Diagnostic Ultrasound - Abdomen and Pelvis

Renal Infarct
Diagnoses: Urinary Tract
TERMINOLOGY
• Global or focal renal hypoperfusion → tissue ischemia and
eventually, parenchymal loss
IMAGING
• Sonographic diagnosis is difficult; evaluation by CT/MR
more common
• ± alteration in grey scale appearance with ↓
corticomedullary differentiation
• Focally diminished or absent Doppler flow
• May involve all or part of 1 kidney
• Insults to accessory renal arteries tend to cause polar
infarcts
• Wedge shaped, corresponding to vascular territory in
kidney
• May be hypoechoic or hyperechoic, depending on timing
• When focal, tends to be wedge shaped and extend all the
way from hilum to capsule
• Focal or global loss of parenchymal flow
KEY FACTS
• Optimize settings to detect slow flow
PATHOLOGY
• Arterial disease: Trauma, atherosclerosis, vasculitis,
dissection
• Embolism: Endocarditis, arrhythmias with clot
• Thrombosis: Trauma or hypercoagulability
• Iatrogenic: Small polar arteries may be sacrificed in AAA
repair or transplant harvest
DIAGNOSTIC CHECKLIST
• Clinical context will usually help to exclude the other items
in differential diagnosis
• Look for ancillary signs of infection or trauma on CT exams
to narrow the differential
• Small polar infarcts are common after endovascular repair
of AAA
(Left) US shows a subtle,
wedge-shaped, hyperechoic
infarct st in the lower pole of
the right kidney in a patient
with dilated cardiomyopathy.
Correlative CECT
demonstrates the
corresponding enhancement
defect . Note the preserved
capsular enhancement, a.k.a.
the cortical rim sign, due to
patent capsular arteries that
perfuse the capsule. (Right)
Absent color Doppler flow
is shown in the upper pole of a
patient with segmental renal
infarct.
(Left) Absent power Doppler
flow is shown in the lower
pole of a patient with renal
infarct from atrial fibrillation.
Power Doppler is most
sensitive for slow flow and
should be used as a
confirmatory test when infarct
is suspected. (Right) Contrastenhanced
CT in the same
patient shows absent
perfusion in the anterior
cortex of the kidney.
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