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Updated: Jun 19, 2026
Multimodality Diagnosis of Mesenteric Ischemia
Published on: July 21, 2023
THE STATE OF THE VESSELS OF THE MESENTERY IN SHOCK PRODUCED BY CONSTRICTING THE LIMBS AND THE BEHAVIOR OF THE VESSELS
1Lilly Laboratory for Clinical Research, Indianapolis, Indiana, and the Department of Anatomy, Medical School, University of Pennsylvania, Philadelphia.
Insights
Shock in cats causes mesenteric artery and arteriole constriction, reducing blood flow but not stopping it. Veins and lymphatics also constrict, with no blood pooling even near death.
Area of Science:
- Physiology
- Pathophysiology
- Vascular Biology
Background:
- Understanding the microcirculatory response to shock is crucial for developing effective treatments.
- Previous studies have suggested various mechanisms involved in shock, but direct observations of mesenteric vessels during shock have been limited.
Purpose of the Study:
- To directly observe and characterize the morphological changes in mesenteric arteries, arterioles, capillaries, veins, and lymphatics in cats experiencing shock.
- To investigate the effects of different shock induction methods on these vascular structures.
Main Methods:
- Direct observation of mesenteric microvasculature in anesthetized cats subjected to shock via limb circulation occlusion.
- Hematocrit determination to assess hemoconcentration.
- Autopsy to identify hemorrhages.
- Experimental manipulation including bilateral nephrectomy, suprarenalectomy, pancreatectomy, blood withdrawal, and pithing to induce hypotension.
Main Results:
- Incomplete limb circulation occlusion led to marked, prolonged constriction of arteries and arterioles, reducing mesenteric blood supply without interrupting flow.
- Veins and lymphatics also constricted; no blood pooling or leukocyte sticking was observed.
- Progressive hemoconcentration and small hemorrhages in organs were noted.
- Surgical removal of kidneys, adrenal glands, or pancreas did not significantly alter the shock-induced vascular response.
- Blood withdrawal caused rapid mesenteric vasoconstriction.
- Pithing-induced hypotension did not alter vessel diameter or mesenteric appearance.
Conclusions:
- Mesenteric vasoconstriction is a prominent feature of shock induced by limb circulation restriction, characterized by reduced blood flow but maintained patency.
- The observed vascular responses are not significantly modulated by the removal of kidneys, adrenal glands, or pancreas.
- Hypotension induced by central nervous system disruption does not elicit the same mesenteric vascular changes as circulatory shock.
Abstract:
1. Direct observations of the arteries, arterioles, capillaries, veins, and lymphatics in the mesentery of anesthetized cats put into shock by incomplete occlusion of the circulation of the limbs showed that: (a) Marked constriction of the arteries and arterioles, produced by muscular contraction, occurred usually within an hour after incomplete occlusion of the limbs, lasted several hours, and finally gave way in most instances to relaxation an hour or more before death. The constriction reduced the blood supply to the mesentery and intestine and the venous return from them. It did not, however, interrupt the blood flow. No pooling or stagnation of blood was seen even as a terminal phenomenon. (b) The veins of the mesentery also became constricted but showed less tendency to dilate as death approached. The lymphatics likewise became somewhat narrowed. Even during the terminal stage the leukocytes moved along without change in shape or sticking to the walls of the capillaries or venules. (c) Hematocrit determinations showed progressive hemoconcentration of moderate degree. (d) Autopsy usually showed the presence of small hemorrhages in many parts of the body, especially the heart, liver, spleen, and lungs. (e) Bilateral nephrectomy, suprarenalectomy, and pancreatectomy did not significantly alter the morphological picture elicited by shock induced by restriction of the circulation to the limbs. 2. Removal of large amounts of blood was always followed within a short time by constriction of arteries, arterioles, veins, and lymphatics of the mesentery. 3. Fall in arterial pressure produced by pithing was not accompanied by change in diameter of the arteries, arterioles, veins, or lymphatics, or by blanching of the mesentery or gut.
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