Global or focal renal hypoperfusion → tissue ischemia and eventually, parenchymal loss

Sonographic diagnosis is difficult; evaluation by CT/MR more common

± alteration in grayscale 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

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

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

Scanning in lateral decubitus or oblique position in coronal scan plane through posterior axillary line results in shorter Doppler distance and improved color Doppler sensitivity

Optimize settings to detect slow flow in color and power Doppler

Make sure to scan kidneys in horizontal presentation such that both upper pole and lower poles are located at similar depth from transducer; this will ensure entire kidney is interrogated equally with color Doppler

Reduce size of Doppler box while still including kidney to optimize visualization of vascular defects