Portal system
Key points
Normal portal pressure in children: 5-10mmHg
>10mmHg = Hypertension
Measure with wedge hepatic vein pressure
Causes of portal hypertension:
Primary venous obstruction
Pre-hepatic: Portal thrombosis - e.g. from umbilical vein catheterisation
Post-hepatic: Budd-Chiari
Intrinsic Liver disease
Biliary atresia - cirrhosis
Cystic fibrosis
α1 Antitrypsin deficiency
Anatomy
Superior mesenteric vein (SMV) is joined by the splenic vein to form the portal vein, the inferior mesenteric vein (IMV) joins the splenic vein
Portal vein variants rare - but usually involve IMV joining in different positions
Hepatic artery supplies 25% of blood flow but 50% of oxygen
Variants in 45% e.g. right hepatic artery arising from the superior mesenteric artery or left hepatic artery arising from the left gastric artery
Umbilical vein runs in lower (free) edge of falciform (when obliterated - becomes ligamentum teres or round ligament) - joins the left portal vein at porta hepatis - bypasses the liver into ductus venosus (becomes ligamentum venosus) - also supplies left and right hepatic sinusoids
8 Porto-systemic anastomosis
Oesophagus
Rectum
Splenorenal
Umbilicus
Retroperitoneum via vein of retzius
Bare area of liver
Omentum
Patent ductus venosus
Abnormalities of portal vein
Preduodenal portal vein
Duplication
Abnormal drainage into right atrium, the superior vena cava, pulmonary veins and umbilical vein
Aneurysm
Management of portal hypertension in children
Options:
Meso-rex bypass - Graft (left internal jugular vein harvest) between SMV + Rex recess of left portal vein
Distal splenorenal shunt - cut splenic vein and anastomose to left renal vein
Mesocaval shunt - synthetic graft between SMV + IVC
Transjugular intrahepatic portosystemic shunt (TIPS) not often used as high complication and reoperation rate (90%) in children
Monitor spleen size post op
Liver transplant for cirrhosis
Complications of bypass:
Leak/stricture/failure etc
Hepatic encephalopathy
Patent ductus venosus
Blood from portal vein is shunted to IVC
Leads to galactosemia, hypoxia, hyperammonemia, hepatic dysfunction, and encephalopathy
Managed surgically with embolisation or catheter closure
Prostaglandin infusion would maintain the patency of the ductus venosus
Ascites
Mechanisms:
Impaired absorption of lymph fluid - e.g. in hepatic failure, decreased albumin, decreased oncotic pressure in lymphatics
Increased production - e.g in increased hydrostatic pressure in lymphatics in portal hypertension, heart failure, cirrhosis, or exudate into peritoneum from malignancy etc.
Reduced excretion e.g renal - activation of renin-angiotensin-aldoseterone system (RAAS)
Serum ascites albumin gradient (SAAG) = Serum albumin minus ascites albumin
High gradient = low protein content of fluid
Treatment:
Sodium and fluid restriction
Spironolactone - acts at distal tubule, blocks RAAS
References
Gugig R, Rosenthal P. Management of portal hypertension in children. World J Gastroenterol. 2012 Mar 21;18(11):1176-84. doi: 10.3748/wjg.v18.i11.1176. PMID: 22468080; PMCID: PMC3309906.
Guérin F, Bidault V, Gonzales E, Franchi-Abella S, De Lambert G, Branchereau S. Meso-Rex bypass for extrahepatic portal vein obstruction in children. Br J Surg. 2013 Nov;100(12):1606-13. doi: 10.1002/bjs.9287. PMID: 24264782.
Carneiro C, Brito J, Bilreiro C, Barros M, Bahia C, Santiago I, Caseiro-Alves F. All about portal vein: a pictorial display to anatomy, variants and physiopathology. Insights Imaging. 2019 Mar 21;10(1):38. doi: 10.1186/s13244-019-0716-8. PMID: 30900187; PMCID: PMC6428891.
Sitaram, Barath & Kheradia, Dharav & Gopalkrishnan, Shakti & R., Rahul & K., Mohammed. (2022). Review of Applied Anatomy, Hemodynamics, and Endovascular Management of Ectopic Varices. Journal of Clinical Interventional Radiology ISVIR. 06. 10.1055/s-0041-1730868.
Kamali L, Moradi M, Ebrahimian S, Masjedi Esfahani M, Jafarpishe MS. Patent ductus venosus in an infant with direct hyperbilirubinemia. Clin Case Rep. 2019 Jun 14;7(7):1430-1434. doi: 10.1002/ccr3.2266. PMID: 31360505; PMCID: PMC6637328.