Hypertensive anal cushions as a cause of the high anal canal pressures in patients with haemorrhoids

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Abstract
Anorectal manometry and electrophysiology studies were conducted in 25 men with non-prolapsing haemorrhoids, ten men with prolapsing haemorrhoids, and 20 age-matched normal men. Mean(s.e.m.) minimum basal pressures were significantly higher in patients with non-prolapsing haemorrhoids than in normals (61(5) versus 43(7) cmH2O; P < 0·05) or patients with prolapsing haemorrhoids (55(4) cmH2O; P < 0·05). There were no significant differences in maximum basal pressures and maximum squeeze pressures. During rectal distension, all normal subjects showed relaxation in all anal channels. However, 92 per cent of patients with non-prolapsing haemorrhoids and 40 per cent of patients with prolapsing haemorrhoids showed no relaxation in the outer anal channels, even when relaxation occurred in the inner anal channels; internal sphincter electrical slow waves were suppressed and the integrated electrical activity of the external sphincter had returned to predistension values. Maximum residual anal pressures during balloon distension were significantly higher in patients with non-prolapsing haemorrhoids than normals (75(7) versus 45(7) cmH2O; P < 0·01), or patients with prolapsing haemorrhoids (53(3) cmH2O; P < 0·05). When subjects increased intra-abdominal pressure rectal pressure was significantly higher in patients with non-prolapsing haemorrhoids than in normal subjects (157(10) versus 105(15) cmH2O; P < 0·05), but not in patients with prolapsing haemorrhoids (126(14) cmH2O). Resting anal cushion pressures in patients with non-prolapsing or prolapsing haemorrhoids were much higher than normal capillary or venous pressure and significantly higher than those recorded in normals (median 35, 35 versus 10 cmH2O; P < 0·0001). Pressures recorded during coughing (60, 60 versus 30 cmH2O) and straining (78, 80 versus 55 cmH2O) were also significantly higher (P < 0·0001) in patients than in normals. Pressures after straining were higher than those recorded before (38 versus 29 cmH2O; P < 0·05) in 60 per cent of patients but no normal subjects and took 18–36 s to return to baseline. This study suggests that the abnormally high pressures in the anal canal in patients with haemorrhoids may be related to an increased vascular pressure in the anal cushions.