Q. Why is there splenomegaly in hemolytic anemias with intravascular hemolysis? For example, in hereditary spherocytosis, where there is intravascular hemolysis, why is the spleen big? Is it that both types of hemolysis, occur and it’s just that intravascular is increased a little bit more than extravascular?
A. The likelihood of a patient having splenomegaly depends on which particular hemolytic anemia the patient has.
In hereditary spherocytosis (HS), for example, there actually is a good deal of extravascular hemolysis (in addition to the intravascular component). The spleen is the main site of destruction for the abnormal red cells in HS. Spherocytes have a hard time passing through the cords of Bilroth, and they back up in the spleen, causing splenomegaly. Check out the image above of splenomegaly in a child with HS, from the Pediatric Surgery Department at Brown Medical School. Eventually, macrophages devour them and they disappear from circulation.
There is also some intravascular hemolysis in HS; spherocytes are more fragile than regular red cells, so they’re more likely to bust open in blood vessels. It’s not really the main thing that’s going on, though – it’s just a byproduct of the disease. So in HS, there is big-time splenomegaly, because that’s the site of most of the destruction.
So, in HS, do they remove the spleen? Isn’t it dangerous to even walk with an enlarged spleen?
It depends on the severity of the disease. Some people with HS have few or no symptoms, and there is no need for treatment of any kind. Others have severe disease, and removal of the spleen is very helpful in treating the disease (because you’re removing the site where the red cells are destroyed). Having a very enlarged spleen does present a danger in and of itself, as you mentioned – you’d need to avoid contact sports for sure!
Another couple of reasons to avoid splenectomy when possible:
(1) Increased risk of sepsis with encapsulated organisms
(2) Some evidence of a higher risk of microemboli to the lungs, with subsequent development of pulmonary hypertension.
Absolutely right! Lifetime vaccination against S. pneumo and H. flu required.
A student homework answer seemed wrong to me, but I’m not confident of my answer. Can you correct the missing pieces?
“Splenomegaly in liver disease causes increased hemolysis which produces more bilirubin”
My answer: Not exactly. Splenomegaly does cause sequestration of platelets but there should not be increased breakdown of RBCs, which are typically only taken up by splenic macrophages when they are deformed or senescent. Splenomegaly in hemolytic anemias like sickle cell or hereditary spherocytosis happens Because Of the destruction of RBCs (see post at Pathology Student). The increased bilirubin in cirrhosis is due to the hepatocyte dysfunction—inability to conjugate the normal bilirubin for excretion in the gut.
The reason why platelets are taken up in splenomegaly due to portal hypertension, but red blood cells are not) is ….???
Thank you for your many enlightening posts and material!
Hi Lori – your answer is great! The splenomegaly that you see in cirrhosis is, as you mentioned, due to portal hypertension. This means that the blood has a hard time getting through the fibrotic liver, so it backs up into the spleen (and in other places). The spleen becomes enlarged because it has more blood in it – and we call this “sequestration.” All the cells/elements of the blood are sequestered in the spleen – red cells, white cells, and platelets! (just to clarify your last question.)
I’m guessing that the original question was something like “Why do patients with cirrhosis have an increased serum bilirubin?” And the student’s answer was incorrect, as you noted. The reason for the increased serum bilirubin in patients with cirrhosis has to do with the liver’s failure to excrete bilirubin into the gut (so it backs up into the blood).
Hemolysis can cause hyperbilirubinemia – but that’s not the mechanism at play in patients with cirrhosis.
Not sure if you saw this post on conjugated vs. unconjugated bilirubinemia – might be helpful to your student 🙂