The Spleen

10.1055/b-0034-87864

The Spleen

The spleen is a wedge-shaped organ that is convex supero-laterally and concave inferomedially with a vascular hilum. It can be affected either by primary pathologic process or by multiorgan or systemic disease. Its histology varies with age, with little white pulp in the neonate, which increases with age.

**Table 2.22 Normal imaging**
Diagnosis	Findings	Comments
US	Homogeneous, slightly hyperechoic than normal kidney.	With high-frequency transducers, a granular pattern can be seen in children aged 1 to 5 y.
CT	Unenhanced CT: Homogeneous. With contrast, irregular, bizarre patterns of enhancement that disappear in portal phase (> 70 s).
MR	Neonate: Hypointense on T2 and hyperintense (to liver) on T1. From 1 year of age, adult pattern: hyperintense on T2 and hypointense on T1. Irregular pattern of enhancement.
Nuclear medicine (NM)	99mTc-labeled heat-damaged red cells are only taken up by the spleen.	Useful if a normal spleen is not detected by other imaging methods.

**Table 2.23 Changes in position and shape**
Diagnosis	Findings	Comments
Notches, clefts, and lobulations	Lobules are located near the hilum or extending anterior to the upper pole of the kidney. Clefts are sharp, located in the superior border, and sometimes 2–3 cm deep.	Normal in fetal period, usually disappear, but may be present into adult life.
Positional anomalies Fig. 2.39	Situs inversus. Wandering spleen: migration from its original position to a more caudal location because of laxity or lack of ligament fixation.	Wandering spleen is more common in females. It usually presents as an abdominal mass or as an acute abdomen due to torsion of the vascular pedicle with possible infarction.
Accessory spleen (s) Fig. 2.40	Common anomaly (> 30%). Usually < 15 mm and located near the hilum, but can be multiple and in other locations. Same pattern that normal spleen.	Clinically insignificant. Increase in size after splenectomy.
Polysplenia syndrome (levoisomerism)	Multiple discrete spleens, right- or left-sided (at the same side of the stomach). Cardiac anomalies. Liver centrally located. No intrahepatic IVC, with azygous continuation. Mirror location of GI organs.	Wide range of abdominal anomalies. Most patients have severe cardiac anomalies, but 5%–10% reach adulthood without symptoms. More frequent in females.
Asplenia syndrome (dextro-isomerism) Fig. 2.41	Absence of spleen. Severe congenital heart disease. Liver and gallbladder in midline. IVC and aorta lie on the same side of column. Short pancreas. Midgut malrotation.	Most die in the first year. Male predominance.
Vascular shunts	Splenogonadal, splenorenal, splenohepatic.

**Fig. 2.39 Situs inversus.** Transverse US through epigastrium shows a left-located liver and gallbladder and a right-sided air-distended stomach (ST).

**Fig. 2.40 Accessory spleen.** Longitudinal US shows an isoechoic splenic parenchyma nodule (arrowhead) near the splenic hilum, representing accessory tissue.

**Fig. 2.41 Asplenia syndrome.** Plain film in a neonate showing the central position of liver.

**Table 2.24 Splenomegaly**
Diagnosis	Findings	Comments
Infection, sepsis	Usually homogeneous splenomegaly.	Many causative organisms: Bacterial, viral, protozoal, fungal. Some of them produce isolated splenomegaly: Ebstein-Barr virus, malaria, histoplasma, mycobacterium.
Portal hypertension	Often due to extrahepatic portal vein thrombosis: Doppler US with absent or reversed flow or with cavernomatous transformation. Splenomegaly with heterogeneous hepatomegaly with lobulated margins.	Common causes: liver disease, umbilical vein catheterization, tumor, dehydration, omphalitis, hypercoagulability states.
Malignant diseases: leukemia, lymphoma, Langerhans cell histiocytosis, metastases	Either homogeneous splenomegaly or single or multiple masses can be present.	Look for other manifestations of disease.
Metabolic disease: Gaucher, Niemann-Pick, mucopolysaccharidosis, tyrosinosis	Homogeneous splenomegaly. Usually correlates with severity of disease.	Abnormal products of metabolism are stored in spleen parenchyma.
Hemolytic anemia		Due to sequestration of abnormal red cells.
Extracorporeal membrane oxygenation		Due to increased number of damaged red cells.
Right heart failure		Due to congestion.

**Table 2.25 The small spleen**
Diagnosis	Findings	Comments
Normal variant		Congenital hypoplasia.
Infarction (late phase)	Small spleen, sometimes with capsular calcification.	Secondary to emboli, torsion, portal hypertension, Gaucher disease.
Autosplenectomy		In sickle cell disease, thalassemia.
Celiac disease		In late phases of disease.

**Table 2.26 Focal anomalies, solitary**
Diagnosis	Findings	Comments
Cyst: serous, epidermoid, dermoid, echinococcal, pseudocyst (trauma, infarct) Fig. 2.42a, b, p. 170	Usually unilocular, with clear and homogeneous fluid.	Echinococcal and pseudocyst may calcify Echogenicity (US), density (CT), and signal intensity (MR) may vary due to composition of fluid.
Hemangioma	Septate, subcapsular cystic lesions. No contrast enhancement.	Solitary or multiple.
Lymphangioma	May appear cystic, solid, or a combination.	May cause Kasabach-Merritt syndrome if large.
Hamartoma	Solid and avascular lesions, heterogeneous.	Most common primary neoplasm.
Solitary focus of a typically multifocal disease (see Table 2.27)

**Fig. 2.42a, b Epidermoid cyst.** (a) Longitudinal US depicts a splenic cystic mass (C) with low-level echoes. (b) Contrast-enhanced CT of the same cyst.

**Table 2.27 Focal anomalies, multiple**
Diagnosis	Findings	Comments
Abscess Fig. 2.43 Fig. 2.44 Fig. 2.45	Centrally located, rounded, or irregular in shape with central fluid/necrosis. Avascular. Fungal abscess are small lesions (few millimeters).	Seen in immunosuppressed population (on chemo-therapy, acquired immunodeficiency syndrome [AIDS])
Trauma	Lacerations, rupture, intrasplenic and subcapsular hematomas.	Sometimes, minor trauma can affect spleen.
Lymphoproliferative disorders, Langerhans cell histiocytosis, metastases Fig. 2.46 Fig. 2.47	Multiple focal masses. Lymphoma can invade the capsule. Lymphadenopathy in hilum and retroperitoneum can be seen.	Look for other manifestations of disease.
Gaucher, Niemann-Pick disorders	Multiple nodules. On MRI, T1 signal is lower than for normal spleen.

**Fig. 2.43** **Salmonella abscess.** Longitudinal US in a 17-year-old boy with *Salmonella* infection and fever. A solitary abscess (between arrowheads) was found in splenic parenchyma.

**Fig. 2.44** **Candida abscess.** In a neutropenic 5-year-old girl treated for neuroblastoma, transverse US shows multiple fungal abscess cavities.

**Fig. 2.45 Pyogenic abscess.** Contrast-enhanced CT in a 15-year-old boy with a pyogenic abscess treated with percutaneous drainage.

**Fig. 2.46 Non-Hodgkin lymphoma.** Longitudinal US shows multiple heterogeneous solid nodules.

**Fig. 2.47 Metastasis.** Contrast-enhanced CT shows a discrete splenic mass (between arrowheads) representing metastasis from renal sarcoma.

**Table 2.28 Diffuse anomalies**
Diagnosis	Findings	Comments
Lymphoproliferative disorders, Langerhans cell histiocytosis, metastases		Depending on underlying disease.
Infarction (early phase)	Hypoattenuating (CT) spleen, with only capsular enhancement.	Patients with sickle cell disease are prone to infarction.
Iron deposition disease	MRI: low signal on T1 and T2.
Hemangioma, hemangioendothelioma		May affect the entire spleen.

**Table 2.29 Splenic calcifications**
Diagnosis	Findings	Comments
Granulomatous diseases	Multiple tiny foci of calcium.	Histoplasma, cat-scratch, chronic granulomatous disease.
Infarction	Isolated peripheral, associated with scarring.
Cysts, hematoma, abscesses	Peripheral calcification.
AIDS	Arterial splenic calcifications.