Pleural effusion and ultrasonography in dengue Fever.

I read with interest the recent study on “Clinical manifestations and trend of dengue cases admitted in a tertiary care hospital, Udupi district, Karnataka” by Kumar et al.(1) and have the following comments to offer:

The authors have mentioned that breathlessness was present in 83 (17.8%) patients with dengue fever. Breathlessness in patients with dengue fever can occur due to pleural effusion, acute respiratory distress syndrome, pneumonia or metabolic acidosis and shock. As per “Table 2,” only 66 children had complications in the form of pleural effusion, ARDS, pneumonia, encephalopathy or metabolic acidosis and shock. The authors have not discussed the reason for breathlessness in the remaining 17 children.

Only 20 (4.29%) of the 466 patients in the study had pleural effusion, and none had ascitis. The authors have not mentioned whether ultrasonography or chest X-ray was used to diagnose pleural effusion. They have also not mentioned after how many days of fever was the imaging done. Both the above points have clinical significance in the diagnosis of dengue fever. In a study performed by Balasubramanian et al., ultrasonography was found to be superior to radiography in detecting pleural effusion.(2) The authors also found that when the various parameters suggested by the World Health Organization as indirect evidences of capillary leak (hemoconcentration and hypoalbuminemia) were compared with ultrasonography and radiography, ultrasonography was found to have the highest sensitivity and negative predictive value in detecting pleural effusion They have suggested that ultrasonography would be ideal, owing to its safety, in that it is nonionizing and would assist detecting plasma leakage even before it manifests clinically. Similar findings have been reported in a study from Indonesia.(3) In a study performed by Venkata Sai et al., the yield of ultrasonography was found to be higher in the later stages of the disease. Repeat ultrasonography on the fifth to seventh days detected pleural effusion in a significantly higher number of patients with dengue fever.(4)

Through this letter, I wish to highlight that radiographic films are not ideal for detecting small amounts of effusion, while ultrasonography is highly useful. Also, a repeat ultrasonography performed in the later stage of dengue fever will detect more cases with pleural effusion.