What causes postrenal acute kidney injury (AKI)?

Updated: Dec 24, 2020
  • Author: Biruh T Workeneh, MD, PhD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Mechanical obstruction of the urinary collecting system, including the renal pelvis, ureters, bladder, or urethra, results in obstructive uropathy or postrenal AKI. Causes of obstruction include the following:

  • Stone disease
  • Stricture
  • Intraluminal, extraluminal, or intramural tumors
  • Thrombosis or compressive hematoma
  • Fibrosis

If the site of obstruction is unilateral, then a rise in the serum creatinine level may not be apparent, because of preserved function of the contralateral kidney. Nevertheless, even with unilateral obstruction a significant loss of GFR occurs, and patients with partial obstruction may develop progressive loss of GFR if the obstruction is not relieved.

Bilateral obstruction is usually a result of prostate enlargement or tumors in men and urologic or gynecologic tumors in women. Patients who develop anuria typically have obstruction at the level of the bladder or downstream to it.

To summarize, causes of postrenal AKI include the following:

  • Ureteric obstruction - Stone disease, tumor, fibrosis, ligation during pelvic surgery
  • Bladder neck obstruction - Benign prostatic hypertrophy (BPH), cancer of the prostate (CA prostate or prostatic CA), neurogenic bladder, tricyclic antidepressants, ganglion blockers, bladder tumor, stone disease, hemorrhage/clot
  • Urethral obstruction - Strictures, tumor, phimosis
  • Intra-abdominal hypertension - Tense ascites
  • Renal vein thrombosis

Diseases causing urinary obstruction from the level of the renal tubules to the urethra include the following:

  • 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, or papillary necrosis

  • Urethral obstruction - Benign prostatic hypertrophy; prostate, cervical, bladder, or colorectal carcinoma; bladder hematoma; bladder stone; obstructed Foley catheter; neurogenic bladder; stricture


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