The Portal System...made EZ

The Portal system? I was asked that during my NCLEX review class last week by some Jr students, and figured there may be more that are more than confused by this term. So what follows is a simple description of this system that is involved in some of the more common pathologies in the hospital.

The liver is a selfish organ. It demands first access to blood that is bringing anything new into the system, kind of like a checkpoint at the border. At this checkpoint, the liver removes anything toxic by metabolism or excretion, converts nutrients into useable or stored forms, as well as a host of other responsibilites. There are four main areas that drain their blood to the liver, before it is dumped into the system. Check out the picture below, to get an idea before we discuss this.


The easiest to picture, is blood coming from the intestines, where new food was just absorbed. The liver wants first access to this blood, and gets it via the portal system. The problem is, what if the liver is congested or scarred and little blood can get through the liver. Well anyone who has ever been on the interstate understands, that there is backup, when something is blocking the road. The blood trying to get to the liver now backs up and dilates these portal veins. In the intestines, this blood can leak out into the tissue, becoming Ascites.

The next drainage, comes from the rectum. That is a port of entry into your body, right? Well the liver wants to analyze blood coming from this area of your body (that is good when there is a medication jammed in there) and gets that blood through the portal system. If this blood backs up, you will get big dilated veins in the rectum, called Hemorrhoids.

The Spleen also drains into the Liver before its blood has access to the main system. That is good, since broken down RBCs (bilirubin) get processed there. If this part of the portal system backs up you would see Splenomegaly.

The final system that drains via the portal system, is the other port of entry into your body, the esophagus. Veins partially drain this area in case there are invaders or new toxins to metabolize. If this backs up you would see big, dilated veins in the esophagus, called Esophageal Varices (Varicose veins in the throat). This is a significant issue...imagine our patient is eating a Dorito, and an edge of that cool ranch chip nicks the dilated vein. You would get bleeding into the esophagus. Remember that the liver also makes important clotting factors, and if the liver is damaged and congested we are not going to clot well. (Remember that PT measures one of the key clotting factors? It is also the fastest lab value to change with liver damage so check that PT/INR!)

So Esophageal Varices are a very important pathology to notice in any liver patient as we must stop that bleeding. Luckily, blood is very irritating and is usually thrown at you with very violent, bloody vomiting, so you shouldn't miss that sign. One you may miss is if you forget that the Liver also makes Albumin, which, because it is so attractive to water, is what keeps volume in your blood. If you lose this albumin from a diseased liver, you are already looking at a patient that has falling blood pressure. Now take some blood away via these Esophageal varices, and you may see significant Hypotension. So make sure you are measuring those vital signs frequently!

Here is a picture that hopefully summarizes what we just covered. Now you should at least be able to recognize what the portal system is, and why we see certain signs in Liver patients, like Splenomegaly, Ascites, Hemorrhoids, Esophageal Varices, and Hypotension.

Bilirubin made EZ

Ah good ole Bilirubin. One of those famous lab values that seems so important to so many people, but why? Understanding this simple lab concept can not only help you when it comes to NCLEX or USMLE time, but will help you as an RN, ARNP or MD to recognize certain pathologies that you will frequently encounter.


OK, lets take a look at Bilirubin in general. On most circulations through the body, RBCs have to pass through the ultimate inspection. They file through tight spaces in the spleen and are closely inspected by the watchful eye of WBCs. Any weakness is immediately noticed, and that poor RBC is bound for destruction. Their life is on average, only 40 days, and then they suffer an awful end. When they are ripped out of line, they have their core of iron ripped out to be recycled, and their skin stripped off and dumped. Talk about a bad way to go. This skin is the origin of what we see in a lab value as Bilirubin. At this point, it is simply unconjugated Bilis, often termed indirect bilirubin. It is dumped into the drainage system of the spleen, which is the bloodstream that leads to the liver, known as the Portal system. When it reaches the liver, it is then conjugated, which simply means the liver alters the structure a little bit, and we now have conjugated or direct bilirubin. This new product is now stored in the gall bladder to be used as bile salts. Bile salts are released when you eat a fatty meal, and assist the body in absorbing the fat molecules. Unabsorbed Bile salts are broken down by bacteria in your gut, and are what make your stool brown.


OK got that picture in your head? Heres how knowing this helps. If Bilirubins become elevated in the blood stream, it is usually because the liver is too congested to accept new deliveries, and they then build up in the bloodstream causing pruritis, yellow jaundice skin and sclera, and give their brown color to the urine. Meanwhile the stool is a light color with no bilis, and fat is not absorbed.


But there is more. I can use this lab value to tell what the cause of that liver congestion is. If the liver itself is the blame, such as in the case of Liver diseases like Cirrhosis, any new bilirubin is not conjugated, so I will get UNconjugated or Indirect bilirubins that are elevated. On the other hand if the Bile duct is the source of the back up congestion in the liver, the new bilis are conjugated by the liver, but can not pass on into the gall bladder or GI tract, so Conjugated or Direct bilirubins are elevated in the blood. Make sense? So don't just be satisfied to know that bilirubin is elevated, but look closer and see what type of bilirubin is elevated, and you will have a very good idea if this is a liver dysfunction or a biliary obstruction...big difference right!?

OK. One other thing you will see in the picture below. Another way you can have elevated bilis is if you are simply killing way too many RBCs, and your liver can't keep up with the delivery. This would happen in the case of Hemolysis, where RBCs are actively being destroyed in great numbers.


Check out these cheesy drawings, and hopefully they will truly be worth a 1000 words.