Step 1: Rule-out Postrenal

• • History:
  • Postrenal failure usually occurs in older men with prostatic obstruction and symptoms of urgency, frequency, and hesitancy. Patients may present with asymptomatic high-grade urinary obstruction because of chronicity of their symptoms.
  • History of prior gynecologic surgery or carcinoma often can be helpful in providing clues to the level of obstruction.
  • Flank pain and hematuria should raise a concern about renal calculi or papillary necrosis as the source of urinary obstruction.
  • Use of acyclovir, methotrexate, triamterene, indinavir, or sulfonamides implies the possibility of tubular obstruction by crystals of these medications.