Reprints Available Directly from the Publisher Photocopying Permitted by License Only the Use of Prosthetic Stents in Tracheobronchial, Gastrointestinal, and Genitourinary Diseases Which Is Being Marketed by American Medical Systems

The concept of using a stent to maintain patency of a lumen is not new. As early as 1969, stents were being investigated in the peripheral medal system as a means of preventing restenosis after dilata-tion by balloon angioplasty (Dotter, 1969). Since then, numerous reports have demonstrated the use of stents in both the peripheral and coronary artery systems (Maass et al. Concomitant with the investigation of expandable en-dovascular metal prosthesis has been the development of prosthetic devices for management of tra-cheobronchial, gastrointestinal, and genitourinary diseases. We will review the use of endoscopically placed prosthetic devices in the management of diseases affecting these systems. was the first to describe the use of a stent or spiral in the lower urinary tract. He placed a metallic endoprosthesis in the prosthetic urethra of poor surgical risk patients in urinary retention as a result of an enlarged prostate. Based upon these results and the successful outcome of others, it became clear that stenting of the lower urinary tract was a workable concept (Fabricius et al., 1983; Flier and Seppelt, 1987). At the present time, there are a number of intraurethral endoprostheses being developed for use in the lower uri-nary tract. However, the two permanently implanted in-traurethral stents that have been investigated most extensively in both Europe and the United States are the Intraprostatic Stent by advance surgical intervention (San Clemente, California), and the UroLume Endoprosthesis, (Minnetonka, Minnesota). The Intraprostatic Stent has been evaluated primarily as a treatment of bladder outlet obstruction secondary to an enlarged prostate gland. However, the UroLume Endoprosthesis has been investigated as a treatment option for three urologic conditions: 1) recurrent bulbar urethral strictures; 2) benign prostatic hypertrophy; and 3) detrusser external sphincter duissyn-ergia. In the discussion that follows, the data relating to the role of the UroLume Endoprosthesis in the lower uri-nary tract are reviewed. The initial experience with this permanently indwelling endoprosthesis in the treatment ofrecurrentbulbar urethral strictures comes from England. In 1988, Milroy and colleagues (Milroy et al., 1988) reported their preliminary re-suits on eight patients. All of these men (mean age: 57 years; range: 33-78 years) hadbeenpreviously treated with a minimum of two direct vision internal urethrotomies (DVIU) and multiple urethral dilatations without success

a).The Intraprostatic Stent has been evaluated primarily as a treatment of bladder outlet obstruction secondary to an enlarged prostate gland.

However, the UroLume Endoprosthesis has been investi- gated as a treatment option for three urologic conditions: 1) recurrent bulbar urethral strictures; 2) benign prostatic hypertrophy; and 3) detrusser external sphincter duissyn- ergia.In the discussion that follows, the data relating to the role of the UroLume Endoprosthesis in the lower uri- nary tract are reviewed.


Recurrent Bulbar Urethral Strictures

The initial experience with this permanently indwelling endoprosthesis in the treatment ofrecurrentbulbar urethral strictures comes from England.In 1988, Milroy and col-  leagues (Milroy et al., 1988) reported their preliminary re- suits on eight patients.All of these men (mean age: 57 years; range: 33-78 years) hadbeenpreviously treated with a minimum of two direct vision internal urethrotomies (DVIU) and multiple urethral dilatations without success and were awaiting a formal urethroplasty.After first dilat- ing the dense stricture to 30-French (1.0 cm), the UroLume Endoprosthesis was placed across the stenosed area.

In two patients (25%), the endoprosthesis was inserted under radiological control, and in six (75%), the stent was positioned in the bulbar urethra under direct vision using an optical telescope.With a mean followup of 8 months (range: 6 months-1 year), no patient developed a recurrent stricture.All men had total resolution of their obstructive symptoms and an excellentcaliberurethraonfollowupcys- toscopic examination.For the seven patients with urody- namic data available, the mean peak urinary flow rate increased from 8.3 +/-1.8 ml/second prestent placement to 22.6 +/-7.0 ml/second postprocedure (p < 0.001).The only side effect observed in this preliminary study was occa- sional post-micturation dribbling for several weeks after stent placement.In the following year, these same investi- gators presented a followup report on 12 patients (mean age: 59 years; range: 31-88 years) with recurrent bulbar urethral strictures who were treated with the UroLume Endoprosthesis (Milroy et al., 19

).A total of 17 stents were inserted;
9 patients (75%) received one stent, one man (8%) had two stents, and 2 individuals (17%) had three stents inserted to completely cover the stdctured area.With the followup period ranging from 2 to 13 months (mean: 7 months), no stricture recurred.For the 11 evaluable pa- tients, the mean peak urinary flow rate increased by 200% (7.6 +/-2.3 ml/second pre-insertion to 22.8 +/-8.4 ml/second poststent placement).By 4 to 6 months after placement, the stents were completely covered with urothelium, and thus no longer exposed to the urine during micturation.Untoward effects included transient, mild discomfort at the stent site for 2 to 3 weeks in five men (42%); five other pa- tients complained of mild postvoid dribbling after stent in- sertion.There was no evidence of encrustations or infection, and no patient complained of alteration in ejaculation or ability to achieve an erection.Ashken and colleagues (Ashken et al., 1991) reported the European experience with the UroLumeEndoprosthesis as a treatment for difficult bulbar urethral strictures.With four urologic centers participating, 71 patients (mean age: 56 years; range: 30-81 years) were managed with the en- doprosthesis over a 3-year period.The most common eti- ology was iatrogenic, and all patients had undergone multiple previous treatments without success.All men were followed for a minimum of 6 months, and 12 (17%) had been monitored for over 2 years after stent placement.Subjectively, 96% (68 patients) were pleased with the out- come.Objectively, the mean peak urinary flow rate in- creased from 6 ml/second pre-insertion to 20 ml/second in 3 months (p < 0.01), 18 ml/second at 8 months (p < 0.01), and 22 ml/second at 15 months (p < 0.01) post-stem place- ment.No patient developed a recurrent stricture.The au- thors, however, commented that none of the patients in the series had a traumatic stricture; they recommended that traumatic strictures, which can be associated with very dense fibrous tissue, should not be managed with the UroLumeEndoprosthesis.As forthe present series, the only notable untoward effects were urethral and perineal dis- comfort and occasional postvoid dribbling in the immedi- ate postoperative period.There was no difficulty with infection or encrustations.The North American UroLume Study Group also evaluated the UroLume Endoprosthesis in a multicenter clinical trial (Oesterling et al., 1993).One hundred and seventy-five patients (mean age: 52 years; range: 17-90 years) with recurrent bulbar urethral strictures underwent treatment with the UroLume Endoprosthesis.

The mean number of previous treatments (urethral dilata- tion or DVIU) per patient was 18. Stricture length for the entire cohort varied from 0.4 cm to 5.5 cm (mean: 2.2 cm).

The results at 12 months followup were most encouraging.

The total symptom score decreased from 12.7 +/-5.1 pre-in- sertion to 2.1 +/-2.3 (p < 0.001).With voided volumes in ex- cess of 150 cc, the peak urinary flow rate increased from 9.7 _ 6.1 cc/second pre-insertion to 22.2 +/-10.8cc/second (p < 0.001).At 6 months post-insertion, 74% of the endo- prostheses were completely covered with epithelium (Fig. 4).As of this time, there has been no difficulty with infec- tion, erosion, encrustations, migration, continence, or potency.Several ofthe younger patients, however, have noted perineal discomfort with nocturnal erections in the postop- erative period.For all such patients, this untoward effect re- solved within 6 to 8 weeks.Approximately 50% of the patients did have a mild degree of postvoid dribbling.Twenty-six men (15%) have required a second treatment to manage the urethral stricture; sixteen patients underwent placement of a second endoprosthesis, eight patients had an endourethral resection, one patient was managed with urethral dilatation, and one person had laser ablation of the tissue regrowth.Six patients (3%) have undergone stent re- moval; all prostheses were removed without difficulty and subsequent sequelae.These preliminary results from both Europe and the United States suggest that the flexible, self- expanding intraurethral stent may be an effective treatment for recurrent bulbar urethral strictures.Investigations with more patients and extended followup (years), however, will be necessary to determine the true durability of the endo- prosthesis and assess late complications.


Benign Prostatic Hyperplasia

As for bulba urethral strictures, the early experience with the UroLume Endoprosthesis in the treatment of BPH comes from England, where this device has been utilized since January 1989 in patients who are a poor surgical risk.In a series of 12 patients described by Chapple and asso- ciates, 11 (95%) were "fully satisfied" and able to urinate without difficulty during a mean followup of 8.2 months (range: 1-11 months) (Chapple et al., 1990).The one dis- satisfied patient complained of significant frequency and urgency; this phenomenon was found on subsequent uro- dynamic evaluation to be associated with severe, persistent detrusor instability.The mean peak urinary flow rate at followup for the 12 patients, 9 of whom were in urinary retention prior to stent placement, was 13.6 +/-4.7 ml/sec- ond.The postvoid residual urine volume after stent placement was minimal.With respect to untoward effects, all 12 patients experienced some degree of irdtative voidings symptoms in the immediate postoperative period.These symptoms subsided markedly within 4 to t5 weeks.

In a more recent report of 45 surgically unfit patients treated with the UroLume Endoprosthesis, Milroy and colleagues, indicated that 42 (93%) were pleased with the outcome; all were "passing urine normally with suffi- ciently reduced residual urine volumes" (Milroy, 1991).Most patients, however, suffered urgency, frequency, and occasional urge incontinence following stent placement; these symptoms tended to resolve within several months, as the endoprosthesis became covered with epithelium

ost often, the stem becomes c
vered with urothelium within 4 to 6 months' time, which is somewhat faster than that which occurs in the bulbar urethra.At 6 to 9 months after stent placement, these investigators did notice a sig- nificant amount of hyperplastic tissue growing through the intertices of the wall of the stent.However, by 12 to 18 months post-stent insertion, this had subsided markedly and was of no concern.No encmstations were observed on any part of the endoprosthesis located within the prostatic urethra.However, if the proximal end of the stent is allowed to extend across the bladder neck into the bladder, "fine encmstations" can develop on this aspect ofthe device 6 to 12 months after placement.In the Milroy series, it has been necessary to remove five stents.All de- vices were removed without difficulty.Two were not po- sitioned properly at the time of deployment and were removed immediately, and a second stent was inserted; two others were removed 4 weeks after placement, and one was taken out 11 months after insertion.The tech- nique for removing an endoprosthesis aft r it has become covered with epithelium is as follows.Once the overlying epithelium has been resected with a low-current resecto- scope, the stent is jarred from it's bed in the prostatic ure- thra with a forceps.The stent is then grasped approximately 0.5 cm from its distal edge and pulled gen- tly; it will lengthen and decrease in diameter (much like a Chinese finger toy) so that it can be pulled inside a re- sectoscope sheet and removed without trauma to the ure- thra or the external urinary spinchter (Chapple and Milroy,  1989).McLoughlin and co-workers (McLoughlin et al., 1990) described 19 major-risk patients, all of whom were in urinary retention, who underwent placement of the en- doprosthesis in the prostatic urethra with local anesthesia only.All patients tolerated the procedure with minimal to no discomfort, and all were able to "void spontaneously" during the followup period (mean: 4 months; range: 3-7 months).Fifteen patients (79%) had severe urgency, fre- quency, or discomfort with urination for 3 to 4 days after stent placement.For most patients, this untoward effect resolved within 8 weeks.All stents were noted to be cov- ered with epithelium after 4 months.At the 1993 annual meeting of the American Urological Association, Oesterling (Oesteding 1993) reported the results of the North American Clinical Trial.Ninty-five healthy patients (mean age: 68 +/-7.5 years) with obstructive BPH elected to be treated with the UroLume Endoprosthesis.Unlike most patients being considered for treatment with the de- vice in Europe, these men were sexually active and could have readily undergone a transurethral resection of the prostate gland.All patients were evaluated prior to stent placement and in followup with a standard symptom ques- tionnaire, peak urinary flow rate, postvoid residual urine volume, and cystoscopic examination.The patients found to have a large, median lobe or considered to have a hypotonic bladder were excluded from participation.The re- suits at 12 months followup were excellent.The total symptom scored decreased from 15.0 +/-5.5 pre-insertion to 6.3 +/-5.8 (p < 0.001).With voided volumes in excess of 150 cc, the peak urinary flow rate increased from 8.6 +/-3.5 cc/second pre-insertion to 15.6 +/-6.2 cc/second (p < 0.001).The postvoid residual urine volume decreased from a 129 +/-14.6 cc to 24 +/-44 cc (p < 0.001).By 6 months, 55% of the endoprostheses were completely cov- ered with epithelium; 45% still had some aspect of the stent exposed at the bladder neck.There was no signifi- cant difficulty with infection, erosion, migration, conti- nence, or potency; 67% ofthe patients, however, had some irritative symptoms (urgency, frequency, or dysuria) for at least 1 month after stent placement.Nine stents have been removed; all prostheses were removed without in- jury to the external urinary sphincter or the urethra.These results from both Europe and the United States are en- couraging.Nevertheless, additional studies with extended followup will be necessary to establish.thetrue, long-term usefulness of this endoprosthesis in the management of symptomatic BPH.A prospective, randomized clinical trial, comparing the UroLume Endoprosthesis with transurethral section of the prostate gland, is now under- way in the United States and Canada.


Detrusor External Sphincter Dyssynergia

Supraspinal cord injuries most often result in some degree of detrusor external sphincter dyssynergia (Barkin et al.,  1983).The majority of patients develop significant detru- sor-external sphincter dyssynergia and require theraputic intervention.The two standard treatments are: 1) anti- cholinergic therapy (to decrease uninhibited bladder con- tractions and improve vesical compliance) with clean intermittent catheterization, and 2) external striated sphincterotomy to reduce bladder outlet resistance.The former option is only a consideration ifthe patient has suf- ficient manual dexterity.The latter treatment, on the other hand, does not always result in a favorable outcome.The results of endoscopic external sphincterotomy have been variable; overall, the success rate of this procedure is ap- proximately 79 to 90%, as destruction of the entire exter- nal urinary sphincter is not always technically easy (Whitmore et al., 1978).Side effects, such as rectal dys- function and hemorrhage, also can be significant.Thus, there is much interest in developing a more simple, yet re- liable, approach to achieving a functional external sphinc- terotomy.To this end, the UroLume Endoprosthesis is being investigated both abroad and in the United States as an alternative treatment for detrusor-extemal sphincter dyssynergia.In 1990, Shaw and colleagues (Shaw et al., 1990) described nine patients with complete quadraple- gia and detrusor-external sphincter dyssynergia who were managed with the UroLume Endoprosthes

instead of sphincterotomy; followup ran
ed from 12 weeks to 10 months.In six men (67%), a 3-cm endoprosthesis was suf- ficient to completely traverse the external sphincter; three patients (33%) required additional stents.Eight patients (89%) had marked improvement in bladder emptying; the mean postvoid residual urine volume decreased from 268 ml prestent insertion to 92 ml following the procedure.The other patient did not achieve complete bladder emp- tying and is awaiting urinary diversion.No complications were encountered in this series.McInerney and associates (McInemey et al., 1991) placed this endoprosthesis in 22 patients with neurological conditions resulting in significant detrusor-external sphincter dyssynergia.Fourteen (64%) of these men had undergone previous surgery on the outflow tract; eleven had had repeated unsuccessful external sphincterotomies, and three had undergone placement of an artificial urinary sphincter at the bladder neck.With a maximum follow-up of 1 year, 15 (68%) achieved complete voiding after the procedure; 3 (14%) developed bladder neck obstruction after stenting the external uri- nary sphincter.The endoprosthesis was of no value in the three patients who had an artificial urinary sphincter placed previously at the bladder neck.Chancellor (Chancellor et al., 1993) most recently reported the re- suits of the North American Clinical Trial evaluating the UroLume Endoprosthesis as a treatment for detrusor-ex- ternal sphincter dyssynergia (Fig. 6A and 6B).One hun- dred and nineteen spinal cord-injured men with this condition, as verified by urodynamic evaluation, were managed with an endoprosthesis and followed for 3 to 21 months.Thirty-two patients (27%) required two prosthe- ses to completely bridge the external urinary sphincter.Voiding pressures decreased from 77.7 + 26.2 cm ofwater before prosthesis placement, to 40.7 +_. 16.5 cm of water at 3 months, 30.2 _ 15.2 cm of water at six months, and 26.1 +_.13.4 cm of water at twelve months (p 0.001).The postvoid residual urine volume decreased from 188.9 _.+ 128.9 ml preoperatively to 112.5 _ _ .128.6 ml at 12-months followup (p 0.008).Bladder capacity, however, re- mained constant (p 0.3).All the patients with a pros- thesis in proper position were able to achieve spontaneous reflex voiding without constant dribbling.Encrustations, infection, erosion, pain, and obstructive hyperplastic epithelial overgrowth did not occur in any patient.No deliri- ous effects were seen with regard to renal or erectile function.In five patients, however, it was necessary to re- move the device because of stent migration.Based on these preliminary results, it appears that the flexible, epithelizing UroLume Endoprosthesis may be an effective treatment for select patients requiting an external sphinc- terotomy.Nevertheless, it is only through long-term fol- low-up of many patients that the real effectiveness of this device will be demonstrated.Ideally, a prospective, ran- domized clinical trial comparing the UroLume Endoprosthesis with the goal of standard care, the endo- scopic external sphincterotomy, should be conducted.


ENDOSCOPIC PLACEMENT OF PROSTHETIC DEVICES IN GASTROENTEROLOGY

Endoscopic placement of prosthetic devices has been shown to be effective in three areas of gastroenterology.This includes obstruction from esophageal carcinoma, malignant biliary tract obstruction, and obstruction of the pancreatic ducts.


Esophageal Stenting

Adenocarcinoma of the esophagus continues to rise dra- matically as a leading cause of cancer death worldwide.The presentation of a patient with esophageal cancer is frequently by symptoms due to obstruction.In planning therapy, the level of tumor involvement is important.The esophagus is divided into three segments.The upper, which extends from the cdcopharyngeus to 23 cm from the dentures, the middle level, which extends from 24 cm to 32 cm, and the lower esophageal segment, which is from 33 cm to the junction of the stomach.Tumors of the upper and middle third are generally beyond surgical cure at the time of their clinical presentation.It is has been estimated that 15 to 20% of patients with advanced esophageal car- cinoma should be considered for esophageal stenting.This is particularly so after surgery, radiotherapy, chemother- apy, and laser therapy have been utilized.The tubes that have been used are constructed of polyvinyl plastic, latex rubber, or silicone rubber.They may be reinforced by a metal spiral, and have a proximal funnel construction which facilitates endoscopic placement.

A self-expanding silicone-covered tube (Gianturco stent) was used for palliation of esophago-respiratory

s- tula related to esophageal cancer in eight patients by Do (D
et al., 1993) at the Korea Cancer Center Hospital.All fistula were successfully occluded by these expanding tubes.The expanding tubes imbed themselves into the esophageal wall, and a significant tissue hyperplasia oc- curs, particularly at

e edge of the tube.
Radiologists at the University Hospital, Lund, Sweden have implanted nitinol self-expanding stents in 40 patients with dysphagia (Cwikiel et al., 1993).There were no im- mediate complications, although ingrowth of the tumor was seen in eight patients.Two of the patients had occlu- sion of the stent by tumor and required laser resection to re-establish luminal patency.

The Gianturco metallic stent was used by Iwasaki and  collegues (Iwasaki et al., 1993) to bridge a malignant stric- ture of a esophagojejunostomy.Truong and collegues (Truong et al., 1992) also reported palliative treatment of malignant gastric outlet obstruction using a self-expanding metal stent.


Biliary Duct and Pancreatic Duct Stenting

The placement of biliary and pancreatic endoprostheses is also receiving intensive study and experimentation.Endoscopic stent placement has become accepted pallia- tion for patients with inoperable malignant biliary tract ob- struction.Specific conditions that may be amenable to stenting include pancreatic and biliary carcinoma, or metastatic lesions that either compress or infiltrate the bil- ary tree such as carcinoma of the gallbladder, carcinoma of the stomach, or cancers arising in the colon, breast, etc.The major condition that has benefitted from endoscopic stenting has been pancreatic adenocarcinoma.Ofthis group ofpatients, 22 percent also had malignant hilar obstruction.

The success rate for endoscopic placement of biliary stents is approximately 80 to 93% and the overall success of insertion is judged by evaluating complications en- countered in obtaining the goals of the procedure.A pre- liminary goal in the treatment of malignant obstruction is the relief ofjaundice.Kodakin and Starnes (Kodakin and Starnes, 1992) have compared the 10 French and the 11.5 French polyethylene biliary stents, and their effectiveness in obtaining relief of icterus, and decline of total bi iru- bin.They concluded that there is no significant advantage between these stent sizes.However, the stent patency is approximately twice as long for the 10 French polyethylene stent compared to the 7 French stent.There is a slight tendency for a higher complication rate using the larger stent (P

ersen, 1993).

The occlusion rate most cer
ainly impacts on the ac- ceptance of stenting of the biliary ductal system as palliative therapy.The occlusion rate for a 10 French or 11.5 French stent at 3 months is 42%, and at 6 months is 10.8% (Davids et al., 1992).Furthermore, a worse clinical re- sponse and poorer survival is seen in the group of patients who have undergone stenting for metastatic cancer (Frakes et al., 1993).

The search for a better stent is primarily based on the ease of insertion and stent patency.This search has led to the use of metal expandable stents.The University of Amsterdam investigators have compared an expandable metal stent with a polyethylene stent (Davids et al., 1992).The median patency f r the first stent insertion was significantly prolonged in patients with a metal stent com- pared with the polyethylene stem, 273 days versus 126 days, respectively.The major cause of stent dysfunction was tumor ingrowth in the metal stent group, and sludge deposit in the polyethylene group.When stent blockage was encountered, a polyethylene stent was inserted.Of those patients in the metal stent group, 14 required a polyethylene stent insertion, and no further occlusions were encountered.In the group who had a polyethylene stent initially inserted, 23 required an additional stent inserted.

Eleven of the 23 (48%) who had a new polyethylene stent inserted had an additional episode of occlusion.This fact suggests that re-occlusion is more likely to occur when the endoscopist uses only polyethylene stents.

Since plastic stents are removable, they have been em- ployed in the treatment of benign biliary strictures.A non- randomized study by Davids (Davids et al., 1993  retrospectively compared surgical management and endo- scopic management of benign biliary strictures.Endoscopically placed biliary stents, which were ex- changed every third month for a 1 year period, were com- pared to patients who were surgically manag d.Seventeen percenthadrecurrent stricture afterundergoing endoscopic dilatation and stenting.Another way that this result can be stated is that 83% oftheir strictures were patent after being submitted to endoscopic care, while the literature fre- quentl states that surgical management of strictures has an 80% long-term success.The authors conclude that this practice scheme is an acceptable way to initially manage strictures, and that the surgical repair should be reserved for patients who have complete transection of the duct, failed previous surgical repair, or failed an endoscopic treatment program.This recommended approach seems to be an oversimplification of a very complex situation.Millis (Millis et al., 1992) retrospectively analyzed 194 patients who were consecutively treated at UCLA for bile duct strictures.Those seen from 1955 to 1979 were sep- arately analyzed in group 1, and those seen from 1980 to 1990 were reviewed in group 2. The recurrent stricture rate was 21 and 23% respectively.The re-operation rate for group 1 was 21% and for group two, 6%.An expla- nation as to why there was a striking eduction in re-op- eration, was that 20 patients in group 2 underwent biliary dilatation.Yet, the success of biliary dilatation varies greatly depending upon the pathologic condition giving rise to stricturing.Ninety-three percent of those treated with anastomatic strictures were adequately eared for by dilatation, while only 50% ofpatients with a primary stric- ture benefited from dilatation.

Biliary endoprostheses have been used in elderly symp- tomatic patients with large bile duct stones.The use of a stent has proven to be an effective treatment for nonex- tractable stones.An excellent article by Chung (Chung et   al., 1991) from the Prince ofWales Hospital, Hong Kong, reviewed their experience clearing biliary ducts of large stones.Mechanical lithotripsy was successful in 81% and the remaining patients had their ducts cleared of calculi by electrohydraulic lithotripsy, surgery, or stenting.

The pancreas and its aff icfions are being approached with the insertion of straight stents.Therapeutic endo- scopists hope that bypassing obstructive lesions will di- minish pain and restore or pres rve function.Segmental stenotic lesions in the head region and intraductal calculi, that are not removable, are being stented.Polyethylene pancreatic duct stents induce changes in the pancreas of normal dogs (Sherman et al., 1993).Similar changes have been observed in humans (Kozarek, 1990).It appears the cause of this damage is related to stent occlusion or from local ductal trauma.Due to this known complication, cau- tion must be exercised in application of pancreatic stents.


ENDOSCOPIC PLACEMENT OF TRACHEOBRONCHIAL PROSTHESES

Many patients with malignant airway obstruction present with disabling dyspnea that is not amenable to surgical in- tervention.Laser resection of tumor has provided pallia- tion in some of these patients.Unfortunately, many pa- tients have obstruction from extrinsic compression by tu or or enlarged lymph nodes.The development of en- dobronchial prosthetic devices may offer some of these patients an alternative to disabling dyspnea.

The concept of an airway prosthetic device is not new, but unfortunately, materials and techniques for insertion have been previously unsatisfactory.Developmentofproducts that are easer to insert and more tolerable to the patient has led to an expanded use of prosthetic devices in the management of airway obstruction.Several types of tracheobronchial pros heses are currently available (Clark,   1980; Cooper et al., 1981; Dumon, 1990; lnsall and  Morritt, 1991; Montgomery, 1965; Montgomery, 1968   Neville etal., 1972; Oflowski, 1987; Paliero and Shepherd,  1974; Simonds et al., 1985; Uchida et al., 1988; Wallace  et al., 1986 Westaby et al., 1982; Westaby and Shepard,  1983).Three basic types ofprosthetic devices are currently available: 1) molded silicone prostheses, 2) expandable metal prostheses, or 3) combinations ofmetal and silicone.

Dumon (Dumon, 1990) reported results of a silicone stent with studs on its external surface to prevent migration.In this series, a total of 118 prostheses were inserted in 66 patients.Immed

te relief of respiratory symptoms with significant q
ality of survival was achieved in all but two cases.The prosthesis was placed in the trachea in 59 cases, the left mainstem bronchus in 34 cases, and the fight mainstem bronchus in 16 cases.Obstruction of the prosthesis by dried secretion was recorded in two patients.Granulomas were noted in 10 cases.The authors report migration of the prosthesis in 12 patients.Becker (Becker, 1992) reported experience with ex- pandable metal pr stheses, mainly the Strecker stent and the Palmaz stent.These prostheses are made of tantalum or stainless steel compressed onto balloons and expanded after introduction by inflation with saline solution.The expandable metal stents become epithelialized in the ideal situation.Becker reports 36 implantations of the Strecker stent with complications occurring in the majority ofthese patients.Complications included granulomatous forma- tion with obstruction and integration into the bronchial wall.As a result of this experience, the author does not recommend use ofthese prosthesis for airway obstruction.

Self-expanding metal prothesis have also been used in the management of malignant or benign airway obstruc- tion.Several authors have reported their experience with these devices (Bohndorfetal., Rauber et al., 1992).Becker reported implanation of 77 Nitinol stents.The complica- tions appeared less than with the Strecker stents.Rousseau reported an experience with self-expandable type pros- thetic devices.He reported 74 stents in 62 patients (Rousseau etal., 1992).Thirty-nine Wallstents (trachea 14, bronchi 25), and 35 Gianturco.This series represented con- secutive patients with contraindications for surgery or presented with noninflammatory lesions of the trachea or bronchus.Rousseau reported complications in 6 of 19 pa- tients (31%) with the Gianturco self-expanding stent.

At our institution, we have had the opportunity to use Dumon silicone stents and a specially designed Stent

Introducer System (Bryan Copr, Woburn, MA.).Forty stents have been inserted into thirty patients.The majority of these patients had malignant airway obstruction.Other causes of airway narrowing included benign stric- ture, Wegener's granulomatosis, and mediastinal fibrosis.

One patient has had the prosthetic device in place for more than 48 months.The major complication has been ob- struction by inspisated secretions.One patient experienced stent dislodgement and one patient had a stent removed due to intractable cough.Our experience supports the use of silicone prostheses in selected patients with airway ob- st uction due to malignant or benign processes.

The ideal prosthetic device for tracheobronchial ob- struction has not yet been witnessed.Depending on the cir- cumstances, the silicone prosthesis ofthe Dumon type may have advantages over the self-expanding metal stents.Clearly, for the benign stricture in patients who are not sur- gical candidates, the silicone prosthesis is the instrument of choice.As more development occurs, the metal self-ex- panding stents may find more appropriate applications.The combined metal silicone stents that are currently under de- velopment may also provide a new class of stents that will be more appropriate for patients with airway obstruction.


Summary

Endoscopic placement of endoluminal prosthetic devices continues to expand.Significant pal iation can be accom- plished in patients with diseases that effect not only the vascular system, but also the genitourinary, gastrointesti- nal, and tracheobronchial tree.Symptoms ofrecurrent bul- bar urethral strictures, benign prostatic hypertrophy, and detrusor external sphincter dyssynergia may be managed in some patients using these new devices.Obstruction of the esophagus by arcinoma or obstruction of the biliary or pancreatic ducts may also be palliated using new prosthetic devices.Malignancies and benign processes caus- ing airway obstruction with resulting dyspnea may be managed by dilatation and placement ofprosthetic devices in the tracheobronchial tree.Although devices are avail- able for each ofthe above conditions, further development and investigat on needs to be undertaken to improve both methods of application as well as analyze long-term re- sults in these disorders.
 
European experience with the urethral Wallstent for urethral strictures. M H Ashken, C Coulange, E J G Milroy, J P Sarramon, Eur Urol. 191991

The urologic care of the spinal cord injured patient. M Barkin, D Dolfin, S Herschorn, N Bharatwal, R Comisarow, J Urol. 1291983

Implantation selbstexpandierender Endoprothesen (Wallstent) bei benignen Traehealobstmktionen. H D Becker, Bohndorfk, G Kureja, D Schlondorff, R W Vorwerk, The 7th World Congress for Bronehology. J Kollath, D Liermann, Rochester Min

sotaSept
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. I I Stents, -- Sehnetstor, Verlag, 1992Konstanz

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