Friday, March 12, 2021

Small Bowel Mesenteric Angina Case File

Posted By: Medical Group - 3/12/2021 Post Author : Medical Group Post Date : Friday, March 12, 2021 Post Time : 3/12/2021
Small Bowel Mesenteric Angina Case File
Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 20
A 62-year-old woman complains of the sudden onset of severe midabdominal pain that has been increasing over the past 3 h. She has a history of myocardial ischemia and peripheral vascular disease. The patient states that she has had nausea and vomiting. On examination, she is writhing in pain. Her abdomen has normal bowel sounds and minimal tenderness. A small amount of blood is present in the stool specimen. The electrolytes show a low bicarbonate level at 15 mEq/L, and the serum lactate level is high, which are indicative of tissue receiving insufficient oxygenation leading to tissue injury. A surgeon who is concerned about intestinal ischemia has been called to evaluate the patient.

What is the most likely diagnosis?
 What anatomical structure is likely involved?


ANSWER TO CASE 20:

Small Bowel Mesenteric Angina
Summary: A 62-year-old woman with widespread atherosclerotic vascular disease complains of a 3-h history of severe midabdominal pain accompanied by nausea and vomiting. Although she is writhing in pain, her bowel sounds are normal, and there is minimal tenderness. Blood is present in the stool, and electrolytes show low levels of bicarbonate at 15 mEq/L and high levels of lactate; these findings are attributed to a lack of oxygen to intestinal tissue, leading to anaerobic metabolism. The surgeon is concerned about ischemia.
• Most likely diagnosis: Mesenteric ischemia

• Anatomical structures likely involved: Arteries that supply the small bowel, probably branches of the superior mesenteric artery (SMA)


CLINICAL CORRELATION
This elderly woman complains of sudden-onset severe midabdominal pain that is inconsistent with the physical findings. She has a history of widespread atherosclerotic vascular disease affecting the coronary arteries and peripheral vasculature. The presence of blood in the stool suggests bowel injury, and the low level of serum bicarbonate is consistent with a metabolic acidemia. Bowel ischemia or necrosis is causative. Arterial occlusion may occur from rupture of the atherosclerotic plaque or embolization from another clot. This patient’s midabdominal symptoms suggest arteriography of the SMA, and the celiac artery might be diagnostic. On confirmation, surgical embolectomy is usually helpful. The mortality rate is high in such patients.

Although the first part of the duodenum is supplied by the superior pancreaticoduodenal artery, which receives its blood from the celiac artery, the remainder of the small intestines is supplied by branches of the SMA.


APPROACH TO:
Vascular Supply to the Bowel

OBJECTIVES
1. Be able to describe the general plan for the arterial blood supply to the abdominal viscera
2. Be able to describe the anatomy and distribution of the SMA


DEFINITIONS
ATHEROSCLEROTIC VASCULAR DISEASE: Disease in which deposits of plaques of cholesterol and lipid form within the intima of small and medium arteries

ANGINA: Pain, often severe, due to decreased blood flow to an organ such as the heart or intestines

SUPERIOR MESENTERIC ARTERY: Unpaired arterial branch of the abdominal aorta that supplies portions of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and most of the transverse colon


DISCUSSION
The abdominal gastrointestinal viscera are supplied by the three major unpaired branches of the abdominal aorta: celiac artery (trunk), SMA, and inferior mesenteric artery (IMA). These three arteries supply organs embryologically derived from the foregut, midgut, and hindgut, respectively.

The duodenum proximal to the entrance of the common bile duct receives its blood supply from the superior pancreaticoduodenal artery, a branch of the gastroduodenal artery from the celiac artery. The remainder of the small intestines is supplied by the SMA (Figure 20-1). The SMA arises from the abdominal aorta at the level of the lower border of L1, posterior to the neck of the pancreas. As it emerges from behind the pancreas, it passes anterior to the uncinate process of the pancreas and the third part of the duodenum and enters the root of the mesentery. As it enters the mesenteric root, it gives off its inferior pancreaticoduodenal and middle colic arteries, the latter to the transverse colon within its mesentery, the transverse mesocolon.

Small Bowel Mesenteric Angina anatomy

Figure 20-1. Superior mesenteric arterial supply to the small bowel. (Reproduced, with permission, from Lindner HH. Clinical Anatomy. East Norwalk, CT: Appleton & Lange, 1989:353.)

As the SMA descends toward the ileocolic junction, 15 to 18 intestinal branches arise, which pass between the layers of the mesentery, and are united by increasingly complex anatomical arcades. The arcades closest to the mesenteric attachment to the jejunum and ileum give off increasingly shorter straight arteries (vasa recta) that enter the small intestines. Other branches of the SMA include the right colic to the ascending colon and the ileocolic to the cecum, appendix, and ascending colon.


COMPREHENSION QUESTIONS

20.1 During a surgical procedure, you have elevated the transverse colon and note an artery in the transverse mesocolon. What is this vessel?
A. Right gastroomental (gastroepiploic) artery
B. Middle colic artery
C. Inferior pancreaticoduodenal artery
D. Right colic artery
E. Left colic artery

20.2 During surgery you note a retroperitoneal artery crossing the right side of the posterior abdominal wall and supplying the ascending colon. Which vessel is this?
A. Middle colic artery
B. Left colic artery
C. Ileocolic artery
D. Right colic artery
E. Sigmoidal artery

20.3 A 44-year-old accountant develops a bleeding ulcer around tax time. The gastroenterologist visualizes the ulcer in the proximal duodenum. A radiologist has been called to cannulate and embolize the artery supplying the ulcer. Which of the following arteries does the radiologist need to cannulate?
A. Celiac artery
B. SMA
C. IMA
D. Superior epigastric artery


ANSWERS

20.1 B. The middle colic artery courses through the transverse mesocolon to supply the transverse colon.
20.2 D. The right colic artery supplies the ascending colon and is retroperitoneal.
20.3 A. The superior pancreaticoduodenal artery is a terminal branch that arises from the celiac artery.


ANATOMY PEARLS
 The SMA arises from the aorta opposite L1 posteriorly to the neck of the pancreas but crosses anterior to the third part of the duodenum.
 The celiac artery and SMA anastomose with each other through the pancreaticoduodenal arteries.
 The SMA intestinal arcades increase in complexity, but the vasa recta decrease in length from proximal to distal.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:190−191. 

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:226−228, 243−246. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 287−288.

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