Which of the following is pathognomonic of renal disease -

Casts are cylindrical structures composed mainly of mucoprotein (the Tamm-Horsfall mucoprotein) which is secreted by epithelial cells lining the loops of Henle, the distal tubules and the collecting ducts. The factors responsible for the precipitation of this mucoprotein are not fully understood, but may relate to the concentration and pH of urine in these areas. Casts may form in the presence or absence of cells in the tubular lumen. If cells (epithelial cells, WBC) are present as a cast forms, they may adhere to, and subsequently be surrounded by, the fibrillar protein network. ref Harrison20th edition 2212