We have taken the most significant images of splenic diseases from our RIS-PACS archive.
First of all, radiologists should be able to recognize splenic anomalies, such as congenital variants. These conditions usually have not clinical relevance, but to recognize them is useful in order to avoid misdiagnosis. Splenic notches, for example, are remnants of fetal lobulations, but they could be mistaken for splenic injuries during a CT scan done for trauma. Accessory spleens are the most common congenital anomalies (more than 10 % of the population has them) [1]. It Is easy to recognize them because they are spherical, homogenous masses, up to a few centimeters, with the same enhancement of the spleen after intravenous contrast administration. Their typical localization is near to the splenic hilum.
Understanding the differences in shapes and compositions, in radiological findings and in contrast enhancement of various splenic lesions is important to narrow the differential diagnosis, between the wide spectrum of diseases involving the spleen. The most common benign lesions are cysts, hemangiomas, hamartomas and lymphangiomas.
Cystic lesions are often found incidentally and the most important thing to do, not always easy, is to classify them in cysts and pseudocysts. The primary ones have a peripheral cellular lining that can be made up from epidermoid epithelium to transitional cells and can be divided into nonparasitic (congenital or neoplastic) and parasitic (the most common cause is Echinococcus), instead of the other ones, pseudocysts, in which wall is composed of dense fibrous tissue and are the result of traumatic lesions or infections.
Simple Cysts appear usually as sharply circumscribed low-density lesions and are usually uniloculated and fluid-filled, without enhancement after contrast administration (Fig.1). Only rarely they could have cholesterol crystals or hemorrhagic debris inside, so they appear iperdense during CT scan without contrast agent. Solitary cystic splenic neoplasms are uncommon.
Lymphangioma is a rare benign lesion usually diagnosed in childhood. It can be solitary or multifocal. It usually appears with a solid central area and multiple thin-walled cysts of different sizes filled with clear fluid (Fig.2). Sometimes it could have a diffuse involvement in splenic parenchyma and in this case could be defined “Lymphangiomatosis”. Lymphangioma is usually a well-defined, subcapsular, multilocular lesion with thin septations. Sometimes calcifications could be present. They are hypoechoic on US, hypodense on CT, and without enhancement, except for septa.
Hemangioma (Fig.3) is the second most common benign focal lesion involving the spleen, after cysts. It can be considered a slow flow venous malformation, because they are composed of vascular channels, with a single layer endothelium, of varying sizes ranging from capillary to cavernous. After intravenous contrast administration during CT scan or MRI it shows centripetal fill-in (from the peripherical layer). It is homogeneously hyperintense in T2. Hemangioma is usually asymptomatic, but it can occasionally cause hypersplenism and Kasabach-Merritt syndrome. [2] It can be a manifestation of Sistemic angiomatosis syndrome, such as Beckwith-Wiedemann syndrome and Klippel-Trenaunay-Weber syndrome.
Splenic hamartomas are very rare lesions. They are round, well-circumscribed, unencapsulated and compounded by a mixture of normal splenic structures, with sometimes focal fibrosis or cystic areas inside: they can be considered foci of disorganized overgrowth of splenic cells. During non-contrast CT they appear iso-attenuating to the splenic parenchyma, with an early arterial and persistent delayed enhancement after contrast administration. They are isointense in T1 and midly hyperintense in T2.
The echinococcal cysts are rare in nonendemic areas: it could be distinguished because echinococcal disease in the spleen is usually accompanied by involvement of other organs and isolated splenic involvement is less common. Lesion can contain daughter cysts, that are less dense. If it increases in size, it may lead to compression of the hilar vessels of the spleen.
Abscess are collections of necrotic inflammatory tissue, caused by bacteria, parasites or fungi. They are caused by immunodeficiency conditions, infection (through hematogenous or contiguous bacteria dissemination), trauma or splenic infarction. Fever and leukocytosis are frequent symptoms. They are shaded lesion, with a variable appearance, hyper-echoic or hypo-echoic, with septa, during ultrasound. On CT scan they appear with a centrally low-density lesions (20-40HU), with peripheral contrast enhancement; they have low signal on T1-weighted MR images and intermediate or increased signal on T2-weighted MR images. (Fig.4)
Lymphoma, is the most common malignant cancer involving the spleen. Primary splenic lymphoma is rare compared to the secondary one, known as lymphomatous involvement of the spleen. Primary lymphoma represents just 1% of all lymphomas and is usually non-Hodgkin, in detail large B-cell lymphoma (DLBCL) is the most common subtype. [2] Splenomegaly (more than 13 cm in diameter) is the most common manifestation, but a normal size spleen does not exclude Lymphoma (Fig.5) Focal spleen Lymphoma can have various and different appearances: small, well circumscribed multiple nodules or lesions (if>1cm), or a single mass (bulky lesion). In this disease clinical presentation can suggest the correct diagnosis because systemic symptoms, such as weight loss, fever and night sweats are often present, as well as left quadrant fullness and pain, if the spleen is enlarged. Nodules appear hypo-enhancing compared to the background parenchyma during MDCT, particularly in a late venous phase. They appear low or iso-intense in T1 and T2, without contrast enhancement. Nuclear Medicine gives important information: PET, with 18 F-FDG, is very useful in staging lymphoma, because it can show a diffusely FDG-avid spleen or multiple FDG-avid focal lesions. [3]
Splenic metastases are unusual, but they should be punctually diagnosticated. Metastasis can be solid or cystic lesions, because of the necrosis inside it, that may occur in melanoma repetitive lesions, or they can have mucinous component, characteristic of ovarian cancer.
Frequently splenic lesions are “incidentalomas”, incidentally detected during medical imaging for an unrelated reason. In these cases, it is mandatory to make a careful analysis with any history of malignancy and clinical signs and symptoms, in order to reassure patients or refer them to a second level diagnostic exam or to invasive diagnostic procedures. Minimize unnecessary biopsy and splenectomy is a main topic to reduce patient’s anxiety and risks and cost of public healthcare system, too.
Nowadays, the ACR white paper, published in 2013, recommends follow-up for all non-cystic splenic masses larger than 1 cm, that have not clearly benign characteristics [4]; in patients with no symptoms and no history of malignancy, regardless of mass size, lesion, according to the literature, will be malignant in only 1% of incidental splenic masses. [5] Whereas in patients with constitutional symptoms, or pain in the left upper quadrant or history of malignancy, splenic lesions should be evaluated with MR imaging or PET/CT. [5]
