Cracking the nutcracker myth: CT-based risk stratification of symptomatic left renal vein Compression

To evaluate computed tomography (CT) findings in patients with nutcracker anatomy and identify imaging features associated with clinically symptomatic nutcracker syndrome.

This retrospective single-center study screened CT reports performed between 2015 and 2025 using terms related to nutcracker anatomy and left renal vein compression. Patients were included if arterial- and venous-phase CT images demonstrated focal left renal vein narrowing at the aortomesenteric angle, defined by a beak-like appearance and validated diameter-ratio criteria, and if at least 1 year of clinical follow-up was available. Patients were classified as having nutcracker syndrome when symptoms attributable to left renal venous hypertension or pelvic venous disorder were documented; otherwise, they were classified as having nutcracker phenomenon. CT findings related to collateral venous recruitment were assessed, and diagnostic performance was evaluated using univariable analysis, receiver operating characteristic analysis, and multivariable logistic regression.

The final cohort included 71 patients, of whom 43 (60.6%) had nutcracker phenomenon and 28 (39.4%) had nutcracker syndrome. Patients with nutcracker syndrome more frequently demonstrated left gonadal vein dilation, gonadal vein asymmetry, gonadal vein reflux, pelvic varices or varicocele, left-predominant pelvic varices or varicocele, and left lumbar vein dilation with reflux. The findings supported the DReL score, based on left gonadal vein Dilation ≥7 mm, gonadal vein Reflux, and Left-predominant pelvic varices or varicocele, which stratified the likelihood of nutcracker syndrome with increasing specificity.

In patients with CT-defined nutcracker anatomy, imaging findings reflecting collateral venous recruitment were associated with symptomatic disease. These results suggest that the hemodynamic consequences of left renal vein compression, rather than anatomic narrowing alone, may help distinguish clinically significant nutcracker syndrome from incidental nutcracker phenomenon.