Levator bowl volume during straining and its relationship to other levator measures

• Published in: International Urogynecology Journal 2019-09, Vol.30 (9), p.1457-1463
• Main Authors: Nandikanti, Lahari, Sammarco, Anne G., Chen, Luyun, Ashton-Miller, James A., DeLancey, John O.
• Format: Article
• Language: English
• Subjects: Adult; Anal Canal - diagnostic imaging; Anal Canal - pathology; Case-Control Studies; Failure; Female; Gynecology; Humans; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Medicine; Medicine & Public Health; Middle Aged; Obstetrics; Organ Size; Original Article; Pelvic Floor - diagnostic imaging; Pelvic Floor - pathology; Pelvic organ prolapse; Pelvic Organ Prolapse - diagnostic imaging; Pelvic Organ Prolapse - pathology; Surgical outcomes; Urology
• ISSN: 0937-3462; 1433-3023
• DOI: 10.1007/s00192-019-04006-8

Introduction and hypothesis This study was aimed at measuring levator ani bowl volume at rest and while straining, comparing women with and without prolapse (controls), and assessing the ability of measures of the mid-sagittal bowl area, levator hiatus (LH), and urogenital hiatus (UGH) to predict bowl volume. Methods Forty MRI scans previously acquired in case-control prolapse studies, including 20 women with prolapse and 20 women without prolapse, of similar age and parity, were selected. 3D models of rest and strain bowl volumes were made using sagittal scans and 3D Slicer®. Mid-sagittal bowl area, UGH, and LH were measured using ImageJ. Data were analyzed using two sample t tests, effect sizes, and Pearson’s correlation coefficients at the 0.05 significance level. Results Data were acquired in a total of 40 total women. Levator bowl volume at strain had a correlation coefficient of 0.5 with bowl volume at rest. During straining, prolapse subjects had a 53% larger bowl volume than control subjects (254 ± 86 cm 3 vs 166 ± 44 cm 3 , p   0.75). The strongest correlation with straining bowl volume was mid-sagittal straining bowl area (r = 0.86), followed by LH strain (r = 0.80), then UGH strain (r = 0.76). Conclusions Straining levator bowl volume is substantially different than measures made at rest, with only a quarter of straining values explained by resting measurements. The bowl area at strain is the best 2D measurement estimating bowl volume and explains 74% of straining bowl volume.