Age- and sex-specific CT reference trajectories for abdominal organ volumes and attenuation: a large-scale automated...

Reference values for adult abdominal organ volumes and attenuation remain limited, although they are important for accurate CT interpretation and opportunistic imaging assessment.

This retrospective cross-sectional study included 25,161 abdominal CT examinations from 15,408 adult patients aged 18-100 years, comprising 5,559 women, 9,848 men, and one non-binary patient. Attenuation measurements were derived from the unenhanced phase available in 9,548 examinations. Organ volumes and attenuation values were quantified using a fully automated segmentation pipeline (TotalSegmentator). Percentile reference curves (P3-P97) were generated using generalized additive models for location, scale, and shape (GAMLSS).

Men had higher organ volumes than women across nearly all organs and age groups. Age-group-averaged model-derived P50 estimates showed organ-specific trajectories: liver, pancreas, and kidney volumes followed an inverted U-shaped pattern, increasing from young adulthood to midlife and declining thereafter. Liver volume peaked in midlife and declined thereafter, rising from 1,303.1 to 1,450.2 mL in women and from 1,560.7 to 1,774.1 mL in men, before decreasing to 1,019.6 and 1,234.9 mL at 90-100 years, respectively. Pancreatic volume peaked at 40-49 years (67.7 mL in women; 86.2 mL in men) and declined to 35.5/46.4 mL. Right/left kidney volumes increased from 115.6/126.6 to 138.2/143.2 mL in women and from 154.6/163.4 to 179.4/183.3 mL in men, before declining to 87.8/84.5 and 113.1/112.8 mL, respectively. Spleen volume decreased overall with age, whereas adrenal volume increased into later adulthood. Organ attenuation generally declined with age, most markedly in the pancreas and adrenal glands.

Percentile-based trajectories derived from large-scale automated CT analysis provide descriptive reference values for abdominal organ volume and attenuation across adulthood.