Medicine:Portosystemic shunt
A portosystemic shunt or portasystemic shunt (medical subject heading term) (PSS), also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital (present at birth) 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.[1] Thus a large part of medical and scientific literature on the subject is grounded in veterinary medicine.
Background
Blood leaving the digestive tract is rich in nutrients, as well as in toxins, which under normal conditions undergo processing and detoxification in the liver. The liver's position downstream to the intestines in the body's circulatory system - the hepatic portal vein conveys blood from the intestines to the liver - allows it to filter this nutrient rich blood before it passes to the rest of the body.
The presence of a shunt, bypasses the liver and causes blood to flow directly to the heart. This blood is no longer filtered by the liver and reaches the systemic circulation, resulting in a number of symptoms and complications with effects on the cardiovascular, neurophysiological, gastro-intestinal, urinary and endocrinal systems.[2]
Congenital porto-systemic shunts are vascular malformations which occur during the development of the organism and are present at birth. In contrast, acquired porto-systemic shunts occur after birth and typically develop secondary to portal hypertension.[3]
Congenital porto-systemic shunts (CPSS) are classified occurring to the position of the anastomose. If the anastomosis occurs outside of the liver, the shunt is considered to be extrahepatic. On the other hand, if the anastomosis is located within the liver, it is considered to be intrahepatic. The clinical manifestations of intra- and extra- hepatic portal systemic shunts can be similar; however the pathophysiology and treatment of the two types are distinct.[4]
CPSSs occur with a prevalence of 1 in 30 000 births and are typically unique occurrences; however multiple shunts can occur.[4][3] It is generally agreed amongst specialists that the majority of CPSSs should be closed by radiological or surgical intervention.[5]
Physiopathology
There are no major and direct communications between the portal and hepatic veins within the liver, nor between the systemic veins and the portal, superieur mesenteric or splenic veins.[6] Two distinct systems provide the liver with blood. Oxygen rich blood is sent to the liver from the heart via the hepatic artery, while the portal vein brings nutrient rich (but depleted in oxygen) blood to the liver from the intestines. This blood passes by the network of capillaries before being evacuated by the hepatic veins into the inferior vena cava and subsequently the heart. The division between these two systems helps assure the liver's physiological roles.
A CPSS results in a direct communication between the portal circulation and the systemic circulation. This breaks down the separation between these two systems which is crucial in ensuring normal physiological function. A reduction in the proportion of blood flowing from the digestive system to the liver during the first pass results.[5] The coefficient of filtration is therefore reduced, less blood rich in nutrients and toxins is filtered, and an accumulation of toxins in the blood circulatory system occurs.
Epidemiology
CPSS occur with a prevalence of 1 in 30 000 births. The prevalence of PSS in the general population, including acquired PSS, or those not closed by surgical intervention, is 1 in 50 000 people.[4][3]
Clinical Manifestation
The size of the liver in patients affected by PSS is typically 45% to 65% of the standard volume for a given age.[3] Neonatal cholestasis, liver tumours, hepatopulmonary syndrome, pulmonary hypertension and encephalopathy are common clinical manifestations of CPSS.[3] In adults, the discovery of a CPSS is often fortuitous but can also occur in response to the detection of one or several characteristic complications such as hepatic encethalopathy, hepatopulmonary syndrome and pulmonary hypertension. These complications are generally induced by long term portosystemic derivations and are more commonly observed in children than in adults.[4] Unexplained neurocognitive dysfunction and other behavioural issues linked to hepatic encephalopathy occur in 17% to 30% of cases.[6]
Gastrointestinal bleeding is another common complication of PSS and has been observed in 8.1% of patients with extrahepatic portosystemic shunts.[7] Other complications of CPSS are hyperandrogenism, pancreatitis, vaginal bleeding, and lower urinary tract symptoms like nephrolithiasis (kidney stones) and haematuria (presence of blood in the urine).
Classification
Various classification systems for PSS have been described which take into account the clinical manifestation, liver histopathology, and/or other anatomic parameters such as localisation, configuration, size, vessels involved, the number of pathways and the presence of intrahepatic portal branches.[4] The most common classification system distinguishes between intrahepatic and extrahepatic PSS.
Treatment
Spontaneous closure of CPSS can ocur in some anatomic forms during the first year of life.[8] However, in instances where spontaneous closure does not occur, radiologic or surgical closure of the CPSS is recommended to prevent, resolve and/or stabilise complications.
Upon discovery of a CPSS in a child, it is important to rule out portal hypertension or hepatic hemangioma as the cause of the shunt, either of which would require a specific treatment. Once the congenital, and isolated, nature of the shunt has been ascertained, closure by surgical intervention is usually recommended.[3]
On-going research
An International Registry of Porto-Systemic Shunts (IRCPSS) has been elaborated in order to better understand the underlying causes, as well as the signs and symptoms of PSS. The primary aim of the registry is to "better identify patients who are at risk of developing complications and to offer them standardized care." The registry can be found at http://ircpss.com/IRCPSS.html
See also
References
- ↑ Alonso-Gamarra, Eduardo; Parrón, Manuel; Pérez, Ana; Prieto, Consuelo; Hierro, Loreto; López-Santamaría, Manuel (2011-05-01). "Clinical and Radiologic Manifestations of Congenital Extrahepatic Portosystemic Shunts: A Comprehensive Review". RadioGraphics 31 (3): 707–722. doi:10.1148/rg.313105070. ISSN 0271-5333. https://pubs.rsna.org/doi/10.1148/rg.313105070.
- ↑ "IRCPSS". http://ircpss.com/.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Bernard, O.; Franchi-Abella, S.; Branchereau, S.; Pariente, D.; Gauthier, F.; Jacquemin, E. (November 2012). "Congenital Portosystemic Shunts in Children: Recognition, Evaluation, and Management" (in en). Seminars in Liver Disease 32 (04): 273–287. doi:10.1055/s-0032-1329896. ISSN 0272-8087. http://www.thieme-connect.de/DOI/DOI?10.1055/s-0032-1329896.
- ↑ 4.0 4.1 4.2 4.3 4.4 Papamichail, M.; Pizanias, M.; Heaton, N. (2018-03-01). "Congenital portosystemic venous shunt" (in en). European Journal of Pediatrics 177 (3): 285–294. doi:10.1007/s00431-017-3058-x. ISSN 1432-1076. PMID 29243189. PMC 5816775. https://doi.org/10.1007/s00431-017-3058-x.
- ↑ 5.0 5.1 "Interview d’Amaria Remil, Cheffe de projet du Centre de Référence AVB-CG, et du Pr Stéphanie Franchi-Abella, Responsable du secteur de radiologie interventionnelle pédiatrique (Université Paris-Saclay)" (in fr-FR). 2020-12-17. https://www.filfoie.com/interview-franchi-remil-crmr-avb-cg-ircpss-registre/.
- ↑ 6.0 6.1 Stringer, Mark D. (2008). "The clinical anatomy of congenital portosystemic venous shunts" (in en). Clinical Anatomy 21 (2): 147–157. doi:10.1002/ca.20574. ISSN 1098-2353. https://onlinelibrary.wiley.com/doi/abs/10.1002/ca.20574.
- ↑ Gong, Ying; Zhu, Hui; Chen, Jun; Chen, Qi; Ji, Min; Pa, Mier; Zheng, Shan; Qiao, Zhongwei (December 2015). "Congenital portosystemic shunts with and without gastrointestinal bleeding – case series" (in en). Pediatric Radiology 45 (13): 1964–1971. doi:10.1007/s00247-015-3417-6. ISSN 0301-0449. http://link.springer.com/10.1007/s00247-015-3417-6.
- ↑ the International Registry of Congenital Portosystemic Shunt members; Franchi-Abella, Stéphanie; Gonzales, Emmanuel; Ackermann, Oanez; Branchereau, Sophie; Pariente, Danièle; Guérin, Florent (August 2018). "Congenital portosystemic shunts: diagnosis and treatment" (in en). Abdominal Radiology 43 (8): 2023–2036. doi:10.1007/s00261-018-1619-8. ISSN 2366-004X. http://link.springer.com/10.1007/s00261-018-1619-8.
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