Diagnosing pubovisceral avulsions: a systematic review of the clinical relevance of a prevalent anatomical defect

In this systematic literature review, we assessed the clinical relevance of diagnosing pubovisceral avulsions in women with pelvic floor dysfunction. Diagnostic methods of interest were MR imaging and perineal ultrasonography. The presence of pubovisceral avulsions was shown to be relevant with respect to POP symptoms and POP stage, especially in the anterior and central compartment. Recurrence of POP after surgery was also related to avulsions according to the available studies. There was no clear relation between pubovisceral avulsions and SUI, but in this respect, there might be a difference between minor and major defects [26]. Studies with regard to the relation between symptoms of anorectal dysfunction and pubovisceral avulsions yielded contradictory results.

Even though it has long been recognized that the levator ani muscle plays a critical role in pelvic organ support, in what way pregnancy and/or childbirth injure the pelvic floor has not been proven conclusively. Pelvic floor injury might be caused by compression, stretching or tearing of nerves, muscles, and/or connective tissue [42, 43]. Evaluation of the importance of muscle integrity has gone through an exponential growth over the past decade with the assessment of pubovisceral avulsions initially being performed using MR imaging. Therefore, this diagnostic method became the reference standard. The research group of Professor DeLancey was the first to standardize the evaluation of MR images [44]. However, nowadays a growing amount of studies use perineal ultrasonography to assess pubovisceral muscle integrity as this diagnostic method has the advantage over MR imaging of easier implementation in routine clinical care together with the benefits of significantly lower cost and superior availability. The standardization of perineal ultrasonography when evaluating pubovisceral avulsions was performed under the supervision of Professor Dietz [31]. Approximately half of the studies in this review focused on using MR imaging to detect pubovisceral avulsions while a slightly higher number of studies used perineal ultrasonography.

There was a notable variance in the naming for the subdivision of the levator ani muscle of interest for this review. In 2004, Kearney et al. [45] performed a literature search on the various descriptions and terminology for this muscle. They found that even though there was a great diversity regarding the terms chosen in the available literature, the number of origin and insertion pairs was relatively consistent among authors. Overall, the levator ani muscle comprises three subdivisions, namely, the iliococcygeal, puborectal, and pubovisceral muscles. The pubovisceral muscle includes the puboanal, puboperineal, and pubovaginal muscles and, together with the puborectal muscle, originates from the pubis [15]. Another frequently used term for the pubovisceral muscle is pubococcygeus muscle; however, this implies a connection between the pubis and coccyx while in fact the muscle originates from the pubis and inserts into the wall of the vagina and anorectum. It is thus our belief that pubovisceral muscle is the correct term to be used.

We had some difficulty to decide on the inclusion of one study by Adekanmi et al. [46]. The muscle injuries that were evaluated differed from injuries as described in all other studies with a distinction being made by Adekanmi et al. between central and lateral (endopelvic) fascial defects as well as changes in vaginal configuration after surgery. Based on subsequently published literature and correspondence with the authors, we came to the conclusion that the researchers had not studied pubovisceral avulsions as included in this review. The paper was therefore excluded.

The present review showed that the relation between POP and pubovisceral avulsions is eminent as all but one paper [28] found a significant difference in POP incidence (Table 4). This relation was strongest in the compartments with highest recurrence rates after POP surgery, namely, the anterior and central vaginal compartment. DeLancey et al. [13] were the only researchers to perform a case-control study with group matching for POP status in which, after multivariable regression, avulsion was still identified as an independent risk factor for POP. We were not able to further assess the correlation between avulsions and POP stage, POP surgeries, and POP recurrences from the accumulated data in this review. However, as up to 30 % of POP surgeries are currently performed due to relapse of POP [2], pubovisceral avulsions seem clinically relevant as an independent risk factor for POP. It has been suggested that women with pubovisceral avulsions might benefit from primary vaginal mesh surgery [47, 48]. However, Wong et al. [37] found that mesh implementation in these women did not fully compensate for the effect of pubovisceral avulsions on recurrence rates. Evaluating pubovisceral muscle integrity in appropriate clinical POP outcome studies will be needed to further lead the way, especially with regard to different strategies in surgical repair of various POP stages. Which diagnostic method, MR imaging or perineal ultrasonography, should be used remains to be assessed as well [49].

While the association between urinary symptoms and childbirth is beyond dispute [50], this is presumably not directly related to pubovisceral avulsions, since available studies have shown contradictory results. Women with pubovisceral avulsions were less likely to suffer from SUI (subjective and/or objective as confirmed by urodynamics) [33]. When pubovisceral avulsions were divided into major and minor avulsions, it was found that women with major defects are less likely and women with minor defects are more likely to have lower urinary tract symptoms [26]. The lack of a clear association between avulsions and SUI might be due to the fact that these avulsions do not seem to affect urethral mobility as much as they affect bladder support [51, 52]. Moreover, Morgan et al. [28] suggested that damage to the pudendal nerve could explain the difference in frequency of urinary symptoms between major and minor defects. They proposed that with a minor injury the preservation of one side of the muscle or parts of both sides can result in an asymmetry that alters reflexive responses of the urethra, bladder, and pelvic floor leading to symptom exacerbation, while a complete injury may be symmetrical leading to the absence of a motor and sensory reflex and therefore potentially having a less dramatic effect on symptoms. Electromyographic research to support this hypothesis is currently lacking.

The fact that pubovisceral avulsions are caused by vaginal delivery is beyond question and the same accounts for the occurrence of sphincter tears due to vaginal delivery. As the latter association is found to be related to symptoms of anorectal dysfunction, e.g., fecal incontinence (FI), together with the similar etiology of pubovisceral avulsions and sphincter tears, we expected a relation between symptoms of anorectal dysfunction and pubovisceral avulsions. This expectation is strengthened by the finding of Heilbrun et al. [24] that women with major levator defects have a higher prevalence of anal sphincter tears. Moreover, Lewicky-Gaupp et al. [25] found that older women with FI were more likely to have levator defects than women without FI (both younger and older) and that this association remained significant after correcting for external anal sphincter tears. Rodrigo et al. [36] reported a higher prevalence of RI among a group of women with pubovisceral avulsions. After multivariable analysis, this relation came on the account of hiatal area size on Valsalva and was not the effect of avulsions per se.

A limitation of this review was the heterogeneity of the available studies. Due to the variation in diagnostic methods used, study populations included, and outcome measures assessed, it was not possible to pool the available data into reliable relative risk factors for pubovisceral avulsions. To perform a patient-specific risk analysis and to ultimately individualize therapy for POP, it is our recommendation to evaluate the integrity of the pubovisceral muscle in those women who are most affected by the consequences of pubovisceral avulsions, i.e., women visiting tertiary urogynecological clinics. Therefore, both standardized questionnaires regarding symptoms of pelvic floor dysfunction and clinical examination, e.g., POP-Q, should be registered in this population.

Another limitation was that all studies but one [35] on perineal ultrasonography are coauthored by Professor Dietz (Sydney, Australia). With regard to the technique of MR imaging, Professor DeLancey (Ann Arbor, MI, USA) coauthored six of eight of the included studies. Both researchers are renowned experts within their field, but external validation therefore seems relevant and is awaiting. Little data are currently available on agreement between MR imaging and perineal ultrasonography in the evaluation of pubovisceral avulsions. Regarding this, Zhuang et al. [41] are the first to compare ultrasonography to MR imaging. They reported a substantial agreement for both agreement between methods (Cohen’s kappa = 0.79) and for agreement regarding the extent of the avulsion (Cohen’s kappa = 0.65). To further evaluate the agreement between MR imaging and perineal ultrasonography with regard to pubovisceral avulsions and to obtain the level of agreement between observers, the translabial 3D-ultrasonography for diagnosing levator defects (TRUDIL) study is currently being performed in the Netherlands [49].

Besides visualizing pubovisceral avulsions, these muscle defects can also be palpated. Using palpation, a pubovisceral avulsion is diagnosed if there is a detachment of the pubovisceral muscle from its insertion on the pubis [38]. Palpation can be easily incorporated in the standard gynecological examination, but it has been reported to have a considerable learning curve with only moderate agreement between different observers [38, 40]. No studies could be identified that used palpation of the pubovisceral muscle defect as a diagnostic method solely. Three studies have, however, been published on the agreement between palpation and ultrasonography or MR imaging [38‐40]. In 2006, Dietz et al. [39] evaluated palpation versus perineal ultrasonography in a cohort of 54 patients and found poor agreement (Cohen’s kappa = 0.098) between both methods with only two avulsions diagnosed by both methods. The agreement between two observers performing palpation of the muscle defect and an independent blinded reviewer of ultrasonographic data showed moderate and fair agreement, respectively [38]. Agreement between palpation and MR imaging was reported to be moderate (Cohen’s kappa = 0.444) [40]. In the latter study, a pubovisceral avulsion was detected by both methods in only 3 of 24 women. We believe that this might be explained by the fact that palpation appears to rely more on the comparison of findings with a supposedly intact contralateral side hereby making bilateral defects much more difficult to detect digitally than on imaging. Overall, it seems that even though palpation of the muscle defect appears to be the easiest diagnostic method to implement in routine clinical care, the value of this method is limited. Implementation of either perineal ultrasonography or MR imaging in the diagnostic workup of women with complaints of pelvic floor dysfunction appears more feasible and of added value.