Categorical Course - How to Do Researchin Interventional Radiology: A PracticalGuide for the Tinkerer in All of Us

PART II (C202)Moderator: Michael A. Bettman, MD

3:30 pm

Considerations in Pediatric PatientsPatricia E. Burrows, MD

3:55 pmAssessment, Sedation & AnalgesiaMichael A. Bettman, MD

4:20 pm

Recognition & Management of DysrhythmiasGregory S. Ferguson, MD

4:45 pm

Discussion: Contrast Reaction ScenariosFaculty

Tuesday, March 11,19972:30-5:00 pm

Part III (C301)Moderator: John 1. Doppman, MD

2:30 pm

Mesenteric Angiography (Vascular Disease,Bleeding, Tumors)Stewart R. Reuter, MD, jD

Learning objectives: At the end of this session, the at­tendees should be able to: (1) understand the collateralpathways involved in patients with mesenteric vasculardisease; (2) understand the role of angiography in thediagnosis and treatment of lower gastrointestinal bleed­ing; and (J) identify small bowel leiomyomas and car­cinoid tumors.

IN patients with celiac artery stenosis, the primarysource of collateral blood flow to the organs supplied bythat artery develops from the superior mesenteric artery(SNlA), primarily over the pancreatoduodenal arteriesand gastroduodenal artery. The degree of celiac stenosiscan be assessed by evaluating the relative filling of thehepatic and splenic arteries from the SMA. If the stenosisis 80% to 90%, the entire celiac distribution will be sup­plied from the SMA, and the celiac stenosis can be iden­tified as the contrast medium passes the orifice. If lessthan 80%, the collateral flow from the SMA supplies theliver to varying degrees, whereas the spleen receivesblood supply from the celiac artery.

In patients with distal aortic occlusions, many ofwhich also include occlusion of the inferior mesenteric

artery (IMA), the SMA becomes the primary source ofcollateral blood flow to the pelvis and legs. The collat­erals develop over the middle colic artery, left colic ar­

tery, and superior hemorrhoidal artery to the inferiorhemorrhoidal branches of the internal iliac arteries. The

marginal artery of Drummond also frequently partici­pates in this pattern of collateral flow. In patients withinfradiaphragmatic IVe occlusions, the superior mesen­teric and portal veins have a similar collateral function in

the reverse direction.

Mesenteric Occlusive DiseaseMesenteric artery occlusion may be either chronic oracute. Most chronic occlusions are caused by atheroscle­rosis--usually, by aortic atherosclerotic disease that im­pinges on the SMA or IMA orifice. Most acute occlusionsare caused by emboli.

Long-term gradual SMA occlusions may be identifiedby the collaterals that develop from the celiac axis or theIMA in a direction opposite from that described in the

previous section.In patients with IMA occlusion, the SMA is the pri­

mary source of collateral blood flow to the left colon.

This occurs over the middle colic and left colic arteries tothe distribution of the IMA. The marginal artery of Drum­mond frequently participates in this collateral pattern. Ifboth the SMA and IMA are occluded, the celiac arteryand hemorrhoidal vessels may be the only collateralblood supply to the bowel. The syndrome of mesentericischemia probably requires that at least two major ves­sels be involved before the syndrome occurs because ofthe effectiveness of the collateral blood flow between

adjacent arteries.If individual branches of the SMA or IMA are oc­

cluded, many potential collateral pathways are availableover the multiple arcades that exist between adjacentmesenteric artery branches.

Most emboli to the SMA lodge at branches of the

mesenteric arteries, and the defect in the artery is usuallyreadily apparent. The acuteness can be determined bythe absence of collateral arteries. Although most mesen­teric occlusions proceed to bowel necrosis, on occasion,adequate collateral blood flow may develop to prevent

necrosis and the patient may develop a long-term occlu­sive pattern with collateral blood flow as describedabove.

Nonocclusive mesenteric ischemia is an unusualcause of mesenteric occlusion. This usually occurs inelderly, hypovolemic patients and has a rather typicalappearance. All of the jejunal and ileal arteries are trun­cated at the origins from the SMA. As the disease pro­gresses, the arteries may develop a somewhat beadedappearance. If not detected early, this process will leadto bowel necrosis, but the process may be reversed withthe infusion of vasodilatory drugs if discovered earlyenough.

The vascular pattern of ischemic small bowel disease

is hypovascularity. The SMA branches beyond the occlu­sion are absent. With acute mesenteric occlusions, an

element of vasoconstriction is present that accentuatesthe hypovascularity. With the ischemic colon, on theother hand, the vasa recta may be quite hypervascular

with a great deal of arteriovenous shunting. This iscaused by invasion of the ischemic mucosa by the many

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