Levator-Urethra Gap: Normative Data in a Nonpregnant Nulliparous Population

Area of Science:

• Pelvic floor imaging and diagnostics
• Female pelvic medicine and reconstructive surgery
• Anatomical variation and measurement standards

Background:

• The levator ani muscle is crucial for pelvic floor support.
• Assessing levator ani injury often relies on indirect measurements.
• Establishing normative data is essential for accurate clinical assessment.

Purpose of the Study:

• To determine the normative range of the levator-urethra gap (LUG) in nonpregnant, nulliparous women.
• To establish a reference standard for evaluating levator ani muscle injury or avulsion.
• To compare LUG measurements obtained via MRI and 3D transperineal ultrasound.

Main Methods:

• High-resolution magnetic resonance imaging (MRI) and 3D transperineal ultrasonography were performed.
• The levator-urethra gap (LUG) was measured in the plane of minimal hiatal dimensions.
• Measurements were taken on both right and left sides across three contiguous image slices.

Main Results:

• 134 MRIs and 70 ultrasounds were evaluable from 135 participants.
• The 99th percentile for LUG was ≤2.39 cm for both MRI and ultrasound.
• Putative injury thresholds were identified as low as 2.1 cm (MRI) and 2.25 cm (ultrasound).

Conclusions:

• The study established normative levator-urethra gap (LUG) values for nulliparous women.
• These normative ranges can serve as a standard for diagnosing levator ani injury.
• Specific LUG thresholds suggestive of injury were identified for both MRI and ultrasound modalities.