Abstract
The retroaortic left renal vein (LRRV) is a rare anatomical variant, reported in 2.1–3.4% of the population, whose clinical relevance remains debated. By coursing posterior to the aorta, LRRV may cause posterior ureterovascular compression, producing symptoms that resemble those of nutcracker syndrome (NCS). However, data on its prevalence and symptom associations remain scarce, particularly in Middle Eastern populations. This study aimed to estimate the prevalence of LRRV and evaluate whether this venous variant is independently associated with flank pain, hematuria, or other urological symptoms in an Iranian cohort. A total of 4,260 abdominopelvic CT scan reports obtained between 2021 and 2024 at Baqiyatallah Hospital were retrospectively reviewed. The prevalence of LRRV was calculated, and clinical data were compared between 93 patients with CT-confirmed LRRV and 93 age- and sex-matched controls without LRRV. Urological symptoms—including flank pain, hematuria, hypogastric pain, dysuria, urinary frequency, urinary retention, and hypertension—were assessed through structured clinical interviews. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression analysis. The prevalence of LRRV was 2.18%. Compared with controls, patients with LRRV exhibited significantly high-er rates of flank pain (64.5% vs. 47.3%; OR = 2.01, 95% CI = 1.10–3.68; P = 0.023) and hematuria (54.8% vs. 39.8%; OR = 1.85, 95% CI = 1.02–3.34; P = 0.041), while no significant differences were observed for other symptoms (P > 0.05). In sex-stratified analyses, hematuria was more strongly associated with LRRV in men (OR = 2.12, P = 0.018), whereas flank pain was more prevalent among women (70.3% vs. 48.6%, P = 0.035). Symptom data were obtained through structured retrospective interviews and self-reported clinical history, without routine hemodynamic confirmation of renal venous hypertension. Accordingly, the observed associations reflect imaging–symptom correlations rather than definitive diagnostic confirmation of posterior nutcracker syndrome. The prevalence of LRRV in the Iranian population is consistent with global estimates. Its significant association with flank pain and hematuria supports the hypothesis that LRRV may act as an anatomic substrate for posterior nutcracker–like symptomatology in a subset of patients. These findings emphasize the importance of evaluating LRRV in patients presenting with unexplained left-sided urological symptoms.