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Determining required stent length in endoscopic retrograde biliary stenting
popular, probably because of the limited availability of primate research, animal rights issues, prohibitive costs, complexities of the required setups, and the lack of an inherent reality sensation, especially with comp u t e r simulation. T h e advantages of our m e t h o d over other simulation techniques include quick and easy assembly at a nominal cost, unlimited availability of papillary complexes to practice the technique, duplication of the actual cutting mechanism, reproduction of complications u n d e r a controlled setting, and familiarization with initiation of s p h i n c t e r o t o m y at various power settings of the diathermic unit so t h a t effects on tissue, ranging from excessive coagulation with no cutting to rapid cutting without coagulation, can be observed. Although the perception of cutting porcine papilla is almost identical to t h a t of performing s p h i n c t e r o t o m y in humans, f u r t h e r studies are needed to assess the efficacy of this technique, particularly regarding its impact on the learning curve of a novice endoscopist. In summary, the porcine papillary complex provides a simple and cheap model for teaching endoscopists the basic skills n e e d e d to p e r f o r m endoscopic retrograde s p h i n c t e r o t o m y and for familiarizing t h e m with the "feel" of the procedure and the principles of elec-
trocauterization before they actually perform sphinct e r o t o m y in h u m a n subjects.
Determining required stent length in endoscopic retrograde biliary stenting
ing these m e a s u r e m e n t s be accurately adjusted for radiographic magnification as well as requiring the endoscopist to leave the patient. T h e other m e t h o d involves the exchange of a regular cannula for a specialized measuring cannula with radiopaque markings. T h e measuring cannula requires a catheter exchange, adding to the cost and procedure time as well as placing at risk access across an often difficult stricture. A new m e t h o d for determining required stent length for successful endoscopic retrograde biliary stent p l a c e m e n t is r e p o r t e d below.
Bradley J. Kendall, MB, BS, FRACP Rome Jutabha, MD Loretta So, RN Priya A. Jamidar, MD Endoscopic retrograde biliary stenting is widely used in the m a n a g e m e n t of benign and malignant biliary strictures. 1-4 Successful stent p l a c e m e n t requires accurate d e t e r m i n a t i o n of the length of stent required to cross the stricture. Two m e t h o d s are currently used to d e t e r m i n e this length. T h e first involves taking m e a s u r e m e n t s from the cholangiogram obtained prior to stenting. This m e t h o d has the limitation of requir-
Received February 25, 1994. For revision June 21, 1994. Accepted July 25, 1994. From the Division of Gastroenterology, University of CaliforniaLos Angeles Medical Center, Los Angeles, California. Reprint requests: Bradley J. Kendall, MB, BS, FRACP, Department of Gastroenterology, Royal Brisbane Hospital, Bowen Bridge Road, Herston, Qld. 4029, Australia. 0016-5107/95/4103-024253.00 ÷ 0 GASTROINTESTINAL ENDOSCOPY Copyright © 1995 by the American Society for Gastrointestinal Endoscopy 37/69/59371
242 GASTROINTESTINAL ENDOSCOPY
1. 2. 3.
4. 5. 6. 7. 8. 9. 10. 11.
REFERENCES Cotton PB. Progress report: ERCP. Gut 1977;18:316-41. Geenen JE, Vennes JA, Silvis CE. Resume of a seminar on therapeutic retrograde sphincterotomy. Gastrointest Endosc 1981; 27:31-8. Noar MD, Hon D, Moore R. Endoscopy simulation teaching station: the future direction of learning, evaluation and certification of endoscopic technique and practice. Gastrointest Endosc 1992;38:280-1. Williams CB, Baillie J, Gillies DF, et al. Teaching gastrointestinal endoscopyby computer simulation: a prototype for colonoscopy and ERCP. Gastrointest Endosc 1990;36:49-54. Falkenstein DB, Abrams RM, Kerster RE, et al. Endoscopic retrograde cholangiopancreatography in the dog: a model for training and research. Gastrointest Endosc 1974;21:25-6. Siegel JH, Korsten MA. ERCP in non human primate. Gastrointest Endosc 1989;35:557-9. Gholson CF, Provenza M, Doyle JT, et al. Endoscopic retrograde sphincterotomy in swine. Dig Dis Sci 1991;36:1406-9. Geddes LA, Baker LE. The specificresistance of biological material--a compendium of data for the biomedical engineer and physiologist. Med Biol Eng 1967;5:271-93. Baker LE. Principles of impedence technique. IEEE Engineering in Medicine and Biology 1989;8:11-5. Koch H, Classen M, Schaffner O, Demling L. Endoscopic papillotomy: experimental studies and initial clinical experience. Scand J Gastroenterol 1975;10:441-4. Dodds WJ. The pig model for biomedical research. Federation Proceedings 1982;41:247-56.
METHOD The following is performed under fluoroscopic guidance. A 5F radiopaque tipped ERCP cannula and guide wire are passed across the stricture, taking care to ensure the cannula is as straight as possible with minimal looping in the biliary tree distal to the stricture. The guide wire is then pulled back through the cannula to a position where the tip of the guide wire corresponds to the desired position of the proximal end of the stent (Fig. 1). The guide wire is maintained in this position and a piece of paper tape (Tape 1) is placed around the guide wire at the point where it emerges from the cannula. With maintenance of the endoscopic and cannula position, the guide wire is pulled back, under endoscopic visualization, to the desired luminal position of the distal end of the stent (Fig. 2). The guide wire is maintained in this position and a second piece of paper tape (Tape 2) is placed around the VOLUME 41, NO. 3, 1995
Figure 1. Radiograph showing a radiopaque tipped ERCP cannula and guide wire across a malignant stricture of the right hepatic duct. The tip of the guide wire (arrow) is at the desired position of the proximal end of the biliary stent.
guide wire where it emerges from the cannula. A measure is then made between the edge of Tape 1 closest to the cannula and the edge of Tape 2 closest to the cannula. This measure is the total length of stent required (Fig. 3). To obtain the required stent length between the flaps (the measure manufacturers use to describe stent length) this total length is reduced by the length of stent proximal and distal to the flaps. This length varies with stent type, for example in the Amsterdam stent this measure is 2.5 cm. Once the required stent length is determined, the guide wire is passed back through the cannula into the proximal biliary tree, the cannula removed, and the stent placed over the guide wire in the usual fashion.
Figure 2. Endoscopic view with the ERCP cannula maintained proximal to the stricture and the tip of the guide wire (arrow) pulled back to the desired luminal position of the distal end of the biliary stent.
Wire Tape I Total leng~/thof stent required
/
J
/ Tape 2
ERCP Cannula
DISCUSSION Based on our initial experience, this m e t h o d a p p e a r s to overcome the limitations of the c u r r e n t l y used m e t h o d s for d e t e r m i n i n g required s t e n t length for endoscopic r e t r o g r a d e stenting of biliary strictures. A p r o s p e c t i v e s t u d y of this and other m e t h o d s c u r r e n t l y used for s t e n t m e a s u r e m e n t is needed. I f this m e t h o d is shown to be superior to c u r r e n t l y used m e t h o d s , this has p o t e n t i a l i m p o r t a n t implications, particularly with the increasing t r e n d t o w a r d s the p l a c e m e n t of e x p a n d able m e t a l stents where precise d e t e r m i n a t i o n of required s t e n t length is critical for successful s t e n t placement.
REFERENCES 1. Davids PH, Groen AK, Rauws EA, Tytgat GN, Huibregtse K. Randomised trial of self-expanding metal stents versus polyethylene stents for distal malignant biliary obstruction. Lancet 1992;340:1488-92. 2. Speer AG, Cotton PB, Russell RC, et al. Randomised trial of endoscopic versus percutaneous stent insertion in malignant obstructive jaundice. Lancet 1987;2:57-62. V O L U M E 41, NO. 3, 1995
Biopsy Channel IEndoscope Figure 3. Schematic diagram showing the endoscope, cannula, guide wire, and Tape 1 and 2. The total length of biliary stent required is the distance between the edge (closest to the cannula) of Tape 1 and the edge (closest to the cannula) of Tape 2. 3. Polydorou AA, Cairns SR, Dowsett JF, et al. Palliation of proximal malignant biliary obstruction by endoscopic endoprosthesis insertion. Gut 1991;32:685-9. 4. Davids PH, Rauws EA, Coene PP, Tytgat GN, Huibregtse K. Endoscopic stenting for post-operative biliary strictures. Gastrointest Endosc 1992;38:12-8. GASTROINTESTINAL ENDOSCOPY
243
trocauterization before they actually perform sphinct e r o t o m y in h u m a n subjects.
Determining required stent length in endoscopic retrograde biliary stenting
ing these m e a s u r e m e n t s be accurately adjusted for radiographic magnification as well as requiring the endoscopist to leave the patient. T h e other m e t h o d involves the exchange of a regular cannula for a specialized measuring cannula with radiopaque markings. T h e measuring cannula requires a catheter exchange, adding to the cost and procedure time as well as placing at risk access across an often difficult stricture. A new m e t h o d for determining required stent length for successful endoscopic retrograde biliary stent p l a c e m e n t is r e p o r t e d below.
Bradley J. Kendall, MB, BS, FRACP Rome Jutabha, MD Loretta So, RN Priya A. Jamidar, MD Endoscopic retrograde biliary stenting is widely used in the m a n a g e m e n t of benign and malignant biliary strictures. 1-4 Successful stent p l a c e m e n t requires accurate d e t e r m i n a t i o n of the length of stent required to cross the stricture. Two m e t h o d s are currently used to d e t e r m i n e this length. T h e first involves taking m e a s u r e m e n t s from the cholangiogram obtained prior to stenting. This m e t h o d has the limitation of requir-
Received February 25, 1994. For revision June 21, 1994. Accepted July 25, 1994. From the Division of Gastroenterology, University of CaliforniaLos Angeles Medical Center, Los Angeles, California. Reprint requests: Bradley J. Kendall, MB, BS, FRACP, Department of Gastroenterology, Royal Brisbane Hospital, Bowen Bridge Road, Herston, Qld. 4029, Australia. 0016-5107/95/4103-024253.00 ÷ 0 GASTROINTESTINAL ENDOSCOPY Copyright © 1995 by the American Society for Gastrointestinal Endoscopy 37/69/59371
242 GASTROINTESTINAL ENDOSCOPY
1. 2. 3.
4. 5. 6. 7. 8. 9. 10. 11.
REFERENCES Cotton PB. Progress report: ERCP. Gut 1977;18:316-41. Geenen JE, Vennes JA, Silvis CE. Resume of a seminar on therapeutic retrograde sphincterotomy. Gastrointest Endosc 1981; 27:31-8. Noar MD, Hon D, Moore R. Endoscopy simulation teaching station: the future direction of learning, evaluation and certification of endoscopic technique and practice. Gastrointest Endosc 1992;38:280-1. Williams CB, Baillie J, Gillies DF, et al. Teaching gastrointestinal endoscopyby computer simulation: a prototype for colonoscopy and ERCP. Gastrointest Endosc 1990;36:49-54. Falkenstein DB, Abrams RM, Kerster RE, et al. Endoscopic retrograde cholangiopancreatography in the dog: a model for training and research. Gastrointest Endosc 1974;21:25-6. Siegel JH, Korsten MA. ERCP in non human primate. Gastrointest Endosc 1989;35:557-9. Gholson CF, Provenza M, Doyle JT, et al. Endoscopic retrograde sphincterotomy in swine. Dig Dis Sci 1991;36:1406-9. Geddes LA, Baker LE. The specificresistance of biological material--a compendium of data for the biomedical engineer and physiologist. Med Biol Eng 1967;5:271-93. Baker LE. Principles of impedence technique. IEEE Engineering in Medicine and Biology 1989;8:11-5. Koch H, Classen M, Schaffner O, Demling L. Endoscopic papillotomy: experimental studies and initial clinical experience. Scand J Gastroenterol 1975;10:441-4. Dodds WJ. The pig model for biomedical research. Federation Proceedings 1982;41:247-56.
METHOD The following is performed under fluoroscopic guidance. A 5F radiopaque tipped ERCP cannula and guide wire are passed across the stricture, taking care to ensure the cannula is as straight as possible with minimal looping in the biliary tree distal to the stricture. The guide wire is then pulled back through the cannula to a position where the tip of the guide wire corresponds to the desired position of the proximal end of the stent (Fig. 1). The guide wire is maintained in this position and a piece of paper tape (Tape 1) is placed around the guide wire at the point where it emerges from the cannula. With maintenance of the endoscopic and cannula position, the guide wire is pulled back, under endoscopic visualization, to the desired luminal position of the distal end of the stent (Fig. 2). The guide wire is maintained in this position and a second piece of paper tape (Tape 2) is placed around the VOLUME 41, NO. 3, 1995
Figure 1. Radiograph showing a radiopaque tipped ERCP cannula and guide wire across a malignant stricture of the right hepatic duct. The tip of the guide wire (arrow) is at the desired position of the proximal end of the biliary stent.
guide wire where it emerges from the cannula. A measure is then made between the edge of Tape 1 closest to the cannula and the edge of Tape 2 closest to the cannula. This measure is the total length of stent required (Fig. 3). To obtain the required stent length between the flaps (the measure manufacturers use to describe stent length) this total length is reduced by the length of stent proximal and distal to the flaps. This length varies with stent type, for example in the Amsterdam stent this measure is 2.5 cm. Once the required stent length is determined, the guide wire is passed back through the cannula into the proximal biliary tree, the cannula removed, and the stent placed over the guide wire in the usual fashion.
Figure 2. Endoscopic view with the ERCP cannula maintained proximal to the stricture and the tip of the guide wire (arrow) pulled back to the desired luminal position of the distal end of the biliary stent.
Wire Tape I Total leng~/thof stent required
/
J
/ Tape 2
ERCP Cannula
DISCUSSION Based on our initial experience, this m e t h o d a p p e a r s to overcome the limitations of the c u r r e n t l y used m e t h o d s for d e t e r m i n i n g required s t e n t length for endoscopic r e t r o g r a d e stenting of biliary strictures. A p r o s p e c t i v e s t u d y of this and other m e t h o d s c u r r e n t l y used for s t e n t m e a s u r e m e n t is needed. I f this m e t h o d is shown to be superior to c u r r e n t l y used m e t h o d s , this has p o t e n t i a l i m p o r t a n t implications, particularly with the increasing t r e n d t o w a r d s the p l a c e m e n t of e x p a n d able m e t a l stents where precise d e t e r m i n a t i o n of required s t e n t length is critical for successful s t e n t placement.
REFERENCES 1. Davids PH, Groen AK, Rauws EA, Tytgat GN, Huibregtse K. Randomised trial of self-expanding metal stents versus polyethylene stents for distal malignant biliary obstruction. Lancet 1992;340:1488-92. 2. Speer AG, Cotton PB, Russell RC, et al. Randomised trial of endoscopic versus percutaneous stent insertion in malignant obstructive jaundice. Lancet 1987;2:57-62. V O L U M E 41, NO. 3, 1995
Biopsy Channel IEndoscope Figure 3. Schematic diagram showing the endoscope, cannula, guide wire, and Tape 1 and 2. The total length of biliary stent required is the distance between the edge (closest to the cannula) of Tape 1 and the edge (closest to the cannula) of Tape 2. 3. Polydorou AA, Cairns SR, Dowsett JF, et al. Palliation of proximal malignant biliary obstruction by endoscopic endoprosthesis insertion. Gut 1991;32:685-9. 4. Davids PH, Rauws EA, Coene PP, Tytgat GN, Huibregtse K. Endoscopic stenting for post-operative biliary strictures. Gastrointest Endosc 1992;38:12-8. GASTROINTESTINAL ENDOSCOPY
243