Cortical Necrosis

Renal cortical necrosis is a rare but severe cause of acute kidney injury (AKI) that occurs secondary to extensive ischemic damage to the renal cortex.
The condition is characteristically bilateral and extensive, although focal and patchy forms have been documented in clinical practice.
The ischemic insult selectively destroys the cortex while characteristically sparing the medulla, the juxtamedullary cortex, and a thin subcapsular rim of the cortex.
The pathogenesis is initiated by intense vasospasm of the small vessels, which, when prolonged, leads to the necrosis and thrombosis of distal arterioles and glomeruli.
In specific conditions like hemolytic-uremic syndrome (HUS) and septic abortion, endotoxin-mediated endothelial damage significantly contributes to the worsening of vascular thrombosis.
The underlying etiologic factors differ significantly depending on the age of the patient.

Age Group	Common Etiologies	Less Common / Specific Etiologies
Newborns	Hypoxic or ischemic insults due to perinatal asphyxia, placental abruption, and twin-twin or fetal-maternal transfusion.	Renal vascular thrombosis and severe congenital heart disease.
Older Children	Septic shock and severe hemolytic-uremic syndrome (HUS).	Malaria, extensive burns, snakebites, infectious endocarditis, and medications (e.g., non-steroidal anti-inflammatory agents).
Adolescents	Obstetric complications (in females of childbearing age) including prolonged intrauterine fetal death, placental abruption, septic abortion, or amniotic fluid embolism.	SLE-associated antiphospholipid antibody syndrome.

Patients clinically present with severe acute kidney injury in the context of one of the aforementioned predisposing conditions.
Urine output is markedly diminished, resulting in anuria or severe oliguria.
Gross and/or microscopic hematuria is a defining feature upon urinalysis.
Hypertension is a highly common physical finding in these patients.
Thrombocytopenia is frequently observed and is attributed directly to the associated renal microvascular injury and thrombosis.
Laboratory investigations consistently demonstrate elevated blood urea nitrogen (BUN) and serum creatinine, alongside hyperkalemia, metabolic acidosis, and anemia.
Urine microscopy classically reveals red blood cell or granular casts, accompanied by proteinuria.
On Doppler ultrasound, there is decreased perfusion to both kidneys; the kidneys may appear enlarged in the initial stages but typically become shrunken in later stages.
Contrast-enhanced CT scanning, the most sensitive imaging modality, shows absent opacification of the renal cortex with notable enhancement of the subcapsular and juxtamedullary regions.
A classic radiologic hallmark is the presence of "tram lines" (thin cortical shells of calcification), though these only develop 4 to 5 weeks after the initial ischemic insult.
In cases where CT contrast is contraindicated, a radionuclide renal scan is the imaging technique of choice, revealing decreased uptake and significantly delayed or absent kidney function.

The most critical factors dictating the prognosis include the overall extent of the necrosis, the duration of the oligoanuric phase, and the severity of any associated systemic conditions.
If left untreated, renal cortical necrosis is associated with a remarkably high mortality rate that exceeds 50%.
Early initiation of dialysis is a key prognostic determinant that significantly diminishes the mortality rate.
Appropriate supportive management—including restoration of hemodynamic stability, volume repletion, correction of asphyxia, and aggressive treatment of sepsis—is essential for optimizing survival outcomes.
Approximately 20% to 40% of surviving patients will experience a partial recovery of renal function; the degree of recovery is strictly dependent on the amount of cortical tissue that remains preserved.
Patients generally require dialysis for extended and variable periods of time.
Because the injury to the renal parenchyma is severe and largely irreversible, all patients require long-term follow-up for the management of chronic kidney disease.