There are two aspects of the pelvic function that will be discussed next

*Urodynamic Events: Patterns of Urine Exit*
There are two aspects of the pelvic function that will be discussed next. Following each description a tentative interpretation of the physiological significance of these phenomena will be presented. First, we will show what happens to the urine after it leaves the ducts of Bellini at the tips of the papilla. Secondly, we will show how the papilla is milked by the pelvic wall and the effect that this has on the papilla and its fluid compartments.	Urine Exit
Urine leaving the ducts of Bellini at the tip of the papilla will generally flow directly down the ureter following each contraction. Occasionally however, it fans out around the tip of the papilla, briefly bathing the lower 50 m with urine. This pattern, which we call *tip refluxes*, is seen during constant or decreasing urine flow.	Tip Refluxes
When the urine flow rate is rapidly increasing, however, a different flow pattern is seen. The urine no longer flows directly down the ureter as it leaves the ducts of Bellini. Instead, the urine is swept up into the pelvis where it reaches all the fornices and secondary pouches. During the next contraction, the urine is swept down over the papilla and enters the ureter. This pattern we call full pelvic refluxes. Full pelvic refluxes can also be induced by lifting the ureter about one centimeter or by mechanical stimulation of the ureter. In this case, the urine refluxes from the ureter into the pelvis following each peristaltic contraction of the pelvic wall. During full pelvic reflux, when the urine reaches all the pelvic extensions, it contacts the thin epithelium covering the outer medulla.	Full Pelvic Refluxes
Full pelvic refluxes do not actually occur during decreasing or constant urine flow. They are physiologically induced when the rate of urine flow increases faster than 0.05 m l/min². They continue for several minutes after the flow rate is no longer increasing. During rising urine flow, the osmolality of the urine is decreasing. The urine being swept up into the pelvic extensions has a lower osmolality than the papillary tissue. It has been shown that full pelvic refluxes, under these circumstances, serve to reduce the osmolality and urea concentration of the renal medulla. Thus pelvic refluxes may serve to shorten the time it takes for a water diuresis to develop following a large intake of water. This may be particularly useful for desert animals that drink large amounts of water periodically, and therefore have to be able to dilute the urine promptly to avoid water intoxication	Full pelvic refluxes