Imaging of the Inferior Mesenteric Vasculature

The inferior mesenteric artery (IMA) and inferior mesenteric vein (IMV) supply and drain blood from the distal colon and rectum, respectively. Routinely imaged at cross-sectional imaging of the abdomen and pelvis, these vessels play a vital role in gastrointestinal tract health but may be neglected due to their diminutive caliber relative to other mesenteric vessels and potential lack of inclusion in routine search patterns. The authors describe and illustrate normal and abnormal appearances of the IMA and IMV and findings that are diagnostic of primary vascular abnormalities or can offer diagnostic clues. After the embryologic features, normal anatomy, and anatomic variants of the IMA and IMV are reviewed, various manifestations of IMA and IMV abnormalities, such as aneurysm and pseudoaneurysm, stenosis, occlusion, dissection, hemorrhage, arteriovenous malformations and fistulas, tumoral invasion, vasculitis, and perivascular lymphatic dilatation, are explored with use of case examples. The role of the IMA and IMV as collateral vasculature, including the clinical scenarios of superior mesenteric arterial occlusion, aortic endoleak, and portosystemic venous shunt, are discussed. Finally, diagnostic clues that the inferior mesenteric vessels and adjacent soft tissues can provide, including mesenteric venous gas, compression or displacement from bowel volvulus or internal hernias, lymphadenopathy, and venous flow artifacts, are highlighted. The authors provide a comprehensive reference for radiologists who evaluate the IMA and IMV on cross-sectional images and shine a spotlight on these neglected but important vessels. ©RSNA, 2024 Supplemental material is available for this article.

Correlation of Riolan's arch diameter to treatment choice in patients with isolated superior mesenteric artery dissection

OBJECTIVE

To investigate the diameter changes of Riolan's arch in patients with isolated superior mesenteric artery dissection (ISMAD) and to evaluate the implication for treatment selection.

METHODS

Ninety-five patients with CT angiography (CTA) confirmed ISMAD were retrospectively included, and another 95 cases with no positive findings on abdominal CTA were included as controls. According to the treatment methods, the patients were subsequently divided into conservative treatment (n = 68) or invasive treatment (n = 27) subgroups. According to the initial CTA images, the prevalence of Riolan's arch as well as its diameter (D_R) were determined in each subject, and compared between ISMAD and control cases, as well as between patients with different treatments. In patients with ISMAD, dissections were classified according to the Li classification.

RESULTS

Riolan's arch prevalence and D_R were significantly elevated in the ISMAD group compared with the control group (83.16% vs. 35.79%, P < 0.001; 2.63 ± 0.56 mm vs. 2.12 ± 0.39 mm, P < 0.001). Patients with invasive treatment had significantly higher baseline D_R (2.93 ± 0.57 mm vs. 1.89 ± 1.14 mm, P < 0.001), and higher proportion of high-risk dissection (P < 0.001) than those administered conservative treatment. Binary logistic regression revealed D_R (OR = 2.771, 95% CI 1.157-6.638, P = 0.022) and Li classification (OR = 0.107, 95% CI 0.019-0.586, P = 0.010) were independent risk factors for treatment selection. With cutoff of 2.635 mm, the area under the curve, sensitivity, and specificity were 0.805, 0.778 and 0.794, respectively.

CONCLUSION

Dilation of Riolan's arch is common in patients with ISMAD, and Riolan's arch diameter could be a convenient indicator of disease severity and inform subsequent treatment.

Redefining the collateral system between the superior mesenteric artery and inferior mesenteric artery: a novel classification

AIM

The aim of this study was to evaluate the arterial collateral vasculature between the superior mesenteric artery and the inferior mesenteric artery (IMA) from a surgical perspective.

METHOD

A total of 107 fresh adult cadavers (94 male) were studied with emphasis on the vascular anatomy of the left colon. Dissections were carried out mimicking the anterior resection technique. The vasculature of the left mesocolon and the collaterals between the superior mesenteric artery and the IMA with respect to their relationship to the inferior mesenteric vein (IMV) were assessed and classified. Collaterals were classified into three different groups: marginal anastomoses (via the marginal = pericolic artery), intermediate mesocolic anastomoses (parallel to the marginal artery but neither adjacent to the IMV nor close to the duodenum) and central mesocolic anastomoses (next to the IMV at the level of the duodenojejunal junction and the lower border of the pancreas).

RESULTS

All patients had a marginal anastomosis. However, the marginal anastomosis, as the only anastomosis between the superior and inferior mesenteric arteries at the splenic flexure, was observed in 41 cases (38%). In addition to the marginal artery, intermediate mesocolic anastomoses were found in 49 (46%) and a central mesocolic anastomosis was observed in 17 (16%) of the 107 cases in the splenic flexure mesocolon. It is in this latter variant that collateral vessels can be compromised during ligation/transection of the IMV.

CONCLUSION

This new classification can contribute to a precise mesocolic dissection technique and splenic flexure mobilization and help prevent ischaemic damage to the descending colon.

Basic Arterial Anatomy and Interpretation of CT Angiography for Intra-Abdominal or Gastrointestinal Bleeding: Correlation with Conventional Angiographic Findings for Beginners

복강 내 혹은 소화기계의 활동성 출혈이 있는 경우, 원인이 되는 동맥 혈관을 파악하는 것이 중요하다. 조영증강 컴퓨터단층촬영술을 이용한 혈관조영술과 고식적인 카테터 혈관조영술에서 원인이 되는 동맥을 파악하기 위해서는 기본적인 혈관 해부학을 숙지하고 있어야 한다. 기본 해부학을 숙지하고 있다면 혈관의 기원과 주행에 다양한 변이가 있다고 하더라도 이에 대한 접근이 한결 쉬워질 것이다. 영상의학에 갓 입문한 초심자들을 대상으로 하여, 복강 내 혹은 소화기계 활동성 출혈의 원인이 될 수 있는 혈관들을 파악하는 데 도움이 될만한 기본 해부학을 설명하고자 한다.

Reversal of Acute Mesenteric Ischemia by Salvation of the Meandering Mesenteric Artery with Stenting of the Left Internal Iliac Artery

The presence of the meandering mesenteric artery, which is a nonconstant tortuous arterial component unifying the peripheral intestinal circulation, is evidence of chronic occlusive disease of the main intestinal arteries. This collateral intestinal arterial pathway, when present, must be preserved in any abdominal intervention, as it is often the only remaining arterial supply of the intestine; its ligation can be accompanied by intestinal ischemia. We present herein, the case of a 42-year-old man, heavy smoker, who had chronic mesenteric ischemia without particular clinical manifestations till the hospitalization for acute myocardial infarction for which he underwent balloon angioplasty and stenting of the left circumflex coronary artery. Three days later, he experienced acute-on-chronic intestinal ischemia with crescendo clinical manifestations; intra-arterial angiography revealed the presence of a meandering mesenteric artery in a milieu of celiac, superior and inferior mesenteric, and right internal iliac artery occlusion accompanied by a tight stenosis of the left internal iliac artery. Successful stenting of the orifice of the left internal iliac artery was followed by a well-defined dilatation of the meandering artery, revascularization of the peripheral branches of the inferior-through the superior hemorrhoidal artery-and superior mesenteric arteries and complete resolution of the acute mesenteric ischemia. Thus, time was gained for the patient in order to have, if needed, a future elective open revascularization of the mesenteric artery, when the perioperative risk of mortality from the recent myocardial infarction and the coronary angioplasty and stenting will be minimal.

Multidetector Computed Tomographic Angiography for Optimal Cartography of the Visceral Abdominal Arterial Network: An Extensive Pictorial Review with Emphasis on Common and Uncommon Collateral Pathways, Complications and some Specific Syndromes

Multidetector computed tomographic angiography (MDCTA) is the new gold standard for diagnostic evaluation of the abdominal and/or mesenteric arteries. It is not invasive and provides a 2D and 3D global cartography of all abdominal arteries and that with only a limited amount of contrast media.

MDCTA allows the optimal diagnosis of single or multiple arterial stenosis and easily analyses sometimes very complex collateral pathways. It constitutes a major advance to plan the arterial visceral safety of major commonly performed abdominal surgical procedures such as aorto-iliac surgery, endovascular aneurysm repair (EVAR), but also complex pancreatic and gastrointestinal or colonic surgery. It also allows to plan the most optimal strategy for revascularization of the mesenteric system through percutaneous angioplasty, stent placement or surgical bypass.

This extensive pictorial review illustrates a large variety of situations which may be found during clinical practise. Single compression or stenosis of each digestive artery, combined and/or complex associations of stenosis and/or compressions of several arteries, secondary complications like aneurysms and classical but also sometimes unusual patterns of collateralization are richly illustrated. Specific syndromes comprising the median arcuate ligament syndrome (MALS) and the Leriche’s syndrome are also discussed.