Extra small spleen (splenule) seen by chance on a scan
A CT, MRI or ultrasound of the belly done for something else may report an "accessory spleen", "splenule" or "spare spleen". This means a small extra piece of normal spleen tissue near the main spleen. It is common and is usually a normal variant. (Vikse 2017)(Nelson 2024) This page covers what the report means, how common it is and when another scan is suggested, not treatment.
What the report words mean
- Accessory spleen or splenule. A small piece of spleen tissue separate from the main spleen. It forms before birth when parts of the spleen do not fully join. (Nelson 2024)
- Where it is. Most sit near the hilum, the inner side of the spleen where its blood vessels enter. Others are near the lower end of the spleen or close to the tail of the pancreas and the left kidney. (Vikse 2017)(Romer 2012)(Mortele 2004)
- How it looks. Usually a round, smooth spot under 2 cm that looks the same as the spleen on CT. Very small ones, under about 1 cm, can look a little darker than the spleen just because of their size on the scan. (Mortele 2004)(Rashid 2014) In one CT study they measured 3 to 20 mm, about 10 mm on average. (Romer 2012)
- One or more. A report may describe one or several. (Rashid 2014)(Romer 2012)
- Inside the pancreas. About 1 in 6 accessory spleens sit in the tail of the pancreas, where one can look like a pancreas growth on CT. It matches the spleen on every phase of the scan. (Spencer 2010) See pancreatic cyst found by chance for other pancreas findings.
- Splenosis is different. Splenosis means pieces of spleen tissue that have grown elsewhere in the body after an injury to the spleen. A splenule is present from birth. (Nelson 2024)
How common it is
A review that pooled 81 studies with 22,487 people found an accessory spleen in 14.5%. (Vikse 2017) Single studies give similar numbers:
| Study | Who and how | Share |
|---|---|---|
| Romer 2012 | 1,735 people, belly CT | 11% |
| Groshar 2010 | 913 people with cancer, PET/CT | 15% |
| Mortele 2004 | Belly CT with contrast | 16% |
| Rashid 2014 | 334 people aged 13 to 82, belly CT | 19% |
| Vikse 2017 | 81 studies pooled, 22,487 people | 14.5% |
Sources: (Romer 2012) (Groshar 2010) (Mortele 2004) (Rashid 2014) (Vikse 2017) Autopsy studies have found them in 10% to 30% of people. (Rashid 2014) The sources here do not give clear numbers by age or sex.
Why it is usually a normal variant
- Harmless in most people. A position paper on chance spleen findings on ultrasound says extra spleens are harmless and need no further tests. (WFUMB 2021)
- Typical look. Knowing the typical look helps a radiologist tell a splenule apart from other findings in the upper left belly, such as a swollen lymph node. (Mortele 2004)(Romer 2012)(Nelson 2024)
- Stays the same. In a study of people with cancer, 69 spots that looked like accessory spleens and had a follow-up scan 3 to 16 months later showed no change in size or shape. (Groshar 2010)
When another scan or test is suggested
- An unusual look or place. When a spot does not look like typical spleen tissue, or sits inside the pancreas, the reviews describe spleen-specific scans that can confirm it is spleen tissue, such as a nuclear medicine scan or an MRI with a special contrast. (Nelson 2024)(Spencer 2010) In one report, spots in the pancreas thought to be accessory spleens stayed the same on follow-up scans for 1 to 6 years. (Spencer 2010)
- People with lymphoma. In a PET/CT study, 4 of 56 people with lymphoma who had a spot like this had lymphoma in it, and none of the people with other cancers did. The authors suggest that in lymphoma such a spot may need further checks. (Groshar 2010) See enlarged lymph node seen on CT.
- Rare problems. Rarely, an accessory spleen can twist, bleed, break open or form a cyst. (Rashid 2014)(Nelson 2024) One person in a CT study of 1,735 had a twisted one that had swollen to 5 cm. (Romer 2012)
- Otherwise. Whether you need another scan depends on how the spot looks, your symptoms and the rest of the report. Your doctor decides.
- Worry is real. See after an abnormal screening result.
The NHS says a ruptured spleen is a medical emergency because it can cause life-threatening bleeding. It says to go straight to A&E (your local emergency number elsewhere) if you think you have ruptured or damaged your spleen, for example with pain behind the left ribs that is tender to touch, dizziness and a fast heartbeat. (NHS)
Other things a scan may show
The same scan may mention other spleen findings, each with its own page: an enlarged spleen and a spot (lesion) in the spleen.
Who it applies to
Adults told that a CT, MRI or ultrasound of the belly shows an accessory spleen or splenule. Children, people who have had their spleen removed or injured, people being seen for a blood or spleen condition, and a scan done because of belly pain or an injury are outside this page.
Routine age-based screening
A spleen finding on a scan does not replace the routine screenings for your age. See screenings by age and gender.
Where they differ:
- How common it is. CT studies report 11%, (Romer 2012) 16% (Mortele 2004) and 19%, (Rashid 2014) and the pooled review 14.5%. (Vikse 2017) One study author suggests sharper CT and different groups of people explain the gap. (Rashid 2014)
- More than one. In one CT study, 40% of people with an accessory spleen had more than one. (Rashid 2014) In another, about 1.5% of all people scanned had two or three. (Romer 2012)
- Further checks. A position paper on ultrasound says extra spleens need no further tests. (WFUMB 2021) A PET/CT study says this holds for people with most cancers, but that people with lymphoma may need further checks. (Groshar 2010)
Your doctor decides what your result means for you.
Questions people ask
What is a splenule?
A splenule, also called an accessory spleen, is a small extra piece of normal spleen tissue that sits apart from the main spleen. It forms before birth when parts of the spleen do not fully join together. (Nelson 2024)
How common is an accessory spleen?
Common. A review of 81 studies with 22,487 people found one in about 14.5%. CT studies have found them in 11% to 19% of people, and autopsy studies in 10% to 30%. (Vikse 2017) (Romer 2012) (Rashid 2014)
Is an accessory spleen dangerous?
Usually not. A position paper on chance spleen findings says extra spleens are harmless and need no further tests. Rarely, one can twist, bleed or break open. (WFUMB 2021) (Rashid 2014) (Nelson 2024)
Why might I be offered another scan?
When the spot does not look like typical spleen tissue, sits inside the pancreas, or the person has lymphoma, a study or review may suggest another scan or a spleen-specific scan to confirm it. Your doctor decides what your result means for you. (Spencer 2010) (Groshar 2010) (Nelson 2024)
When is it an emergency?
The NHS says a ruptured spleen is a medical emergency. It says to go straight to A&E if you think you have ruptured or damaged your spleen, with signs such as pain behind the left ribs, dizziness and a fast heartbeat. (NHS)