Large bowel obstruction.

I T HAS LONG BEEN MY IMPRESSION, together with others, that the state of competence of the ileocecal valve is the key to the radiographic picture of mechanical large bowel obstruction. 8~‘4~i9*2’ Continued observation has reinforced some of my previous conclusions. 27 At that time, I described three patterns of obstruction (Fig. 1). Type II obstruction, that associated with incompetence of the ileocecal valve, results in hypertrophy but little distension of the cecum, and multiple loops of small bowel distended as a result of reflux of gas from the colon. This type of obstruction is less likely to result in perforation of the thickened cecum and is best managed by transverse colostomy proximal to the point of obstruction. It represented about 25% of the patients in that series. With a competent ileocecal valve (Type IA), the roentgen picture is one of a large dilated colon with a markedly distended thin walled cecum, and no distension of small bowel (Wangensteen’s classic descriptiod7). As this process progresses small bowel distension occurs (Type IB), probably due to secondary obstruction as a result of the combination of a fluid-filled cecum and a tightly closed ileocecal valve. As the critical level of cecal distension (8 cm)12 is approached, the likelihood of perforation of the cecum increases. Cecostomy has been considered the procedure of choice, with the dual purpose of decompressing the cecum and inspecting it for perforation. The majority of cases reported in my earlier article were Type IB. Type IA was seen only rarely. Supportive evidence indicates that the ileocecal valve is indeed incompetent often enough to affect the radiographic features seen in obstructed large bowel. In 1950, Fleischner and Bernstein stated that they were able to reflux barium into the terminal ileum in 90% of the barium enemas they performed. I9 Buirge believed that the shortness of the lips of the ileocecal valve accounts for its incompetence and reported significant anatomic variations indicating an incompetent valve mechanism in 46% of autopsied cases.8 Rendleman et al. performed barium enema examinations on 25 patients and recorded the pressures necessary to overcome valve resistance by means of a U tube water manometer connected by a Y tube to the enema tubing. 32 Measurements of the pressure required for the ileocecal valve to reflux revealed a wide variation. Readings ranged from 10 cm to 97 cm water pressure with an average of 36.6 cm water pressure. Five of the ileocecal valves tested had a reflux pressure of 20 cm water or lower. Dennis determined the intraluminal pressure in 34 cases of large bowel obstruction at the site of transverse colostomy and found that the average pressure was 14 cm and the highest pressure 34 cm of water. I4 Thus we can infer that sufficient pressure builds up in colon obstruction to overcome the resistance of the ileocecal valve in a certain percentage of patients. Further proof of work hypertrophy of the colon was shown by Guis as he noted hyper-