Role of magnetic resonance defecography in the assessment of obstructed defecation syndrome

Table 1 Pelvic floor measurements using H-line and M-line¹

Grade	H-line (measure of hiatal enlargement)	M-line (measure of pelvic floor descent)
Normal	< 6 cm	< 2 cm
Mild	6-8 cm	2-4 cm
Moderate	8-10 cm	4-6 cm
Severe	> 10 cm	> 6 cm

¹H-line and M-line are measured in mid-sagittal cine gradient echo sequence at maximum strain during defecation.

Table 2 Grading of pelvic organ prolapse using pubococcygeal line as reference line

Grade	Descent below pubococcygeal line1
Mild	1-3 cm
Moderate	3-6 cm
Severe	> 6 cm

¹Descent is measured from the pubococcygeal line to the inferior bladder base (cystocele), anterior cervical lip (cervical descent) and anorectal junction (anorectal junction descent).