What are the possible causes of anuria in patients, including those with underlying kidney disease or other comorbidities?

Causes of Anuria

Anuria results from three main categories: prerenal (impaired renal perfusion), intrinsic renal (parenchymal damage), and postrenal (urinary tract obstruction), with prerenal and intrinsic renal causes accounting for over 97% of cases. 1

Prerenal Causes (Impaired Renal Perfusion)

Prerenal factors represent the most common reversible cause of anuria and result from inadequate blood flow to the kidneys:

• Hypovolemia from dehydration, hemorrhage, or excessive fluid losses (vomiting, diarrhea) 1, 2
• Hypotension from any cause, including septic shock or cardiogenic shock 1
• Decreased cardiac output from congestive heart failure or acute myocardial infarction 1
• Renal artery occlusion (bilateral or to a solitary kidney) from thrombosis or embolism 1, 3
• Volume depletion is particularly common in elderly patients due to age-related impairment in sodium and water conservation 2

Intrinsic Renal Causes (Parenchymal Damage)

Intrinsic renal disease damages the kidney parenchyma directly and includes:

Acute Tubular Necrosis (ATN)

• Ischemic ATN from prolonged prerenal insult, particularly in elderly patients with perinatal hypoxia in neonates 1, 4
• Nephrotoxic ATN from aminoglycosides (which cause excessive accumulation of myeloid bodies in tubules), contrast agents, or other toxins 1, 2

Glomerular Disease

• Rapidly progressive glomerulonephritis presenting with heavy proteinuria and active urinary sediment 1, 2
• Vasculitis affecting renal vessels 1
• Hemolytic uremic syndrome, which is the most common cause of anuria in older children 4

Acute Interstitial Nephritis (AIN)

• NSAID-induced AIN, which may present with heavy proteinuria or nephrotic syndrome (distinguishing it from other drug-induced AIN) 2
• Antibiotic-induced AIN (especially semisynthetic penicillins and ciprofloxacin), typically accompanied by fever, peripheral eosinophilia, and eosinophiluria 2

Other Intrinsic Causes

• Renal infiltration from malignancy or infection 1
• Drug toxicity from various nephrotoxic medications 1, 5

Postrenal Causes (Urinary Tract Obstruction)

Obstructive uropathy accounts for less than 3% of anuria cases but is completely reversible if identified promptly: 1

• Bilateral ureteral obstruction or obstruction of a solitary kidney 1
• Bladder outlet obstruction from benign prostatic hypertrophy (common in elderly men) 1, 2
• Urethral obstruction from strictures or blood clots 1

Note: Obstructive uropathy appears uncommon as a cause of anuria in infants and children 4

High-Risk Populations and Predisposing Factors

Certain patient populations face elevated risk for developing anuria:

• Elderly patients with impaired sodium/water conservation and increased susceptibility to volume depletion 2
• Patients with pre-existing chronic kidney disease who are at higher risk for acute kidney injury 1
• Diabetic patients who have higher prevalence of acute kidney injury regardless of baseline kidney function 1
• Patients with congestive heart failure, chronic liver disease, or diabetic nephropathy who are more susceptible to NSAID-induced acute renal failure 2
• Patients on multiple nephrotoxic medications including diuretics, ACE inhibitors, ARBs, NSAIDs, or aminoglycosides 1, 5
• Peritoneal dialysis patients with higher daily glucose exposure, lower baseline urine volume, and lower serum albumin 6

Rare Causes

Uncommon etiologies that should be considered in specific clinical contexts:

• Reflex anuria from irritation or trauma to one kidney/ureter or severely painful stimuli to nearby organs during urogenital or gynecological surgery 7

Critical Diagnostic Distinctions

Distinguishing between prerenal and intrinsic renal causes is essential for appropriate management:

• Fractional excretion of sodium and urine:plasma creatinine ratio reliably distinguish prerenal acute renal failure from ATN, though these indices become unreliable once prerenal failure has progressed to ATN 2
• Prompt response to fluid challenge (increased urine output, increased urinary sodium excretion, rapid decrease in blood urea nitrogen) constitutes strong evidence for prerenal acute renal failure 2
• Ultrasound of kidneys and bladder should be performed in all cases to rule out obstruction, especially in elderly men; normal ultrasound findings after 48+ hours of oliguria/anuria make obstruction very unlikely 2