Internal sphincter and the nature of haemorrhoids.

Internal anal sphincter activity has been studied in 84 patients with haemorrhoids and 40 asymptomatic subjects. Activity was estimated by measuring maximum resting anal pressure with a water filled anal balloon probe 7 mm in diameter connected to a strain gauge pressure transducer. There was greater activity of the internal sphincter in patients with haemorrhoids than in controls, but there was no significant relationship between sphincter activity and duration of symptoms, predominant symptom (bleeding or prolapse), severity of symptoms, history of pain, history of straining at stool, or size of haemorrhoids. Straining at stool occurred significantly more often in patients whose main complaint was prolapse than in those whose main complaint was bleeding. Anal dilatation reduced sphincter activity and the best clinical results were obtained in those with the most active sphincter. An internal sphincter abnormality may be an aetiological factor in some patients but there must be other factors as well. Straining at stool may determine whether bleeding or prolapse is the predominant symptom.