Reply to the Letter of Dr. Mosca

Dear Sir

I appreciate the opportunity to expound on the issues raised by Dr. Mosca. The first issue is the use of a retrograde contrast (enema) study to assess the degree of stenosis and to exclude the presence of synchronous lesions, specifically in the patient with an acute (total) colonic obstruction. Although Dr. Mosca raises the concern about explosion, microperforation and bacteremia in patients with acute obstruction, I can personally attest that I have encountered many patients with acute colonic obstruction who have undergone water-soluble retrograde contrast studies without complications [1]. While it is unclear that it is absolutely necessary to perform a retrograde study prior to endoscopic stent placement, an experienced radiologist will not introduce air or excessive pressure in the presence of complete colonic obstruction. I agree with Dr. Mosca that the need to identify synchronous lesions is less important in patients with de novo acute obstruction compared with patients with known metastatic or recurrent malignancy (for example, widespread ovarian cancer).

Although the retrograde enema study may not be needed and the lesion can be identified at endoscopy using endoscopic retrograde cholangiopancreatography (ERCP) catheter techniques, it is surprising that Dr. Mosca would feel that this carries less risk of perforation than the retrograde enema study. Air insufflation during the procedure may also produce perforation. Nonetheless, I have advocated for years the ERCP approach as described by Dr. Mosca [2], although this may not have been emphasized in our review. The technique I have recommended in the past is to use ERCP catheters, ball-tip or otherwise [2]. With the advent of double-lumen catheters, a hydrophilic, angle-tip Terumo guide wire is preloaded into one lumen and contrast is placed into the other. The wire and catheter are used to probe the site of obstruction under fluoroscopic guidance. I personally use the floppy hydrophilic wire in all complete obstructions, regardless of whether the lesion is polypoid or not. Once the wire and catheter are across the obstruction, contrast is introduced to confirm entry into the more proximal colon and to exclude extraluminal passage.

One recent ”trick” that I have found useful when the lumen or stricture cannot be seen en face endoscopically, is the use of a soft biliary occlusion balloon (stone-retrieval balloon) as the ”cannulating” catheter. The catheter should be one in which no catheter tip projects beyond the end of the balloon when fully inflated. The inflated balloon can be advanced beyond the tip of the endoscope to ”roll” around corners. When it is advanced against the stricture, contrast injection, guide wire probing, or both, facilitate cannulation of the stricture. Since the balloon is soft and pliable, perforation is unlikely to occur.

Another point raised by Dr. Mosca is use of ”through the scope” (TTS) stent placement compared with the ”over the guide wire” method. While I almost always use TTS stents, there is a legitimate concern about delayed perforation due to exposed bare wires on the end of these stents [3]. Additionally, covered stents are available for the ”over the guide wire” approach, while covered TTS stents are not. Covered stents are required to close fistulas and to help prevent tumor ingrowth [4]. I agree that it is technically difficult to place stents over the guide wire, especially in angulated sigmoid colons or those lesions in the proximal descending colon where there is a lack of mechanical advantage. In these situations, after the lesion has been successfully traversed with the floppy hydrophilic wire, the wire is exchanged for an extremely stiff guide wire (for example, 0.038“ Amplatz extra stiff, Cook Medical, Spencer, Indiana, USA, or Amplatz 0.038“ stiff guide wire, Meditech/Boston Scientific, Watertown, Massachusetts, USA), which facilitates passage of the stent delivery system across the lesion. Additionally, in some cases, after the guide wire is in place, it is helpful to re-advance the endoscope to the site of the lesion and straighten the endoscope prior to advancing the stent over the wire. The straightened endoscope and sigmoid colon can prevent looping of the stent delivery system as it passes alongside the endoscope.

Another point raised by Dr. Mosca, with regard to patients undergoing palliative stent placement, concerns dilation of the stricture to allow endoscopic assessment of the entire lesion and subsequent stent placement. I agree that this is not necessary and may increase the complication rate. However, our expert approach [5] was formulated by an international panel of endoscopists who place expandable metal colonic stents. One of our authors prefers to routinely pass the endoscope across the lesion to define the anatomy endoscopically and to perform the procedure without the use of fluoroscopy. Therefore this was offered as one of several methods of endoscopic colonic stent placement. Similarly to the approach described by Dr. Mosca, I do not routinely attempt to either pass the endoscope across the lesion or to dilate the stricture before or after stent placement. Instead, my approach to colonic stenting is similar to that of ERCP and biliary stent placement for palliation of distal malignant biliary strictures.

In the acutely ill patient with complete colonic obstruction, it is my opinion that the optimal endoscopic result will be obtained by those physicians who are experienced in performing complex procedures that require the use of endoscopy and fluoroscopy, such as therapeutic endoscopists experienced with ERCP. If such a person is not available, then an experienced interventional radiologist should be sought to either perform or assist the endoscopist in performing the procedure. Although our article was written to guide endoscopists performing these procedures, it is important to note that much of the literature on colonic stenting is published by interventional radiologists, who have a high rate of successful stent placement in the left colon without the use of endoscopes, even in the face of complete obstruction [6] [7].

I am grateful to Dr. Mosca for raising several important issues and am hopeful that these responses will be helpful to those physicians caring for patients who may benefit from colonic stent placement.

References

• 1 Canon C L, Baron T H, Morgan D E. et al . Treatment of colonic obstruction with expandable metal stents: radiologic features.  AJR Am J Roentgenol. 1997;  168 199-205
• 2 Baron T H, Dean P A, Yates M R. et al . Expandable metal stents for the treatment of colonic obstruction: techniques and outcomes.  Gastrointest Endosc. 1998;  47 277-286
• 3 Han Y M, Lee J M, Lee T H. Delayed colon perforation after palliative treatment for rectal carcinoma with bare rectal stent: a case report.  Korean J Radiol. 2000;  1 169-171
• 4 Repici A, Reggio D, Saracco G. et al . Self-expanding covered esophageal ultraflex stent for palliation of malignant colorectal anastomotic obstruction complicated by multiple fistulas.  Gastrointest Endosc. 2000;  51 346-348
• 5 Baron T H, Rey J F, Spinelli P. Expandable metal stent placement for malignant colorectal obstruction.  Endoscopy. 2002;  34 823-830
• 6 Camunez F, Echenagusia A, Simo G. et al . Malignant colorectal obstruction treated by means of self-expanding metallic stents: effectiveness before surgery and in palliation.  Radiology. 2000;  216 492-497
• 7 Mainar A, De Gregorio A riza. et al . Acute colorectal obstruction: treatment with self-expandable metallic stents before scheduled surgery - results of a multicenter study.  Radiology. 1999;  210 65-69