Pathologic conditions of the spleen can be classified into the following categories: congenital diseases (accessory spleen,
polysplenia,
and asplenia); trauma; inflammation (abscess,
candidiasis,
histoplasmosis,
and sarcoidosis); vascular disorders (infarction,
diseases affecting the splenic vasculature,
and arteriovenous malformation); hematologic disorders (sickle cell disease and extramedullary hematopoiesis); benign tumors (cysts,
hemangioma,
diffuse hemangiomatosis of the spleen,
and hamartoma); malignant tumors (sarcoma,
lymphoma,
and metastases); and other disease processes that affect the spleen diffusely (portal hypertension,
Gaucher disease,
and sickle cell disease) or focally (Gamna-Gandy nodules).
New magnetic resonance (MR) imaging techniques have increased the role of MR imaging in detection and characterization of splenic diseases [1].
MR imaging is an excellent tool for diagnosis and evaluation of focal lesions and pathologic conditions of the spleen.
There has been a steady increase in the number of performed abdominal magnetic resonance imaging (MRI) studies; therefore,
it is important to be familiar to the major MR imaging characteristics of disease processes involving the spleen,
in order to interpret the findings correctly,
reaching whenever possible the appropriate diagnosis.
Nowadays,
MRI permits the characterization of the most common splenic lesions,
such as cysts,
small hemangiomas,
and hamartomas,
and improvement in the detection of malignant diseases such as lymphoma and metastases [2].
Most frequently,
granulomas are related to inflammatory/infectious diseases,
in particular to histoplasmosis,
sarcoidosis,
tuberculosis and it is fundamental to make differential diagnosis with other diseases,
above all with the malignant disorders.
Normal findings
The spleen is located in the left hypogastric quadrant of the abdomen and is fixed in its intraperitoneal position beneath the 9th to 11th intercostal spaces by the splenorenal,
splenocolic,
splenogastric,
and phrenicosplenic ligaments.
The splenic surfaces are described relative to their locations and are termed the diaphragmatic (phrenic) and visceral surfaces.
On T1-weighted MR images,
the normal signal intensity of the spleen is lower than that of hepatic tissue.
Conversely,
on T2-weighted images,
the spleen shows higher signal intensity,
appearing brighter than the liver [3],
and this hyperintensity could make it hard to detect splenic lesions.
The distinctive microscopic anatomy of the spleen may be reflected on diffusion-weighted images (DWI) and ADC maps.
Prior studies have shown significant differences in the mean ADCs between the spleen and other abdominal organs [4,
5].
The spleen demonstrates a heterogeneous serpentine or arciform pattern enhancement immediately after contrast material administration,
secondary to differences in flow between the red and white pulps,
becoming homogeneous in venous and interstitial phases [3].
Any heterogeneity after this period is considered pathologic [6,
7].
There are few reports in literature about the utility of DWI sequences in the characterization of splenic lesion; in our experience DWI sequence was useful because we used it with the same principles of hepatic lesions,
in particular granulomas didn’t show diffusion restriction like the benign nodules of the liver; this aspect suggested us a benign disease.