AQP2 in urine is reportedly a good marker for the effect of vasopressin on the renal collecting ducts, and many studies have measured the level of AQP2 in whole urine of patients with various diseases related to imbalance of water homeostasis, such as hypertension, DI, SIADH, heart failure, liver cirrhosis, and pregnancy. The gene discussed is AQP2; the disease is heart failure.