الفهرس 
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Abstract
The spleen is found in the left upper quadrant of the abdomen. Spleen size varies with age, nutrition, and hydration. It is relatively large in children, reaching adult size by age 15 years. The average spleen dimensions in adults are 12 cm in length, 7 cm in width, and 3 to 4 cm in thickness. It progressively decreases in size with age.(8) and it weights 100 to 200 gm The maximum crainiocaudal length is 12 to 15 cm.
When we study the role of MDCT in evaluating splenic focal lesion we discuss the normal anatomy of the spleen, congenital variations (eg, accessory spleen, polysplenia, asplenia, and wandering spleen), and acquired abnormalities such as those resulting from trauma, infection, infarction, cysts, and neoplasms.
The capability to image the spleen was limited in the past, with nuclear scintigraphy and angiography as the traditional means. Although these two modalities are still used in selected settings, computed tomography (CT) and ultrasonography (US) have become the modalities of choice for splenic imaging. Magnetic resonance (MR) imaging is currently a complementary examination reserved for use in problem cases (1).
Larger volume coverage in shorter scan times and improved longitudinal resolution became feasible after the broad introduction of four-slice CT systems (147-149). The increased performance allowed for the optimization of a variety of clinical protocols. Examination times be significantly reduced; alternatively, scan ranges could be significantly extended. Furthermore, a given anatomic volume could be scanned within a given scan time with substantially reduced slice width. (150, 151)
On non enhanced CT scan the normal splenic parenchyma is homogenous; it measures 40 to 60 Hounsfield Units (HU), usually 5 to 10 HU less than the normal liver. After IV contrast enhancement, the spleen can have a heterogeneous appearance on early arterial-phase images on both CT and MRI (9).
The cross-sectional imaging of splenic pathology is improved due to the improvement in MDCT technology. MDCT can rapidly image the spleen and is valuable in the diagnosis of a variety of congenital, neoplastic, inflammatory, and traumatic lesions of the spleen (249).
In addition Computed tomography (CT) is an excellent imaging modality for demonstrating the size, shape, and position of the spleen, as well as for depicting intrasplenic pathologic features. Greater accuracy in diagnosing splenic lymphoma may be obtained by demonstrating adenopathy in the splenic hilum or by showing focal splenic defects, in addition to splenomegaly.