Cortical rim sign

The cortical rim sign is useful in distinguishing acute pyelonephritis from a segmental renal infarct and is seen on contrast enhanced CT or MRI.

The wedges of reduced enhancement seen in the setting of acute pyelonephritis represent oedema and ischaemia which involves the whole wedge or renal parenchyma, from medulla to the capsule. This sign seen as a result of cortical necrosis may also be seen in conditions like renal transplant rejection, intravascular haemolysis, shock, and as a consequence of obstetric complication.3

In segmental infarcts, the blood supply to the outer aspect of the cortex is derived from perforating branches of the renal capsular artery which is an early branch of the renal artery. As such, when a branch of the renal artery is occluded (by thromboembolism, dissection, etc) perfusion may be preserved to a thin rim (2-4 mm) of cortex which enhances normally.

Unfortunately the cortical rim sign is only seen in approximately half of renal infarcts.

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Article information

rID: 9958
System: Urogenital
Section: Signs
Tags: kidney, cases
Synonyms or Alternate Spellings:
  • Rim sign (of renal infarction)
  • Renal cortical rim sign

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Cases and figures

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    Absent cortical r...
    Case 1: acute pyelonephritis
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    Cortical rim sign
    Case 2: renal infarction
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