Side-to-side and interpolar renal duplications: the nonpolar variety.

The Weigert-Meyer rule predicts the draining pattern of duplex ureters in bipolar renal duplications. This paper introduces two cases of nonpolar renal duplication. A 3-month-old and a 15-year-old female with history of urinary tract infection were evaluated with intravenous pyelograms (IVP) and eleven different parameters were analyzed. The infant's IVP showed an unobstructed side-to-side right renal duplication with normal-sized nondisplaced lateral moiety and a complete set of calyces, without drooping lily sign. The nonobstructed moiety projected medial and mildly inferior to the lateral moiety which had normal height and axis. The ureters joined each other in lower abdomen. Severe platyspondyly was noted due to hyperalimentation-induced metabolic bone disease. The second case had an unobstructed interpolar extra moiety between the upper and the lower poles with an otherwise unobstructed, normally sized single-system kidney, without drooping lily sign. The paradigm shift from classic anatomic to contemporary cell biological theory validates the nonpolar renal duplication concept, with side-to-side and interpolar arrangements of the moieties, in defiance of Weigert-Meyer rule.