Hemorrhoids are specialized, nonpathologic, vascular cushions found within the anal canal. They are typically organized into three anatomically distinct cushions located in the left lateral, right anterolateral, and right posterolateral anal canal (Fig. 26-1, A). Hemorrhoids are found in the submucosal layer and are considered sinusoids because they typically have no muscular wall. They are suspended in the anal canal by the muscle of Treitz, which is a submucosal extension of the conjoined longitudinal ligament.
Hemorrhoids are classified as internal or external. Internal hemorrhoids are located proximal to the dentate line and have visceral innervation; therefore the most common presentation is painless bleeding. Because they are close to the anal transitional zone (ATZ), internal hemorrhoids can be covered by columnar, squamous, or basaloid cells. External hemorrhoids are located in the distal third of the anal canal and are covered by anoderm (squamous epithelium). Because of the somatic innervation of external hemorrhoids, patients who have these are more likely to be seen with pain (Fig. 26-1, B).
Hemorrhoids are thought to enhance anal continence and may contribute 15% to 20% of resting anal canal pressure. They also provide complete closure of the anus, enhancing control of defecation. In addition to making important contributions to the maintenance of continence through pressure phenomena, hemorrhoids also relay important sensory data regarding the composition (gas, liquid, stool) of intrarectal contents.
The central causative pathway for the development of hemorrhoidal pathology is an associated increase in intraabdominal pressure. This increase may be secondary to straining, constipation, or obesity. Other etiologic factors can include diarrhea, pregnancy, and ascites. Aging is also associated with dysfunction of the supporting smooth muscle tissue, resulting in prolapse of hemorrhoidal tissues.
Hemorrhoids are normal structures and thus are treated only if they become symptomatic. Common complaints include bleeding, pain, and swelling. After nonoperative measures have failed, treatment is largely applied on the basis of size and symptomatology. Hemorrhoids classically are categorized into grade 1, with enlargement, but no prolapse outside the anal canal; grade 2, with prolapse through the anal canal on straining, but with spontaneous reduction; grade 3, manual reduction required; and grade 4, hemorrhoids cannot be reduced into the anal canal.
