Help understanding Portal HTN

[freckles23]

I am currently doing Liver diseases in school and I seem to be stuck on understanding portal HTN. The books I have read on it are way too wordy and confusing me. This is what I have at the moment....

• damaged fibrotic liver causes obstruction of blood flow through the portal vein so there is an increase in systemic blood pressure and that makes fluid leak from vascular system into the abdomen
  
• veins that line wall of esophagus become dilated & engorged and become friable and can rupture
  
• kidneys notice there isn't much circulatory volume so kidneys try to hold onto fluid and more fluid leaks into abdomen so you want to correct the fluid balance from one compartment to the other and get more fluid in circ system and less leaking out into abdomen
  

My question is also if you have Cirrhosis of the liver, why do you have hypotension? I figured you would have Hypertension because of the backflow of fluids in the system. I am very confused. Please clarify with the patho of Portal HTN and Cirrhosis. Maybe someone else explaining it will make me understand it better. Thank you!

[nurseprnRN, BSN, RN]

Your three bullet points are pretty good-- if you understand them, then you've got a good grasp of why people with livers that have turned to rock are in deep doo-doo.

As to your question, when your circulatory system is constantly losing volume into your intra-abdominal cavity from the portal veins, rather than keeping it in the venous system where it would normally be returning to the heart to make a BP, what happens to your BP?

Portal hypertension is venous, higher than normal for veins, in the venous system in the liver and surrounding veins, not in the arteries (where we usually measure it and the one we usually care about most). hard scarred up livers aren't soft and compliant, so the venous pressure in them rises. Then the veins leak, just like the one belonging to old ladies with varicosities and fat feet at the end of the day. Only instead of making fat feet with that fluid coming out of legs, cirrhotics make big balloony bellies with the fluid accumulating in the peritoneum. That fluid also has a lot of protein in it, so there's less protein in the blood to hold onto water there (review "oncotic pressure" in your physiology book), meaning more loss from the vascular system.

[freckles23]

So is this how it goes? So when you have backflow due to the portal HTN the veins dilate (get bigger) due to the congestion. Then since there is congestion the veins leak into the abdomen causing ascites so that causes low BP?

[tokebi]

Liver synthesizes the major protein, albumin, which is responsible for maintaining the oncotic pressure so that fluid stays in the blood vessel. With cirrhosis, liver loses its normal function including making albumin.

So, you have blockage of sorts at the liver, preventing venous return to the heart and causing increased pressure within the portal vein and other veins leading up to it. And then there's not enough albumin to help keep fluid within the blood vessels, so it leaks out causing ascites.

It is confusing because of the name "portal hypertension" but like GrnTea said, portal hypertension is occurring in the venous system. The systemic arterial pressure drops because of the fluid leaking out, decreasing the overall blood volume within the vessels.

[Esme12, ASN, BSN, RN]

This may help....http://www.hopkinsmedicine.org/gastroenterology_hepatology/_pdfs/liver/portal_hypertension.pdf