38 years old female with acute anuric renal failure 7 days after delivery complicated by postpartal hemorrhage.
The arterial phase CT scan shows lack of cortical enhancement of both kidneys (image A). In the nephrographic phase there is enhancement of the renal medulla and the very outer part of the renal cortex (cortical rim sign). Most portions of the renal cortex are still not enhancing (images B and C). The maximum intensity projection of the arterial scan illustrates patency of major renal arteries (image D),
Acute renal cortical necrosis.
Renal cortical necrosis (RCN) is a rare cause of acute renal failure secondary to ischemic necrosis of the renal cortex. The lesions are usually caused by significantly diminished renal arterial perfusion secondary to vascular spasm, microvascular injury, or intravascular coagulation. RCN is usually extensive, although focal and localized forms occur.
RCN is an important cause of acute kidney injury in later pregnancy and associated with obstetric emergencies such as postpartal hemorrhage or amniotic fluid embolism. RCN is responsible for 1 to 2 percent of all cases of delivery-associated acute kidney injuries. Many patients require dialysis, but 20 to 40 percent have partial recovery of renal function. The diagnosis can usually be established by ultrasonography or CT.
In most cases, the medulla, juxtamedullary cortex, and a thin rim of subcapsular cortex are spared. Thus, contrast-enhanced imaging studies show lack of cortical parenchymal enhancement only. The cortical rim sign is a finding suggestive of renal infarction in general and refers to a small part of the subcapsular cortex in which enhancement is preserved due to collateral blood flow through arteries supplying the renal capsule. Sometimes the hypoattenuation of the renal cortex seen against a background of intact medullary perfusion in cases of RCN is also described as reverse rim sign.
Dyer et al.
Classic Signs in Uroradiology
Radiographics (2004) 24(Suppl 1):S247
Renal Cortical Necrosis: Background, Etiology, Epidemiology
Acute kidney injury (acute renal failure) in pregnancy
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