Hemorrhoids

Hemorrhoids are masses of normal vascular tissue in the anal canal and are often the source of a variety of symptoms including bleeding, anal pruritus, prolapse, and anorectal pain due to thrombosis. The prevalence of hemorrhoids is equal in both sexes, peaking between the ages of 45 and 65 years ⁽³⁾. They arise from a plexus or a "cushion" of dilated veins originating from the superior and inferior hemorrhoidal veins, which are located in the submucosal layer in the lower rectum.

Hemorrhoids are classified as internal or external, based on whether they arise above or below the dentate line, and often coexist ⁽⁴⁾. Internal hemorrhoids arise from the superior (internal) hemorrhoidal vascular plexus, and their primary locations are the 3, 6, and 9 o'clock positions corresponding to the end branches of the middle and superior hemorrhoidal veins. External hemorrhoids are dilations of the inferior (external) hemorrhoidal plexus and lie below the dentate line, covered with squamous epithelium that contains numerous somatic pain receptors. External skin tags, which represent residual excess skin associated with prior thrombosis of external hemorrhoids, are often confused with external hemorrhoids but they are not hemorrhoids.

Internal and external hemorrhoids communicate with each other and drain into the internal pudendal veins, ultimately communicating with the inferior vena cava, although they have no direct communication with the portal system.

Hemorrhoids may reside in proximity to rectal varices in patients with cirrhosis but are not more common in patients with portal hypertension. There is no widely used classification system for grading external hemorrhoids, but internal hemorrhoids are graded from I to IV according to the degree to which they prolapse from the anal canal (Table I).

KEYPOINT A thorough physical examination of the anorectum, properly done, is essential to diagnosing diseases of the rectum and anus.

Pathogenesis

The development of symptomatic hemorrhoids has been associated with increasing age, chronic diarrhea, pregnancy, pelvic tumors, prolonged sitting and straining, and possibly chronic constipation ⁽⁵⁾. Internal hemorrhoids are normal vascular cushions containing a rich arteriovenous network, which are present at birth and by partially occluding the anus contribute to continence.

These vascular cushions project into the lumen where they are subjected to downward pressure during defecation. With advancing age or aggravating conditions, the connective tissue muscle fibers that anchor the vascular cushions to the underlying sphincter mechanism become attenuated and deteriorate, allowing the hemorrhoids to slide into the anal canal and become congested, bleed, and prolapse.