British Journal of Radiology (2005) 78, 416-418
© 2005 British Institute of Radiology
doi: 10.1259/bjr/54704044
Role of ultrasound in dengue fever
P M Venkata Sai, MBBS, DMRD, DNB, FICR
B Dev, MBBS, MD, DNB
and
R Krishnan, R S MBSS, MD
Department of Radiology and Imaging Sciences, Sri Ramachandra Medical College & Research Institute (DU), Porur, Chennai – 600 116, Tamil Nadu, India
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Abstract
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This study was performed to find out whether ultrasound is an important adjunct to clinical and laboratory profile in diagnosing dengue fever or dengue haemorrhagic fever and to further determine whether ultrasound is useful in predicting the severity of the disease. Ultrasound was performed on 128 patients (2–9 years) with clinical suspicion of dengue fever. Serological tests were performed to confirm the diagnosis. 40 patients were serologically negative for dengue fever and later excluded from the study. Of the remaining 88 serologically positive cases, 32 patients underwent ultrasound on second to third day, repeated on fifth to seventh day of fever and in 56 patients ultrasound was done only on fifth to seventh day of fever. Of the 32 patients who underwent the study on second to third day of fever, all showed gall bladder wall thickening and pericholecystic fluid, 21% had hepatomegaly, 6.25% had splenomegaly and right minimal pleural effusion. Follow-up ultrasound on fifth to seventh day revealed ascites in 53% left pleural effusion in 22% and pericardial effusion in 28%. Of the 56 patients who underwent the study on fifth to seventh day of fever for the first time all had gall bladder wall thickening, 21% had hepatomegaly, 7% had splenomegaly, 96% had ascites, 87.5% had right pleural effusion, 66% had left pleural effusion and 28.5% had pericardial fluid. To conclude, in an epidemic of dengue, ultrasound features of thickened gall bladder wall, pleural effusion and ascites should strongly favour the diagnosis of dengue fever.
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Introduction
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Dengue is a mosquito-borne infection that in recent years has become a major international public health problem [1]. Dengue fever (DF) has been known for more than a century in the tropical areas of South East Asia and the Western Pacific regions [2]. Clinically dengue manifests with acute onset of fever, severe headache, retro-ocular pain and pain involving the muscles and joints. Haemorrhagic diasthesis and thrombocytopenia with concurrent haemoconcentration is a constant finding.
In early July 2002, there was an outbreak of dengue in Chennai, a coastal city in Southern India. Since there is no single test that can be used to diagnose the condition with a reasonable degree of accuracy and reliability, the diagnosis is based on clinical appearance in combination with serology. Serology takes approximately 7 to 10 days to give a positive result. The purpose of our study was to analyse retrospectively the ultrasound features in patients with DF, to find out whether ultrasound is an adjunct to clinical and lab profile in the diagnosis of DF and to further determine whether ultrasound is useful in predicting the severity of the disease
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Materials and methods
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Our institutional review board approved this retrospective study; informed consent was not required. Between June and July 2002, 128 subjects (80 male, 48 female; mean age, 5 years; age range 2–9 years) who were clinically suspected of having DF were referred for ultrasound scanning of both abdomen and thorax. Common clinical manifestations included fever (n=128), severe headache (n=104), retro-ocular pain (n=84), pain in the muscles and joints (n=80), and purpuric spots on the body (n=22). Blood laboratory investigation in 88 patients revealed thrombocytopenia (average platelet count 40 000 cells mm–3) with concurrent haemoconcentration. Based on the clinical and laboratory findings 65 patients were diagnosed as classical dengue fever (CDF), 19 patients had dengue haemorrhagic fever (DHF) and 4 patients were diagnosed as dengue shock syndrome (DSS).
All ultrasound examinations were performed with a portable machine (L&T symphony model) using 3.5 MHz and 5 MHz probes. Abdominal scanning was done after 6 h of fasting to allow better distension of gall bladder (GB) [3]. GB wall thickening, which was the consistent finding in all the serologically positive cases, was measured by placing the calipers between the two layers of anterior wall [4]. Thoracic scanning was done in either sitting or supine posture. Both the pleural spaces were evaluated through an intercostal approach. Pericardial space was also evaluated for effusion subcostally. In all the patients ultrasound was performed prior to serology.
Serological tests using paired sera was performed to confirm the diagnosis in all the 128 patients which revealed 88 patients to be serologically positive for DF [5, 6]. The remaining 40 patients were serologically negative. The 88 serologically positive patients were then sorted into two groups based on the days of study. Group I (n=32) included patients who had symptoms and signs consistent with DF and in whom ultrasound was performed on the second to third day after onset of fever. These patients also had a follow up scan on fifth to seventh day. Group II (n=56) included patients who underwent ultrasound only on fifth to seventh day after onset of fever. For the 40 serologically negative patients ultrasound was performed on an average of 3.9 days (range, same day to 7 days) after admission.
Ultrasound findings in Group I
Of the 32 patients who underwent the study on second to third day of fever, 7 had hepatomegaly (21.8%), 32 had GB wall thickening and pericholecystic fluid (100%), 2 had splenomegaly (6.25%) and 2 had right-sided pleural effusion (6.25%). None had ascites, left sided pleural effusion or pericardial effusion. On follow-up scan (days 5–7), hepatomegaly was noted in four more patients (12.5%), splenomegaly in three more patients (9.37%) and right sided pleural effusion in 21 more patients (65.6%). GB pathology persisted in all the patients. New findings including ascites were noted in 17 patients (53.12%), left sided pleural effusion in 7 patients (21.8%) and pericardial effusion in 9 patients (28.12%).
Ultrasound findings in Group II
Of the 56 patients who underwent the study on fifth to seventh day of fever, GB pathology was noted in all the 56 patients (100%), 34 patients had hepatomegaly (60.9%), 17 had splenomegaly (30.35%), 4 had ascites (7.14%), 55 had right sided pleural effusion (96.46%), 37 had left sided pleural effusion (66.07%) and 16 had pericardial effusion (28.57%).
40 serologically negative patients
Of the 40 patients who were serologically negative for DF, GB pathology was present in 14 patients initially but disappeared later on follow-up scan. A clinical review of 17 other patients revealed that their symptoms were not classical of DF. Nine patients could not be followed up as they discharged themselves against medical advice.
Our study demonstrated thickened GB wall and pericholecystic fluid (Figure 1
) as the most common initial ultrasound finding in all the 88 serologically positive cases (100%) followed by right sided pleural effusion (71.87%), ascites (53.2%), left sided pleural effusion (21.87%) and pericardial effusion (28.5%). Hepatomegaly and splenomegaly were noted in 34.3% and 15.6% of patients, respectively.
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Discussion
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Dengue is an acute febrile viral disease caused by flavivirus. It occurs in two forms: DF, a milder form of the disease and DHF, the most severe form. Dengue has become a major international public health concern in recent years [2]. It is now endemic in more than 100 countries and threatens the health of 40% of the world's population. It is estimated that 50 million dengue infections occur each year with 5 000 000 cases of DHF and at least 12 000 deaths annually mainly among children [1]. The increase of DF is due to uncontrolled population growth and urbanization in the absence of appropriate water management, global spread of dengue strains via travel and trade and due to erosion of vector control programmes [7]. In India the problem is even more acute because since 1963, more than 50 outbreaks have been reported by the National Institute of Communicable diseases, New Delhi [8].
Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquito. The incubation period of the disease is 3–14 days. The onset of the disease is recognized by the sudden onset of high fever, retro-orbital pain, thrombocytopenia and haemorrhagic manifestations. Common laboratory findings include pancytopenia, neutropenia, increased haemoconcentration, thrombocytopenia and prolonged bleeding time. These findings are consistent with increased vascular permeability, plasma leakage, abnormalities of haemostasis and protein losing shock syndrome, which commonly occur in DF pathogenesis.
Serology is the mainstay in the diagnosis of DF. Haemagglutination inhibition antibodies usually appear at detectable level by day 5 to 6 of febrile illness. The diagnosis of DF is often delayed owing to time taken for availability of results. The aim of our study was to evaluate the ultrasound findings in DF, to find whether ultrasound of the abdomen is an important adjunct to clinical and laboratory profile in diagnosing DF and further if ultrasound is useful in predicting the severity of the disease.
The ultrasound findings in early milder form of DF include GB wall thickening, pericholecystic fluid, minimal ascites, pleural effusion, pericardial effusion and hepatosplenomegaly. Severe forms of the disease are characterized by fluid collection in the perirenal and pararenal region, hepatic and splenic subcapsular fluid, pericardial effusion, pancreatic enlargement and hepatosplenomegaly. These findings have been demonstrated in studies carried out by the Department of Child Health in Indonesia [9] and by Joshi et al [10] in Army Hospital, Delhi Cantt. They had also found abnormal liver parenchyma, which has been attributed to intraparenchymal and subcapsular haemorrhages. In our study however we could not appreciate any significant change in the echotexture of the liver. None of these studies suggested GB wall thickening as the initial finding in DF (100%) as observed in our study, followed and pleural effusion. GB wall thickening in DF may be due to decrease in intravascular osmotic pressure. These findings may also occur in other viral infections, enteric fever and leptospirosis, but in other viral infections the historical profile, symptom complex evolution and physical findings do not mimic those of DF. Ultrasound features of enteric fever include splenomegaly, intra-abdominal lymphadenopathy, bowel abnormalities in the form of intramural thickening of the terminal ileum and caecum, renal abnormalities like arteriectasis and perinephric fluid collection in addition to GB wall thickening and polyserositis. Leptospirosis also shows gross abnormalities involving hepatic and renal parenchyma. GB wall thickening also occurs in association with other conditions such as ascites, hypoalbuminaemia, congestive cholecystopathy and in patients with cirrhosis of liver and portal hypertension. It is a very non-specific finding when considered in isolation and is therefore a major limitation of this study.
To conclude ultrasound of the abdomen is an important adjunct to clinical profile in diagnosing DF and may help to direct further confirmatory investigations. Further diagnosis can be made early in the course of disease compared with other modes of diagnosis. During an epidemic the ultrasound findings of GB wall thickening with or without polyserositis in a febrile patient should suggest the possibility of DF/DHF.
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Acknowledgments
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We thank Dr Uday Charan Murmu, Assistant Professor of Paediatric Medicine, Mr S Porchelvan, Department of Biostatistics and Mr S Santhosh, Department of Radiology & Imaging Sciences Sri Ramachandra Medical College & Research Institute (Deemed University), Chennai for his invaluable help in evaluation for the study.
Received for publication May 24, 2004.
Revision received November 4, 2004.
Accepted for publication December 6, 2004.
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References
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Abstract
Introduction
