Urinary Stones -------------- Urinary stones, either within the kidneys or urinary bladder, may cause serious problems in ferrets. Both sexes seem to be affected equally. Signs of urinary stones include blood in the urine, inability to urinate, a swollen and painful abdomen, vomiting, listlessness and inappetence. Surgery is usually necessary to correct this problem, though a special diet may eliminate certain types of stones or prevent recurrence.