H and M lines on MRI proctography

Case contributed by Dr Vikas Shah


Mixed stress and urge urinary incontinence. Vaginal discomfort. Difficult defecation.

Patient Data

Age: 35 years
Gender: Female

These images show the measurements taken on an MRI proctogram study, and are based on this case.

The measurements are taken at maximal straining and are as follows:
Bladder neck: 37 mm below line (mild cystocele)
Uterine cervix: 12 mm below line (mild uterine descent)
Anorectal junction: 63 mm below line (moderate anorectal junction descent)

H line: 75 mm (mild hiatal enlargement)

M line: 60 mm (moderate pelvic floor descent)

Anterior rectocele: 36 mm in depth (moderate sized anterior rectocele)

Case Discussion

The pubococcygeal line is drawn on a mid sagittal image taken from the evacuatory phase of an MRI proctogram study, from the inferior margin of the pubic symphysis, to the final coccygeal segment, and corresponds anatomically to the plane of the levator muscle. The H line is drawn from the inferior margin of the pubic symphysis to the posterior aspect of the anorectal junction, and represents the diameter of the levator hiatus, and a normal value is < 6 cm. The M line is drawn perpendicularly from the posterior end of the H line to the PCL, and represents the descent of the hiatus, and a normal value is < 2 cm. An increase in the length of the H and M lines over the normal limits indicates pelvic floor laxity.

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Case information

rID: 81476
Published: 26th Aug 2020
Last edited: 28th Aug 2020
Inclusion in quiz mode: Included

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