Tapered intraluminal versus imbricated extraluminal valve: Comparison of two continence mechanisms for urinary diversion

One of the major limitations of continent intestinal reservoirs currently in use is failure of the efferent continence mechanisms. Unsatisfactory results have been reported in the literature in up to 40% of cases. While progress has been made toward better continence in urinary diversions, evolution of the actual continence mechanisms has been along two rather distinct paths: those with a valve mechanism placed inside the pouch (either by intussusception or surgical insertion), and those with the valve outside to the pouch (by imbrication of an externally located ileal segment). A canine experimental model was used to investigate a type of intraluminal continence mechanism and to compare it to an extraluminal imbricated ileocecal valve. In eight mongrel dogs a reservoir was made out of ascending and transverse colon with two different valve mechanisms - one intraluminal and one extraluminal - connected via separate stomas to the skin. Radiographic, sonographic, endoscopic and urodynamic studies of the pouch and its outlets were performed. Results showed that, in contrast to the extraluminal valve, continence in the intraluminal valve was volume dependent. The valve closing pressure of the intraluminal continence mechanism increased far beyond the values of the extraluminal valve (50.38 vs. 30.12 cm. H₂O) at maximum pouch filling. Leakage of the intraluminal valve was observed at significantly higher pouch volumes than in the extraluminal valve (348 cc vs. 215 cc). In view of these results, the volume dependent intraluminal valve mechanism appears superior to an extraluminal type, especially at higher pouch volumes.