Acute Cortical Necrosis

Acute cortical necrosis is ischaemic destruction of the renal cortex with sparing of the medulla, caused by severe, prolonged spasm or thrombosis of the afferent arterioles and glomerular capillaries.

• Obstetric causes (placental abruption, septic abortion, eclampsia and severe pre-eclampsia, postpartum haemorrhage, amniotic fluid embolism, sepsis) account for 50 to 70 percent in low income settings including East Africa.
• Non-obstetric causes: septic shock, haemolytic uraemic syndrome, snakebite (viper), massive burns, transfusion reactions, disseminated intravascular coagulation, pancreatitis, hypovolaemic shock, drug overdose, poisoning (phosphorus, arsenic), and transplant rejection.
• Patchy (focal) necrosis has a better prognosis than diffuse necrosis.

Sudden anuria or severe oliguria lasting over 1 to 2 weeks (anuria beyond 48 hours should raise the suspicion), flank pain, haematuria, hypotension, fever, features of the precipitating illness.

• Rapid biochemical deterioration: hyperkalaemia, metabolic acidosis, uraemia, fluid overload.
• Differential diagnosis: acute tubular necrosis (recovers in 1 to 3 weeks), bilateral renal vein thrombosis, bilateral arterial occlusion, rapidly progressive glomerulonephritis, thrombotic microangiopathy, bilateral obstruction, hepatorenal syndrome.
• Complications: dialysis dependence, partial recovery with chronic kidney disease, end stage kidney disease, cortical calcification, hypertension, anaemia, sepsis and death.

Creatinine, urea, electrolytes, bicarbonate, full blood count and film, coagulation profile (disseminated intravascular coagulation), lactate dehydrogenase, urinalysis (haematuria, proteinuria, casts).

• Contrast CT: non-enhancing hypodense cortex with a thin enhancing rim (subcapsular rim sign) and enhancing medulla, performed with caution if function allows; Doppler ultrasound shows reduced cortical flow; magnetic resonance imaging without gadolinium.
• Plain radiograph or CT 2 to 4 weeks later shows tram-track cortical calcification.
• Renal biopsy (patchy or diffuse necrosis of cortex with thrombosed glomerular capillaries and fibrin) when diagnosis is uncertain and imaging unclear.

Supportive: resuscitation of the precipitating event, correct hypovolaemia and anaemia (haemoglobin below 7 g/dL: transfuse), strict fluid balance, nutrition, treat sepsis, early obstetric measures (evacuation of uterus, delivery, haemorrhage control).

Pharmacological

• Source control and antibiotics for septic abortion and sepsis: ceftriaxone 2 g IV daily plus metronidazole 500 mg IV every 8 hours plus gentamicin (dose adjusted for renal function) or piperacillin-tazobactam 4.5 g IV every 6 to 8 hours (adjusted).
• Correct coagulopathy with fresh frozen plasma 10 to 15 mL/kg, cryoprecipitate and platelets guided by results.
• Hyperkalaemia: calcium gluconate 10 percent 10 mL IV, insulin 10 units with 25 g glucose IV, salbutamol 10 to 20 mg nebulised, sodium bicarbonate.
• Hypertension: amlodipine 5 to 10 mg daily or labetalol; avoid ACE inhibitors in the acute phase.
• Snakebite: antivenom promptly.
• No specific therapy restores necrotic cortex; heparin and vasodilators have no proven benefit.

Procedures: early renal replacement therapy (haemodialysis or peritoneal dialysis where haemodialysis is unavailable) for hyperkalaemia, acidosis, overload and uraemia; dialysis may be needed for weeks to months.

Special groups: obstetric patients (multidisciplinary care, prevention by safe delivery and haemorrhage control), children (haemolytic uraemic syndrome, peritoneal dialysis), snakebite (early antivenom).

Prognosis: 20 to 40 percent recover enough function to be dialysis independent (usually within 1 to 3 months), 20 to 30 percent progress to end stage kidney disease and the rest have chronic kidney disease.

Red flags: anuria beyond 48 hours, haematuria with flank pain, disseminated intravascular coagulation, potassium above 6.5 mmol/L.

Follow-up: renal function monthly for the first 6 months; blood pressure; plan for transplant or long term dialysis if no recovery; family planning counselling.