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Sunday, November 2, 2014

Role of CT Abdomen in Pyrexia of Unknown Origin to Differentiate between Lymphoma and Tuberculosis

Posted by Dr Prahallad Panda on 7:34 PM Comments

Fever of unknown origin (FUO) was defined in 1961 as:
  1. A temperature greater than 38.3°C (101°F) on several occasions,
  2. More than 3 weeks' duration of illness, and
  3. Failure to reach a diagnosis despite 1 week of inpatient investigation.
Now, most of diseases that may cause continuous fever and dilemma in arriving at diagnosis decreased after the advent of various imaging and investigative technologies. 
The most common causes of FUO like tuberculosis, collagen diseases, AIDS and malignancies can be diagnosed by newer serological tests, ultrasonogram, CT, MRI and PET/CT etc..
In spite of all these, there may be occasions, where it may not be possible to differentiate mesenteric lymphadenopathay of lymphoma and tuberculous aetiology without any other associated features.

Intra-Abdominal Lymph Nodes
In multi-detection computerized tomography (MDCT), it has been seen that lymphadenopathy of tuberculous origin mostly affect the LN (Lymph node) adjacent to the intestinal mesenteric boarder, where as in lymphoma more distant LN like para-aortic are involved.
Tuberculosis predominantly involved lesser omental, mesenteric, and upper para-aortic lymph nodes whereas lower para-aortic lymph nodes were involved more often in Hodgkin’s and non-Hodgkin’s lymphoma.
Peripheral enhancement is most commonly seen in tuberculosis, whereas homogeneous enhancement is seen in lymphoma.
The contrast enhancement of tuberculous lymph nodes on contrast-enhanced CT (CECT) have been described as (four patterns) - peripheral rim enhancement, inhomogeneous enhancement, homogeneous enhancement and homogeneous non-enhancement, in that order of frequency.
'Sand-witch' sign, encasing of superior mesenteric vessels and fat (Filling) by the lymph node mass as “Bun” is most commonly seen in lymphoma.
In a study, the mean diameters were 2.95 cm in tuberculous lymphadenopathy, whereas it was 4.10 cm in lymphoma.
Associated findings like thickening of intestine, ascites and peritoneal thickening are more commonly seen in tuberculosis.
In spite of all, a CT/USG guided FNAC or laparoscopic tissue diagnosis is required for the final diagnosis and treatment planning.

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