Objective: To obtain a new insight into the anti-reflux mechanism of the ureterovesical junction by studying the topographical anatomy of the juxta- and intravesical ureter and its relationship to the surrounding bladder musculature.
Materials and methods: Fresh pig bladders were fixed, frozen and serially sectioned. Enzyme histochemistry was performed to demonstrate tissue acetyl- and butyryl- (non-specific) cholinesterase. Smooth muscle cells were identified by immunohistochemistry using a monoclonal anti-alpha actin smooth muscle antibody. Three-dimensional computer reconstructions of the different muscle groups of the bladder and ureterovesical junction were generated.
Results: On the basis of expression patterns of the cholinesterase isozymes, five different groups of muscles were identified: the detrusor, the muscularis mucosae of the bladder, the muscle layer of the intravesical ureter and the separate inner and outer muscular layers of the pelvic ureter.
Conclusion: No separate ureteric sheath was identified. There appeared to be few or no (muscular) connections between the ureter and the bladder musculature. The muscle layer of the ureter ended beneath the mucosa of the bladder, without extension into the trigone. The submucosal section of the ureter was very short, although its length was thought to be of importance in the anti-reflux mechanism. Examination using enzyme histochemistry demonstrated a muscularis mucosae in the bladder which was absent from the trigone.