CC BY-NC-ND 4.0 · Indian J Radiol Imaging 2023; 33(01): 138-140
DOI: 10.1055/s-0042-1759485
Letter to the Editor

Hypodense Sign in Lungs on CT in Immunocompromised Patient

Niveditha N. Naik
1   Department of Radiodiagnosis and Imaging, Postgraduate Institute of Medical Education and Research, Chandigarh, India
,
Anmol Bhatia
1   Department of Radiodiagnosis and Imaging, Postgraduate Institute of Medical Education and Research, Chandigarh, India
,
Kushaljit S. Sodhi
1   Department of Radiodiagnosis and Imaging, Postgraduate Institute of Medical Education and Research, Chandigarh, India
,
Akshay K. Saxena
1   Department of Radiodiagnosis and Imaging, Postgraduate Institute of Medical Education and Research, Chandigarh, India
› Author Affiliations
Funding None.

We read with interest the article entitled “Imaging Approach to Pulmonary Infections in the Immunocompromised Patient” by Grover et al.[1] We would like to add a “hypodense sign” (HyS) to the list of radiological findings described by the authors. The HyS was described by Horger et al as[2] the presence of a central area of hypodensity seen on narrow window settings (width: 110–140 Hounsfield Units [HU]; level: 15–40 HU). This sign can be seen in consolidation or nodule and can be appreciated on unenhanced scans, computed tomography pulmonary angiography (CTPA), and contrast-enhanced scans. This sign has been reported to be associated with invasive pulmonary aspergillosis, mucormycosis, and fusariosis.[3] [4] The hypodense nodule sign has been described in the context of immunocompromised patients. The underlying pathogenesis is infarction secondary to angioinvasion by fungal elements.[3] [4] This sign may be a precursor for forming a cavity.[2] [5] Some studies have described the importance of hypodense sign in diagnosing invasive mold disease ([Table 1]). Hence, it is a helpful sign in arriving at the diagnosis of invasive mold disease with a sensitivity of 23% on high-resolution CT (HRCT) and 64% on CTPA, and a specificity of 100% on HRCT and 98% on CTPA.[3] This sign can help to differentiate between bacterial and fungal diseases in immunocompromised individuals.[2] [3] This sign has also been described in some bacterial infections, particularly in tuberculosis, i.e., a cavity filled with central mucous within or in case of a pulmonary abscess; however, leukocytes play a vital role in abscess formation, and immunocompromised individuals usually have neutropenia.[3] [6] Hence, we would like to add the hypodense sign as a useful diagnostic sign in CTs of immunocompromised individuals.

Table 1

Studies describing hypodense sign in immunocompromised patients

Study

Sample size

Type of scan

Patient population

Horger et al[2]

43

Unenhanced scan

Neutropenic patients

Sassi et al[3]

127

HRCT and contrast-enhanced CT

Hematological Malignancies

Qin et al[5]

25

CT chest with intravenous contrast and without intravenous contrast

Liver transplant patients

Stanzani et al[6]

44

Unenhanced scan and CTPA

Hematological malignancies

Schulze et al[7]

17

Noncontrast CT and volume perfusion CT

Hematological malignancies



Publication History

Article published online:
20 December 2022

© 2022. Indian Radiological Association. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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