Disseminated tuberculosis - CT

Disseminated tuberculosis (TB) is a contagious bacterial infection that has spread from the lungs to other parts of the body through the blood or lymph system. The differential diagnosis of miliary nodules in bilateral lungs are tuberculosis, metastases, sarcoidosis, lymphoma, hypersensitivity pneumonitis and rare causes like silicosis, beryliosis, stanosis. Depending imaging findings and patients clinical deatils, one can differentiate each other.

The differential diagnosis of patients with fever, splenomegaly, and multiple hypoechoic hypoattenuating splenic lesions includes splenic abscesses that may be bacterial, fungal, or granulomatous in nature. Pyogenic abscesses are usually solitary. On US images, they appear as small irregular hypoechoic lesions that may evolve into a poorly defined heterogeneous mass. On CT images, they typically appear as single irregularly marginated hypoattenuating lesions. The presence of intralesional gas is pathognomonic of pyogenic infection, although it occurs infrequently. Multiple splenic abscesses, usually smaller than 2 cm in diameter, are commonly associated with nonbacterial infections (ie, fungal and granulomatous infections). Fungal abscesses, when visible, characteristically appear on US images as round hypoechoic lesions with a central hyperechoic area (ie, “bull's-eye” or “target” appearance) that corresponds to inflammatory cells with a surrounding hypoechoic band of fibrosis. The “wheel-in-a-wheel” pattern is seen when the central portion becomes necrotic and hypoechoic. Contrast-enhanced CT typically depicts fungal splenic abscesses as multiple small low-attenuation lesions. Patients with cat-scratch disease may also develop splenomegaly and splenic microabscesses. Neoplasms that involve the spleen—such as lymphoma (both Hodgkin and non-Hodgkin lymphoma), leukemia, metastasis, or even Langerhans cell histiocytosis—may manifest as focal hypoechoic hypoattenuating lesions. Sarcoidosis, which is a systemic granulomatous disease of unknown origin, may also have abdominal involvement with lymphadenopathy and hypoattenuating nodules in the liver and spleen. It is generally impossible to differentiate visceral TB lesions from fungal infections, lymphoma, or metastasis—unless they are associated with other typical abdominal TB findings, such as lymph node or bowel involvement.