A morphological study of symptomatic uterine niche using three-dimensional models from thin-slice magnetic resonance imaging.

ABSTRACT

RESEARCH QUESTION Is there a correlation between various morphological parameters of the uterine niche and post-menstrual spotting using three-dimensional models from thin-slice (1 mm) magnetic resonance imaging (MRI)? DESIGN: This study retrospectively identified women diagnosed with a symptomatic niche by thin-slice MRI between December 2019 and December 2021. Univariable and multivariable linear regression models assessed the correlations between morphological parameters and the duration post-menstrual spotting. Morphological differences of the niche formed by one versus two Caesarean sections were analysed by univariable and multivariable logistic analysis. RESULTS: A total of 205 women diagnosed with symptomatic niche were included in the study. The niche among most women with post-menstrual spotting was ellipsoidal, with width greater than length greater than depth, from which niche volume was estimated based on manual measurements (volume = 0.520 × length × width × depth). Manually calculated niche length (ß = 0.257, 95% confidence interval [CI] 0.040-0.473, P = 0.020) and radiomically assessed minor axis length (ß = 0.329, 95% CI 0.009-0.795, P = 0.045) both positively correlated with the duration of post-menstrual spotting, whereas the distance between the niche and external os (ß = -0.120, 95% CI -0.202 to -0.038, P = 0.004) was inversely correlated. Women with two Cesarean sections reported more days of post-menstrual spotting (8.76 ± 3.54 versus 6.68 ± 3.90 days, P < 0.001) and had increased niche length diameter (adjusted odds ratio [aOR] 1.304, 95% CI 1.190-1.429) and a smaller surface-area-to-volume ratio (aOR 0.296, 95% CI 0.129-0.680). CONCLUSIONS: Niche-associated post-menstrual spotting correlates with the length diameter of the niche and the distance between the niche and external os. Niches in women after two Caesarean sections tend to be longer in length diameter and more spherical.