To investigate the changes of pelvic floor hiatus in patients with refractory dysdefecation constipation under magnetic resonance imaging (MRI).

Sixty patients with refractory dysdefecation constipation (observation group) and 37 healthy volunteers (control group) were selected prospectively in the First Affiliated Hospital of Shandong First Medical University. The transverse diameter (LH-W), longitudinal diameter (LH-L), posterior angle of pelvic floor hiatus (LH-PA), and the distance of longitudinal axis of pelvic floor hiatus from the center (d-LHVC) were compared between the two groups.

The transverse diameter (LH-W) and longitudinal diameter (LH-L) of the pelvic floor hiatus in the observation group and the control group were respectively [(2.64±1.89) cm, (2.59±2.44) cm; (7.35±2.52) cm, (6.82±2.07) cm], and there was no significant difference between the two groups (t=0.763, 0.39; P＞0.05). The transverse diameter (LH-W) and longitudinal diameter (LH-L) of the pelvic floor hiatus in the observation group and the control group were respectively [(3.37±2.26) cm, (4.11±3.84) cm; (6.64±2.29) cm, (5.54±1.84) cm], and the differences were statistically significant (t=-6.11, 9.71; P＜0.05). The posterior angle of pelvic floor hiatus (LH-PA) in the observation group and the control group were (48.57±5.23)°, (45.12±6.28)°, respectively, and there was no significant difference between the two groups (t=2.58, P＞0.05). The posterior angle of pelvic floor hiatus (LH-PA) in the observation group and the control group were (54.31±7.29)°, (68.84±6.37)°, respectively, with statistical difference (t=26.35, P＜0.05). In the resting state, the distance (d-LHVC) of the longitudinal axis of the pelvic floor hiatus was (8.74±2.21) mm and (5.45±1.87) mm respectively in the observation group and the control group, and the difference was statistically significant (t=16.24, P＜0.05), The distance (d-LHVC) of the longitudinal axis of the pelvic floor hiatus was (12.31±2.32) mm and (6.47±2.16) mm respectively in the observation group and the control group, and the difference was statistically significant (t=-11.36, P＜0.05).

The patients with refractory dysdefecation constipation have the central axis deviation of pelvic floor hiatus in resting state. The transverse diameter and posterior angle of pelvic floor hiatus are smaller than those of normal people under forced defecation state, and the deviation amplitude of pelvic floor hiatus axis is significantly larger than that of normal people, and the shape of pelvic floor hiatus is significantly asymmetric.