Portal Hypertension

Definition And Pathophysiology

Portal pressure >10-12 mm Hg or hepatic venous pressure gradient (HVPG) >4 mm Hg.
Clinically significant portal hypertension exists when pressure exceeds 10-12 mm Hg, posing risk for variceal hemorrhage.
Governed by Ohm's law: ΔP = Q x R (Portal pressure = Portal blood flow x Hepatic vascular resistance).

Increased Vascular Resistance (R):
- Mechanical component (70%): Architectural derangement, fibrosis, nodular regeneration, thrombosis.
- Dynamic component (30%): Active contraction of myofibroblasts and hepatic stellate cells. Driven by imbalance between endogenous vasoconstrictors (endothelin-1, angiotensin II, norepinephrine, thromboxane A2) and vasodilators (reduced nitric oxide).
Increased Portal Blood Flow (Q):
- Hyperdynamic circulation driven by splanchnic vasodilation.
- Mediated by excessive release of endogenous vasodilators (nitric oxide, glucagon, vasoactive intestinal peptide).
- Results in sodium/water retention, hypervolemia, and increased cardiac output.

Category	Specific Disorders
Prehepatic (Extrahepatic)	Portal vein thrombosis (most common extrahepatic cause in children), portal vein agenesis/atresia/stenosis, splenic vein thrombosis, arteriovenous fistula.
Intrahepatic Presinusoidal	Congenital hepatic fibrosis, non-cirrhotic portal fibrosis (idiopathic portal hypertension), schistosomiasis, myeloproliferative diseases, focal nodular hyperplasia.
Intrahepatic Sinusoidal	Liver cirrhosis (biliary atresia, Wilson disease, alpha-1-antitrypsin deficiency, cystic fibrosis, glycogen storage disease type IV, autoimmune hepatitis).
Intrahepatic Postsinusoidal	Venoocclusive disease (sinusoidal obstruction syndrome).
Posthepatic	Budd-Chiari syndrome (hepatic vein or inferior vena cava obstruction/webs), right heart failure, constrictive pericarditis, Fontan circulation.

Gastrointestinal Hemorrhage: Most common presentation. Hematemesis or melena originating from ruptured esophageal/gastric varices or portal hypertensive gastropathy.
Splenomegaly And Hypersplenism: Second most common finding. Causes sequestration of platelets and leukocytes, resulting in thrombocytopenia and leukopenia.
Ascites: Fluid accumulation when hydrostatic pressure exceeds osmotic pressure. Characterized by high serum-ascites albumin gradient (SAAG) $\geq$ 1.1 g/dL. Risk of spontaneous bacterial peritonitis.

System	Manifestations And Pathophysiology
Pulmonary	Hepatopulmonary Syndrome (HPS): Intrapulmonary microvascular dilations causing right-to-left shunting. Presents with hypoxemia, dyspnea, cyanosis, clubbing, orthodeoxia. Diagnosed via contrast-enhanced echocardiography or macroaggregated albumin scan. Portopulmonary Hypertension (PP-HTN): Pulmonary arterial hypertension (>25 mm Hg). Exertional dyspnea. Pulmonary arteriopathy with intimal fibrosis.
Renal	Hepatorenal Syndrome (HRS): Intense renal vasoconstriction secondary to severe splanchnic vasodilation. Presents as oliguria, low urine sodium, rising creatinine.
Neurological	Hepatic Encephalopathy: Especially in cirrhosis or prominent portosystemic shunting. Minimal hepatic encephalopathy compromises attention and psychomotor performance.
Biliary	Portal Hypertensive Biliopathy: Compression of biliary tree by cavernomatous collaterals in extrahepatic portal venous obstruction (EHPVO), causing strictures and cholestasis.

Laboratory: Thrombocytopenia (platelet count represents best non-invasive predictor of varices), altered coagulation (prothrombin time/INR), hypoalbuminemia, elevated transaminases/bilirubin (depending on underlying liver disease).
Abdominal Ultrasonography With Doppler: First-line modality. Defines vascular anatomy, portal vein patency, flow direction (hepatofugal flow suggests severe disease/bleeding risk), spleen size, ascites, and collateral vessels (cavernous transformation).
CT/MR Angiography: Delineates extrahepatic vascular anatomy, spontaneous shunts, and evaluates feasibility for surgical shunting.
Transient Elastography: Non-invasive surrogate for assessing liver/spleen stiffness to predict severe fibrosis and varices.

Esophagogastroduodenoscopy (EGD): Gold standard for detecting and grading esophageal/gastric varices and portal hypertensive gastropathy. Predicts bleeding risk (red wale marks, large varices).
Hepatic Venous Pressure Gradient (HVPG): Measures difference between wedged (WHVP) and free (FHVP) hepatic venous pressures.
- Normal: 1-5 mm Hg.
- $\geq$ 10 mm Hg: Varices formation.
- $\geq$ 12 mm Hg: Variceal bleeding risk.
- Utility: Differentiates sinusoidal PH (elevated WHVP, high HVPG) from presinusoidal PH (normal WHVP, normal HVPG).

Medical emergency prioritizing hemodynamic stabilization and bleeding cessation.

Resuscitation: Intravenous crystalloids followed by packed red blood cells. Target hemoglobin 7-9 g/dL (avoid over-transfusion to prevent rebound portal pressure increase). Correct coagulopathy (vitamin K, fresh frozen plasma).
Pharmacotherapy:
- Vasoactive agents to decrease splanchnic blood flow: Octreotide (1 mcg/kg bolus, followed by 1-5 mcg/kg/hr continuous infusion), Terlipressin, or Vasopressin.
- Intravenous broad-spectrum antibiotics (cefotaxime/ceftriaxone) to prevent infectious complications.
- Acid suppression (intravenous proton pump inhibitors/H2-receptor antagonists).
Endoscopic Intervention: Endoscopic variceal ligation (EVL) preferred over sclerotherapy due to lower complication rates. Sclerotherapy utilized in infants too small for EVL banding device.
Rescue Therapy: Balloon tamponade (Sengstaken-Blakemore or Minnesota tube) for uncontrolled bleeding, serving as bridge to definitive intervention. Maximum inflation time 12 hours.

Primary/Secondary Prophylaxis:
- Non-selective beta-blockers (propranolol, nadolol) lower cardiac output and induce splanchnic vasoconstriction. Usage in young children debated due to reliance on heart rate for maintaining cardiac output.
- Serial endoscopic band ligation or sclerotherapy until varices are completely obliterated.

Intervention	Indication And Mechanism
Transjugular Intrahepatic Portosystemic Shunt (TIPS)	Interventional radiology placement of stent between hepatic and portal vein. Bypasses liver resistance. Indicated for refractory variceal hemorrhage or intractable ascites. Used frequently as bridge to liver transplantation.
Meso-Rex Bypass	Superior mesenteric vein to left portal vein bypass. Procedure of choice for extrahepatic portal vein obstruction (EHPVO). Restores physiologic hepatopetal flow, alleviating hypersplenism, bleeding risk, and resolving neurocognitive/growth retardation.
Portosystemic Shunts	Distal splenorenal shunt (decompresses varices while maintaining hepatic flow; lower encephalopathy risk), mesocaval shunt, or portocaval shunt. Indicated in patients with preserved synthetic function failing endoscopic therapy.
Liver Transplantation	Definitive, curative therapy for portal hypertension secondary to progressive end-stage cirrhotic liver disease, severe hepatopulmonary syndrome, or failed medical/surgical management.