Normative Data on Inferior Mesenteric Vein Caliber in the Pediatric Population.

Objective: The inferior mesenteric vein (IMV) is an important component of the portal venous system; however, normative developmental data during childhood remain limited. This study aimed to evaluate age- and sex-related changes in IMV caliber using contrast-enhanced computed tomography in a pediatric population. Methods: Radiologic images of 200 subjects aged 1-20 years were included in the examination. Terminal (IMV1), intermediate (IMV2), and pelvic (IMV3) calibers of the IMV were measured. Ratios of vessel calibers to the transverse diameter of the first lumbar vertebral body (L1TD) were calculated. In addition, the drainage pattern of the IMV was recorded. Results: L1TD, IMV1, IMV2, and IMV3 demonstrated significant age-related changes (p < 0.001). All IMV calibers increased from infancy to the postpubescent period. Among the calculated ratios, IMV1/L1TD and IMV3/L1TD demonstrated significant age-related variation (p < 0.05), whereas IMV2/L1TD remained relatively stable throughout childhood and adolescence (p > 0.05). No significant sex-related differences were observed for most parameters, although IMV3 was significantly greater in males than in females (p = 0.043). The splenic vein was the most common termination site of the IMV (47.5%), followed by the superior mesenteric vein (29.5%) and the splenomesenteric confluence (23.0%). Conclusions: The present study provides normative age-specific values for IMV caliber and IMV-to-L1TD ratios in the pediatric population. These data may facilitate the radiological assessment of IMV-related abnormalities and provide a practical reference for routine computed tomography evaluation of the pediatric mesentericoportal venous system.