[Postrenal acute renal failure with deficient or minimal dilatation of the renal pelvis]

This article presents the clinical and radiological findings in three patients with acute obstructive renal failure. In a setting of typical clinical symptoms of acute postrenal obstruction, the lack of or only minimal ultrasonographic dilatation of the pelvicalyceal system should not lead to the conclusion that there is no obstruction until supplementary invasive procedures have demonstrated open urinary tracts. Minimal pelvic dilatation in acute obstructive renal failure is typically associated with malignant diseases encasing the distal parts of the ureters, retroperitoneal fibrosis, urinary calculi and urinary infections. Various pathophysiologic mechanisms are discussed.