Sagittal Long-Axis Bladder Diameter and CT-Measured Bladder Wall Thickness in Healthy Female Patients

The objective of this study is to evaluate the association between CT-measured bladder wall thickness (BWT) and sagittal long-axis bladder diameter (SL), defined as the largest midsagittal luminal bladder diameter, in female patients without documented bladder disease or urinary symptoms, using SL as a practical indicator of bladder distension.

This retrospective study included 111 patients aged 16 years or older. An experienced abdominal radiologist measured BWT perpendicular to the anterior wall at the contact point of the SL measurement. Analyses included five descriptive SL categories, analysis of variance with Tukey testing, Pearson correlation, and linear and log-log regression. Post hoc age-adjusted models used heteroscedasticity-consistent type 3 (HC3) standard errors; sensitivity analyses examined an age cutoff of 18 years and omission of the largest SL observation.

Mean BWT was 3.50 mm and mean SL was 62.05 mm. SL was inversely correlated with BWT (r = -0.51; P < 0.001). Mean BWT decreased from 6.00 mm in the 10-<30-mm category to 1.90 mm in the ≥90-mm category (F = 11.26; P < 0.001). Age was not significantly correlated with BWT (r = 0.035; P = 0.714). After age adjustment, the SL association persisted (coefficient, -0.0398 mm/mm; 95% CI, -0.0604 to -0.0193; P < 0.001), whereas the age coefficient was not significant (P = 0.528). Both sensitivity analyses retained the inverse SL-BWT association.

CT-measured BWT decreased as SL increased in female patients. Building on prior evidence relating SL to bladder volume, these findings support recording SL alongside BWT to describe wall thickness in relation to bladder distension. Reader reproducibility and diagnostic usefulness require further evaluation; the descriptive categories do not establish clinical thresholds.