Anatomical Variation of the Rectal Arteries: A Primer for Embolotherapy in Internal Hemorrhoidal Disease

Learning Objectives: • Illustrate typical and variant rectal artery anatomy
• Discuss importance of different variants as they relate to hemorrhoidal embolotherapy
• Provide case examples of different classifications and other examples of variant anatomy

Background: The hemorrhoidal vascular plexus, or the corpus cavernosum recti, is a complex network of arteriovenous anastomoses surrounded by fibro-muscular tissue. This tissue complex forms anal cushions which play a role in fecal continence. {1} Abnormal hypertrophy of the hemorrhoidal vascular plexus can lead to chronic bleeding and prolapse, conditions collectively referred to as internal hemorrhoidal disease.{2} Rectal arterial embolization is a minimally invasive and effective treatment strategy for symptomatic hemorrhoidal disease.{3} Understanding the common anatomical variations in the rectal arterial supply to the hemorrhoidal vascular plexus is essential for appropriate patient selection and procedural planning.

Clinical Findings/Procedure Details: The embryonic development of the rectum involves contributions from both endodermal and ectodermal origins, resulting in dual arterial vascularization from the inferior mesenteric artery (IMA) and the internal iliac artery (IIA). The superior rectal artery (SRA), typically arising as the terminal branch of the IMA, is the primary arterial supply to hemorrhoidal tissue in most patients. The middle rectal artery (MRA), a branch of the IIA that often originates from the internal pudendal artery (IPA), provides arterial supply in a smaller subset of patients (12-36%). {3} {4}

The inferior rectal artery (IRA) contributes to hemorrhoidal vascularization less frequently and with greater variability. An angiographic classification system has proposed three common anatomical patterns of hemorrhoid arterial vascularization (HAVP) by rectal arteries {3}:

• Type 1 HAVP: Characterized by one or more dominant SRAs without a hypertrophic MRA, the most observed pattern.
• Type 2 HAVP: Features a hypertrophic SRA on one side and a hypertrophic MRA on the opposite side.
• Type 3 HAVP: Involves bilateral MRA hypertrophy with no hypertrophy of the SRA.

Select cases of unique anatomic variants outside of these three common anatomical patterns may also be seen and will be reviewed in this exhibit.

Conclusion and/or Teaching Points: A comprehensive understanding of the patterns of arterial hemorrhoid vascularization, anatomical variations, and critical anastomoses that may be encountered during embolization procedures is key to optimizing intraprocedural planning and improving patient outcomes.