Abnormal urine cytology Cylindruria 2014-01-17T12:03:19Z Urinary casts are formed in the distal convoluted tubule or the collecting duct by solidification of protein in the lumen of the kidney tubules. The casts are suibsequently eliminated via the urine and may be seen by microscopy of the urine sediment. A large number of casts can indicate kidney disease. Urinary casts are composed of Tamm-Horsfall protein, which is a mucoprotein that is secreted by the distal loop of Henle. SNOMEDCT_US:5277004 HP:0012615 Urinary casts The presence of renal casts (cylindrical, cigar-shaped structures produced by the kidney in certain disease states) in the urine. UMLS:C0151990