Acute renal failure (ARF) is a clinical syndrome in which a sudden deterioration in renal function results in the inability of the kidneys to maintain fluid and electrolyte homeostasis.

Pathogenesis:

ARF has been conventionally classified into 3 categories:

prerenal,
intrinsic renal, and
postrenal
Prerenal ARF, also called prerenal azotemia, is characterized by diminished effective circulating arterial volume, which leads to inadequate renal perfusion and a decreased glomerular filtration rate (GFR). Evidence of kidney damage is absent. Common causes of prerenal ARF include dehydration, sepsis, hemorrhage, severe hypoalbuminemia, and cardiac failure. If the underlying cause of the renal hypoperfusion is reversed promptly, renal function returns to normal. If hypoperfusion is sustained, intrinsic renal parenchymal damage may develop.

Intrinsic renal ARF includes a variety of disorders characterized by renal parenchymal damage, including sustained hypoperfusion/ischemia

Postrenal ARF includes a variety of disorders characterized by obstruction of the urinary tract. In neonates and infants, congenital conditions such as posterior urethral valves and bilateral ureteropelvic junction obstruction account for the majority of cases of ARF. Other conditions such as urolithiasis, tumor (intra-abdominal or within the urinary tract), hemorrhagic cystitis, and neurogenic bladder may cause ARF in older children and adolescents. In a patient with 2 functioning kidneys, obstruction must be bilateral to result in ARF. Relief of the obstruction usually results in recovery of renal function except in patients with associated renal dysplasia or prolonged urinary tract obstruction

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