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Case 33 Answer
Answer: Nutcracker Syndrome
A vascular compression syndrome where the angle at which the superior mesenteric artery originates from the aorta is much smaller than usual yielding compression of the left renal vein as it runs between them. Normal angle should be in the 40 degree range (21 degrees here).
But in similar to many other radiologic syndromes, there is a large overlap between normal asymptomtatic variants and those that are symptomatic. Just because you see the imaging findings does not necessarily mean it is pathologic. Look for secondary findings of venous obstruction: dilated left renal, venous collateral, gonadal vein dilation, etc. You can measure the aorto-SMA angle or the aorto-SMA distance but it doesn’t sound like there is an agreed upon absolute number. The smaller the more likely but that’s it.
Here, you may note the slight delayed enhancement of the left kidney, compressed left renal vein with proximal dilation. Combined with the history (most commonly hematuria or flank pain), further workup and possibly stent placement is probably worth mentioning.
Nice Radiographics article on vascular compression syndromes (req subscription): https://pubs.rsna.org/doi/abs/10.1148/rg.341125010