• puborectalis muscle
• perineum
• anismus
• dyssynergic defecation

Dynamic transperineal ultrasound (DTPUS) is gaining increasing interest for the study of pelvic floor pathophysiology. It is very useful to evaluate pelvic floor dynamics and morphological changes. Unlike defecography, it is usually performed in a left lateral position, an unnatural position for straining and squeezing maneuvers. This study was aimed at evaluating if body position affects the assessment of puborectalis muscle length (PRL) and anorectal angle (ARA).
Twenty eight consecutive females (mean age:50.6±16.6 yrs) referred for the presence of chronic non organic constipation were enrolled. According to the Rome III criteria they were separated into functional constipation (FC) (14 pts) and functional defecatory disorder (FDD) (14 pts) by using anorectal manometry, Rx defecography and the balloon expulsion test. Control subjects were 12 asymptomatic non-constipated females (mean age 49.7±11.9 yrs). Transperineal images were obtained using a 3-4.5 MHZ convex probe by the same operator in three different positions: left lateral (LL), supine (SP) and sitting (ST). For each position, the ARA and the distance between the symphysis pubis and the posterior limit of anorectal junction (expressing the PRL) at rest and during push straining and squeezing were evaluated. The emptying of the rectal ampulla was assessed after filling the rectum with 120 cc of ultrasound and compared with the balloon expulsion test (BET). Evidence of puborectalis contraction on DTP-US was also compared with paradoxical contraction (PC) during straining.
In basal conditions PRL values in HV were significantly different in ST in comparison with LL and SP. PRL values were lower in FDD than in HV and FC because of contraction or lack of relaxation of PR. During push straining in HV, PR relaxation was better in ST than in SP and LL. A trend toward a less paradoxical contraction of PR was seen in FDD in ST. During squeezing in HV and FC, contraction is less effective in SP than in ST and LL. A good agreement between BET and GET in FDD and FC was found in SIT.