acute tubular necrosis

acute tubular necrosis
Name	Acute tubular necrosis
Field	Nephrology
Synonyms	ATN
Symptoms	Oliguria, anuria, fluid overload, uremia
Complications	Chronic kidney disease, electrolyte disturbances
Onset	Acute
Causes	Ischemia, nephrotoxins
Risks	Sepsis, major surgery, hypotension
Diagnosis	Serum creatinine, urinalysis, fractional excretion of sodium
Treatment	Supportive care, dialysis

acute tubular necrosis Acute tubular necrosis is an acute kidney injury characterized by damage to renal tubular epithelial cells, commonly resulting from ischemic injury or nephrotoxic exposure. It presents with rapid decline in renal function, oliguria or nonoliguria, and laboratory abnormalities reflecting impaired tubular handling of sodium and water. Management centers on supportive measures, removal of causative agents, and renal replacement therapy when indicated.

Signs and symptoms

Patients with acute tubular necrosis typically present with sudden reduction in urine output, fluid overload, and signs of uremia. Clinical features often include peripheral edema, pulmonary crackles, nausea, confusion, and pruritus as renal failure progresses. Laboratory and bedside findings reveal rising serum creatinine, hyperkalemia with peaked T waves on electrocardiogram, metabolic acidosis, and urine sediment that may contain muddy brown granular casts and epithelial cells.

Causes and risk factors

Major causes include prolonged renal ischemia caused by severe hypotension during events such as myocardial infarction, major surgery, or hemorrhage. Exposure to nephrotoxins—aminoglycoside antibiotics, radiographic contrast media, cisplatin, amphotericin B, and intravenous hemoglobin or myoglobin—also precipitates injury. Risk factors include advanced age, preexisting chronic kidney disease, diabetes mellitus, sepsis, liver failure, and use of nephrotoxic agents in the perioperative setting.

Pathophysiology

Ischemic injury and direct tubular toxin exposure lead to death of proximal tubular and thick ascending limb epithelial cells through mechanisms including ATP depletion, disruption of cytoskeletal integrity, loss of cell polarity, and apoptosis or necrosis. Resultant detachment of epithelial cells causes tubular obstruction and increases intratubular pressure, reducing glomerular filtration. Endothelial injury, microvascular congestion, and inflammatory cell recruitment further impair renal perfusion and prolong recovery.

Diagnosis

Diagnosis is based on clinical context, biochemical evidence of acute kidney injury, and urinalysis findings. Key investigations include serum creatinine and blood urea nitrogen trends, electrolytes, arterial blood gas, and urinalysis with microscopy demonstrating granular casts. Calculations such as fractional excretion of sodium and urine sodium concentration help distinguish intrinsic tubular injury from prerenal azotemia. Renal ultrasound excludes obstruction; in unclear cases, kidney biopsy can demonstrate tubular epithelial necrosis and cast formation.

Management and treatment

Initial management targets hemodynamic optimization: restoration of intravascular volume, avoidance of hypotension, and correction of electrolyte disturbances. Discontinuation of offending nephrotoxins and careful medication review are essential. Diuretics may be used to manage volume overload though they do not shorten injury duration. Indications for renal replacement therapy include refractory hyperkalemia, severe acidosis, pulmonary edema unresponsive to diuretics, and uremic complications. Preventive strategies in high-risk settings include perioperative optimization, contrast-sparing protocols, and therapeutic monitoring.

Prognosis and complications

Prognosis depends on severity, duration of ischemia or toxin exposure, and comorbid conditions. Many patients recover partial or full renal function over days to weeks, but prolonged injury increases risk of incomplete recovery and progression to chronic kidney disease or end-stage renal disease requiring long-term dialysis or transplantation. Complications include persistent electrolyte imbalances, secondary infections, and cardiovascular events related to uremia and volume derangements.

Category:Kidney diseases