Critical Evaluation of Acute Ureteral Dilatation: Clinical and Experimental Study*

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Abstract
The present work was designed to investigate the effect of acute dilatation of the intramural ureter on renoureteral integrity. This was done in 20 patients who underwent successful ureteroscopy for stone retrieval after acute ureteral dilatation. Acute dilatation of the intramural ureter on one side was similarly induced in 30 adult male rabbits, with prior ureteral meatotomy in 10 of them. Evaluation over 4 weeks was done by serial intravenous urography, ascending cystography, and DTPA renography as well as by histopathologic examination of the animals after their sacrifice. In humans, transient renal colic and ureteral stasis and dilatation down to the intramural segment was noted in the first postoperative week. In experimental animals, the group undergoing ureteral dilatation showed renoureteral obstruction and dilatation for 3 days to 1 week after the procedure. Histologically, the ureterovesical segment showed disruption of muscles with acute inflammatory changes and ulcerated mucosa. These changes resolved within 2 to 3 weeks. Nevertheless, evident muscle damage and replacement fibrosis of the intramural part of the ureter were noted. In the group with meatotomy prior to dilatation, meatotomy did not prevent these ureteral changes, although it minimized the ill effects. It is concluded that the apparently uncomplicated acute dilatation of the intramural ureter to two to three times its original caliber, as is routinely done during ureteroscopy, is not without risk to the integrity of the ureter itself. The procedure can cause disruption of the intramural ureter and possible damage to its muscle with replacement fibrosis. Prior meatotomy of the intramural ureter could minimize, but does not prevent, these complications.