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Quantification of Levator Ani Hiatus Enlargement by Magnetic Resonance Imaging in Males and Females with Pelvic Organ Prolapse

Published: April 17th, 2019



1Diagnostic Imaging Centre, Iniziativa Medica

Here we present a protocol to standardize the measurement of the levator ani hiatus size by magnetic resonance imaging. The purpose is to extract biomechanical inferences from image analysis by comparing resting and straining values in patients of both sexes with pelvic prolapse, using consistent anatomical bony landmarks.

Here we present a protocol to examine the levator ani hiatus in males and females with pelvic organ prolapse, during the Valsalva maneuver and while evacuating acoustic gel, using a horizontally oriented 1.5 T magnetic resonance (MR) scanner. On midsagittal images, the vertical distance of pelvic organs is measured in millimeters relative to the hymen plane (female) and to the lower border of the symphysis pubis (male), preceded by - (above) or + ( below) signs. On axial images, the levator ani area is calculated in square centimeters with a free-hand tracing method from three key images, passing through the midsymphysis (level I), tangential to the lower border of the symphysis (level II), and at the maximal anterior rectal wall bulging (level III). Areas at rest and strained are compared to find evidence of a percentage of increase. The purpose is to provide objective evidence of the maximal extent of pelvic organs descent and hiatus enlargement without the interference of foreign objects or the examiner's proximity, so as to overcome the limitations of pelvic examination and transperineal sonography (i.e., subjectivity and sex-related limitations [female only]).

Pelvic organ prolapse (POP) develops when the forces acting inside the boundaries of levator ani hiatus are no longer counteracted by those outside, leading to abnormal enlargement and organ impingement. Several factors are responsible for the disease, including ligaments, fascia, or muscular tonic activity. Whatever the mechanism involved, the increased hiatus size has been credited with a reliable index to assess the inability to keep it closed. Usually, the status of pelvic support is determined in women during a pelvic examination1 by observing the location of the cervix, vaginal apex, and vaginal walls during the Valsalva maneuver. However....

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Procedures involving human subjects have been performed according to the National Guidelines of the Italian Radiological Society

1. Patient preparation

  1. Help patients to fill in a form which provides information on their history, current symptoms, treatments (either medical or surgical), and prior medical records, if any.
  2. Obtain each patient's written consent before beginning the examination.
  3. Clearly explain in advance the characteristics and purpose of the p.......

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Between 2012 and 2018, this protocol has been successfully adopted in three different diagnostic centers in Italy at an average cumulative rate of 30 ± 4 exams per month, using the same 1.5 T MR scanner model and technical settings (see Table 1 and Table of Materials). During this period, over 2,000 examinations have been performed in patients of both sexes for the following three main disease categories: pelvic organ prolapse and evacuation disturba.......

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This method has an overt advantage over pelvic examinations that are limited to the assessment of the urogenital hiatus in only females. In contrast, the method presented here examines the entire levator ani hiatus in both sexes. Moreover, although easily examined by palpation by the gynecologist, the female hiatus can be calculated only approximately with a ruler, to produce the area of an oval1. Similarly, an advantage does exist over 2- and 3-D TPUS4,

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The authors are especially indebted to nurses Paola Garavello and Giulia Melara, for their valuable assistance during the examinations.


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Name Company Catalog Number Comments
MR scanner Philips Medical Systems, High Tech Campus  37, 5656 AE, Eindhoven,
The Netherlands
Description: 1.5 T horizontally oriented, Multiva model, SENSE XL Torso coil
Procedure: Position the patient in the left lateral decubitus on the diagnostic table with the coil warpped around the pelvis
Catheter Convatek ltd, First avenue Deeside, Flintshire CH5 2NU
Description: Sterile vaginal catheter, 16 ch,180 mm long, 3 mm wide
Procedure: Gently insert the lubricated tip inside the anal canal for contrast administration with patients in the left side position
Holder Kartell Plastilab, Artiglas Srl, Via Carrara Padua, Italy Description: Universal test-tube holder with multiple 13-mm holes
Procedure: Put 3 empty syringes vertically inside the holes with the outlet cone down
Syringe Pikdare Srl, Via Saldarini Catelli 10 , 22070 Casnate con Bernate (Como) Italy Description: Sterile, latex free,60 mL graduated transparent cylinder, catheter cone
Procedure: Fill with contrast, adjust the plunger and connect to the catheter
Contrast Ceracarta SpA, Via Secondo Casadei 14 47122 Forlì
Description: Eco supergel not irritant, water soluble, salt free
Procedure: Dilute the content of each syringe adding 30 mL of tap water to 50 mL of acustic gel
Mixer device Kaltek Srl, Via del Progresso 2 Padua
Description: Kito-Brush for endovaginal sampling
Procedure: Rotate one full turn 10-20 times until obtaining an homogeneous gel
Pad Fater SpA, Via A. Volta 10, 65129 Pescara
Description: Pad for incontinent subjects
Procedure: Wrap around patient's pelvis to collect any material and prevent diagnostic table contamination
Lubricant Molteni farmaceutici, Località Granatieri Scandicci (Florence)
Description: Luan gel 1%
Procedure: Apply on the tip of catheter before insertion
Apron Mediberg Srl, via Vezze 16/18 Calcinate 24050 (Bergamo)
Description: Kimono
Procedure: Put on counteriwise (opening back) to maintain patient's dignity
Gloves Gardening Srl, Via B. Bosco 15/10 16121 Genova
Description: Nitrile, latex free, no talcum powdered
Procedure: Wear during contrast preparation and catheter insertion; change regularly to prevent cross contamination

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