Diagnostic Ultrasound - Abdomen and Pelvis

Renal Infarct
TERMINOLOGY
Definitions
• Global or focal renal hypoperfusion → tissue ischemia and
eventually, parenchymal loss
IMAGING
General Features
• Best diagnostic clue
○ Sonographic diagnosis is difficult; evaluation by CT/MR
more common
○ ± alteration in gray scale appearance with ↓
corticomedullary differentiation
○ Focally diminished or absent Doppler flow
• Location
○ May involve all or part of 1 kidney
○ Insults to accessory renal arteries tend to → polar infarcts
• Size
○ Variable
• Morphology
○ Wedge shaped, corresponding to vascular territory in
kidney
Ultrasonographic Findings
• Grayscale ultrasound
○ Diminished corticomedullary differentiation
○ May be hypoechoic or hyperechoic, depending on timing
○ When focal, tends to be wedge shaped and extend all
the way from hilum to capsule
• Color Doppler
○ Focal or global loss of parenchymal flow
○ Optimize settings to detect slow flow
– Use power Doppler for increased sensitivity
○ CEUS used to assess perfusion where available
CT Findings
• CECT
○ Decreased attenuation, delayed or absent nephrogram
○ Delayed or absent excretion if global infarct
○ CTA may demonstrate a vascular lesion
Imaging Recommendations
• Best imaging tool
○ Color and power Doppler helps distinguish ischemia
from other renal pathologies
○ CECT has best sensitivity to evaluate infarction and
causes
• Protocol advice
○ Doppler parameters must be optimized to detect slow
flow
DIFFERENTIAL DIAGNOSIS
Pyelonephritis
• Clinical context is key; often has urothelial thickening
• Focal nephritis may appear similar, wedge-shaped,
echogenic
Radiation Effects
• Tend to be nonanatomic in distribution, rather than
segmental
Renal Neoplasm
• More commonly round or ovoid + color flow within lesion
Renal Laceration
• Antecedent trauma history, perinephric fluid is common
PATHOLOGY
General Features
• Etiology
○ 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
Staging, Grading, & Classification
• Clinical significance depends on volume of renal
parenchyma lost
Gross Pathologic & Surgical Features
• Ischemic tissue is pale or white grossly
• Long term, renal scarring, and cortical lobulation results
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Often asymptomatic, depends on etiology
• Other signs/symptoms
○ Flank pain, hypertension; hematuria
Demographics
• Age
○ Given variety of causes, can occur at all ages
Natural History & Prognosis
• Segmental infarcts are well tolerated and rarely have long
term sequelae
• Global infarct can result in "auto nephrectomy"
Treatment
• May include medical management, angioplasty &/or
endovascular stenting
DIAGNOSTIC CHECKLIST
Consider
• Clinical context will usually help to exclude the other items
in differential diagnosis
Image Interpretation Pearls
• 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
SELECTED REFERENCES
1. Piccoli GB et al: Renal infarction versus pyelonephritis in a woman presenting
with fever and flank pain. Am J Kidney Dis. 64(2):311-4, 2014
2. Stenberg B et al: Post-operative 3-dimensional contrast-enhanced
ultrasound (CEUS) versus Tc99m-DTPA in the detection of post-surgical
perfusion defects in kidney transplants - preliminary findings. Ultraschall
Med. 35(3):273-8, 2014
Diagnoses: Urinary Tract
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