BACKGROUND: It has been demonstrated that the maximum squeeze pressure and the mean resting pressure do not reflect the true clinical situation of patients having fecal incontinence, as well as the functional status of the anal canal. Furthermore, a wrong diagnosis could be obtained and therefore misleading to a not effective treatment. AIM: Under the hypothesis that squeezing and sustaining the anal canal contraction is more important than the maximum squeeze pressure, the capacity to sustain the squeeze pressure of the anal canal was analyzed aiming to quantify the sphincteric function. METHODS: Seventy-two patients having fecal incontinence in different degrees (56 female) and 15 normal individuals (9 female) were submitted to anorectal manometry to measure the mean resting pressure, the maximum voluntary squeeze pressure and the capacity to sustain the squeeze pressure. RESULTS: Normal individuals had normal values of mean resting pressure and maximum squeeze pressure, and adequate capacity to sustain the squeeze pressure of the canal anal. Incontinent patients had mean resting pressure and maximum squeeze pressure with normal or below normal pressoric values and similar profile of capacity to sustain which was moderate in the initial phase and worse in the intermediate and final phases, with decreasing of the capacity to sustain more than 35% in 78% of the patients. The maximum squeeze pressure presented excellent specificity (100%), but low sensitivity (46%) for fecal incontinence. Comparatively, the squeeze pressure presented high specificity (93%) and high sensitivity (78%) for fecal incontinence. Although the maximum squeeze pressure did not indicate false positive, it presented a 72% false negative. The probability of this event to happen with the capacity to sustain measure is 20% lower, and it was statistically significant. CONCLUSION: Sphincteric function can be better analyzed by using the capacity to sustain the squeeze pressure. capacity to sustain indicates more precisely the functional capacity of the anal canal in relation to voluntary continence, and it is better than maximum squeeze pressure as an isolated index.
Fecal incontinence; Anus, physiology; Constipation; Manometry; Muscle fatigue
