Complications of portal HTN

Question 1

Portal venous physiology and pathology

Answer 1

• Ligation of either portal vein or hepatic artery in nl person will result in no immediate consequence
• Nl portal pressure 8mmHg
• Portal HTN can be pre-hepatic (in portal vein), hepatic (in sinusoids/liver), or post hepatic (in hepatic vein or heart)
• Prehepatic ex: portal vein thrombosis
• Hepatic ex: cirrhosis (sinusoidal)
• Posthepatic ex: budd chiari (hepatic vein occlusion)
• Hepatic portal HTN most common
• Only cure of portal HTN is liver Tx

Question 2

Cirrhosis

Answer 2

• Advanced fibrosis due to liver damage, leads to distortion of hepatic architecture and formation of regenerative nodules
• Primary cause of portal HTN, increases both outflow and inflow resistance

Question 3

Pathophysiology of portal HTN 1

Answer 3

• Fibrosis causes structural changes to sinusoids and increases hepatic vascular resistance
• Decreased endothelial relaxing factors (NO) and decreased response to these factors leads to increased vascular tone in portal flow
• Endogenous vasoconstrictors further exacerbate the increased vascular tone

Question 4

Pathophysiology of portal HTN 2

Answer 4

• Higher vascular tone contributes to increased hepatic vascular resistance
• Hepatic vascular resistance is aggravated by increased portal venous blood flow
• This is due to Na retention and thus larger blood volume, and increased CO

Question 5

Pressure gradient across liver

Answer 5

• Hepatic venous pressure gradient (HVPG) = portal vein pressure - hepatic vein pressure
• Can measure via balloon catheter
• HVPH 10mmHg associated w/ esophageal varices and ascites
• HVPG >12mmHg associated w/ variceal bleeding

Question 6

Manifestations of portal HTN

Answer 6

• Splenomegaly
• Varices and vatical bleeding
• Ascites
• Hepatorenal syndrome
• Spontaneous bacterial peritonitis
• Hepatic encephalopathy

Question 7

Varices

Answer 7

• Portal HTN leads to re-establishment of portosystemic shunts to relieve pressure
• Most important: esophageal veins (to azygos vein), leads to gastroesophageal varices
• Others: paraumbilical veins, retroperitoneal veins, rectal veins
• Portal gastropathy: not true varices- flow and pressure induced changes in gastric mucosal vessels

Question 8

Esophageal varices 1

Answer 8

• Most common lethal complication of cirrhosis
• Can lead to hematemesis/melena, hemodynamic instability
• Management: protect airway, blood transfusion (keep Hg >8)
• Use splanchnic vasoconstrictor to reduce portal flow: octreotide
• Endoscopic Rx: band ligation

Question 9

Esophageal varices 2

Answer 9

• TIPS (trans-jugular intrahepatic portal systemic shunt): can decompensate a sick liver leading to further damage, only works for intra-hepatic HTN (or rare cases of post-hepatic HTN), and only to reduce variceal bleeding
• Liver Tx is option
• Prophylaxis: regular endoscopy for pts w/ cirrhosis, BBs good for prophylaxis (to reduce splanchnic blood flow) but not for acute even

Question 10

Ascites 1

Answer 10

• Most common complication of cirrhosis, cirrhosis most common cause of ascites
• PE: ab distension, buldging flands, hernias, scrotal edema, fluid wave, shifting dullness
• Pathogenesis is complicated, but essentially there is a drop in systemic BP in portal HTN due to endotoxemia (presence of LPS from GI tract in circulation causes vasodilation) and increased PGs/vasodilators
• Endotoxemia due to intestinal disturbance, reduced reticuloendothelial system, and porto-systemic shunts
• These lead to arterial vasodilation, BP falls and baroreceptors are activated
• RAAS and ADH pathways initiated, leading to renal vasoconstriction, Na/H2O retention, and ascites develops

Question 11

Ascites 2

Answer 11

• Management goal: make Na intake < Na output
• To do this must Rx any underlying factors: hepatitis, etoh, metabolic diseases, avoid nephrotoxic drugs that promote Na retention (ACEIs, NSAIDs)
• Put on low Na diet, use spironolactone to oppose RAAS (ACEIs can increase risk for renal failure), loop diuretics to aid in natriuresis
• <10% of pts develop refractory ascites: renal failure, worsening encephalopathy, electrolyte disturbances
• In these pts must do paracentesis w/ colloid (albumin) replacement, can do TIPS in some pts, liver Tx is option

Question 12

Spontaneous bacterial peritonitis and hepatorenal syndrome

Answer 12

• SBP: Infection of preexisting portal HTN ascites
• Dx via paracentesis: absolute PMNs >250
• Rx w/ antibios and albumin replacement to decrease incidence of hepatorenal syndrome
• HRS: severe renal vasoconstriction leading to renal failure (in presence of cirrhosis and ascites), due to drop in systemic BP (see mechanism above)
• Type 1 is rapid onset, type 2 is >2 wk onset
• Poor prognosis
• Rx: octreotide to constrict splanchnic circulation and improve renal perfusion, hemodialysis, liver Tx

Question 13

Hepatic encephalopathy 1

Answer 13

• From ammonia buildup due to inability of liver to convert to urea, and from false neurotransmitters from GI tract
• Direct neurotoxicity of ammonia causes cerebral edema
• Prevalence increases w/ severity of cirrhosis
• Worsened by intrahepatic and extra hepatic shunts from portal HTN
• Splenorenal shunt is risk factor for developing overt hepatic encephalopathy, TIPS may worsen underlying hepatic encephalopathy

Question 14

Hepatic encephalopathy 2

Answer 14

• Sx: neurocognitive, motor, psychiatric impairment, can be from mild confusion to coma, may see asterixis and/or myoclonus
• Rx: elimination of precipitating factors (infection, bleeding, dehydration, electrolyte imbalance, sedatives, constipation), pharmacologic, liver Tx, reduce protein intake
• Pharmacologic Rx: enemas, rifaximin/neomycin (antibio) to decrease bacteria in GI tract leading to decreased ammonia production, and lactulose (a non-absorbable disaccharide) is broken down by bacteria in GI tract and acidifies the lumen leading to decreased ammonia absorption