1. Pre-renal azotemia

Volume depletion (diuretics, poor intake, vomiting, diarrhea)

Vascular constriction (CNI toxicity, NSAID)

2. Intrinsic renal diseases

Arterial or venous stenosis, thrombosis or compression

ATN

Acute or accelerated acute rejection (cellular, humoral or both)

Pyelonephritis

Thrombotic microangiopathy (TMA)

Recurrent glomerular disease (FSGS, aHUS)

3. Post-renal obstruction

Foley catheter obstruction

Perinephris fluid collection (urine leak, hematoma, lymphocele)

Donor ureteral obstruction (kinking, stricture, blood clots)

Neurogenic bladder

Enlarged prostate (BPH, prostate cancer)