The superior mesenteric artery and the variations of the colic patterns. A new anatomical and radiological classification of the colic arteries.

The superior mesenteric artery (SMA) supplies irrigation to the small intestine, ascending and a variable area of the transverse colon. Although medical imaging and surgical procedures have been widely developed in the last decades, the anatomy of the SMA using advanced imaging technology remains to be elucidated. Previous studies have used small sample sizes of cadaveric or radiological samples to propose a number of classifications for the SMA. In this study, we aimed to provide a more detailed description and useful classification of the SMA and its main branches [middle colic artery (MCA), right colic artery (RCA), and ileocolic artery (ICA)]. Samples (n = 50, 28 males and 22 females) were obtained from the repository of human cadavers located at the Department of Human Anatomy and Embryology, Complutense University of Madrid. This sample was dissected by preclinical medical students and completed by two of the authors (Gamo and Jiménez). A second set of samples was obtained from a bank of computerized tomography (CT) (560 CTs, 399 males and 161 females) collected by the Radiology Department at the Clínico San Carlos Hospital, Spain. Based on the results obtained from these studies, we propose a new classification of four patterns for the SMA anatomy. Pattern I as the independent origin of the three main branches of the SMA (cadaveric 40 %; CT 73.69 %); Pattern II is subdivided in three sub-patterns based on the common trunks of origin: Pattern IIa, common trunk between RCA and MCA (cadaveric 20 %, CT 4.28 %); Pattern IIb, common trunk between RCA and ICA (cadaveric 32 %, CT 15 %); Pattern IIc, common trunk for the three main branches (cadaveric 0 %, CT 0.35 %); Pattern III, as the absence of RCA (cadaveric 8 %; CT 2.32 %) and Pattern IV, based on presence of accessory arteries (not found in any of the samples). Although the independent origin of the three colic arteries have been classically described as the most frequent, the right colic artery is responsible of major variations.