Evaluation of intermittent drainage of the renal pelvis as seen in the isotope renogram.

Intermittent drainage (ID) of the renal pelvis is probably due to episodes of aperistalsis in the pelvo-calyceal system. The incidence of ID in adult patients referred for renography for various nephro-urological conditions was found to be 4.5%. Presence of ID was not related to sex or age but more common at a low urine flow. It was then usually bilateral and interpreted as a normal phenomenon. If the urine flow at the renographic examination exceeded 2 ml min-1, ID was typically unilateral and there was often a history of obstructive uropathy and dilatation of the renal pelvis. However, there were no signs of obstruction or flank pains in connection with the recording of ID and follow-up studies did not disclose any deterioration of renal function. It is concluded that ID seen at renography during diuresis should not be regarded as evidence of obstruction of pelvic outflow but merely as an indication of a dilated upper urinary tract.