LEVATOR AVULSION: HOW LIKELY IS AFALSE POSITIVE DIAGNOSIS?
F. TUREL, K. SHEK, H. DIETZ;
Sydney Med. Sch. Nepean, Sydney, Australia.
Introduction: The levator animuscle plays a major role in maintaining pelvic organ support andfunction. Levator trauma (avulsion) as a result of vaginal childbirthis associated with pelvic organ prolapse and prolapse recurrenceafter surgery (1). To date, several methodologies have been used toevaluate the pelvic floor muscle and its avulsion. Tomographicultrasound imaging (TUI) is gaining popularity as it is repeatable,accessible and cost effective (2).
Objective: To test thevalidity of the published TUI method in a group of nulliparous womenby establishing the likelihood of a false positivediagnosis.
Methods: This is a retrospective analysis of 172nulliparous women seen at 2 tertiary Urogynaecological centresbetween June 2012 and September 2016. All patients underwent astandardized interview, clinical examination and 4D translabialultrasound. Postprocessing of volume data was performed by the firstauthor at a later date blinded against all clinical data. Anindependent co-investigator inserted parous patients randomly inorder to provide for blinding against parity. Assessment for avulsionon TUI was performed on a volume obtained at maximum pelvic floormuscle contraction at 2.5 mm slice intervals, from 5 mm below to 12.5mm above the plane of minimal hiatal dimensions (2). To diagnose afull avulsion we used established minimal criteria that require all 3central slices to be abnormal on the affected side (2). In doubtfulcases we measured the levator- urethral gap (see Figure)(3).
Results: Of 172 vaginally nulliparous women seenduring the inclusion period, 9 datasets were incomplete and 1 patienthad had major pelvic surgery due to malignancy and was excluded fromthe study. The results pertain to the remaining 162 women. A completeavulsion was diagnosed in three nulliparous woman (one right- sided,two left-sided). On reviewing these three cases, one was judged aspositive (right sided complete avulsion) by the 2 senior authorsindependently (Fig. 1a). The volume acquisition had been performedwith a Voluson S6 and had been difficult due to vaginal atrophy andprevious surgery. After unblinding we consider acoustic shadowing thelikely cause of this false positive diagnosis. The other two caseswere judged as negative (i.e., not an avulsion) by the two seniorauthors (see Fig 1b for one of those), with incorrect slice placementdue to suboptimal identification of the plane of minimal dimensionsthe likely cause.
Figure: Tomographic imaging innulliparous patients. The left patient was rated as right-sidedavulsion (likely false- positive due to poor imaging conditions), theright was rated as normal by the two senior authors.
Conclusions:The published criteria for diagnosing levator avulsion on 4D translabial ultrasound using Tomographic Imaging are unlikely to result ina false-positive diagnosis.
References: 1.) Int UrogynecolJ. 2011;22:1221-32.
2.) Int Urogynecol J. 2011;22(6):699-704.
3.)Int Urogynecol J. 2016;27(6):909-13.