Screening for the effectiveness of conservative treatment in chronic anal fissure patients using anorectal manometry

Purpose Chemical sphincterotomy (CS) is routinely applied in order to avoid the irreversible anal incontinence associated with the surgical treatment of chronic anal fissure (CAF). However, CS has a lower cure rate than surgery. We developed a screening test (using anal manometry) to separate those patients that are unlikely to benefit from CS and should undergo a more aggressive treatment. Methods Changes in pressure both at rest and during voluntary contraction of the anal sphincter in 187 patients with chronic anal fissure and 25 healthy subjects (control group) of both sexes were measured. Patients were then sequentially treated (1:1:1) with botulin toxin injections (TOX) ( n = 63) or ointments of either nitroglycerine (NTG) ( n = 65) or diltiazem (DTZ) ( n = 59) for 2 months. The cure rate (overall and for each treatment group) and its relationship with changes in anal pressure were determined. Results The overall cure rate was 53% (NTG = 54%, DTZ = 53% and TOX = 51%). Healing was not related to differences in resting or voluntary contraction pressure. However, the probability of healing was associated with an increase in the percentage change between resting and squeeze pressure (PI index) higher than 150% (190 ± 122), similar to that of the control subjects (200 ± 115). Failure of CS was observed in patients with a lower PI (114 ± 77). Conclusions The ratio resting/voluntary contraction pressure may be predictive of healing in CAF, thus allowing the selection of patients at high risk of failure of conservative treatment.