Kidney - Cyst

A variety of renal cysts can be seen in rodent kidneys. Cysts may be congenital, acquired, or associated with chronic progressive nephropathy or chemical administration and may be noted as isolated findings in the absence of other renal pathology (Figure 1 and Figure 2). They can be solitary or multiple and can occur anywhere in the renal parenchyma, cortex, medulla, or papilla. Cysts can arise from tubules or glomeruli (Figure 3). Some cysts may arise from progressive dilation, whereas others have been postulated to arise from tubules undergoing epithelial cell proliferation. Most cysts are lined by flattened to cuboidal epithelium and appear empty or may contain eosinophilic or amphophilic homogeneous fluid. Larger cysts may be associated with pericystic and/or tubulointerstitial inflammation and fibrosis. Cysts may arise from chemical administration (Figure 4). Hereditary conditions manifesting as polycystic kidneys have been reported in rats and mice (Figure 5).