The World Federation for Ultrasound in Medicine and Biology (WFUMB) is addressing the issue of incidental findings (IFs) with a series of publications entitled "Incidental Imaging Findings-The Role of Medical Ultrasound." IFs are less commonly encountered in the spleen than in many other abdominal organs but remain a frequent dilemma in clinical practice. A histological diagnosis is rarely necessary for patient management. Many IFs, such as secondary spleens and splenic cysts, are harmless and do not require any further investigation. The diagnosis of many other focal splenic lesions is, however, often problematic. The following overview is intended to illustrate a variety of incidentally detected spleen pathologies such as size variants, shape variants, secondary spleens, focal splenic lesions and splenic calcifications. It should aid the examiner in establishing the diagnosis. Moreover, it should help the ultrasound practitioner decide which pathologies need no further investigation, those requiring interval imaging and cases in which immediate further diagnostic procedures are required.In patients with splenomegaly (>13 £ 6 cm), an imaging, clinical and laboratory evaluation is usually required to determine the underlying cause.Most congenital variants of the spleen, and accessory spleens, have characteristic ultrasound appearances and do not require further evaluation or follow-up.The use of ultrasound contrast microbubbles (contrast-enhanced ultrasound) is of particular value in ultrasound imaging of the spleen when an indeterminate incidental finding is encountered.Splenosis can be confidently diagnosed with contrast-enhanced ultrasound and usually requires no additional imaging or follow-up.The cause of an inhomogeneous splenic parenchyma must be clarified, especially to exclude sarcoidosis or lymphomatous infiltration. Incidental indeterminate focal splenic lesions (with the exception of simple cysts) are often best managed by an interval follow-up examination (initially after 3 months) unless there clearly malignant clinical or sonographic features.For splenic calcifications, including the "starry sky" spleen, no follow-up is necessary.