shunt

shunt

 [shunt]

1. to turn to one side; to divert; to bypass.

2. a passage or anastomosis between two natural channels, especially between blood vessels. Such structures may be formed physiologically (e.g., to bypass a thrombosis), or they may be structural anomalies.

3. a surgical anastomosis.

arteriovenous shunt a U-shaped plastic tube inserted between an artery and a vein (usually between the radial artery and cephalic vein), bypassing the capillary network, a formerly common means of arteriovenous access.

cardiovascular shunt an abnormality of the blood flow between the sides of the heart or between the systemic and pulmonary circulation; see left-to-right shunt and right-to-left shunt.

jejunoileal shunt an intestinal bypass performed to control obesity.

left-to-right shunt diversion of blood from the left side of the heart to the right side, or from the systemic to the pulmonary circulation through an anomalous opening such as a septal defect or patent ductus arteriosus.

LeVeen shunt peritoneovenous shunt.

mesocaval shunt a portosystemic shunt between the superior mesenteric vein and the inferior vena cava to reduce portal hypertension.

peritoneovenous shunt a device whose purpose is to remove excess ascitic fluid from the peritoneal cavity and return it to the venous system; called also LeVeen shunt.



The shunt consists of a peritoneal tube, a one-way valve, and a tube leading to a large vein, usually the superior vena cava or the jugular vein. The perforated peritoneal tube is placed in the peritoneal cavity and attached to the one-way valve which opens at a pressure of 3 cm H₂O. The valve controls the direction of the flow of ascitic fluid and prevents a backflow of blood from the vein. A tube leading from the valve empties into the venous system.

The shunt is triggered into action by the patient's breathing. Upon inspiration, the diaphragm descends toward the abdominal cavity and causes a rise in fluid pressure in the thoracic superior vena cava. The difference in pressure, usually about 5 cm H₂O, opens the shunt valve, allowing the flow of ascitic fluid into the large vein. The action of the shunt can be enhanced by the patient's inspiring against pressure, as when using a blow bottle.

A disadvantage of the shunt is dilution of the blood and a resultant drop in hematocrit, which necessitates transfusion of packed cells and perhaps a slowing of the rate of flow of ascitic fluid into the venous system. Other inherent risks are infection, leakage of ascitic fluid from the operative site, elevated bilirubin, gastrointestinal bleeding, and disseminated intravascular coagulation.

Peritoneovenous (LeVeen) shunt for chronic ascites moves fluid from the peritoneal (abdominal) cavity into the superior vena cava. From Ignatavicius and Workman, 2000.

portacaval shunt a portosystemic shunt between the portal vein and the vena cava.

portosystemic shunt a surgically created shunt that connects the portal and systemic circulations, such as a mesocaval, portacaval, or splenorenal shunt.

postcaval shunt portacaval shunt.

pulmonary shunt an anomaly in which blood moves from the venous circulation to the arterial circulation without participating in gas exchange, resulting in hypoxemia.

reversed shunt right-to-left shunt.

right-to-left shunt diversion of blood from the right side of the heart to the left side or from the pulmonary to the systemic circulation through an anomalous opening such as septal defect or patent ductus arteriosus.

splenorenal shunt an anastomosis of the splenic vein and the left renal vein, created to lower portal hypertension following splenectomy.

ventriculoatrial shunt the surgical creation of a communication between a cerebral ventricle and a cardiac atrium by means of a plastic tube; done for relief of hydrocephalus.

ventriculoperitoneal shunt a communication between a cerebral ventricle and the peritoneum by means of plastic tubing; done for the relief of hydrocephalus.

ventriculovenous shunt a communication between a lateral ventricle and the venous system by means of a plastic tube; done for relief of hydrocephalus.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

shunt

(shŭnt),

1. To bypass or divert.
See also: bypass.

2. A bypass or diversion of fluid to another fluid-containing system by fistulation or a prosthetic device. The nomenclature commonly includes origin and terminus, for example, atriovenous, splenorenal, ventriculocisternal.
See also: bypass.

[M.E. shunten, to flinch]

Farlex Partner Medical Dictionary © Farlex 2012

shunt

(shŭnt)

n.

1. The act or process of turning aside or moving to an alternate course.

2. Medicine A passage between two natural body channels, such as blood vessels, especially one created surgically to divert or permit flow from one pathway or region to another; a bypass.

v. shunted, shunting, shunts

v.tr.

Medicine To divert or permit flow of (a body fluid) from one pathway or region to another by surgical means.

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shunt′er n.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

shunt

The diversion of the flow of a fluid—in particular blood, but also cerebrospinal fluid—from its normal route to another, which may be accidental, as in a traumatic arterio-venous aneurysm, or by design (e.g., portocaval shunt or ventriculoperitoneal shunt).

Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

shunt  

The diversion of the flow of a fluid from its normal pathway to another, which may be accidental, as in a traumatic AV aneurysm, or by design–eg, portocaval shunt or ventriculoperitoneal shunt. See Arteriovenous shunt, Nodovenous shunt, Denver shunt, Distal splenorenal shunt, LeVeen shunt, Perfusion shunt, Portacaval shunt, Transjugular intrahepatic portosystemic shunt Pediatric cardiology Bypassing the pulmonary circulation–shunting is a normal physiologic process in utero; it becomes abnormal after birth Types

1. Those in which already oxygenated blood in the left heart passes back into the right heart–left-to-right shunt and.

2. Those which partially bypass the lungs, with venous blood directly entering the systemic circulation–right-to-left shunt

Shunt-acyanotic, cyanotic

L→R shunt Acyanotic shunt Right and left sides of the heart communicate by an ASD or VSD and PDA; the blood flows from the region of highest–left heart to lowest–right heart and systemic circulation pressure, as occurs in VSDs and corrected transposition of great arteries; since the blood does not bypass the pulmonary circulation, it is well oxygenated Clinical The plethora of blood causes pulmonary congestion and HTN that becomes significant when the pulmonary blood flow is 1.5-2.0-fold greater than the systemic flow with diastolic overloading and cardiac dilatation which, without correction, results in cardiac failure; a late complication is bacterial pneumonia related to stasis within the pulmonary circulation; L →R shunts may be created surgically–eg, Blalock procedure

R→L shunt Cyanotic shunt Variable degree of pulmonary circulation bypass accompanied by obstruction of blood flow into the pulmonary circulation R→L shunts Fallot's tetralogy–VSD, pulmonary valve stenosis, overriding or dextroposed aorta and 2º right ventricular hypertrophy, transposition of great vessels, tricuspid valve atresia, truncus arteriosus and total anomalous return of pulmonary veins; pulmonary blood flow is less than in L→R shunts Clinical Cyanosis with limited exercise tolerance, neurologic damage and compensatory polycythemia; as children, these Pts are often very sick and by adolescence may suffer acquired coagulopathies

.

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

shunt

(shŭnt)

1. To bypass or divert.

2. A bypass or diversion of fluid to another fluid-containing system by fistulation or a prosthetic device. The nomenclature commonly includes origin and terminus, e.g., atriovenous, splenorenal, ventriculocisternal.
See also: bypass

[M.E. shunten, to flinch]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

shunt

Any bypassing or sidetracking of flow, especially of fluid such as blood or cerebrospinal fluid. A shunt may be the result of disease or may be surgically induced, or inserted as a prosthesis, to effect treatment.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Shunt

A small tube placed in a ventricle of the brain to direct cerebrospinal fluid away from the blockage into another part of the body.

Mentioned in: Cardiac Catheterization, Hydrocephalus

Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

shunt

(shŭnt)

1. To bypass or divert.

2. Bypass or diversion of fluid to another fluid-containing system by fistulation or a prosthetic device.

[M.E. shunten, to flinch]

Medical Dictionary for the Dental Professions © Farlex 2012