What are the causes of oliguria?

Causes of Oliguria

Oliguria results from three broad pathophysiologic categories: pre-renal (inadequate renal perfusion), intrinsic renal (kidney parenchymal injury), and post-renal (urinary tract obstruction), with pre-renal causes being the most common and reversible if identified early. 1

Pre-Renal Causes (Inadequate Renal Perfusion)

Pre-renal oliguria represents an appropriate physiologic response to decreased effective circulating volume or renal blood flow rather than true kidney injury. 2

Hypovolemia

• Hemorrhage (trauma, gastrointestinal bleeding, surgical blood loss) 2
• Gastrointestinal losses (vomiting, diarrhea, nasogastric suction) 3
• Renal losses (diuretic overuse, osmotic diuresis, diabetes insipidus) 3
• Third-spacing (burns, pancreatitis, sepsis, hypoalbuminemia) 3
• Inadequate fluid intake with ongoing insensible losses 3

Decreased Cardiac Output

• Cardiogenic shock following myocardial infarction 4
• Refractory congestive heart failure with chronic cardiac decompensation 4
• Cardiac tamponade or massive pulmonary embolism 3
• Severe arrhythmias compromising cardiac output 3

Systemic Vasodilation

• Septic shock with distributive physiology despite adequate volume 4
• Anaphylaxis with profound vasodilation 3
• Neurogenic shock following spinal cord injury 3

Renal Vasoconstriction

• Hepatorenal syndrome in advanced liver disease 3
• Medications (NSAIDs, ACE inhibitors, ARBs, calcineurin inhibitors) 5
• Hypercalcemia causing renal vasoconstriction 2

Intrinsic Renal Causes (Kidney Parenchymal Injury)

Acute Tubular Necrosis (Most Common Intrinsic Cause)

• Ischemic ATN from prolonged pre-renal state or severe hypotension 6
• Nephrotoxic ATN from medications (aminoglycosides, amphotericin B, contrast agents, cisplatin) 5
• Pigment nephropathy (rhabdomyolysis with myoglobin, hemolysis with hemoglobin) 2

Acute Interstitial Nephritis

• Drug-induced AIN (antibiotics, NSAIDs, proton pump inhibitors, diuretics) 5
• Infection-related AIN (pyelonephritis, viral infections) 5
• Autoimmune disorders (lupus, Sjögren's syndrome) 5

Glomerular Disease

• Rapidly progressive glomerulonephritis (ANCA-associated, anti-GBM disease, immune complex) 5
• Severe pre-eclampsia/HELLP syndrome with glomerular endotheliosis 2

Vascular Causes

• Renal artery thrombosis or embolism 3
• Renal vein thrombosis 3
• Thrombotic microangiopathy (HUS, TTP) 5
• Atheroembolic disease following vascular procedures 5

Crystal Nephropathy

• Uric acid crystallization in tumor lysis syndrome causing acute oliguric renal failure 2
• Calcium phosphate deposition in the renal interstitium and tubules with hyperphosphatemia 2
• Oxalate crystals (ethylene glycol toxicity) 5
• Drug crystals (acyclovir, methotrexate, sulfonamides) 5

Post-Renal Causes (Urinary Tract Obstruction)

Post-renal oliguria requires bilateral obstruction (or unilateral in a solitary kidney) to manifest. 3

Upper Urinary Tract Obstruction

• Bilateral ureteral obstruction from retroperitoneal fibrosis, malignancy, or stones 3
• Obstructive uropathy contraindicated for diuretic use 2

Lower Urinary Tract Obstruction

• Bladder outlet obstruction (benign prostatic hyperplasia, prostate cancer, urethral stricture) 3
• Neurogenic bladder with urinary retention 3
• Blocked urinary catheter (must be excluded first when assessing oliguria) 3

Special Clinical Contexts

Perioperative Oliguria

• Inadequate volume resuscitation during surgery 2
• Excessive blood loss requiring transfusion 2
• Anesthetic effects on renal perfusion 2

Critical Illness

• Sepsis-induced AKI with combined pre-renal and intrinsic components 4
• Multi-organ dysfunction in ICU patients 7
• Abdominal compartment syndrome causing renal vein compression 3

Obstetric Causes

• Severe pre-eclampsia progressing to acute tubular necrosis or cortical necrosis 2
• HELLP syndrome with hemolysis, elevated liver enzymes, and thrombocytopenia 2
• Postpartum hemorrhage with hypovolemic shock 2

Important Clinical Caveats

Duration matters more than presence alone: Transient oliguria (<48 hours) has significantly lower mortality than prolonged or permanent oliguria, with transient oliguria patients actually having better outcomes than non-oliguric patients. 7 However, oliguria persisting beyond 12 hours or occurring in 3 or more episodes is associated with increased mortality. 8

Oliguria may be appropriate: Not all oliguria represents kidney injury—it can be a normal physiologic response to volume depletion requiring resuscitation rather than indicating AKI. 2 This distinction is critical for appropriate management.

Weight-based calculations are problematic in obesity: The standard definition of <0.5 mL/kg/hour becomes unreliable in obese patients due to the nonlinear relationship between body weight and expected urine output; consider using adjusted body weight. 2, 1

Diuretics confound interpretation: Loop diuretics can increase urine output without improving kidney function, potentially masking true oliguria or falsely suggesting improvement. 2 Avoid using diuretics to "treat" oliguria without first addressing the underlying cause.