Failure

Postrenal Failure

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Postrenal Failure, Postrenal Azotemia, Acute Postrenal Failure, Hydronephrosis, Urinary Tract Obstruction, Postrenal Obstruction, Urinary Outflow Obstruction

  • Epidemiology
  1. Accounts for 1-10% of Acute Renal Failure cases
  2. More common in elderly
  • Pathophysiology
  1. Urinary Tract Obstruction
  2. Results in renal Pelvis dilatation
  3. Progressive decrease in Renal Function
    1. Increased intratubular pressure
    2. Decreased capillary filtration pressure
  • Symptoms
  1. Abdomen or Groin Pain (colic-type attacks)
  • Signs
  1. Mass at flank, suprapubic, or central Abdomen
  2. Abdominal exam
  3. Pelvic exam
  4. Rectal exam
  5. Anuria (Indicates obstruction in 90% cases)
  • Labs
  1. See Renal Function
  2. Urine Sediment
    1. Normal sediment
    2. Hematuria
    3. Pyuria
    4. Crystals
  • Diagnostic Testing
  1. Post-void residual >100 ml
    1. Indicates Bladder outlet obstruction
  2. Ultrasound or Intravenous Pyelogram
    1. Dilated ureters or renal Pelvis
  3. Abdominal CT or Abdominal MRI
  4. Percutaneous nephrostomy drainage trial
  • Management
  1. See Acute Kidney Injury Management
  2. Exclude reversible causes rapidly
  3. Renal Function recovery reflects obstruction duration