الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Abdominal lymphadenopathy may be encountered in a variety of clinical settings ranging from asymptomatic patients to patients who are critically ill. Etiologies for abdominal lymphadenopathy include infectious and inflammatory processes, primary lymphoma, metastatic and systemic disease. The differential diagnosis of abdominal LAP is sometimes difficult on the basis of US, CT or conventional MRI findings. The most accurate method to determine the composition of a lymph node and to differentiate benign from malignant involvement is histopathological analysis. However, tissue sampling can be very challenging in the abdomen and false-negative results due to inadequate samples are not uncommon.
Contrast-enhanced Computed Tomography (CECT) has been widely used for imaging of abdominal lymphadenopathy as well as its follow-up for a long time. However, it does not provide metabolic or functional information and this may compromise the identification of the disease in non enlarged lymph nodes. 18F-fluorodeoxy- glucose (FDG) Positron Emission Tomography/Computed Tomography (PET/CT) has been recently considered as the functional imaging method of choice as it depends on the identification of elevated glucose metabolism in lymphomatous lesions. However, not many institutions have this facility; it is expensive and carries the risk of exposure to radioactive material and ionizing radiation. It has been proposed that diffusion-weighted magnetic resonance imaging (DWI) may be a possible radiation-free alternative to FDG-PET/CT for imaging of lymph nodes. It is a functional MRI technique that depends on the restriction of water movement in highly cellular tumors due to narrowing of the extracellular space.
Diffusion weighted imaging (DWI) is based on the irregular diffusion motion of water molecules and provides more detailed information at the cellular level than conventional magnetic resonance imaging (MRI). Conventional MRI studies can not distinguish the nature of abdominal lymph nodes before management planning .as the conventional MRI is based on morphological information.
Combination of DWI with ADC map added more information to conventional MRI in the differentiation between benign and malignant abdominal lymph nodes.
This work was conducted aiming to study the added value of DWI MRI in differentiating benign from malignant abdominal lymphadenopathy and to investigate whether Apparent Diffusion Coefficient (ADC) measurements can help in the discrimination between lymphomatous, metastatic and benign abdomino-pelvic lymph nodes. 30 patients were referred to Radio-diagnosis Department of Alexandria University. They were subjected to thorough history taking, US examination on the abdomen, CT pre and post contrast, conventional T2 sequence of MRI, DWI with ADC map.
Regarding the distribution of the studied cases according to pathological lesions found; in general, lymphoma ,HCC ,colorectal carcinoma and cancer stomach represented 26.7%, 13.3%, 10% and 6.7% respectively, while cholangiocarcinoma, HIV, malignant melanoma, breast cancer, urinary bladder carcinoma, renal cell carcinoma, tuberculosis, liver cirrhosis and ulcerative colitis represented 3.3% each.
Females comprised 62.5% of distribution of malignant adenopathy and males comprised 37.5 % .Whereas benign adenopathy comprised 42.9% of males and 57.1 % of females. Females are more common to have lymphomatous cause of abdominal lymphadenopathy (8 cases of lymphoma out of 9 were females) but males are more common to have metastatic lymphadenopathy(8 cases out of 14 metastatic adenopathy).
Regarding malignant lesions, the common primary malignant neoplasm found was lymphoma (30% of all lesions), and the common metastatic neoplasm was from cancer colon (representing10%) of all lesions found in this study.
In our study we found that ADC cut off value was 0.9x10 -3 with sensitivity 95.6% and specificity 85.7%. Mean ADC value for malignant lymphadenopathy was (0.8 x 10-3 mm2/s) and for benign one (1.59 x 10-3 mm2/s).
Diffusion weighted imaging is highly practical because of its short duration when added to other imaging examinations.