|ECR 2018 / C-0529|
|Is MRI the gold standard imaging technique to diagnose levator ani muscle avulsion?|
Aims and objectives
The levator ani muscle (LAM) is a broad muscular sheet of variable thickness attached to the internal surface of the bony pelvis. There is significant controversy about the sub-divisions of the muscle, however, it is broadly accepted that it is subdivided into parts according to their attachments, namely the iliococcygeus, pubococcygeus, and ischiococcygeus. The pubococcygeus is further subdivided into separate parts according to the viscera they are related to e.g pubourethralis, pubovaginalis and puborectalis1-6.
The components of the LAM differ from most other skeletal muscles in their function; as they maintain constant tone; allow voiding and defaecation; contract quickly at the time of acute stress such as cough and sneeze; have ability to distend considerably during labour and then resume normal functioning. The degree of required distension of the puborectalis muscle varies greatly between individuals.
Trauma of the LAM can occur by overdistention of the muscle and by disconnection of the muscle from its insertion to the pubic bone (avulsion).
Levator ani muscle avulsion is known to be associated with pelvic floor dysfunction (PFD) such as pelvic organ prolapse.
Magnetic resonance imaging (MRI) was the first imaging technique to demonstrate LAM avulsion and is considered the reference standard. Currently, three-dimensional (3D) ultrasound (US), a technique which is less expensive and more easily accessible, is being used extensively for the diagnosis of LAM avulsion. However, before US can be implemented in clinical practice its diagnostic accuracy needs to be assessed. For detection of LAM avulsion 3D transperineal ultrasound (TPUS) has shown reasonable agreement with MRI in women with a stage ≥2 cystocele7 and 3D endovaginal ultrasound (EVUS) has been shown to be comparable to MRI in a small sample (n=21)8.
Our aim was to assess the accuracy of all three imaging techniques (TPUS, EVUS and MRI) in the diagnosis of LAM avulsion and to correlate them with signs and symptoms of PFD, with a view to establish if US can substitute MRI for the diagnosis of LAM avulsion.
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