- Hemorrhoids are anatomic subtype of Varicose Veins affecting the hemorrhoidal plexus.
- Hemorrhoids appear as thin-walled, dilations of veins in the large intestine submucosa which generally protrude from beneath the large intestine epithelium. Initially, protruding hemorrhoidal veins remain within the anal canal and are thus described as "Internal Hemorrhoids". However, as disease progresses, protruding veins may emerge from the anal canal and are then referred to as "External Hemorrhoids".
- The venous hemorrhoidal plexus becomes engorged and thus experiences spikes in intravascular pressure during abdominal straining, especially as a result of defection. A lifetime of such spikes in pressure ultimately deteriorates the anatomic support for these veins resulting in their protrusion into the anal canal. Conditions which increase the frequency or intensity of such straining, such as chronic constipation, can increase the possibility of developing hemorrhoids are aggravate existing lesions. Additionally, the hemorrhoidal plexus is a point of portal-systemic junction and thus conditions which raise portal pressures, such as pregnancy as well as cirrhosis, or other causes of portal hypertension, can result in or aggravate hemorrhoidal lesions.
- The most common clinical consequence of hemorrhoids is bright red lower GI bleeding. Hemorrhoids are somewhat painful but their thrombosis can result in extreme pain.