Renal diseases described in ferrets include renal cysts, acquired hydronephrosis (a condition that typically occurs when one kidney becomes swollen due to the failure of normal drainage of urine from the kidney to the bladder), pyelonephritis ( a sudden and severe kidney infection), renal calculi (stones), chronic interstitial nephritis ( a kidney condition characterized by swelling in between the kidney tubules), toxic nephropathy (adverse functional or structural changes in the kidney due to the effect of a chemical or biological product that is inhaled, ingested, injected, or otherwise absorbed, or that yields toxic metabolites), immune complex glomerulonephritis (acute inflammation of the kidney) and tumors.
Renal cysts may be one or more in number and affect one or both kidneys. Often cysts do not cause a problem for the ferret and will go undetected until found during routine physical examination. Cysts do cause a problem when a significant amount of the renal structure is disruptured by the size of the cysts. Signs among ferrets with primary polycystic disease include weight loss, decreased appetite, lethargy/weakness, increased thirst and urination, difficulty or discomfort in swallowing, diarrhea, melena (dark sticky feces containing partly digested blood), vomiting, ptyalism (excessive salivation), seizure and trembling. There is no treatment for bilateral cystic disease. If one kidney is compromised, it can be removed. Those ferrets that show no ill effects from polycistic disease do not require medical or surgical intervention.