Splenic Cyst
A splenic cyst is a fluid-filled lesion within the spleen. Most are benign and asymptomatic, and they are typically discovered incidentally on abdominal imaging. Splenic cysts are broadly divided into “true” cysts (with an inner cellular lining, including congenital epithelial cysts and parasitic cysts) and “false” or pseudocysts (without a cellular lining, often related to prior trauma, infarction, or infection). Imaging—particularly ultrasound, CT, and MRI—is central to characterization, and most splenic cysts require no specific treatment beyond reassurance and—in selected cases—periodic follow-up.
What is it?
The spleen is an organ in the upper left abdomen that helps filter blood, supports immune function, and plays roles in defense against certain infections. A splenic cyst is a fluid-filled lesion within the spleen. Most splenic cysts are benign, do not affect the overall function of the spleen, and cause no symptoms. They are increasingly detected as incidental findings on cross-sectional imaging done for other reasons. Most fluid-filled lesions of the spleen are small, simple, and stable, and they do not require treatment.
Splenic cysts are traditionally divided into two broad categories. “True” cysts have an inner cellular lining and can be either congenital (such as epithelial cysts, including epidermoid cysts) or parasitic. Congenital epithelial cysts are more common in younger patients, often present from childhood or young adulthood, and are typically thin-walled and uncomplicated on imaging. Parasitic cysts are most often caused by infection with Echinococcus species (hydatid cysts), which are more common in regions where this parasite is endemic; they may have characteristic imaging features and require specific treatment. “False” or pseudocysts do not have a cellular lining and are most often the result of prior trauma, infarction (such as in sickle cell disease), or prior infection or inflammation. Pseudocysts are the most common type of splenic cyst in many regions today, related in part to the higher frequency of recognized abdominal trauma. Less commonly, splenic cysts can represent abscesses (collections of pus from infection), vascular lesions, or—rarely—cystic neoplasms.
The clinical importance of a splenic cyst depends on its size, type, location, contents, and whether it has caused complications. Most splenic cysts are small and asymptomatic. As they grow larger, they can produce upper left abdominal pain or fullness, early fullness with meals from pressure on the stomach, and discomfort that may radiate to the left shoulder. Very large cysts can be palpable, displace nearby organs, and—rarely—compress the diaphragm or contribute to shortness of breath. Less commonly, splenic cysts can become complicated by infection, bleeding within the cyst, or rupture. Rupture of a large or complicated cyst can produce sudden severe abdominal pain and, in some cases, signs of shock, and is a medical emergency.
Diagnosis is generally based on imaging characteristics. Ultrasound is often the first imaging study and typically shows a well-defined, anechoic (fluid-filled) lesion within the spleen, with smooth walls in simple cysts. CT with contrast provides detailed information about size, location, internal characteristics, wall features, and relationship to surrounding structures. MRI with contrast offers excellent characterization of cyst contents and is particularly helpful when imaging features are atypical, when a cyst contains hemorrhage or proteinaceous material, or when distinguishing between specific cyst types is important. Characteristic features—such as the typical appearance of hydatid cysts with internal daughter cysts or characteristic membranes—can help identify the underlying cause. Blood tests are often unnecessary for simple cysts but may include serology for echinococcal infection in selected patients, particularly those with exposure history or atypical imaging features. Image-guided sampling of splenic cysts is generally avoided because of the risk of bleeding and—in the case of hydatid cysts—the risk of spreading infection; it is reserved for highly selected situations.
Important to Know
For the great majority of patients with splenic cysts, no specific treatment is needed. Once the diagnosis is confidently established by imaging, most splenic cysts can be managed with reassurance and—in selected cases—periodic follow-up. Many small, stable, simple cysts do not require any specific surveillance once the diagnosis is clear, while larger or more complex lesions may be monitored with periodic imaging for a defined time to confirm stability.
Lifestyle changes are generally not needed for typical splenic cysts. Patients can usually maintain normal diet, exercise, and activity levels without restriction. There is no need to avoid specific foods solely because of a splenic cyst, although general healthy habits remain important for overall health.
Treatment is considered in selected situations. These typically include cysts that cause significant and persistent symptoms (such as pain or early fullness) not explained by other conditions; large cysts (commonly greater than approximately 5 centimeters, although thresholds vary); rapidly enlarging cysts; cysts with complications such as bleeding, infection, or rupture; and cysts with atypical imaging features in which malignancy or specific infection cannot be confidently excluded. Parasitic cysts—particularly hydatid cysts—typically require specific antiparasitic medications and, in many cases, surgical or interventional treatment in centers with experience.
When treatment is indicated, spleen-preserving approaches are preferred whenever feasible, given the spleen’s important immune functions. Options include partial splenectomy, cyst fenestration or unroofing (laparoscopic or open), cystectomy, or—in selected cases—percutaneous drainage with sclerotherapy. Total splenectomy is reserved for situations in which spleen-preserving approaches are not feasible, such as very large, centrally located cysts; complicated parasitic cysts; significant bleeding or infection; or other specific scenarios. Decisions are individualized and made in collaboration with hepatobiliary or general surgeons, interventional radiologists, and—when relevant—infectious disease specialists.
Patients undergoing total or partial splenectomy require specific attention to infection prevention. This includes vaccinations against encapsulated bacteria (such as pneumococcal, meningococcal, and Haemophilus influenzae type b vaccines) and other infections as appropriate (such as influenza and COVID-19 vaccines), antibiotic prophylaxis in selected patients, education about prompt evaluation of fevers, and consideration of travel-related risks. These measures are essential parts of long-term care after splenectomy.
Care is typically coordinated by primary care clinicians and, when relevant, radiologists, hepatobiliary or general surgeons, gastroenterologists, hematologists, interventional radiologists, and infectious disease specialists. Imaging findings are interpreted alongside the patient’s symptoms, examination, and broader clinical context rather than in isolation.
Although a typical simple splenic cyst is almost always benign and asymptomatic, any new abdominal symptoms should be evaluated based on their own clinical features rather than automatically attributed to a previously identified cyst.
Red flag symptoms include sudden severe upper left abdominal pain (especially after trauma to the abdomen), lightheadedness or fainting, rapid heart rate, cool clammy skin or signs of shock, high fever with chills (which may suggest infection of the cyst or abscess), severe vomiting with abdominal pain, sudden severe shortness of breath, or signs of severe infection. These warrant prompt or urgent medical evaluation, as they may indicate rupture, infection, hemorrhage, or other serious complications of a splenic cyst.