Observations on the Dynamics of Acute Urinary Retention in the Dog

Abstract

The dynamics of acute urinary retention were studied in a group of mongrel dogs, which were anesthetized with Na pentothal. A method is presented which enables one simultaneously to determine the pressures which obtain in different parts of the urinary tract under varying conditions. During acute urinary retention the pressure within the dog''s bladder increases to a peak and then progressively decreases although the volume of the bladder is constantly increasing. Exogenous filling of a dog''s bladder at a slow, constant rate results in abnormally high bladder pressure with resultant extravasation of urine into the peritoneal cavity without a gross disturbance of bladder continuity, after which the bladder pressure decreases as it does in the normal bladder. Urinary output decreases as intranephric pressure increases during acute urinary retention, which could account for the normally low peak bladder pressures which occur during acute urinary retention. Another explanation lor the oliguria may be that it is caused reflexly as a result of distention of the bladder. Rapid distention of a dog''s bladder at a rate of 19 cc./min. to a total of 500 cc. results in extravasation of a portion of the distending fluid into the peritoneal cavity although no gross break in bladder continuity is observed. Blood-tinged free peritoneal fluid is produced in every case of prolonged acute urinary retention. A method is given for experimentally producing a fibrotic urinary bladder which is of some exptl. interest especially in the detn. of the secretory pressure of the kidney. Acute urinary retention of great degree causes submucosal hemorrhages and thromboses with the formation of blood-tinged urine. The dome of the bladder appears to be the site of predilection for these hemorrhagic phenomena. In every case of acute urinary retention within 24-36 hrs. bilateral hydroureter, hydropelvis and moderate hydrocalyx develop In these dogs no instance was encountered at any level of pressure at which there was evidence of incompetency of the ureterovesical junction. Attempts to arrive at an effective modulus of stretch for smooth muscle of the bladder, or the bladder as a whole cannot be used reliably in physiological work since the rate of distention is a determining factor in the type of curve produced. The secretory pressure of the dog''s kidney is approx. 126 cm. of water.