Abdominal and Visceral Vascular Testing: Aorta, Renal, and Mesenteric Arteries
Core Concepts
Abdominal vascular ultrasound evaluates the aorta (aneurysm, stenosis, dissection), renal arteries (stenosis), mesenteric arteries (celiac and superior mesenteric stenosis), and the portal/hepatic venous system. Know normal aortic diameter thresholds (infrarenal >3 cm suggests aneurysm) and the appearance of mural thrombus. For renal artery stenosis, understand direct velocity criteria and indirect signs (tardus-parvus waveform, low resistive index, small kidney).
Mesenteric and Portal Evaluation
Celiac and SMA stenosis show elevated peak systolic velocities and post-stenotic turbulence; know that the celiac artery normally has a lower resistance waveform than the SMA, which is high-resistance in fasting states. Portal hypertension shows enlarged portal vein, hepatofugal flow, and varices.
Traps
Common traps: measuring the aorta at the wrong level or including mural thrombus in the diameter; mistaking aortic tortuosity for aneurysm; and overdiagnosing renal artery stenosis from velocity alone without indirect signs. Another trap is interpreting SMA velocity without accounting for fasting vs postprandial state, which alters waveform and velocity.
Worked Example
A patient has a renal artery PSV of 220 cm/s with a tardus-parvus distal waveform and a small kidney. The elevated velocity plus indirect signs supports hemodynamically significant stenosis. The trap: if the distal waveform were normal, the velocity alone might reflect a non-significant lesion or hyperdynamic flow.
Rule of Thumb
For visceral vessels, combine direct velocity with indirect downstream signs. Measure aortic diameter outer-wall to outer-wall at the maximal infrarenal level and document thrombus separately.