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What is an Accessory Spleen?

Mary McMahon
Updated Mar 03, 2024
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An accessory spleen is a small mass of splenic tissue that is separated from a patient's primary spleen. Around one in ten people has one, and less than one percent of the population has multiple accessory spleens. For the most part, these spleens are not harmful and they may, in fact, go undiagnosed for a patient's entire life unless medical imaging studies of the abdomen are performed for unrelated reasons.

In some patients, the accessory spleen is the result of developmental variations. When a fetus develops, there are numerous stages of development where organs move around and reposition themselves, sometimes setting up situations where extra organs can develop in the process. Other people develop extra spleens as a result of trauma. The lump of tissue is usually very small and close to the spleen itself, although sometimes it can be located at a distance in the abdomen.

In some cases, the accessory spleen retains some spleen function and processes red blood cells along with the primary spleen. In others, the mass of tissue is simply a benign growth in the abdomen. While not necessary harmful, it also does not serve any function in the body. Sometimes, the growth may only be discovered after death during an autopsy, illustrating the fact that secondary spleens usually do not cause health problems.

There are some situations when an accessory spleen can become a problem. Patients who undergo a therapeutic splenectomy to address medical problems related to the spleen will not experience a resolution of these problems if the secondary spleen is not removed at the same time. Sometimes, the tissue mass can become deprived of blood supply and develop necrosis, or tissue death. This can cause abdominal pain and other symptoms. Torsion of an accessory spleen, a condition where the spleen moves out of position and cuts off its own blood supply, is another problem that can develop.

Another issue that can arise for people with an accessory spleen is that medical imaging studies may be misread. The mass of tissue could look like a tumor, leading a radiologist to recommend surgery to remove it. This may lead to unnecessary surgical procedures. Patients who know that they have an accessory spleen should make sure that this is noted in their medical charts and that imaging studies are kept on file, so new studies can be compared with previous ones in order to monitor changes in the location or appearance of the secondary spleen.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a The Health Board researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By anon1004844 — On Apr 30, 2021

On 4/22/21 during a CT scan for severe stomach pain, it was discovered that I have multiple small Accessory splenic tissue anterior to the spleen, but no significant splenomegaly.

I decided to research what Accessory spleen means and is it possible to develop problems resulting in sever pain and tenderness in the upper left-side of the stomach.

By anon924043 — On Jan 01, 2014

I'm a 19 year old female who was diagnosed as having five spleens, along with multiple other strange abnormalities when I was 13. I visit specialists often for check ups and yearly tests just for me to be told that I'm doing just fine with them. The plan is to keep the spleens due to them causing no harm.

By anon923910 — On Dec 31, 2013

My son is 20 years old and was just diagnosed with two different anticoagulant disorders: Antiphospholipid Antibody disorder and Factor II, which is very rare. He has had a lot of problems with blood clots and having Factor II has to be on Lovenox injections for the rest of his life, since Coumadin doesn't work with Factor II.

He has also had problems with producing too many red blood cells, but it is not Polycythemia Vera. His hematocrit stays over 50 and he has to have 500ml of blood removed about every two weeks and replaced with saline. During a recent abdominal ultrasound, it was discovered that he has an accessory spleen, as well as his primary spleen being enlarged. I'm now wondering if this accessory spleen is producing red blood cells too, and is causing part of his problem?

By anon354494 — On Nov 08, 2013

I went in to have a MRI for gallstones when it was discovered that I have an accessory spleen. I am 29 years old now and cannot really say if it has affected me as I have always had it. However, it doesn't give me any problems (again, that I'm aware of though I have nothing to compare it too).

I have, however, been very lucky in the realm of fighting off infection, viruses, and bacterias. I never "caught" chicken pox growing up even though I was exposed to it numerous times (this was before they vaccinated for it) and I've only had the flu once and that was for a few days. However, I do have allergies and the symptoms that occur then seem more severe than other people I know who have likewise allergies (seasonal).

It's hard to determine whether or not any of this is due to the accessory spleen (which is functional by the way). But, like I said, as far as I know, it doesn't give me any trouble.

By anon348758 — On Sep 19, 2013

My husband never seemed to get sick and if he did, he was over whatever it was in a day, 48 hours max. A cold would affect him for two days, while the rest of us were hacking and feeling horrible for more than a week. I used to joke with him that he must have a super-spleen.

He was diagnosed with Hodgkin's lymphoma and went into remission for five years, then was diagnosed again with Hodgkin's with a spot on his spleen. They wanted to do chemo, but after a lot of discussion, he decided to opt for a splenectomy. The doctor said his scans showed he had an accessory spleen, and I told her our joke that about the super-spleen.

After his surgery, she came out to tell me everything went well and she said I was right: he did have a super-spleen. He had three accessory spleens, all with blood flow. She said it was the first time she had ever seen a patient with more than two accessory spleens. Ever since his surgery, he gets sick almost like a real human. Well, his colds still only last two ro three days.

By malmal — On Jul 01, 2011

@seHiro - Judging by what TheGraham said about the spleen mass being the same whether a person has a regular spleen or a primary spleen and an accessory spleen, I'd imagine if the accessory spleen was the functional kind then there would be absolutely no change in spleen function from what a regular person would have.

TheGraham did point out an interesting idea, though -- that a benign non-working accessory spleen won't contribute to the body's spleen function of processing red blood cells. I wonder if the primary spleen keeps processing at the same rate as the spleen of a person who does not have an accessory spleen?

At any rate, no, I don't think there's much difference between the body functions of one-spleen people and two-spleen people. That's why most people only learn about even having an accessory spleen from doing x-rays during some other medical procedure or during an autopsy after the person has died.

By TheGraham — On Jul 01, 2011

Did you know that whether a person has one spleen or a regular one and an accesory spleen, they always have around the same amount of spleen material that they would have if they had only been born with one spleen?

I think that's kind of lousy for the poor people whose accesory spleens aren't the working kind -- imagine, they probably have decreased spleen function!

By Hawthorne — On Jun 30, 2011

Hmm...the fact that a small accessory spleen still can process red blood cells like a full-size one, coupled with the fact that one in ten people has an accessory spleen, really makes me wonder if at some point in our evolution we actually were supposed to have multiple spleens.

One in ten is a pretty high number for a random developmental abnormality! And if an accessory spleen is a functional one and your body has no problem with using it, it seems almost like the body was made to do so. Can the body even tell the difference between an accessory spleen and your regular one?

If you think that non-working accessory spleens are evidence that humans were never intended to have more than one spleen, consider the fact that they don't harm the body even if they don't work. It's like the body is made to have them there; unlike a tumor, the body doesn't have any adverse reaction to the accessory spleen's presence.

Finally, I find the information about someone being able to develop an accessory spleen from trauma very interesting. It sounds like maybe it's a natural response of the human body that if your regular spleen gets damaged, it wants to fall back on an accessory spleen, and might grow one for that purpose when the body is injured.

By seHiro — On Jun 30, 2011

Wow, interesting stuff! I was super curious what an accessory spleen was after seeing the article title, and just had to click and see for myself.

I wonder if there are any accessory spleen symptoms to let you know that you have one? I don't mean to say it's a disease or a bad medical condition or anything, "symptoms" is just the best word I can think of to explain what I'm talking about.

What I mean is, is there any difference at all in how your body works that reveals you have an accessory spleen? You would think if it's a functional accessory spleen that processes red blood cells like your regular spleen does, that maybe the blood levels of processed red blood cells would be higher, or that any other stuff that your spleen puts out into your blood would be found in higher levels.

Does anybody know?

By ceilingcat — On Jun 30, 2011

@indemnifyme - An extra pinky toe? That must make shoe shopping awfully difficult!

I actually know someone that has an accessory spleen. She was having an ultrasound done on her abdomen for another problem and the extra spleen showed up! She was lucky enough that her doctor figured out what it was right away and didn't think it was a tumor. Since the accessory spleen wasn't causing her any problems they just left it in!

By indemnifyme — On Jun 29, 2011

Wow so interesting! When I was taking biology we learned a little bit about human anatomy and possible variations. My teacher mentioned that even though our textbooks show how all of the internal organs are usually situated that's not always the case. In a lot of people there can be extra things and sometimes organs are situated a different way, such as in the case of a retroverted uterus.

I've never heard of an accessory spleen though. However, I do have a few friends with some interesting biological anomalies including an extra pinky toe, an extra floating rib, and a friend that was born with only one kidney!

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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