Portacaval shunt

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Portacaval shunt
Liver veins.jpg
Under normal conditions, blood flows into the liver via the portal vein and exits through the hepatic vein, eventually reaching the inferior vena cava. A portacaval shunt connects the portal vein directly to the inferior vena cava, bypassing the liver entirely.

A portacaval shunt, portocaval shunt, or portal-caval shunt is a surgical procedure where a connection (a shunt) is made between the portal vein and the inferior vena cava.

Contents

Under normal circumstances, the portal vein drains blood from the abdomen to the liver. The blood is deoxygenated and carries nutrients and waste products from the intestines, spleen, pancreas, and gallbladder to the liver. [1] The deoxyenated blood then exits the liver through the hepatic vein and empties into the inferior vena cava, the vein that carries blood from the lower two-thirds of the body to the heart.

The portacaval shunt connects the portal vein to the inferior vena cava, allowing blood to travel directly from the portal vein to the inferior vena cava, bypassing the liver entirely. The shunt is typically used to manage complications of portal hypertension, such as upper gastrointestinal bleeding. However, technological advancements have shifted towards minimally invasive methods rather than surgical shunting.

Portal hypertension is commonly seen with liver cirrhosis and/or other liver diseases such as Budd–Chiari syndrome, primary biliary cirrhosis (PBC), and portal vein thrombosis. [2] The purpose of the shunt is to divert blood flow away from the liver, reducing the high pressure in the portal venous system and decreasing the risk of bleeding. [3]

A portacaval anastomosis is analogous in that it diverts circulation; as with shunts and anastomoses generally, the terms are often used to refer to either the naturally occurring forms or the surgically created forms.

History

Portacaval shunts were first developed and performed in the mid-20th century to control bleeding varicose veins in cases of portal hypertension. These efforts successfully controlled the bleeding; however, liver failure remained a concern and often worsened after shunt placement. Eventually, selective shunts were introduced, and soon liver transplantation became the definitive surgical solution to treating portal hypertension. [4]

Over time, less invasive treatments for portal hypertension were developed. Sclerotherapy, a minimally invasive procedure that uses chemicals to shrink varicose veins through endoscopy, was later enhanced with the introduction of variceal band ligation. Technological advancements also led to pharmacological therapies and interventional radiologic procedures like transjugular intrahepatic portosystemic shunt (TIPS), which is now the preferred treatment for managing portal hypertension. [5] Portacaval shunting is no longer commonly used as the first line treatment for variceal bleeding due to the increased safety and effectiveness of the newer treatments.

Indications

Portacaval shunting is primarily indicated for uncontrolled upper gastrointestinal bleeding when medical therapy, endoscopic methods, or TIPS are not possible or ineffective. [6] Additionally, surgical shunting may also be indicated for patients with a history of splenectomy, splenic vein or hepatic vein thrombosis, a splenorenal shunt, or ascites, as minimally invasive methods would not be recommended in these cases. [6]

The purpose of the shunt is to redirect blood flow from the portal venous system into the systemic venous system, which reduces the pressure gradient in the portal venous circulation, thereby lowering the risk of bleeding varices. [3]

Types of shunt

The side-to-side and end-to-side portacaval shunts are extrahepatic shunts shown in the lower left of the image. Classifying Porto-Systemic Shunts - Intra- vs. Extra- -Hepatic.jpg
The side-to-side and end-to-side portacaval shunts are extrahepatic shunts shown in the lower left of the image.

Several types of shunts connect the portal circulation to the systemic venous circulation. The portacaval shunt specifically connects the portal vein to the inferior vena cava through a direct connection. There are two major types of portacaval shunts.

Both surgical procedures reduce portal venous pressure by diverting blood flow away from the portal venous circulation and into the systemic venous circulation. [7]

Outcomes

The success rate depends on several factors, including the patient's condition and the severity of the disease. Studies have shown that surgical shunting is highly effective in controlling upper gastrointestinal bleeding. [8] The Child–Pugh score can be used to help determine the severity and prognosis of patients with severe liver disease. Additionally, factors such as the event's timing, whether an emergent or elective procedure is performed, and the technical success of the surgical procedure can affect the outcomes and prognosis.

Risks and complications

The primary complication of the procedure is hepatic encephalopathy (HE), a cognitive dysfunction caused by the liver's reduced ability to filter toxins from the blood. Signs of symptoms of HE include confusion, disorientation, impaired memory, changes to mood, lethargy, and asterixis. [9]

Patients that undergo portacaval shunting may have an increased risk of HE because blood bypasses the liver and allows unfiltered toxins to enter the bloodstream and reach the brain, causing cognitive dysfunction. [10] Additionally, increased intestinal absorption of encephalopathogenic substances in combination with the reduced hepatic blood flow may also contribute to the high risk of developing HE. [10] Surgical shunts have a higher risk of encephalopathy compared to less invasive measures due to the total redirect of blood flow away from the liver. [4]

There are general surgical risks, such as bleeding and infection, along with specific complications related to liver function with portacaval shunting. Compared to the less invasive approaches (endoscopy, TIPS), surgical shunts have an increased risk of morbidity and mortality, especially in patients with advanced disease. [3] Complications include liver dysfunction due to altered blood flow, shunt thrombosis, and hepatic insufficiency.

Alternatives

Alternatives to surgical portacaval shunts include:

An interventional radiologist typically performs TIPS, which involves placing a stent between the portal vein and hepatic veins to lower blood pressure in the portal circulation. Compared to portacaval shunting, TIPS is less invasive, safer, and is now the preferred option for patients with advanced liver failure or those at high surgical risk. [11]

Both TIPS and portacaval shunting effectively reduce portal pressure but share the risk of hepatic encephalopathy (HE) due to bypassing the liver's detoxification process. In TIPS, HE symptoms can often be managed by adjusting the stent, whereas portacaval shunting provides a permanent solution without the ability to make such adjustments.

Additionally, portacaval shunting carries significantly higher morbidity and mortality rates, making TIPS the more favorable option in most cases. [3]

Related Research Articles

<span class="mw-page-title-main">Shunt (medical)</span> Hole or passage within the human body that allows fluids to move throughout it

In medicine, a shunt is a hole or a small passage that moves, or allows movement of, fluid from one part of the body to another. The term may describe either congenital or acquired shunts; acquired shunts may be either biological or mechanical.

<span class="mw-page-title-main">Budd–Chiari syndrome</span> Blockage of the hepatic veins that drain the liver

Budd–Chiari syndrome is a very rare condition, affecting one in a million adults. The condition is caused by occlusion of the hepatic veins that drain the liver.

<span class="mw-page-title-main">Esophageal varices</span> Dilated veins in the lower oesophagus

Esophageal varices are extremely dilated sub-mucosal veins in the lower third of the esophagus. They are most often a consequence of portal hypertension, commonly due to cirrhosis. People with esophageal varices have a strong tendency to develop severe bleeding which left untreated can be fatal. Esophageal varices are typically diagnosed through an esophagogastroduodenoscopy.

<span class="mw-page-title-main">Portal hypertension</span> Abnormally increased portal venous pressure

Portal hypertension is defined as increased portal venous pressure, with a hepatic venous pressure gradient greater than 5 mmHg. Normal portal pressure is 1–4 mmHg; clinically insignificant portal hypertension is present at portal pressures 5–9 mmHg; clinically significant portal hypertension is present at portal pressures greater than 10 mmHg. The portal vein and its branches supply most of the blood and nutrients from the intestine to the liver.

<span class="mw-page-title-main">Gastric varices</span> Dilated submucosal veins in the stomach lining

Gastric varices are dilated submucosal veins in the lining of the stomach, which can be a life-threatening cause of bleeding in the upper gastrointestinal tract. They are most commonly found in patients with portal hypertension, or elevated pressure in the portal vein system, which may be a complication of cirrhosis. Gastric varices may also be found in patients with thrombosis of the splenic vein, into which the short gastric veins that drain the fundus of the stomach flow. The latter may be a complication of acute pancreatitis, pancreatic cancer, or other abdominal tumours, as well as hepatitis C. Gastric varices and associated bleeding are a potential complication of schistosomiasis resulting from portal hypertension.

<span class="mw-page-title-main">Caput medusae</span> Appearance of distended and engorged superficial epigastric veins

Caput medusae is the appearance of distended and engorged superficial epigastric veins, which are seen radiating from the umbilicus across the abdomen. The name caput medusae originates from the apparent similarity to Medusa's head, which had venomous snakes in place of hair. It is also a sign of portal hypertension. When the portal vein, that transfers the blood from the gastrointestinal tract to the liver, is blocked, the blood volume increases in the peripheral blood vessels making them appear engorged. It is caused by dilation of the paraumbilical veins, which carry oxygenated blood from mother to fetus in utero and normally close within one week of birth, becoming re-canalised due to portal hypertension caused by liver failure.The appearance is due to cutanous portosystemic collateral formation between distended and engorged paraumbilical veins that radiate from the umbilicus across the abdomen to join systemic veins.

<span class="mw-page-title-main">Ductus venosus</span> Vein in the human fetus

In the fetus, the ductus venosus shunts a portion of umbilical vein blood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver. Compared to the 50% shunting of umbilical blood through the ductus venosus found in animal experiments, the degree of shunting in the human fetus under physiological conditions is considerably less, 30% at 20 weeks, which decreases to 18% at 32 weeks, suggesting a higher priority of the fetal liver than previously realized. In conjunction with the other fetal shunts, the foramen ovale and ductus arteriosus, it plays a critical role in preferentially shunting oxygenated blood to the fetal brain. It is a part of fetal circulation.

<span class="mw-page-title-main">Transjugular intrahepatic portosystemic shunt</span> Artificial channel within the liver

Transjugular intrahepatic portosystemic shunt is an artificial channel within the liver that establishes communication between the inflow portal vein and the outflow hepatic vein. It is used to treat portal hypertension which frequently leads to intestinal bleeding, life-threatening esophageal bleeding and the buildup of fluid within the abdomen (ascites).

<span class="mw-page-title-main">Portal vein thrombosis</span> Formation of a blood clot in the hepatic portal vein, reducing blood to the liver

Portal vein thrombosis (PVT) is a vascular disease of the liver that occurs when a blood clot occurs in the hepatic portal vein, which can lead to increased pressure in the portal vein system and reduced blood supply to the liver. The mortality rate is approximately 1 in 10.

<span class="mw-page-title-main">Gastric antral vascular ectasia</span> Intestinal bleeding due to widening of blood vessels in the stomach

Gastric antral vascular ectasia (GAVE) is an uncommon cause of chronic gastrointestinal bleeding or iron deficiency anemia. The condition is associated with dilated small blood vessels in the gastric antrum, which is a distal part of the stomach. The dilated vessels result in intestinal bleeding. It is also called watermelon stomach because streaky long red areas that are present in the stomach may resemble the markings on watermelon.

A portosystemic shunt or portasystemic shunt, also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital or acquired condition and occurs in humans as well as in other species of animals. Congenital PSS are extremely rare in humans but are relatively common in dogs. Improvements in imaging and awareness have contributed to an increase in cases.Thus a large part of medical and scientific literature on the subject is grounded in veterinary medicine.

<span class="mw-page-title-main">Distal splenorenal shunt procedure</span> Medical procedure

In medicine, a distal splenorenal shunt procedure (DSRS), also splenorenal shunt procedure and Warren shunt, is a surgical procedure in which the distal splenic vein is attached to the left renal vein. It is used to treat portal hypertension and its main complication. It was developed by W. Dean Warren.

In the course of the round ligament of the liver, small paraumbilical veins are found which establish an anastomosis between the veins of the anterior abdominal wall and the portal vein, hypogastric, and iliac veins. These veins include Burrow's veins, and the veins of Sappey – superior veins of Sappey and the inferior veins of Sappey.

A portacaval anastomosis or portocaval anastomosis is a specific type of circulatory anastomosis that occurs between the veins of the portal circulation and the vena cava, thus forming one of the principal types of portasystemic anastomosis or portosystemic anastomosis, as it connects the portal circulation to the systemic circulation, providing an alternative pathway for the blood. When there is a blockage of the portal system, portocaval anastomosis enables the blood to still reach the systemic venous circulation. The inferior end of the esophagus and the superior part of the rectum are potential sites of a harmful portocaval anastomosis.

<span class="mw-page-title-main">Portal hypertensive gastropathy</span> Changes in the mucosa of the stomach in patients with portal hypertension

Portal hypertensive gastropathy refers to changes in the mucosa of the stomach in patients with portal hypertension; by far the most common cause of this is cirrhosis of the liver. These changes in the mucosa include friability of the mucosa and the presence of ectatic blood vessels at the surface. Patients with portal hypertensive gastropathy may experience bleeding from the stomach, which may uncommonly manifest itself in vomiting blood or melena; however, portal hypertension may cause several other more common sources of upper gastrointestinal bleeding, such as esophageal varices and gastric varices. On endoscopic evaluation of the stomach, this condition shows a characteristic mosaic or "snake-skin" appearance to the mucosa of the stomach.

Portal venous pressure is the blood pressure in the hepatic portal vein, and is normally between 5-10 mmHg. Raised portal venous pressure is termed portal hypertension, and has numerous sequelae such as ascites and hepatic encephalopathy.

Anorectal varices are collateral submucosal blood vessels dilated by backflow in the veins of the rectum. Typically this occurs due to portal hypertension which shunts venous blood from the portal system through the portosystemic anastomosis present at this site into the systemic venous system. This can also occur in the esophagus, causing esophageal varices, and at the level of the umbilicus, causing caput medusae. Between 44% and 78% of patients with portal hypertension get anorectal varices.

The Sugiura procedure is a surgical technique that involves the removal and transection of the blood vessels that supply the upper portion of the stomach and the esophagus. The procedure also involves a splenectomy. The operation was originally developed to treat bleeding esophageal varices that were untreatable by other conventional methods. It was originally developed as a two-step operation, but has been modified numerous times by many surgeons since its original creation.

Portosystemic shunts are a type of vascular abnormality that causes blood to be emptied into the circulation, without passing through the liver. This prevents the liver from detoxifying the blood. The condition may be either congenital or acquired.

Balloon-occluded retrograde transvenous obliteration (BRTO) is an endovascular procedure used for the treatment of gastric varices. When performing the procedure, an interventional radiologist accesses blood vessels using a catheter, inflates a balloon and injects a substance into the variceal blood vessels that causes blockage of those vessels. To prevent the flow of the agent out of the intended site, a balloon is inflated during the procedure, which occludes.

References

  1. ↑ Comar, Kevin M.; Sanyal, Arun J. (2004), "Portal Hypertension and Esophageal Varices", Encyclopedia of Gastroenterology, Elsevier, pp. 212–219, doi:10.1016/b0-12-386860-2/00250-1, ISBN   978-0-12-386860-2 , retrieved 2024-11-21
  2. ↑ Berzigotti, Annalisa; Seijo, Susana; Reverter, Enric; Bosch, Jaime (February 2013). "Assessing portal hypertension in liver diseases". Expert Review of Gastroenterology & Hepatology. 7 (2): 141–155. doi:10.1586/egh.12.83.
  3. 1 2 3 4 Brand, Martin; Prodehl, Leanne (2015-09-18). Cochrane Hepato-Biliary Group (ed.). "Surgical portosystemic shunts versus transjugular intrahepatic portosystemic shunt for variceal haemorrhage". Cochrane Database of Systematic Reviews. doi:10.1002/14651858.CD001023.pub2.
  4. 1 2 Li JC, Henderson JM. Portal hypertension. In: Holzheimer RG, Mannick JA, editors. Surgical Treatment: Evidence-Based and Problem-Oriented. Munich: Zuckschwerdt; 2001. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6973/
  5. ↑ Orozco, Héctor (2000-12-01). "The Evolution of Portal Hypertension Surgery: Lessons From 1000 Operations and 50 Years' Experience". Archives of Surgery. 135 (12): 1389. doi:10.1001/archsurg.135.12.1389. ISSN   0004-0010.
  6. 1 2 3 Crossan, Kaitlyn; Jones, Mark W. (2024), "Portacaval Shunt", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   33085359 , retrieved 2024-11-10
  7. ↑ Fong, Yuman (2007). Atlas of Upper Gastrointestinal and Hepatic-Pacreato-Biliary Surgery. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 727–774. ISBN   978-3-540-20004-8.
  8. ↑ Bai, Yu & Li, Zhao-Shen. (2009). Management of variceal hemorrhage: Current status. Chinese medical journal. 122. 763-5. 10.3760/cma.j.issn.0366-6999.2009.07.001.
  9. ↑ Weissenborn, Karin (February 2019). "Hepatic Encephalopathy: Definition, Clinical Grading and Diagnostic Principles". Drugs. 79 (S1): 5–9. doi:10.1007/s40265-018-1018-z. ISSN   0012-6667. PMC   6416238 . PMID   30706420.
  10. 1 2 Iwatsuki S (September 1974). "A case of hepatic encephalopathy after portacaval shunt". The Japanese Journal of Surgery. 4 (3): 183–188. doi:10.1007/bf02468624. PMID   4464374. S2CID   10001207.
  11. ↑ Amesur, Nikhil B.; Novelli, Paula (2024), "Transjugular Intrahepatic Portosystemic Shunt", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   30020640 , retrieved 2024-11-21
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