Any of several types of cysts in the kidneys .
Some are present at birth; others are caused by tubular obstruction. Large cysts can cause backaches and a dragging sensation. Multiple cysts occur as a result of various disorders, including kidney vascular diseases, lymphatic vessel blockage, congenital diseases, and tapeworm infestation. The most serious is medullary cystic disease, which has no warning symptoms but causes anemia , low blood sodium levels, and uremia . The kidneys become shrunken, grainy, and scarred. Cysts should usually be checked surgically to rule out cancer. See also urogenital malformation .