[Ultrasonography in the diagnosis of acute obstructive renal insufficiency: a cautionary note]

Ultrasonography (US) has recently been considered in nephrology as the imaging method of choice in the differential diagnosis of acute renal failure (ARF). A dilated renal collecting system is the hallmark of obstructive nephropathy (ON). We report 4 cases of ARF due to ON in which US detected no dilatation of collecting system. Similar data were obtained by computer tomography (TC). The normal size and structure of the kidneys and the clinical suspicion prompted us to perform retrograde pyelography which revealed ON. Ureteral catheterization determined a marked improvement of renal function in all the patients (pts). 2 pts were one kidney, 3 pts had renal stones, in 2 pts dehydration and sepsis were present. We conclude that ON has not ever been excluded on the criterion of absence of dilated urinary tract from US and TC.