposed to the risk of trauma, infection, general 
anesthetic, as well as requiring extended recuperation time. It would 
therefore be desirable to provide for therapies for diseased organs which 
can effectively eliminate the organ without the necessity of open surgical 
intervention. 
In recent years, a number of therapies have been developed as an 
alternative to open surgery, often referred to as "least invasive 
surgery." While least invasive surgical procedures have no fixed 
definition, they are generally characterized by the use of specialized 
surgical tools in combination with visual or radiographic imaging 
techniques. The specialized tool is generally inserted through an open 
body orifice or a small surgical incision, and the tool is then positioned 
within the body using the imaging technique to allow manipulation of the 
affected organ or structure. A common example of least invasive surgery is 
arthroscopic knee surgery where penetration of the surgical tools is 
minimal. Less accessible body organs, such as the heart and interior blood 
vessels, may be reached by specialized catheters which may be routed 
through the vascular system over relatively long distances. Typical of 
such vascular catheters are balloon dilatation catheters which are used to 
expand regions of stenosis within diseased blood vessels. 
For the above reasons, it would be desirable to provide least invasive 
surgical methods and apparatus for the destruction or ablation of diseased 
hollow body organs, such as the gallbladder, the appendix, and the like. 
Such methods and apparatus should also be suitable for the treatment of 
relatively small body structures, such as blood vessels, and should be 
able to effect ablation without undue risk to surrounding body tissues and 
structures. In particular, the method and apparatus should be able to 
provide for the controlled application of thermal energy in order to 
destroy the hollow body organ with a minimal chance of regeneration. 
2. Description of the Background Art 
Coleman, Non-Surgical Ablation of the Gallbladder, Proc. 1988 SCVIR, pp 
214-219, is a review article discussing various techniques for 
non-surgical gallbladder ablation, including the work of Salomonowitz and 
of Getrajdman relating to the introduction of an externally heated medium 
to induce fibrosis of the gallbladder. The article further presents data 
demonstrating thermal ablation of a dog's gallbladder after open surgical 
injection of hot contrast media. The work of Salomonowitz is described in 
Salomonowitz et al. (1984) Arch. Surg. 119:725-729. The work of Getrajdman 
is described in Getrajdman et al. (1985) Invest. Radiol. 20:393-398 and 
Getrajdman et al. (1986) Invest. Radiol. 21:400-403. The use of sclerosing 
agents to induce gallbladder fibrosis is described in Remley et al. (1986) 
Invest. Radiol. 21:396-399. See also Becker et al. (1988) Radiology 
167:63-68. U.S. Pat. No. 4,160,455, describes a device for internally 
heating a body cavity for therapy, where the heat is intended to inhibit 
the growth of tumor cells. German Patent 37 25 691 describes a catheter 
combining a heater at its distal tip and a balloon proximate the heater, 
where the heater is not directly exposed to the fluid environment 
surrounding the catheter tip. Other patent documents describing heated or 
cooled catheters include U.S. Pat. Nos. 4,676,258; 4,638,436; 4,469,103; 
4,375,220; 3,901,224; USSR 1329781-A; and USSR 281489. 
SUMMARY OF THE INVENTION 
The present invention is a method and apparatus for thermally ablating 
hollow body organs in order to induce fibrosis of the interior of the 
organ and eventual resorption of the organ by the body. The method relies 
on introducing a substantially unheated thermally conductive medium into 
the interior of the hollow body organ and subsequently heating the medium 
to a temperature sufficient to destroy the endothelial lining or mucous 
membrane. Use of an unconstrained media allows heat to be transferred 
effectively to a convoluted interior surface of the hollow body organ. 
Usually, all ducts, passages, and the like, opening into the hollow body 
organ will be blocked in order to inhibit leakage of the medium during the 
treatment procedure. The heating will be stopped after the desired thermal 
injury has occurred, and the thermally conductive medium may either be 
aspirated or left within the organ. The organ will subsequently fibrose 
and be resorbed over time. 
The introduction of a substantially unheated thermally conductive medium 
minimizes the risk of injury to tissue, organs, and other body structures 
surrounding the hollow body organ being treated, as well as to medical 
personnel adminstering the treatment. The use of a radiologically 
detectable thermally conductive fluid such as contrast media allows visual 
confirmation that the medium is contained within the desired body organ 
and is not subject to leakage prior to heating of the medium. 
The catheter of the present invention comprises an elongate member having 
proximal and distal ends with a heating means mounted near the distal end. 
The heating means is exposed to the fluid environment surrounding the 
distal end of the catheter and is thus able to directly heat the thermally 
conductive medium which has been introduced to the hollow body organ. 
Conveniently, the catheter includes a lumen or other means for introducing 
the thermally conductive medium. Thus, the catheter may be introduced into 
the interior of the hollow body organ and utilized both for introducing a 
thermally conductive medium and for heating the medium to ablate the 
lining of the organ. Usually, the catheter will also include one or more 
inflatable balloons for blocking ducts or other passages communicating 
with the hollow body organ. The catheter is introduced in such a way that 
the balloons are disposed within the ducts or passages and by then 
inflating the balloons, the desired sealing of the hollow body organ may 
be achieved.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
The present invention is useful for ablation of a wide variety of hollow 
body organs and body passages which have an endothelial lining, mucous 
membrane, or other internal surface which may be thermally injured to 
induce necrosis and subsequent fibrosis of the surrounding tissue. 
Exemplary hollow body organs include the gallbladder, the appendix, the 
uterus and the like. Exemplary hollow body passages include blood vessels, 
fistulas, and the like. Usually, the hollow body organs and body passages 
will be diseased or in some way abnormal prior to ablation according to 
the present invention. In some cases, however, it may be desirable to 
ablate and destroy apparently healthy body organs or parts in order to 
achieve a desired purpose, e.g., blockage of a blood vessel in a 
varicocele procedure. For convenience hereinafter, the phrase "hollow body 
organ" is intended to embrace both hollow body organs and hollow body 
passages. 
The method of the present invention relies on introducing a thermally 
conductive medium into the interior of the hollow body organ in such a way 
that the organ is filled with the medium and the medium is in good thermal 
contact with substantially the entire interior surface of the organ. In 
this way, by heating the medium as will be described hereinafter, the 
temperature of the endothelial lining or mucous membrane of the body organ 
can be raised to a preselected temperature for a preselected minimum time 
period in order to permanently injure the lining and subsequently induce 
necrosis The thermally conductive medium can be virtually any 
physiologically-compatible liquid, solution, slurry, gel, and the like, 
which may be percutaneously or directly introduced into the interior of 
the hollow body organ. Exemplary thermally conductive media include water, 
saline, contrast medium, physiological irrigating solution, and the like. 
The thermally conductive medium will be introduced to the interior of the 
hollow body organ at a temperature below that which will have a 
deleterious effect on the tissue and organ surrounding the hollow body 
organ being treated. The temperature will be below about 60.degree. C., 
usually being below about 50.degree. C., and more usually being at body 
temperature (37.degree. C.) or room temperature (about 20.degree. C.). In 
some cases, however, it may be desirable to introduce the contrast medium 
above body temperature, usually in the range from about 37.degree. C. to 
50.degree. C., in order to shorten the time necessary to raise the 
temperature of the medium to the treatment temperature, discussed 
hereinafter. 
In order to induce necrosis of the endothelial lining or mucous membrane of 
the hollow body organ, the temperature of the thermally conductive medium 
will be raised above a threshold level which results in injury to the 
endothelial lining or mucous membrane. The threshold temperature will 
generally be above 60.degree. C., usually being in the range from 
60.degree. C. to 120.degree. C., more usually being in the range from 
65.degree. C. to 100.degree. C., and preferably being in the range from 
about 70.degree. C. to 90.degree. C. Depending on the precise temperature 
employed and on the nature of the particular organ being treated, the 
thermally conductive medium will be maintained above the threshold 
temperature for a period of time in the range from about 1 to 60 minutes, 
usually being in the range from about 1 to 30 minutes, more usually being 
in the range from about 2 to 20 minutes, and preferably being in the range 
from about 2 to 10 minutes. Usually, the temperature of the thermally 
conductive medium will be raised as rapidly as possible and maintained at 
a substantially constant treatment temperature for the desired treatment 
period. Alternatively, the treatment temperature may be varied during the 
treatment period with the total treatment time being adjusted to take the 
variation in temperature into account. 
After the hollow body organ has been treated with the heated thermally 
conductive medium at a temperature and for a time sufficient to induce 
necrosis of the endothelial lining or mucous membrane of the organ, the 
thermal energy being delivered to the medium will be terminated. The 
thermally conductive medium may then be aspirated from the hollow body 
organ, typically using the same catheter which was employed to deliver the 
medium and raise the temperature of the medium as described above. 
Usually, however, the thermally conductive medium will not be aspirated 
until the temperature has decreased sufficiently so that its withdrawal 
will not expose tissues and organs surrounding the catheter to risk. 
Normally the withdrawal temperature will be below about 55.degree. C., 
preferably being below about 45.degree. C. Alternatively, the thermally 
conductive medium can be left within the hollow body organ where it will 
be resorbed or eliminated by normal physiological processes. 
The catheter of the present invention comprises an elongate member having 
proximal and distal ends. The elongate member may be flexible or rigid, 
although flexible catheters are preferred for most applications. The 
length of the catheter will vary depending on the application with short, 
rigid catheters typically having a length in the range from about 10 to 20 
cm, and long flexible catheters typically having a length in the range 
from about 20 to 40 cm. Rigid elongate members may be formed from metals, 
typically stainless steel, rigid plastics, and the like, while flexible 
elongate members will typically be formed from extruded organic polymers, 
such as silicone rubber, polyurethane, polyvinyl chloride, nylon, and the 
like. Elongate members will typically include a multiplicity of lumens to 
provide for fluid communication between the proximal end (outside the 
patient) to the distal end (inside the patient). Normally, a lumen will be 
provided for delivering and/or aspirating the thermally conductive medium 
to the hollow body organ. Additional lumens may be provided for inflation 
of one or more balloons, for delivery of the catheter over a movable 
guidewire, for venting the hollow body organ while the thermally 
conductive medium is being delivered, and the like. 
A heating means for raising the temperature of the fluid environment 
surrounding the distal end of the catheter will be provided at or near the 
distal tip of the elongate member typically being within about 10 cm, more 
typically being within about 5 cm. The heating means will generally 
provide a heated surface for convectively heating fluid surrounding the 
catheter tip, typically comprising a resistive heater, a radiating block 
heated by laser energy, or the like. The heating means may also comprise a 
microwave emitter capable of heating the fluid directly or a 
radiofrequency heating element. In some cases, it may also be possible to 
heat the thermally conductive medium using dispersed laser radiation. In 
that case, it will be desirable to color or dye the thermally conductive 
medium so that it can absorb radiation at the wavelength of the laser 
source. 
A system will be provided for controlling the temperature to which the 
thermally conductive medium is heated by the heating means. Such a 
temperature control system may comprise a feedback controller where a 
temperature sensing element (typically a thermocouple or thermistor) is 
mounted on the catheter at a location chosen to accurately measure the 
heated environment surrounding the catheter, and the energy delivered to 
the heating means is regulated based on the measured temperature of the 
medium. Alternatively, numerous autoregulating heaters are available which 
do not require a separate control loop. 
Usually, the catheter will include at least one inflatable balloon for 
occluding a duct or passage which would otherwise allow drainage of the 
thermally conductive medium from the hollow body organ during the course 
of the treatment. At least one balloon will generally be located at the 
distal tip of the elongate member of the catheter and will be inflatable 
through an inflation lumen running through the catheter from the distal to 
the proximal end thereof. For many applications it will be desirable to 
inflate the occluding balloon with a thermally conductive medium, 
frequently the same medium used to fill the hollow body organ, so that the 
area in contact with the balloon will be heated and necrosed. Optionally, 
means for heating the medium within the balloon to a temperature 
sufficient to induce necrosis in the endothelial lining or mucous membrane 
surrounding the inflated balloon may be provided. Alternatively, a 
thermally insulating medium such as carbon dioxide may be used to inflate 
the balloon when it is desired to protect the surrounding tissue and 
organs. 
One or more additional inflatable balloons may also be provided in order to 
seal other passages communicating with the hollow body organ. For example, 
a second inflatable balloon spaced proximally from the first on the other 
side of the heating element may be provided. The first and second balloons 
may then be used to define a volume to be treated therebetween. Other 
balloon configurations may also be used for trapping the thermal media in 
a particular hollow body organ or portion of a hollow body organ. 
Referring now to FIGS. 1-4, a catheter 10 comprises an elongate flexible 
body 12 having a proximal end 14 and a distal end 16. The elongate member 
12 includes a plurality of axial slots 18 formed at or near the distal end 
16 and a heating element 20 disposed within the slots. The heating element 
20 is of a type which provides a heated external surface, typically being 
a resistive heating element where a pair of wires 22 are run from the 
heating element to the proximal end 14 of the catheter where they are 
taken out through a sealed port 23 in a proximal housing 24. The wires 22 
will typically be run through a central lumen 26 and will be connected to 
a suitable power supply (not shown) for heating the heating element 20 to 
a desired temperature. 
The central lumen 26 extends from the proximal end 14 of the elongate 
member 12 and terminates at the proximal end of heating element 20 (FIG. 
2). A plurality of radial passages 28 (FIG. 2) are provided between the 
distal end of the central lumen 26 and the proximal end of the heater 20, 
which passages open into the axial slots 18. The proximal end of central 
lumen 26 is connected through a side port 30 on the proximal housing 24. 
In this way, thermally conductive medium may be delivered through the 
central lumen 26 past the heating surface of heating element 20 and into 
the hollow body organ. The thermally conductive media is thus rapidly 
heated as it passes the heater 20 into the hollow body organ. 
The catheter 10 also includes an inflatable balloon 34 at its distal tip. 
The balloon 34 may be inflated through inflation lumen 36 which extends 
from an inflation port 38 on housing 24 to an outlet port 40 communicating 
directly with the interior of the balloon 34. The balloon 34 will usually 
be inflated with a heat conductive medium which will be heated by 
conduction from the heated fluid trapped by the balloon within the hollow 
body organ. An optional system (not illustrated) for heating the balloon 
within the medium may be provided. Systems for heating inflation medium 
within a balloon are described in U.S. Pat. No. 4,754,752, the disclosure 
of which is incorporated herein by reference. 
A third lumen 42 is formed in a tubular extension 43 disposed in central 
lumen 26. Lumen 42 extends through the distal tip of the catheter 10 and 
is axially-aligned with a lumen 45 (FIG. 3) through the heater 22. The 
tubular extension 43 is usually separated from the main portion of 
flexible body 12 and attached to the heater (not illustrated) to allow 
thermally conductive fluid to flow unobstructed from the central lumen 26 
past the heater 22 and through the slots 18. Together, the lumens 42, 43, 
and 45 are intended to form a fluid tight passage which can receive a 
movable guidewire which can be used to facilitate placement of the 
catheter 10 within the desired hollow body organ, as described in more 
detail hereinafter. 
Referring now to FIGS. 5-7, a catheter 50 which is similar to catheter 10 
but includes a pair of spaced-apart inflation balloons 52 and 54 is 
illustrated. The catheter 50 includes an elongate flexible member 56, a 
heating element 58, and is generally constructed as described previously 
for catheter 10. The catheter 50, however, includes the second inflatable 
balloon 54 which is spaced-apart proximally from the first balloon 52, 
with the two balloons being disposed on opposite sides of heating element 
58. In this way, the two balloons 52 and 54 are able to isolate a volume 
therebetween which includes the heater 58. By introducing the thermally 
conductive medium between the two balloons 52 and 54, the heater 58 may 
then be used to heat the isolated medium in treating a desired portion of 
a hollow body organ. The catheter 50 includes first inflation lumen 60 to 
inflate the first balloon 52 and a second inflation lumen 62 to inflate 
the second balloon 54. A central lumen 64 serves both to introduce 
thermally conductive medium and to receive a guidewire to facilitate 
placement of the catheter. The guidewire may be received in a tubular 
extension (not illustrated) or a seal, such as an O-ring, may be provided 
to inhibit leakage of medium. 
Referring now to FIGS. 8A-8H, the use of a two-balloon catheter of the type 
illustrated in FIG. 5 for ablating a gallbladder will be described. 
Gallbladder ablation will be desirable in cases of cholecystolithiasis 
where the diseased gallbladder is likely to continue production of gall 
stones. Gallbladder ablation according to the present invention will 
generally be performed after the removal of gall stones by established 
least invasive procedures, typically by either percutaneous 
cholecystostomy or by lithrotriptor. 
The intact gallbladder is illustrated in FIG. 8A and includes a hollow sac 
structure connected to the cystic duct through the neck of the 
gallbladder. The cystic duct, in turn, is connected to the hepatic duct 
and common bile duct. The gallbladder is located on the lower (inferior) 
surface of the liver in a hollow (fossa) beneath the right lobe. The upper 
(superior) surface of the gallbladder is attached to the liver by 
connective tissue. 
In treating the gallbladder according to the method of the present 
invention, a percutaneous guidewire 80 (FIG. 8B) is inserted into the 
gallbladder through the trans-hepatic route and into the common bile duct. 
A sheath 82 (FIG. 8C) is then placed over the guidewire 80 to provide for 
access into the interior of the organ. The catheter 50 may then be 
inserted over the guidewire 80 and positioned so that the first balloon 52 
lies beyond the neck of the gallbladder and just proximal to the junction 
between the hepatic duct and the common duct 50 (FIG. 8D). The second 
balloon 54 will remain within the sheath 82, while the heater 58 is 
located within the main body of the gallbladder. 
After the catheter 50 is in place, the thermally conductive medium 84 is 
introduced into the interior of the gallbladder through the catheter (FIG. 
8E). The medium 84 is introduced until the main sac is entirely filled, as 
illustrated in FIG. 8F, and the first and second balloons 52 and 54 are 
inflated in order to inhibit loss of the medium through the cystic duct 
and the sheath 82. During the introduction of the thermally conductive 
medium to the gallbladder, it may be necessary to adjust the position of 
the patient in order to expel trapped gases 86 (FIG. 8E). The gases 86 may 
be released through either the cystic duct or the sheath 82, or may be 
vented through a specially provided vent (not illustrated) within the 
catheter 50. 
Once the main sac of the gallbladder is completely filled with thermally 
conductive medium 84 (which may be confirmed by fluoroscopic examination 
of a radiopaque medium), the heating element 58 will be activated to raise 
the temperature of the medium, either by convection, radiation, or high 
frequency heating (FIG. 8G). Optionally, the thermally conductive medium 
84 may have been partially heated by the heating element 58 as the medium 
is introduced by the catheter 50. Heat will be conducted from the interior 
of the organ through the thermally conductive media in the first balloon 
52 in order to necrose the mucosa of the cystic duct in order to assure 
that the gallbladder lining will not regenerate. Usually, the second 
balloon 54 will be inflated with a thermally insulating medium to protect 
the liver from the heat of the medium 84. 
After maintaining the temperature of the heat conductive medium 84 (and 
optionally the inflation medium with balloon 52) at the desired ablation 
temperature for a sufficient time to completely necrose the mucosa of the 
gallbladder, the heating element 58 may be deenergized. 
After allowing cooling, the thermally conductive medium 84 may be aspirated 
through the catheter or optionally through the sheath 82 after balloon 54 
has been deflated (FIG. 8H). Alternatively, the thermally conductive 
medium 84 may be left within the main sac of the gallbladder from which it 
will eventually drain through the cystic duct and be eliminated by normal 
physiologic processes. 
After about six weeks, the endothelial lining of the gallbladder will be 
completely necrotic. The inflammation process will completely replace the 
lining of the gallbladder with fibrotic tissue within about twelve weeks 
and the organ will start to resorb. 
Although the foregoing invention has been described in detail for purposes 
of clarity of understanding, it will be obvious that certain modifications 
may be practiced within the scope of the appended claims.