Anal Dilation Treatment

Abstract

The theoretical background to the employment of dilatation for the treatment of haemorrhoids depends principally on the following precepts: 1) Haemorrhoids consist of loose connective tissue which contains thin-walled sinusoids fed with oxygenated blood via small arterioles. The sinusoids drain via vessels which run upwards in the submucosa of the lower rectum for at least three centimetres before they penetrate the muscular lamina propria to eventually link with the portal system (Fig. 7.1). While the draining vessels are in the submucosa they are easily obstructed by any raising of intrarectal or intra-abdominal pressure, causing backflow and rapid engorgement of the haemorrhoid plexus (Fig. 7.2). Much of our current understanding of the nature of haemorrhoids, and their relation to anal cushions — normal structures present from birth — stems from the work of W.H. Thomson. 2) That, in cases of haemorrhoids, a band (or bands) of fibrosis can be felt in the circular muscle of the anal sphincter and lower rectum. Attention to the existence of this band was originally drawn by Ernest Miles (1919) who named it the “pecten band”, although he thought wrongly that the band lay in the subcutaneous tissue. As a consequence of the fibrous ring(s), even when the anal sphincter relaxes to allow stool to pass, the lumen remains restricted, thus generating higher intrarectal pressures. 3) Chronic persistent rise in pressure in the lower rectum and anal canal during defaecation causes permanent stretching and enlargement of the haemorrhoid veins and other supporting tissues, converting normal cushions to abnormal haemorrhoids. Straining habits of defaecation contribute an important element for backpressure on the pelvic and haemorrhoidal veins, increasing the degree of engorgement. 4) Once the presence of a haemorrhoid is established, mechanical pressure, as when a hard constipated stool is squeezed through the constricted anal outlet, dislocates the pile in a downward direction, causing progressive problems of prolapse as well as aggravating venous engorgement of the anal veins.