"B‑mode ultrasound shows focal narrowing of the left renal vein as it passes between the aorta and the superior mesenteric artery, with pre‑stenotic dilatation at the renal hilum"
"spectral Doppler often shows an elevated peak systolic velocity at the compressed segment with an increased velocity ratio between the compressed and hilar segments; although ratios above commonly cited thresholds are used for nutcracker syndrome, similar values can be seen in asymptomatic nutcracker phenomenon, so clinical correlation is essential 3-5"
"increased hilar‑to‑aortomesenteric calibre ratio of the left renal vein, reflecting a step‑change in diameter across the compressed segment; similar ratios are described in symptomatic patients but may also occur in asymptomatic individuals 3,5"