Wilms' tumour in a horseshoe kidney. Diagnostic difficulties.

A case of Wilms' tumour in a horseshoe kidney is presented. Until 1980, twenty-one cases were reported. Diagnosis may be difficult, especially as x-ray investigations, including IVP and renal angiograms, give the impression of a tumour arising outside the kidney. The distortion and dispersion of the renal pelvis and calyces usually seen with a Wilms' tumour are lacking. This is probably due to the special anatomic pattern of the horseshoe kidney, specifically the rotation of the renal pelvis around the long axis of the kidney.