What is the most common cause of Acute Kidney Injury (AKI) in hospitalized patients?

Most Common Cause of AKI in Hospitalized Patients

Prerenal AKI (decreased renal perfusion) is the most common cause of acute kidney injury in hospitalized patients, accounting for more than 60% of all cases. 1, 2

Specific Context: General Hospitalized Patients vs. Cirrhosis

The etiology varies significantly based on the patient population:

In General Hospitalized Patients

• Prerenal causes dominate at >60% of cases, resulting from decreased renal perfusion without initial structural kidney damage 1, 2
• Intrarenal causes (primarily acute tubular necrosis) account for approximately 35% of cases 1
• Postrenal obstruction represents <3% of hospitalized AKI cases 1

In Hospitalized Patients with Decompensated Cirrhosis

• Prerenal AKI accounts for approximately 68% of cases in this specific population 3
• The most common precipitating factors include infections (particularly spontaneous bacterial peritonitis), diuretic-induced excessive diuresis, GI bleeding, therapeutic paracentesis without adequate volume expansion, and nephrotoxic drugs 3

Key Precipitating Factors Across All Hospitalized Patients

Volume depletion mechanisms:

• Hemorrhage, gastrointestinal losses, burns, or excessive diuresis causing absolute volume depletion 1, 2
• Third-space fluid sequestration in pancreatitis or peritonitis 1, 2
• Severe hypoalbuminemia from nephrotic syndrome 1, 2

Hemodynamic compromise:

• Decreased cardiac output from heart failure, cardiogenic shock, or arrhythmias 1, 2
• Systemic vasodilation from sepsis, anaphylaxis, or cirrhosis 1, 2

Medication-related causes (critical contributor):

• Drugs account for 20% of community-acquired AKI requiring hospitalization and approximately 25% of ICU-acquired AKI 3
• The "triple whammy" combination of NSAIDs, diuretics, and ACE inhibitors/ARBs dramatically increases risk through combined hemodynamic effects 1, 2
• Each additional nephrotoxin increases AKI odds by 53%, and receiving three or more nephrotoxins more than doubles the risk 1

Common Pitfalls in Diagnosis

Do not assume all creatinine elevations represent AKI:

• Creatinine increases up to 30% from baseline with RAS blockers should NOT be confused with AKI and do not require discontinuation in the absence of volume depletion 2

In cirrhotic patients, standard diagnostic tools have limitations:

• Fractional excretion of sodium (FENa) <1% has 100% sensitivity but only 14% specificity for prerenal causes in cirrhosis 3, 1
• Fractional excretion of urea (FEUrea) <28.16% may better discriminate hepatorenal syndrome from ATN (75% sensitivity, 83% specificity) 3, 1

Immediate Management Priorities

Regardless of suspected etiology, initiate these steps immediately:

• Discontinue all diuretics irrespective of AKI stage 3, 2
• Stop nephrotoxic medications including NSAIDs, vasodilators, and potentially beta-blockers 3, 2
• Screen for and treat infections immediately, as infection is the most common precipitant of hepatorenal syndrome 3
• Administer fluid challenge with albumin at 1 g/kg (maximum 100 g/day) to differentiate prerenal from intrinsic causes 3, 1

Volume replacement should match the cause:

• Crystalloids for diarrhea or excessive diuresis 3
• Packed red blood cells for acute GI bleeding to maintain hemoglobin 7-9 g/dL 3
• Albumin infusion for therapeutic paracentesis in patients with tense ascites 3

Response to volume expansion is diagnostic:

• Hypovolemic (prerenal) AKI should show reduction in serum creatinine to within 0.3 mg/dL of baseline 3
• Patients with hepatorenal syndrome-AKI have bland urine microscopy but do not respond to fluid challenge alone 3