Teaching Case

A 57-year-old woman presented at our department with intermittent abdominal pain for a few months. No pathologic finding was detected in her physical and laboratory examinations.

A radio opacity with lobulated contour measuring 4x3.5 cm in size was observed in the right upper quadrant of the abdomen in abdominal plain radiograph [Figure-1]. Ultrasonography showed a right upper pole cystic lesion with echogenic debris layering at the dependent part causing shadowing [Figure-2]. Contrast enhanced CT scan revealed a cyst with layering milk of calcium with a horizontal upper edge [Figure-3A-C]. The patient was followed conservatively.

Renal milk of calcium is a very rare condition in which fine calcific sediment is contained in a pyelogenic cyst or dilated collecting system [1]. Characteristic ‘half moon ‘ contour occurs due to the calcific suspension layers at the bottom, beneath the cyst fluid or urine because of gravity [2]. The radiological findings of this condition are an intrarenal opacity showing changes of shape due to patient’s position and layering at the dependent part. It is a clinically important entity because it may be misinterpreted as renal calculus for which various interventions may be performed unnecessarily [3]. The differential diagnosis includes gallbladder stones and adrenal mass on the plain radiography. The US is vital and localizes the organ, here the fluid-fluid level is the key and when this clear, CT may be avoided, especially in young. The entity of milk of calcium is not SO rare, not least because it is often misdiagnosed as stones. The most important differential is stones layering out in a caliceal diverticulum, and sometimes, for small cysts CT prone and supine with prone study done urographic phase post contrast is required to see if there is communication with the collecting system. This is important when the patient presents with recurrent urinary infections and a caliceal diverticulum stone would be considered for treatment [1-4].