Increased intra-abdominal pressure results in both obstructive and nonobstructive types of impairments of renal pelvic excretion

An experimental study has been conducted to evaluate the effects of increased intra-abdominal pressure (IAP) on the excretion function from renal pelvis into the ureter. Methods: Sixteen adult male New Zealand rabbits were randomly allocated in two groups after obtaining basal scintigraphies. Group I consisted of 8 rabbits which were subjected to an increased IAP for ten day period. In Group II an other 8 rabbits were subjected to an increased IAP for 60 day period. At the end of the periods of increased IAP the post-pressure scintigraphic evaluations of both groups were carried out. Time to maximum activity (T_max), T_1/2 and T_2/3 values of the radiopharmaceutical in the kidneys and down slope parameters (DS_1/2, DS_2/3) were calculated from the renogram curves of both right and left kidneys. Comparison of basal and post-pressure scintigrapies and the mean difference of the renogram parameters between groups were performed. Results: All basal scintigraphies were normal. Post-pressure scintigraphies revealed an obvious delay in the excretion phase in both groups. Both kidneys of a rabbit in group I revealed a non-obstructive pattern through responding well to administration of diuretic. Furthermore both kidneys of a rabbit from group II have revealed an obstructive pattern. T_1/2 and T_2/3 values were significantly elevated and mean DS_1/2, DS_2/3 were significantly decreased in post-pressure scintigraphies of the both groups without revealing a statistically significant difference between groups I and II. The mean difference of T_max was significantly increased in group II. Conclusion: The increases in IAP, through the compressive effect upon ureters together with a concomitant increase in intravesical pressure, may impair the passage of urine from renal pelvis into ureter. The impaired passage may play a role in the development of hydronephrosis which may either reveal a nonobstructive and/or obstructive pattern.