Tuesday, October 9, 2012

Right Gastric Artery

Localization of the right gastric artery ("pyloric artery")  is critical before a hepatic embolization procedure or placement of a chemoinfusion catheter, where nontarget radioactive spheres or chemotherapeutic molecules have the potential to lodge in the capillaries of the stomach and duodenum, causinge a nasty spot of ulcerative necrosis.

But unlike its large compatriot, the left gastric artery, the right gastric artery is a small twig-like artery that, when it is seen, most frequently arises off the proper hepatic artery (53%) and extends backward across the lesser curvature of the stomach to anastomose with the left gastric... and it can easily be missed if one is not looking for it.

Celiac trunk angiogram in preparation for a hepatic chemoembolization.  This early image in the run shows a small twig-like right gastric artery originating off the proximal proper hepatic artery, near an almost trifurcation of the left and right hepatic arteries and the GDA (first red arrow: origin of the R gastric artery; second red arrow: course of the R gastric artery)

A zoomed image of the spot image above.  The right gastric artery often arises off the proper hepatic artery and the origin can sometimes be tricky to see due to superimposed vessels.

An image from Gray's Anatomy illustrating the right gastric artery.  In this diagram, the right gastric originates from the common hepatic artery, which is a less common configuration (20%).

A later image from the run shows the right gastric beginning to opacify more completely.

An later image from the run shows the right gastric artery filling even further and shows its anastomosis with the left gastric artery.

As mentioned above, errant radiospheres can travel through hepatic artery side branches such as the retroduodenal artery, the gastroduodenal artery, and the right gastric artery if they are not coil embolized at their origins, potentially resulting in pretty nasty gastric and duodenal ulcers.

On the left is a "large punched-out ulcer" from a patient treated with radioembospheres who presented with GI bleeding.  Histologic analysis of the ulcer margins demonstrated radioactive microspheres (ref 2).

Infusion of Tc-MAA can be used as a surrogate for microspheres and used to determine the distribution of flow through side branches and potential for errant embolization to the gastric mucosa.

Slide 2
(a)  Planar hepatic nuclear medicine scintigraphy following trans-arterial infusion of Tc 99-MAA. Hepatic activity with a focal area of extrahepatic activity (arrow) is identified.  (b)  Gastric endoscopy following 90Y microsphere delivery via the left hepatic artery. Gastric ulcers (arrows) are noted. (c) Gastric biopsy (H&E stain). Gastric ulceration (arrow heads) adjacent to the submucosal basophilic circular foreign material characteristic of the resin microsphere (arrows). (d) Left hepatic arteriogram. Retrospective review of the arteriogram demonstrates a variant origin of the right gastric artery (arrow heads) that was interpreted as a branch of the left hepatic artery (thin arrow). The GDA had been coil embolized at the time of therapy planning arteriogram (bold arrow). (ref 3)

As demonstrated in the image above, identifying and properly localizing the right gastric artery can be tricky since its not always seen, and when its present, its usually buried among multiple other arteries in the region.  If the right gastric has a variant origin as a branch off the left hepatic branch (15%), the problem is only compounded (incidentally, the variant of the right gastric off the left hepatic may be more common when the right hepatic arterial circulation is replaced off the SMA).

Because of its twig-like size and the hairpin turn at its origin, coil embolization of the right gastric artery is sometimes more easily approached via the left gastric artery.  Coil embolization of the right gastric artery and other branch arteries such as the gastroduodenal artery has been shown to be durable, and 89% of patients did not develop collaterals or recanalization of the side branches, with only minimal development of collaterals over the longer term.

1. von Eckmann I, and Krahn V. Studies concerning the frequency of the different possibilities of the origin of the right gastric artery. Anat. Anz. 155:65-70. 1984
2. Konda A, Savin MA, Cappel MS, et al. "Radiation microsphere–induced GI ulcers after selective internal
radiation therapy for hepatic tumors: an underrecognized clinical entity" Gastrointestinal Endoscopy. Volume 70, No. 3 : 2009
3. Murthy R, Brown DB, Salem Riad, et al. "Gastrointestinal Complications Associated with Hepatic Arterial Yttrium-90 Microsphere Therapy" JVIR Vol 18:4 (2007) pp. 553-561
4. "Gastrointestinal Angiography" Reuter SR, Redman HC, Cho KJ. 3rd ed (1986)
5.Yamagami T, Kato T, Iida S, et al. "Embolization of the Right Gastric Artery Before Hepatic Arterial Infusion Chemotherapy to Prevent Gastric Mucosal Lesion: Approach Through the Hepatic Artery Versus the Left Gastric Artery" AJR. Vol 179:6 (2002) pp 1605-1610
6. Yamagami T, Kato T, Iida S, et al. "Efficacy of the Left Gastric Artery as a Route for Catheterization of the Right Gastric Artery" AJR. Vol 184:1 (2005) pp 220-224.
7.  Petroziello MF, McCann JW, Gonsalves C, et al. "Side-Branch Embolization Before 90Y Radioembolization: Rate of Recanalization and New Collateral Development" AJR. Vol 197:1 (2011) pp W169-W174.