A Comprehensive Review of the Anatomy of the Inferior Mesenteric Artery: Branching Patterns, Variant Anatomy and Clinical Significance

Abstract

The objective of this review is to describe the normal and variant anatomy of the inferior mesenteric artery (IMA), including a brief overview of the relevant embryology, as well as proposing a classification system of the IMA vasculature, and clinical significance. A systematic review of articles published in Google Scholar and PubMed database using search terms: inferior mesenteric artery anatomy, inferior mesenteric artery variation, inferior mesenteric artery development, mesenteric circulation anatomy and variation, inferior mesenteric artery angiography. This was followed by review of the reference list of relevant publications to reveal publications missed during the initial search. Several standard anatomy and surgery text books were also referred for normal anatomy. The anatomy of the inferior mesenteric system is highly variant, with only a small proportion of anatomical, angiographic or surgical studies providing support for what is traditionally taught to be normal anatomy. Whilst the origin of the inferior mesenteric artery is less variant, the branching into left colic, sigmoidal and superior rectal arteries is variable between individuals in terms of origin of branches, number of branches and the presence or absence of certain branches. Whilst there did not appear to be a common classification system, similarities included three main variants of branching with a colo-sigmoid trunk, recto-sigmoid trunk or common trifurcation. There is a disparity between what is described in anatomical texts as the ‘normal’ IMA, and what is seen in anatomical, radiological and surgical research studies. The variable anatomy of the inferior mesenteric artery and its branches is significant in radiological interpretation and colorectal surgery from both an oncological perspective when considering resection, as well as in colonic ischaemia. A classification system has been introduced with a step-wise approach to the assessment of the IMA anatomy to avoid misleading nomenclature and provide a framework for surgeons to assess the vasculature.