Volume related configurational changes in the aetiology of pelvi-ureteric junction obstruction

The aetiology of pelivi-ureteric junction (PUJ) obstruction is controversial. We present four patients who had normal or equivocal intravenous pyelograms and non-obstructive Whitaker tests in whom complete pelvi-ureteric obstruction was precipitated by more rapid distension of the renal pelvis. We speculate that in vivo physiological urine flow rates and temporary kinking of PUJ produces a critical increase in pelvic volume and subsequent valvular kinking of the upper ureter, which cannot be usually achieved by maximal urine flow rates alone. Co-existence of vesico-ureteric reflux (VUR) may be a contributory factor to critical pelvic distension and tortuous PUJ. Volume related configurational changes of this type are probably a more frequent cause of PUJ obstruction than is generally recognised.