The levator ani muscle has a compound anatomy tightly linked to its function. Three-dimensional endovaginal ultrasound (3D EVUS) assesses the muscle components in detail including the puboperineal/puboanal, puborectal and pubococcygeual/iliococcygeal components. The extent of levator injury visualized by 3D EVUS has been suggested as “levator ani deficiency” (1). Levator ani deficiency score (LAD score) have shown high interrater agreement (2). Several studies have demonstrated the association between levator injuries and anatomical pelvic organ prolapse, but the evidence on the relationship between levator injuries and other pelvic floor dysfunction  is controversial. The aim of this study was two-fold: First to test the hypothesis that levator ani deficiency is associated with pelvic floor dysfunction, including urinary, vaginal and bowel symptoms, one year postpartum; and second, to explore at what cut-off of LAD score such pelvic floor dysfunction arises.

This a nested case-control study that recruited participants from the POPRACT (pelvic floor in pregnancy and childbirth) cohort. The POPRACT study was a prospective cohort study whose full methodology has been published previously. Nulliparous women were enrolled in early pregnancy at maternity health care visits between 2014 and 2017. Women completed web-based questionnaires on four occasions during pregnancy and postpartum and the last questionnaire was sent out one year postpartum. The questionnaires included items derived from validated instruments on pelvic floor dysfunction. Out of the original POPRACT cohort, women who reported pelvic floor symptoms to a certain degree of bother or frequency at one year postpartum (potential cases) were invited to a clinical examination of the pelvic floor including 3D EVUS. The following pelvic floor symptoms and degree of bother or frequency, the latter within parentheses, served as criteria to be invited into the case group: urinary incontinence (moderately or a quite a bit), urinary incontinence during sexual activity (always, often or sometimes), fear of urinary or stool incontinence restricting sexual activity (always, often or sometimes), vaginal bulging (sometimes or often), need for vaginal digitation or splinting to complete bowel evacuation (moderately or quite a bit), vaginal chafing (often), need for anterior vaginal wall lifting to start or complete voiding (sometimes or often), or avoidance of sexual intercourse due to vaginal bulging (always, often or sometimes), sensation of vagina being loose, incontinence to solid and/or liquid stools (any degree of bother), and incontinence to flatus (moderately or quite a bit). From the POPRACT cohort, a group of randomly selected asymptomatic women symptoms were also invited aiming at reaching at an equally large control group. Women were examined using a BK Medical Flexfocus machine with two different probes, BK 8838 6-16 MHz and BK 2052 6-16Mhz. The levator ani muscle was divided into three subgroups: puboperinealis/puboanalis, puborectalis and pubococcygeus/iliococcygeus. The scores of each subgroup on both sides were summed into LAD score (0-18 points). LAD score was categorized as 0-6 (mild deficiency), 7-12 (moderate deficiency) and 13-18 (severe deficiency), see figure 1.

Of the 706 women responding to the questionnaire at one year postpartum in the POPRACT cohort, 212 were identified as potential cases and were invited to examination. A total of 103 women underwent 3D EVUS examination according to protocol and were included as cases. Among the 488 women who did not report significant symptoms, 87 were examined according to protocol and were included as controls. Overall, the rate of levator ani deficiency was low and most women in both case and control groups had a LAD score of 0. Among cases, seven participants had moderate (7%) and five had severe levator ani deficiency (5%), whereas among controls, 13 had moderate levator ani deficiency (15%) and none had severe levator ani deficiency. Increasing LAD score was significantly associated with urinary incontinence (adjusted risk ratio (aRR) 1.08 (95% confidence interval (CI): 1.01, 1.16)) and sensation of loose vagina (aRR 1.12 (95% CI: 1.05, 1.2)) (Table 1). When LAD score was categorized, severe LAD was associated with sensation of loose vagina (aRR 6.05 (95% CI: 3.35, 10.94)) and with flatus incontinence (aRR 3.85 (95% CI: 1.12, 13.23)) (Table 2). The risk of urinary incontinence was increased when cut-off for LAD scores was set to from ≥ 1 points and up to ≥ 4 points. The risk of sensation of loose vagina was increased when cut-off for LAD score was set from ≥ 8 points and up to ≥ 14 points. The risk of flatus incontinence was increased when cut-off for LAD score was set to ≥ 13 points or ≥ 14 points.

To the best of our knowledge, this is the first study to evaluate the association between levator ani deficiency assessed by 3D EVUS and urinary incontinence. Most previous studies on the association between levator avulsions or other levator defects visualized by either magnetic resonance imaging or three-dimensional transperineal ultrasound (3D TPUS) and urinary incontinence found no association. In the present study, urinary incontinence was associated with levator ani deficiency based on cut-offs at lower LAD scores. The capacity of 3D EVUS to visualize even such minor levator defects might explain that we found an association, while most studies using 3D TPUS did not. Cut-offs for LAD score between ≥1 and ≥4 may include defects of the most medial levator ani muscle portions. The puboperineal/puboanal portions of the levator ani muscle supports the mid-urethra through the perineal membrane, which is an important continence mechanism, and derangement of this support is a possible pathophysiological explanation to our finding. 

We found that severe levator ani deficiency is associated with a sensation of wide vagina, which is consistent with previous studies assessing levator avulsion using 3D TPUS. We found an association between levator ani deficiency and flatus incontinence but not with levator ani deficiency and fecal incontinence. Flatus incontinence was included as a symptom earlier when planning this study, but has been considered to mostly reflect bowel function. Thus, we interpret this finding with caution.

This nested case-control study showed that levator ani deficiency was associated with both urinary incontinence and sensation of loose vagina, and the risk of each symptom increased at different cut-offs of LAD score. While the risk of urinary incontinence increased already by minor levator ani deficiency, the risk of sensation of loose vagina increased first at extensive levator ani deficiency. Defects of the most medial levator ani muscle portions normally supporting the mid urethra offers a possible pathophysiological explanation for the observed increase of urinary incontinence already at minor levator ani deficiency. Increased understanding of the symptomatology of levator ani deficiency may guide patients and health care providers alike when to seek healthcare and how to provide them with a correct treatment plan.

Rostaminia G, White D, Hegde A, Quiroz LH, Davila GW, Shobeiri SA. Levator ani deficiency and pelvic organ prolapse severity. Obstet Gynecol. 2013;121(5):1017-24.
Rotstein E, Ullemar V, Starck M, Tegerstedt G. Three-dimensional endovaginal ultrasound assessment using the levator ani deficiency score in primiparas: A replication study. Acta Obstet Gynecol Scand. 2023;102(9):1236-42.

Continence 12S (2024) 101655
DOI: 10.1016/j.cont.2024.101655