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 colosigmoid 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 stepwise approach to the assessment of the IMA anatomy to avoid misleading nomenclature and provide a framework for surgeons to assess the vasculature.

Evaluation of the mesenteric arterial vasculature by computed tomography angiography and its implications for colorectal cancer surgery

“…Among the 100 patients evaluated, the median age was 53.3 years, and 53% were men. In accordance with the McSweeney et al IMA classification system (5) , we identified type 1A in 9% of the patients, type 1B in 47%, type 1C in 24%, type 2 in 16%, and type 3 in 4%. As can be seen in Table 1, there were no statistically significant differences between men and women in terms of the frequency of the anatomical variations of the IMA (p = 0.04).…”

“…The branching pattern of this artery also varies among individuals, and there are few anatomical, angiographic, or surgical studies that support what is traditionally taught as normal in anatomy texts (3) . Although the origin of the IMA is fairly constant, the branching pattern of its arteries-the left colic artery (LCA), sigmoid trunk, and superior rectal artery-is highly variability in terms of the origin and number of those branches, as well as the presence or absence of secondary branches (4,5) . Identifying these variations is essential to devising preoperative strategies, in order to determine the arterial branching pattern, the knowledge of which is quite helpful to surgeons, who must make decisions regarding vessel resection and lymph node dissection, to avoid anastomotic complications (6)(7)(8) .…”

The Atlas of the Inferior Mesenteric Artery and Vein under Maximum-Intensity Projection and Three-Dimensional Reconstruction View

“…In recent years, several reviews have systematically reviewed the historical development of IMA classification and utilized meta-analysis to statistically evaluate the classical types [23][24][25]. The Yada and Zebrowski classifications seem to be the most widely applied; however, the Yada classification overlooks the description of the SA, and the Zebrowski classification is somewhat complex.…”

Assessing anatomical variations of the inferior mesenteric artery via three-dimensional CT angiography and laparoscopic colorectal surgery: a retrospective observational study

“…In this study, the pattern of the IMA and its branches were observed and classified according to the classification described by McSweeney et al 14 . We classified the branching patterns of the IMA into five types (1A, 1B, 1C, 2, and 3).…”