Imaging in scrub typhus – a pictorial review

Abstract

Scrub typhus (STy) is a common yet underrecognized and life-threatening rickettsial zoonosis endemic to the Asia-Pacific region. It is transmitted by the bite of chigger mites infected with Orientia tsutsugamushi. In the US, it is primarily encountered among recent travellers. STy presents as an acute febrile illness with non-specific features. Eschar at the site of a mite bite and positive serology clinch the diagnosis. However, the classic eschar may not be seen in all cases, and serology may be negative in early cases. Multisystemic involvement is the rule in STy, and the underlying pathology is vasculitis & perivasculitis across multiple organs. Imaging features are nonspecific. However, awareness about common radiological features such as a combination of gallbladder wall edema, hepatosplenomegaly, and reticulonodular lung opacities is crucial to raise suspicion of STy in those at risk and thus prompt specific diagnostic testing. Imaging features are particularly useful in flagging cases of early disease with negative serology or those without the characteristic eschar. STy responds promptly to antirickettsial antibiotics. Delayed institution of antibiotics carries an adverse prognosis. Hence, early diagnosis is important. Further, imaging also helps with prognostication and early detection of complications.