To the Editor: The medical mystery in the January 2 issue1 involveda 55-year-old man with a history of recurrent flank pain thatwas due to renal stone disease. A metabolic evaluation led tothe discovery of distal renal tubular acidosis, and an abdominalradiograph (Figure 1) showed numerous calcifications with abizarre distribution on the left side. Retrograde pyelographicstudies (Figure 2) showed that the patient also had a malformationof the urinary tract called "crossed renal ectopy," with theright kidney in a transverse position in the left paramedianspace at the level of the L4 vertebra.
Figure 2. Retrograde Pyelographs of the Right (Panel A) and Left (Panel B) Collecting System, Showing Crossed Renal Ectopy.
The right kidney is in a transverse position in front of the L4 vertebra. The pelvis of each kidney is indicated by an arrow.
Paul Isenring, M.D., Ph.D. Gérald Guay, M.D. Hôtel-Dieu de Québec Quebec, QC G1R 2J6, Canada
Editor's note: We received 156 responses to this medical mystery;31 percent gave explanations that were consistent with the presenceof nephrocalcinosis with a range of renal calcifications. Otherresponses provided explanations that included both the renaland gastrointestinal organ systems affected by physiologicallycalcified conditions. Ingested foreign bodies were proposedas the explanation in 14 percent of responses.
References
Isenring P, Guay G. A medical mystery. N Engl J Med 2003;348:41-41. [Free Full Text]
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