A spleen ultrasound is a painless, radiation-free imaging exam that uses sound waves to produce real-time pictures of your spleen, the fist-sized organ tucked under your left ribcage. Doctors order it for a surprisingly wide range of reasons, from checking for enlargement after an infection to evaluating blood disorders, liver disease, or unexplained abdominal pain. The exam typically takes about fifteen minutes, requires no needles or contrast dye in its standard form, and can be performed right at the bedside in an emergency room or outpatient clinic.
What Happens During the Exam
You will usually be asked to fast for several hours beforehand, because a full stomach can push gas-filled bowel loops into the way and degrade the image. You’ll lie on your back or roll onto your right side so the spleen moves closer to the body wall. The sonographer applies warm gel to your left upper abdomen and slides a probe, typically operating between 3.5 and 5 MHz, along the spaces between your lower ribs.1PubMed. The ultrasound examination of the spleen You’ll be asked to take a deep breath and hold it a few times. That drops the diaphragm, pushing the spleen downward into better view. The whole process is painless; the only sensation is light pressure from the probe.
Because the spleen sits high under the ribs, it can be trickier to image than, say, the liver or kidneys. A sonographer experienced in abdominal scanning will angle the probe through the intercostal spaces, the narrow gaps between ribs, to get clear pictures. Body habitus matters: in larger patients, a lower-frequency probe that penetrates deeper tissue may be needed, while thinner patients can be scanned with a higher-frequency probe that produces sharper images.
What the Sonographer Measures and Looks For
The spleen normally appears on ultrasound as a crescent-shaped organ with a smooth, homogeneous texture. Its tissue is slightly brighter (more echogenic) than the adjacent liver and kidney, which gives sonographers a built-in comparison tool. If the spleen’s brightness is dramatically different from its neighbors, that alone can signal a problem.
Size is the single most important measurement. In healthy adults, average spleen length runs about 10 to 11 cm, with a width around 7 cm and a thickness of roughly 4 cm.2PubMed Central. Sonographic measurement of splenic size and its correlation with body parameters These numbers vary with height, weight, and sex, so there is no single cutoff that works for everyone. A spleen measuring 13 cm in a tall man might be perfectly normal, while the same length in a petite woman could indicate enlargement. In children, normal spleen size changes rapidly with age, and dedicated pediatric reference tables exist so that radiologists can compare a child’s measurement against what’s expected for their age, height, and weight.3PubMed. Normal Values of Spleen Length and Volume: An Ultrasonographic Study in Children
Beyond size, the sonographer checks the parenchyma (the internal tissue) for uniformity. A healthy spleen should look consistently granular throughout, without dark patches, bright spots, or areas of mixed texture. The edges should be smooth. Any focal abnormality, whether a cyst, a solid mass, or a calcified spot, gets documented and measured so the radiologist can characterize it further.
Trauma and Emergency Use
The spleen is the most commonly injured abdominal organ in blunt trauma, whether from a car accident, a sports collision, or a fall. When someone arrives at the emergency department after an abdominal impact, the first imaging step is usually a FAST scan, short for Focused Assessment with Sonography for Trauma. This rapid bedside ultrasound looks for free fluid, usually blood, pooling around the spleen and other organs.4PubMed Central. Splenic Heterogeneity in Focused Assessment With Sonography for Trauma (FAST) Scan Led to the Diagnosis of Grade 2 Splenic Injury in a Pediatric Blunt Abdominal Trauma
A FAST scan is fast and portable, but it has real limitations. In a study of over 200 trauma patients with confirmed liver or spleen injuries, FAST had roughly 80% sensitivity, meaning it missed about one in five injuries. Specificity was high at over 99%, so a positive FAST is quite reliable, but a negative one does not rule out a splenic tear, especially for lower-grade injuries.5PubMed Central. The accuracy of FAST in relation to grade of solid organ injuries: a retrospective analysis of 226 trauma patients with liver or splenic lesion That is why a CT scan usually follows if clinical suspicion remains high after a negative FAST. One case report illustrated this well: a child’s FAST scan showed no free fluid, but the sonographer noticed abnormal heterogeneity within the spleen itself, which led to a CT that confirmed a grade 2 splenic injury.4PubMed Central. Splenic Heterogeneity in Focused Assessment With Sonography for Trauma (FAST) Scan Led to the Diagnosis of Grade 2 Splenic Injury in a Pediatric Blunt Abdominal Trauma
Contrast-enhanced ultrasound, which involves injecting microbubble contrast through an IV, dramatically improves the picture. The microbubbles light up blood flow inside the spleen, making tears, lacerations, and active bleeding visible in real time. Studies describe CEUS reaching accuracy levels comparable to CT for splenic trauma, which matters when you want to avoid radiation, especially in children, or when a patient can’t be moved to the CT scanner.6PubMed Central. Role of contrast-enhanced ultrasound (CEUS) in the diagnosis and management of traumatic splenic injuries
Infectious Mononucleosis and Return to Activity
If you’ve ever had mono, or have a teenager who just got diagnosed, there’s a good chance a spleen ultrasound entered the conversation. Infectious mononucleosis, caused by the Epstein-Barr virus, frequently enlarges the spleen. The real worry is splenic rupture, a rare but potentially life-threatening complication that affects roughly 0.1% to 0.5% of mono patients.7PubMed Central. Association of Splenic Rupture and Infectious Mononucleosis: A Retrospective Analysis and Review of Return-to-Play Recommendations Current guidelines generally recommend at least three weeks of activity restriction after symptoms begin to reduce this risk.
Ultrasound is useful here in two ways. First, it can document whether and how much the spleen has enlarged, giving the clinician a baseline. Second, serial scans over the following weeks can confirm when the spleen has returned to normal size, which helps guide decisions about when it’s safe for an athlete to return to contact sports. The three-week timeline is a floor, not a guarantee; some spleens stay swollen longer, and ultrasound gives an objective measurement instead of relying on guesswork.
Sickle Cell Disease and Splenic Sequestration
People with sickle cell disease have a particularly complicated relationship with their spleens. In homozygous sickle cell disease (HbSS), repeated episodes of sickling damage the spleen over time, causing it to gradually shrink and lose function, a process called autosplenectomy. Ultrasound studies of children with HbSS have documented this age-related decline in splenic length, with genetic factors that inhibit sickling slowing the shrinkage.8PubMed Central. Spleen size in homozygous sickle cell disease: trends in a birth cohort using ultrasound
Before the spleen fibroses completely, it can trap large volumes of red blood cells in episodes called acute splenic sequestration. This causes the spleen to balloon rapidly while the patient’s hemoglobin crashes, sometimes within hours. Point-of-care ultrasound in the emergency department can identify the telltale signs: sudden splenomegaly and altered echogenicity compared to the adjacent left kidney. In some reported cases, the ultrasound findings appeared before the characteristic hemoglobin drop showed up on lab work, giving clinicians an early warning.9JEM Reports. ED point-of-care ultrasound evaluation of acute splenic sequestration in sickle cell disease On imaging, sequestration often shows as an irregular rim of hypoechoic (darker) tissue at the spleen’s periphery.10PubMed. Splenic sequestration in the adult: cross sectional imaging appearance of an uncommon diagnosis
Liver Disease and Portal Hypertension
The spleen and liver are connected by a shared blood supply, the portal venous system, so liver disease often shows up in the spleen first. In cirrhosis, scarring in the liver raises pressure in the portal vein, a condition called portal hypertension. That back-pressure causes the spleen to enlarge, sometimes considerably. Studies have found a strong correlation between spleen volume and portal vein size in cirrhotic patients.11PubMed. Measurement of spleen size and its relation to hypersplenism and portal hemodynamics in portal hypertension due to hepatic cirrhosis In these patients, Doppler ultrasound shows that blood flow through the splenic artery is significantly increased compared to healthy individuals, and this elevation tracks closely with the degree of splenomegaly.12PubMed. Splanchnic blood flow in patients with cirrhosis and portal hypertension: investigation with duplex Doppler US
Duplex Doppler ultrasound, which combines standard imaging with blood-flow velocity measurements, allows clinicians to assess splanchnic circulation without invasive catheterization. Research dating back decades has shown that both splenic artery and superior mesenteric artery blood flow rise as chronic liver disease progresses, reflecting a hyperdynamic circulatory state that develops in the gut and spleen.13PubMed. Splenic artery and superior mesenteric artery blood flow: nonsurgical Doppler US measurement in healthy subjects and patients with chronic liver disease
Spleen Stiffness as a Window Into Portal Pressure
An emerging application that has generated considerable interest in hepatology is spleen stiffness measurement using elastography, a technique that gauges how stiff or compliant an organ’s tissue is by tracking how shear waves travel through it. It works a bit like pressing on a mattress to judge its firmness, except the “press” is a controlled acoustic pulse. In patients with chronic liver disease, spleen stiffness correlates strongly with hepatic venous pressure gradient, the gold-standard measurement of portal hypertension that otherwise requires an invasive catheter procedure. Some studies have found spleen stiffness to be a better predictor of portal pressure than liver stiffness itself.14PubMed Central. Role of spleen elastography in patients with chronic liver diseases
This matters clinically because portal hypertension drives many of the dangerous complications of cirrhosis, including esophageal varices (swollen veins in the esophagus that can rupture and bleed). Combining liver and spleen stiffness readings has been shown to predict the presence of esophageal varices with around 90% accuracy, potentially sparing patients from repeated endoscopies. Shear wave elastography is now integrated into many high-end ultrasound machines, and it can even be performed in patients with ascites (fluid in the abdomen), which is a common problem in advanced liver disease.15BMJ Open Gastroenterology. Spleen stiffness measurement as a non-invasive assessment in patients with portal hypertension Pediatric hepatology is also exploring spleen stiffness, with research suggesting it could improve risk stratification in children with biliary atresia after surgery.16Scientific Reports. Spleen and liver shear wave elastography for assessment of portal hypertension in children with biliary atresia
Incidental Findings and Focal Lesions
Sometimes a spleen ultrasound turns up something nobody was looking for. Incidental splenic findings are common enough that radiologists have developed systematic approaches to handling them. The most frequent benign finding is a small calcified spot, often a granuloma, left behind by a long-resolved infection such as histoplasmosis or tuberculosis. While calcified splenic lesions are often presumed to be granulomas, the differential diagnosis is broader than most people realize, and pattern recognition on imaging helps sort them out.17PubMed. Calcified Splenic Lesions: Pattern Recognition Approach on CT With Pathologic Correlation
Splenic hemangiomas, benign tangles of blood vessels, are another incidental discovery. On ultrasound, they usually appear as well-defined bright spots smaller than 2 cm. Larger ones can look more complex, with mixed solid and cystic components. The challenge is that the ultrasound appearance of splenic hemangiomas is more variable than their liver counterparts, and splenic lesion imaging tends to be nonspecific, making it hard to confidently distinguish benign from malignant on conventional ultrasound alone.18European Congress of Radiology. Splenic cavernous and capillary hemangiomas – Imaging key findings and differential diagnosis This is where contrast-enhanced ultrasound adds real value: it can characterize many splenic lesions well enough to avoid biopsy or further cross-sectional imaging, while flagging the ones that genuinely need a closer look.19PubMed Central. Contrast-enhanced ultrasound of the spleen
Accessory Spleens
About one in ten people has an accessory spleen, a small nodule of normal splenic tissue located near the main spleen, often at its hilum or near the tail of the pancreas. These are almost always harmless and discovered by accident. On ultrasound, an accessory spleen appears as a round or oval structure whose echogenicity matches the main spleen, and a confirming sign is finding a blood supply from the splenic artery or vein, which can be demonstrated sonographically in the vast majority of cases.20PubMed. Sonography of the accessory spleen
Accessory spleens become clinically relevant in one specific scenario: when someone has had their spleen removed (splenectomy) for a blood disorder like immune thrombocytopenic purpura, and the condition recurs. A missed accessory spleen can take over the function of the removed organ, continuing the disease process. Identifying all accessory splenic tissue before surgery, or tracking down a suspected one after surgery, is a job for targeted ultrasound or contrast-enhanced ultrasound.19PubMed Central. Contrast-enhanced ultrasound of the spleen
How Ultrasound Compares to CT for Spleen Imaging
Ultrasound’s main advantages are its portability, lack of radiation, low cost, and the ability to perform repeat exams without worry. Its main disadvantage is that it consistently underestimates spleen size compared to CT. A comparative analysis found that ultrasound measurements of splenic diameter ran about 1 cm shorter on average than the corresponding CT measurements, a discrepancy of roughly 17%.21PubMed Central. Discrepancies in Splenic Size Measurement: A Comparative Analysis of Ultrasound and Computed Tomography This doesn’t make ultrasound unreliable, but it means that a spleen measuring 12 cm on ultrasound might actually be 13 to 14 cm on CT. When precise volumetric measurement matters, such as monitoring treatment response in a hematologic malignancy, CT or MRI may be preferred.
For detecting splenic malignancies, a meta-analysis comparing different imaging modalities found that PET scanning had the highest diagnostic accuracy, followed closely by contrast-enhanced ultrasound, contrast-enhanced CT, and contrast-enhanced MRI. The differences among those last three were not statistically significant, and all outperformed non-contrast techniques.22European Journal of Radiology Open. Diagnostic performance of different imaging modalities for splenic malignancies: A comparative meta-analysis This is worth knowing because it means that if your doctor is concerned about a splenic mass, adding microbubble contrast to a standard ultrasound can bring its diagnostic power close to CT, and in some centers, this is the approach of choice for patients who cannot receive iodinated CT contrast due to kidney problems or allergies.
Monitoring After Splenic Injury or Treatment
When a splenic injury is managed without surgery, which is increasingly the approach for lower-grade injuries, follow-up imaging tracks how the healing process unfolds. Ultrasound is well suited for serial monitoring because it can be repeated without radiation. In documented cases, a splenic hematoma typically grows slightly during the first week after injury, then gradually shrinks and changes in echogenicity, becoming darker and more complex before eventually resolving completely over about three months.23PubMed Central. Ultrasonography of the healing process during a 3-month follow-up after a splenic injury
In patients who undergo splenic artery embolization, a procedure where a radiologist partially blocks blood flow to the spleen to stop bleeding, Doppler ultrasound provides a way to track the recovery of blood flow inside the organ over time. Measurements of flow velocity and resistance index at intervals from one day to ten months after embolization have shown that internal blood flow gradually improves, confirming that the spleen is regaining perfusion rather than dying off.24PubMed. Intraparenchymal Doppler ultrasound after proximal embolization of the splenic artery in trauma patients This kind of noninvasive longitudinal tracking would be difficult and impractical with CT alone due to cumulative radiation exposure.
Pregnancy and the Spleen
Pregnancy causes numerous changes throughout the body, and the spleen is not exempt. Blood volume increases substantially during pregnancy, and some studies have explored whether normal splenic length changes across trimesters. Pilot data from a Nigerian tertiary hospital established reference ranges for splenic length during normal pregnancy, providing a benchmark so that clinicians can distinguish physiological enlargement from pathological splenomegaly in pregnant women with conditions like malaria, preeclampsia, or HELLP syndrome.25PubMed Central. Sonographic Evaluation of the Splenic Length in Normal Pregnancy in a Tertiary Hospital in Southern Nigeria: A Pilot Study The key practical point is that a spleen that measures slightly larger than the typical non-pregnant reference range is not necessarily cause for alarm if you’re in your third trimester, but your clinician needs pregnancy-specific reference data to make that call, and ultrasound is the obvious imaging choice because it avoids radiation entirely.