Renal obstruction in patients with ileal loops: US evaluation.

Ultrasound (US) is often employed as a screening test for hydronephrosis in the nondiverted kidney and has been used recently to evaluate the diverted kidney, specifically ileal loops, for obstruction. The utility of US in evaluating obstruction in patients with ileal loops has apparently not been previously explored. During a 2-year period, 87 kidneys drained by an ileal loop diversion were examined with US because of clinical indications of possible renal obstruction. In 33 kidneys, no hydronephrosis was seen on sonograms, and no obstruction was later proved; in 51 kidneys, shown by US to be hydronephrotic, only 19 (37%) were obstructed. Three left kidneys were not visualized with US. The percentage of hydronephrotic kidneys subsequently shown to be obstructed increased rapidly as the US appearance progressed from grade 1 (20%) to grade 3 (80%). In this series, US had a 100% sensitivity and a 50% specificity in evaluating patients with ileal loops for renal obstruction. Thus, for the adult patient, a direct contrast evaluation of the collecting system is suggested; for the pediatric patient, initial use of US is justified as a means to avoid radiation exposure.