Experimental hydronephrosis. An electrophysiologic investigation before and after release of obstruction.

Pelvi-ureteric function was studied in pigs with experimental urinary tract obstruction, and again, 5 weeks after relief of the obstruction. Study parameters comprised EMG records taken from pelvis and ureter, measurements of intrapelvic pressure and urine flow, and some supplementary studies of renal function. Total obstruction of 5 and 6 weeks duration induced by cuffing the proximal ureter occasioned severe hydronephrosis and renal failure. Pelvic peristaltic activity was of low frequency, and abnormality was clearly more marked after the longer period of obstruction. There was, for example, some preservation of pelvi-ureteric synergism at 5 weeks, but at 6 weeks ureteric activity was wholly autonomous. Pelvic function was similarly isolated, and non productive. Inspection 5 weeks after reconstruction by pelvis resection and neo-anastomosis of the ureter showed continued absence of renal function and no restitution of normal peristaltic patterns. Partial obstruction, effected by implantation of the ureter in the psoas muscle, induced mild pelvic dilatation and impaired renal function, but there were only minor signs of disruption of normal anterograde pelvi-ureteric activity - irregularities, pauses in activity, and double activity complexes. When the ureter was freed functional patterns returned to normal. Both during obstruction and after relief, pelvic pressure increases during forced diuresis were the equivalent of or lower than the pre-determined norm. Cautery at the pelvi-ureteric junction destroyed the musculature and induced a progressive (fibrous stenosis. There was progressive dissociation of pelvi-ureteric activity, total when obstruction was total in which case ureteric activity was only autonomous, and partial when obstruction was partial in which case varying degrees of synergism and autonomous activity were seen. Successful reconstruction (pelvic resection and neo-anastomosis of the ureter) restored an apparent synergism in pelvi-ureteric function.