Postrenal: Differential

• • Tubular Obstruction: from crystals (eg, uric acid, calcium oxalate, acyclovir, sulfonamide, methotrexate, myeloma light chains)
  • Ureteral Obstruction - Retroperitoneal tumor, retroperitoneal fibrosis (methysergide, propranolol, hydralazine), urolithiasis, papillary necrosis
  • Urethral Obstruction - Benign prostatic hypertrophy; prostate, cervical, bladder, colorectal carcinoma; bladder hematoma; bladder stone; obstructed Foley catheter; neurogenic bladder; stricture