[Recurrent renal colic with passing of horny lamellae. A rare differential diagnosis of renal calculi].

A 64-year-old man reported left-sided renal colics recurring regularly every 5-10 months for the past 25 years. After a typical colic urinary sediment was found to contain brownish, flaky elastic material which histologically consisted of nucleus-free keratoid lamellae. Calcium concentration in serum and urine was normal, as were the serum parathormone (215 pg/l) and inorganic phosphate levels. The intravenous pyelogram revealed a polycyclicly circumscribed filling defect (15 x 20 mm) in the left renal pelvis. At ureteroscopy a lamellar brown-grey tumour was identified which arose from the medial wall of the pelvis. Histological examination demonstrated hyper- and parakeratotic hornified squamous epithelium without malignant degeneration. This finding suggested a cholesteatoma originating from squamous epithelial metaplasia. The tumour was removed endoscopically and the renal wall coagulated by laser, a procedure repeated after 3 months. The patient has been free of symptoms for 3 years.