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


Sample size

Type of scan

Patient population

Horger et al[2]


Unenhanced scan

Neutropenic patients

Sassi et al[3]


HRCT and contrast-enhanced CT

Hematological Malignancies

Qin et al[5]


CT chest with intravenous contrast and without intravenous contrast

Liver transplant patients

Stanzani et al[6]


Unenhanced scan and CTPA

Hematological malignancies

Schulze et al[7]


Noncontrast CT and volume perfusion CT

Hematological malignancies

Publication History

Article published online:
20 December 2022

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  • References

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