Target sign in hepatic tuberculosis
Diagnosed case of Pott disease. The patient presented with bloating and abdominal discomfort.
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There is lytic destruction with associated soft tissue mass involving the T10 to T12 vertebral bodies. The lesion extends posteriorly to the anterior epidural space from T8 to T12 compressing on the spinal canal. A paravertebral component is also observed on the left side from T9 to T12, insinuating into the left neural canals at T10-T11 and T11-T12 with encasement of intercostal arteries. These findings are consistent with the clinically proven tuberculous spondylitis (Pott disease).
The liver is enlarged with a span of 17.6 cm in craniocaudal dimension. Plain and contrast-enhanced images show multiple hepatic nodules with peripheral areas of low attenuation and central calcifications (target sign). The dominant hepatic lesions measure about 2.0 x 2.4 x 2.6 cm (AP x T x CC) at segment II, 2.2 x 2.2 x 2.0 cm at segment IVB and 2.1 x 2.2 x 2.1 cm at segment VI. The rest of the nodules range in size from 0.6 cm to 2 cm in diameter. The intrahepatic and extrahepatic bile ducts are not dilated. The portal vein is patent.
There are enlarged lymph nodes in the gastrohepatic region, mesentery and retroperitoneum.
The rest of the abdominal findings are grossly unremarkable.
This case demonstrates hepatic involvement in a patient with disseminated tuberculosis (TB) with Pott disease. Biopsy of one of the hepatic lesions showed necrotizing granulomatous inflammation in keeping with TB.
TB of the liver is uncommon and accounts for less than 1% of all tuberculous infections. Hepatic TB can occur primarily or it can be secondary to a tubercular focus elsewhere in the body. In imaging, it presents with different appearances and can mimic a variety of other conditions. Hepatic TB can be comprehensively classified into micronodular and macronodular forms. Micronodular hepatic TB refers to miliary tuberculosis wherein the lesions measure 0.5 - 2 mm in diameter. The macronodular form may present either as multiple 1 - 3 cm lesions or as a large tumorlike mass. Some macronodular lesions may exhibit a bull’s-eye appearance (“Target” sign), which refers to the central nidus of calcification or central enhancement with surrounding area of low attenuation or ring of enhancement on CT, or central enhancement accompanied by peripheral rim enhancement on post-contrast MRI. This sign is suggestive of, but not pathognomonic for, TB. Image-guided biopsy is often required to obtain a definitive histological diagnosis.
- 1. Tatco V, Mejia-Santos MM, Uy JA. The Many Faces of Hepatic Tuberculosis. TB Corner 2015; 1(2):1-6. [Free text at WFPI].