Pyelocalyceal diverticula containing milk of calcium--CT diagnosis

To present the computed tomography (CT) findings of pyelocalyceal diverticula containing milk of calcium in seven patients.

Three patients were examined because of flank pain, one because a malignant lesion was suspected and the three others were examined for unrelated symptoms. Three repeated scans to the kidney area were performed in every patient: an unenhanced scan, post-contrast scan and a delayed scan.

Unenhanced scans demonstrated an intraparenchymal round lesion with calcific material localized either at the inferior border or filling almost the entire cavity. On post-contrast scans a contrast-fluid level appeared, with some enhancement of the clear fluid in the upper part of the cyst. A further rise in the contrast-fluid level or total opacification with a density identical to that of the collecting system was obtained on delayed scans.

Pyelocalyceal diverticula containing milk of calcium present on CT as a partially calcified renal mass. Slight opacification soon after injection may be mistaken for enhancement arousing suspicion of a tumour. However, a delayed scan will demonstrate a densely opacified cyst filled with contrast from the collecting system which is virtually pathognomonic of the lesion.