The Levator Ani (LA) plays a crucial role in maintaining pelvic organ support and continence, However the puborectalis muscle (PR) often resulting from insufficient control in some conditions like pelvic floor dyssynergia, obstetric trauma, constipation, etc. This study aims to evaluate the puborectalis muscle elasticity through shear-wave elastography (SWE) in posterior compartment disorders. (1-3)

Transperineal ultrasound and endovaginal (endocavitary) shear-wave elastography (SWE) were performed in patients with posterior compartment disorders and healthy volunteers previously evaluated through the Initial Measurement of Patient-Reported Pelvic Floor Complains Tool (IMPACT) for using the Fecal Incontinence Quality of Life (FIQOL) and Constipation Severity Instrument (CSI score). The puborectalis muscle was evaluated during rest, squeezing and valsalva maneuvers to assess the anatomy, dynamic angles and elasticity in kPascal (kPa). During the elastography, five zones were evaluated in the puborectalis muscle, referring to Zone 1 for the Right Insertion, Zone 2 for the Right Sling, Zone 3 for the body or U-shaped, Zone 4 for the Left Sling and Zone 5 for the Left Insertion. All measurements were analyzed, compared, and correlated (Pearson correlation coefficient) between groups.

Among 100 patients who met the criteria, 50 cases (aged 60.12 years (± 10.72 SD) and 50 controls (aged 55.67 years (± 6.91 SD)). There was a significant difference in the CIS and FIQOL score between groups (15.76 ± 2.11 vs 8.10 ± 2.63 and 6.42 ± 3.26 vs 17.41 ± 2.65, respectively). The mean value for cases and controls in Zone 1 was (17.77 kPa (5.56) vs 12.36 kPa (2.32), P = 0.03), for Zone 2 (17.12 kPa (5.12) vs 16.63 kPa (6.83), P = 0.134), for Zone 3 (18.73 kPa (6.91) vs 17.25 kPa (5.91), P = 0.05), for Zone 4 (15.69 kPa (4.56) vs 15.25 kPa (6.65),  P = 0.452), for Zone 5 (19.74 kPa (8.74) vs 17.78 kPa (9.49), P = 0.02). The global mean value was 17.42 kPa (3.69) for cases and 16.23 kPa (3.69) for controls, (P = 0.002). The mean LPDA and ARA (Valsalva) was 29.38° (10.69) and 113.41° (21.30), respectively. A positive correlation was found between the difference in ARA (resting and valsalva) and global elastography, the Pearson correlation coefficient was 0.52 (moderate correlation).

The results showed a clear relationship between patients who presented defecation disorders and the grade of elastography in the puborectalis muscle against controls, with a positive correlation in the anorectal angle.

Transperineal SWE is a noninvasive and feasible alternative method to evaluate the function of puborectalis muscle in posterior compartment disorders, providing comparable good outcomes with potentially reduced misinterpretations. Future studies should focus on large populations.

Morin M, Salomoni SE, Stafford RE, Hall LM, Hodges PW. Validation of shear wave elastography as a noninvasive measure of pelvic floor muscle stiffness. Neurourol Urodyn. 2022 Sep;41(7):1620-1628. doi: 10.1002/nau.25010. Epub 2022 Jul 17. PMID: 35842828.
Aljuraifani R, Stafford RE, Hug F, Hodges PW. Female striated urogenital sphincter contraction measured by shear wave elastography during pelvic floor muscle activation: Proof of concept and validation. Neurourol Urodyn. 2018 Jan;37(1):206-212. doi: 10.1002/nau.23275. Epub 2017 Apr 13. PMID: 28407305.
Horwood G, Flaxman T, McInnes M, McLean L, Singh SS. Ultrasound Elastography in Benign Gynecology: A Scoping Review. Reprod Sci. 2024 Aug;31(8):2508-2522. doi: 10.1007/s43032-024-01535-6. Epub 2024 Apr 25. PMID: 38664357.