1. Patients
In this study, we analyzed the outcomes of 158 SEMS insertion procedures performed by a single endoscopist (Cheon JH) in patients with malignant colorectal obstruction who were treated at Severance Hospital, Yonsei University College of Medicine, Seoul, Korea between March 2006 and December 2009. Our study was performed by a retrospective review of prospectively collected data on patient sex, age, cancer location, type of obstruction, purpose of SEMS insertion, type of stent, stent length, and number of stents. Exclusion criteria were as follows: 1) extrinsic obstruction by other cancerous lesions (n=30); 2) a previous history of stent insertion at other hospitals (n=2); 3) benign stricture after a colon cancer operation (n=5); and 4) recurrence after a colon cancer operation (n=1). After excluding 38 patients, we compared the technical success rates, clinical success rates, complication rates, number of stents needed per procedure and procedure duration by quartiles.
This study was approved by the Institutional Review Board of Severance Hospital.
2. Definitions
The location of the cancer was categorized into two groups: right colon and left colon. The ascending colon and the transverse colon were included as the right colon and the other areas were classified as the left colon. Technical failure was defined as failure to deploy a stent across the entire length of a colon stricture. Clinical failure was defined as the absence of the resolution of obstructive symptoms (abdominal distension, vomiting, and abdominal pain) and the absence of gas and stool passage despite achieving technical success.11 Problems such as immediate migration, bleeding, and perforation were considered stent-induced complications.12 Subtotal obstruction was defined as a state with narrow stool caliber or the ability to pass only small amounts of liquid stool or gas. Total obstruction was defined as decreased or absent bowel sounds or the inability to pass any stool or gas.7 Procedure time was calculated only after the colonoscope was advanced to the site of obstruction, then the time required to insert a guidewire and stent and to confirm correct positioning and expansion using fluoroscopy was included.
3. Endoscopic technique
Before placing colonic stents, all patients underwent a computed tomography (CT) scan and bowel preparation by glycerin and warm saline enema. We evaluated the CT scans to assess the extent of the tumor and the location, degree, and length of the obstruction. Stents were placed by one experienced colonoscopist (Cheon JH) from our hospital as previously described.1 Before initiating SEMS insertion, the endoscopist had performed more than 1,000 colonoscopy procedures per year for several years but had no experience with endoscopic retrograde cholangiopancreatography.
A flexible colonoscope (CF-H260AI; Olympus, Tokyo, Japan) was advanced to the site of the obstruction. A biliary guidewire (Jagwire; Boston Scientific, Natick, MA, USA) was inserted into the lumen of a catheter (ERCP-Catheter; MTW Endoskopie, Wesel, Germany), and the guidewire and the catheter were then advanced together beyond the obstruction. The distal and proximal ends of the stricture were confirmed under fluoroscopic guidance by injecting a water-soluble contrast agent (Gastrograffin; Bayer Schering Pharm., Seoul, Korea) through the catheter after removal of the guidewire. The compressed SEMS delivery system was then introduced through the working channel of the endoscope over the guidewire and passed beyond the stricture. Stent release and expansion progressed from the proximal to the distal portion under fluoroscopic and endoscopic control. Abdominal X-rays were obtained on the same day of the procedure, as well as the next day, to confirm correct positioning and expansion.
Stent type was selected according to the preference of the patient and the experience of the endoscopist. Stent length was selected by allowing for at least an additional 2 cm to be exposed distal and proximal to the obstructing lesion. Four types of stents were used in our study: 1) covered Niti-s colonic covered stents (Taewoong Medical, Seoul, Korea); 2) newly developed, covered Comvi stents (Taewoong Medical); 3) uncovered Wall-Flex colonic stents (Boston Scientific, Denver, CO, USA); and 4) uncovered Niti-s colonic D type stents (Taewoong Medical).13
4. Statistical analysis
Data were analyzed to identify the baseline patient characteristics, sites of obstructing lesions, reasons for stenting, outcomes, procedure times, and complications. The data were expressed as the mean±SD, median (range), or no. (%) as appropriate. We compared categorical variables with the chi-square test and one-way ANOVA. Correlations between success rates, procedure times, and level of experience were assessed using Tukey's multiple comparison test and Dunn procedure. A p<0.05 on a two-tailed test was considered statistically significant. Statistical analysis was performed using IBM SPSS version 18.0 (IBM, New York, NY, USA).