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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

Abstract. This study was performed to find out whether ultrasound is an important adjunct to clinical andlaboratory profile in diagnosing dengue fever or dengue haemorrhagic fever and to further determine whetherultrasound is useful in predicting the severity of the disease. Ultrasound was performed on 128 patients (29years) with clinical suspicion of dengue fever. Serological tests were performed to confirm the diagnosis. 40patients were serologically negative for dengue fever and later excluded from the study. Of the remaining 88serologically positive cases, 32 patients underwent ultrasound on second to third day, repeated on fifth toseventh day of fever and in 56 patients ultrasound was done only on fifth to seventh day of fever. Of the 32patients who underwent the study on second to third day of fever, all showed gall bladder wall thickening andpericholecystic 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 pericardialeffusion 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% hadright pleural effusion, 66% had left pleural effusion and 28.5% had pericardial fluid. To conclude, in anepidemic of dengue, ultrasound features of thickened gall bladder wall, pleural effusion and ascites shouldstrongly favour the diagnosis of dengue fever.

Dengue is a mosquito-borne infection that in recentyears has become a major international public healthproblem [1]. Dengue fever (DF) has been known formore than a century in the tropical areas of South EastAsia and the Western Pacific regions [2]. Clinicallydengue manifests with acute onset of fever, severeheadache, retro-ocular pain and pain involving the muscles

and joints. Haemorrhagic diasthesis and thrombocyto-penia with concurrent haemoconcentration is a constantfinding.

In early July 2002, there was an outbreak of dengue inChennai, a coastal city in Southern India. Since there is no

single test that can be used to diagnose the condition witha reasonable degree of accuracy and reliability, thediagnosis is based on clinical appearance in combinationwith serology. Serology takes approximately 7 to 10 daysto give a positive result. The purpose of our study was toanalyse retrospectively the ultrasound features in patientswith DF, to find out whether ultrasound is an adjunct toclinical and lab profile in the diagnosis of DF and tofurther determine whether ultrasound is useful in predict-

ing the severity of the disease

Materials and methods

Our institutional review board approved this retro-spective study; informed consent was not required.Between June and July 2002, 128 subjects (80 male, 48female; mean age, 5 years; age range 29 years) who wereclinically suspected of having DF were referred forultrasound scanning of both abdomen and thorax.Common clinical manifestations included fever (n5128),

severe headache (n5104), retro-ocular pain (n584), pain in

the muscles and joints (n580), and purpuric spots onthe body (n522). Blood laboratory investigation in 88

patients revealed thrombocytopenia (average plateletcount 40 000 cells mm23) with concurrent haemocon-

centration. Based on the clinical and laboratory findings65 patients were diagnosed as classical dengue fever(CDF), 19 patients had dengue haemorrhagic fever

(DHF) and 4 patients were diagnosed as dengue shocksyndrome (DSS).

All ultrasound examinations were performed with a

portable machine (L&T symphony model) using 3.5 MHzand 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 consistentfinding in all the serologically positive cases, was mea-sured by placing the calipers between the two layers

of anterior wall [4]. Thoracic scanning was done ineither sitting or supine posture. Both the pleural spaceswere evaluated through an intercostal approach.

Pericardial space was also evaluated for effusion subcos-tally. 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]. Theremaining 40 patients were serologically negative. The 88serologically positive patients were then sorted into two

groups based on the days of study. Group I (n532)included patients who had symptoms and signs consistentwith DF and in whom ultrasound was performed on the

second to third day after onset of fever. These patients alsohad a follow up scan on fifth to seventh day. Group II(n556) included patients who underwent ultrasound only

on fifth to seventh day after onset of fever. For the 40

serologically negative patients ultrasound was performedon an average of 3.9 days (range, same day to 7 days) afteradmission.

Received 24 May 2004 and in final form 4 November 2004, accepted6 December 2004.

The British Journal of Radiology, 78 (2005), 416418 E 2005 The British Institute of Radiology

DOI: 10.1259/bjr/54704044

416 The British Journal of Radiology, May 2005

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Results (Tables 14)

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 pleuraleffusion or pericardial effusion. On follow-up scan (days

57), 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 spleno-

megaly were noted in 34.3% and 15.6% of patients,

respectively.

Table 1. Profile of 88 serologically positive cases

Day of examination Number of cases

2nd3rd day 32

5th7th day 56+32 (follow up cases)

Table 2. Summary of ultrasound findings in Group I

Days of examination No. of patients (n532)

2nd3rd day 5th7th day

Gall bladder wall thickening

with pericholecystic fluid

32 (100) 32 (100)

Hepatomegaly 7 (21.8) 4 (12.5)

Splenomegaly 2 (6.25) 3 (9.37)

Right pleural effusion 2 (6.25) 21 (65.6)

Left pleural effusion 0 (0) 7 (21.8)

Ascites 0 (0) 17 (53.12)

Pericardial effusion 0 (0) 9 (28.12)

Number in parentheses are percentages.

Table 3. Summary of ultrasound findings in Group II

Features No. of patients (n556)

5th7th day

Gall bladder Wall thickening

with pericholecystic fluid

56 (100)

Hepatomegaly 34 (60.9)

Splenomegaly 17 (30.35)

Right pleural effusion 55 (96.46)

Left pleural effusion 37 (66.07)

Ascites 4 (7.14)

Pericardial effusion 16 (28.57)

Number in parentheses are percentages.

Table 4. Summary of ultrasound findings in Group I andGroup II

Features No. of patients (n588)

5th7th day

Gall bladder Wall thickening

with pericholecystic fluid

100%

Hepatomegaly 34.3%

Splenomegaly 15.6%

Right pleural effusion 71.87%

Left pleural effusion 21.87%

Ascites 53.2%Pericardial effusion 28.5% Figure 1. Ultrasound subcostal view to show gall bladder wall

thickening and pericholecystic fluid.

Ultrasound in dengue fever

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Discussion

Dengue is an acute febrile viral disease caused byflavivirus. It occurs in two forms: DF, a milder form of thedisease and DHF, the most severe form. Dengue hasbecome a major international public health concern inrecent years [2]. It is now endemic in more than 100countries and threatens the health of 40% of the worlds

population. It is estimated that 50 million dengueinfections occur each year with 5 000 000 cases of DHFand at least 12 000 deaths annually mainly among children

[1]. The increase of DF is due to uncontrolled populationgrowth and urbanization in the absence of appropriatewater management, global spread of dengue strains via

travel and trade and due to erosion of vector controlprogrammes [7]. In India the problem is even more acutebecause since 1963, more than 50 outbreaks have beenreported by the National Institute of Communicablediseases, New Delhi [8].

Dengue viruses are transmitted to humans through thebites of infective female Aedes mosquito. The incuba-

tion period of the disease is 314 days. The onset of thedisease is recognized by the sudden onset of high fever,retro-orbital pain, thrombocytopenia and haemorrhagicmanifestations. Common laboratory findings includepancytopenia, neutropenia, increased haemoconcentration,thrombocytopenia and prolonged bleeding time. These

findings are consistent with increased vascular permeabil-ity, plasma leakage, abnormalities of haemostasis andprotein losing shock syndrome, which commonly occur inDF pathogenesis.

Serology is the mainstay in the diagnosis of DF.Haemagglutination inhibition antibodies usually appearat detectable level by day 5 to 6 of febrile illness. Thediagnosis of DF is often delayed owing to time taken for

availability of results. The aim of our study was toevaluate the ultrasound findings in DF, to find whetherultrasound of the abdomen is an important adjunct toclinical and laboratory profile in diagnosing DF andfurther 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 hepato-splenomegaly. Severe forms of the disease are character-ized by fluid collection in the perirenal and pararenalregion, hepatic and splenic subcapsular fluid, pericardialeffusion, pancreatic enlargement and hepatosplenomegaly.

These findings have been demonstrated in studies carriedout 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, whichhas been attributed to intraparenchymal and subcapsular

haemorrhages. In our study however we could notappreciate any significant change in the echotexture ofthe liver. None of these studies suggested GB wallthickening as the initial finding in DF (100%) as observed

in our study, followed and pleural effusion. GB wallthickening in DF may be due to decrease in intravascularosmotic pressure. These findings may also occur in other

viral infections, enteric fever and leptospirosis, but in otherviral infections the historical profile, symptom complexevolution and physical findings do not mimic those of DF.Ultrasound features of enteric fever include splenomegaly,intra-abdominal lymphadenopathy, bowel abnormalities inthe form of intramural thickening of the terminal ileum

and caecum, renal abnormalities like arteriectasis and

perinephric fluid collection in addition to GB wallthickening and polyserositis. Leptospirosis also showsgross abnormalities involving hepatic and renal parench-

yma. GB wall thickening also occurs in association withother conditions such as ascites, hypoalbuminaemia,congestive cholecystopathy and in patients with cirrhosisof liver and portal hypertension. It is a very non-specificfinding when considered in isolation and is therefore amajor limitation of this study.

To conclude ultrasound of the abdomen is an importantadjunct to clinical profile in diagnosing DF and may helpto direct further confirmatory investigations. Furtherdiagnosis can be made early in the course of diseasecompared with other modes of diagnosis. During an

epidemic the ultrasound findings of GB wall thickeningwith or without polyserositis in a febrile patient should

suggest the possibility of DF/DHF.

Acknowledgments

We thank Dr Uday Charan Murmu, Assistant Professorof Paediatric Medicine, Mr S Porchelvan, Department ofBiostatistics and Mr S Santhosh, Department ofRadiology & Imaging Sciences Sri Ramachandra

Medical College & Research Institute (DeemedUniversity), Chennai for his invaluable help in evaluationfor the study.

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