Unilateral renal agenesis and other causes of the solitary photopenic renal fossa.

The differential diagnosis of a solitary photopenic defect in the renal fossa observed at renal scintigraphy is extensive. A case of one of the most unusual causes for this finding, renal agenesis, is presented. Additional cases that illustrate the similarity in the radionuclide appearance of other pathologic entities are also presented. Correlation with clinical findings and other imaging modalities is required to accurately distinguish these conditions.