prérénal

Prérénal, or prerenal, refers to a type of acute kidney injury (AKI) caused by reduced renal perfusion without intrinsic damage to the kidney tissue. It is the most common cause of AKI in hospitalized patients and is often reversible if identified and treated promptly. The term prérénal is used in some languages as a direct translation of prerenal azotemia.

Causes of prérénal AKI include conditions that decrease effective blood volume or renal perfusion, such as dehydration and gastrointestinal losses, acute or chronic heart failure with low cardiac output, liver cirrhosis with portal hypertension and reduced effective arterial volume, sepsis or systemic inflammatory states, and renal artery stenosis or hypotension from drugs that lower blood pressure or renal perfusion.

Pathophysiology involves a drop in renal blood flow leading to a reduced glomerular filtration rate. The kidneys respond by activating the renin-angiotensin-aldosterone system, causing efferent arteriolar constriction and sodium and water reabsorption. If perfusion is restored promptly, tubular function remains intact and kidney function recovers. Prolonged hypoperfusion can lead to acute tubular necrosis, converting prerenal azotemia into intrinsic renal injury.

Diagnosis relies on clinical context and laboratory findings. Typical features include a high BUN/creatinine ratio (often >20:1), low urine sodium (<20 mEq/L), high urine osmolality (>500 mOsm/kg), and a low fractional excretion of sodium (<1%). FeUrea can be useful when diuretics are used. Ultrasound helps exclude post-renal obstruction.

Management focuses on correcting the underlying cause and restoring perfusion with fluids (usually isotonic saline or balanced crystalloids). Avoid nephrotoxins, optimize hemodynamics, and treat comorbid conditions such as heart failure or sepsis. Prognosis is generally favorable with prompt treatment, but delay increases the risk of progression to intrinsic kidney damage. Differential diagnoses include intrinsic renal disease and post-renal obstruction.