Differences between external and internal hemorrhoids
- External hemorrhoids originate distal to the dentate line of the anus and are covered by squamous epithelium. External hemorrhoids may thrombose or become filled with clotted blood. Typically these are painful, involving the anoderm.
- Internal hemorrhoids arise above (proximal to) the dentate line and are covered with transitional and columnar epithelium. First-degree hemorrhoids swell and bleed. Second-degree hemorrhoids prolapse and spontaneously reduce. Third-degree hemorrhoids prolapse and can be manually reduced, whereas fourth-degree hemorrhoids are irreducible. Typically these are not painful above the anoderm.
