Hydronephrosis symptoms and clinical signs vary based upon an obstruction which is acute or chronic. It is even possible for unilateral hydronephrosis, which occurs in only one kidney, to exist without symptoms (asymptomatic).
Potential hydronephrosis symptoms include:
Acute urinary retention (may lead to hydronephrosis)
Creatinine imbalance (blood test)
Electrolyte imbalance (blood test)
Elevated pH (urinalysis)
Enlarged kidney (in complete obstruction) Flank pain
Kidney failure, a.k.a. renal failure (in chronic hydronephrosis)