Characteristics of ureteral bolus in diabetic rats

Changes in the dynamics of the ureteral bolus in diabetics was investigated by using videomicroscopic imaging. Diabetes mellitus (DM) was induced in 8-week-old male rats by the administration of streptozotocin. The pressure of the renal pelvis (via nephrostomy) and visualization of the dynamics of the ureteral bolus were recorded in three groups (DM, sucrose-fed, and control) 8 weeks after administration. Peristaltic velocity, frequency and bolus length were analyzed on the basis of image processing using indigo carmine dissolved in a saline solution. This was perfused via the nephrostomy. The dilated ureters were macroscopically observed in all diabetic rats. There were significant decreases in the velocity of the bolus in diabetics (4.3+/-0.8 mm/s) compared to sucrose-diuretic (11.0+/-3.2 mm/s) and control (8.3+/-1.4 mm/s) rats. In addition, the length of the bolus in diabetics (9.3+/-1.4 mm) was about twofold longer than those of control rats (4.2+/-0.6 mm). There were also significant decreases in the frequency of renal pelvis contraction in diabetics (19.5+/-1.9 min(-1)) compared to sucrose-diuretic (25.3+/-1.0 min(-1)) and control (29.0+/-2.3 min(-1)) rats. These results indicate that the decrease in the velocity of the bolus and the frequency of renal pelvis contraction result in the disability of urine transport in the upper urinary tract in DM although the volume per bolus increases. Besides hyperglycemia, these changes may predispose diabetics to upper urinary tract infections such as pyelonephritis.