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Comparison of ultrasound with plain radiographyand CT for the detection of mediastinallymphadenopathy in children with tuberculosis

Joaquim Bosch-Marcet; Xavier erres-Cre!i"ams; #malia $uasnabar-Cotro; Xavier Codina-

%uig; Margarita Catala& -%uigbo!; Jose! '( imon-)ia*uelo

Abstract

Background :'ymphadenopathy+ with or without parenchymal abnormality+ is the radiological hallmar, ofprimary tuberculosis TB. in children( /owever+ lymph node enlargement may passundetected on plain chest radiographs( 0ltrasonography provides complementaryinformation to that obtained by radiographs(

Objective : To assess the clinical value of 0 for the detection of mediastinal lymphadenopathy inchildren with a positive intradermal tuberculin test(

Materials and methods : Thirty-two children with a mean age of 1 years and a positive Mantou" test underwent chestradiography frontal and lateral. and 0 suprasternal and left parasternal access routes.(Chest CT was performed at the discretion of the attending physician in si" cases(

Results :2leven children had clinical symptoms and 345 a recent contact with a person with active

TB( 6n 34(75 of children with chest radiographic images compatible with TB+ coincident8ndings in the mediastinal 0 study were found( By comparison+ 11(95 of those with normalchest radiography had evidence of mediastinal lymphadenopathy on the 0 scan( 6n allcases but one+ 0 and CT 8ndings agreed(

Conclusions :Mediastinal 0 is useful for the detection of enlarged lymph nodes in children with a positivetuberculin reaction and normal chest radiography(

Keywords : Mediastinum : TB : 'ymphadenopathy : )adiography : 0ltrasound : CT :Children(



6ntroduction

Tuberculosis TB. has re-emerged as a serious public health problem in developedcountries+ particularly among young adults and children( The diagnosis of TB in children isoften dicult to con8rm+ because Mycobacterium TB is cultured only in a small percentageof cases <=+ >?( @hereas the diagnosis of active TB in adults is mainly bacteriological+ inchildren it is usually epidemiological and indirect( 6n the absence of a positive culture+ thestrongest evidence for TB in a child is recent e"posure to an adult with active disease <A?(6ndirect diagnostic techniques+ such as the tuberculin s,in test+ chest radiography andphysical e"amination oer supportive information <?(

Central to the clinical diagnosis of childhood TB is the chest radiograph and thepresence of lymphadenopathy with or without parenchymal involvement is the single mostimportant diagnostic feature <?( The nodal enlargement typically involves the hilar andparatracheal nodes+ with bilateral hilar lymphadenopathy identi8ed in about >75 of cases(Dierent studies have documented light-sided predominance of lymphadenopathy and

parenchymal changes <7?( Both frontal and lateral views are necessary to evaluatelymphadenopathy( Ef interest is the fact that enlarged lymph nodes may be detected byultrafast CT in 145 of children with tuberculous infection and normal 8ndings on chestradiography <1?( /owever+ this technique would not be available in most cases and the costis very high( @e report the clinical value of 0 to detect mediastinal lymph nodeinvolvement in children with a positive intradermal tuberculin s,in test(

Materials and methods# retrospective review of the medical records of A> children+ =9 boys and =7 girls+

with a mean age of 1 years range months to =9 years.+ who had a positive intradermaltuberculin s,in test was made( These patients had been referred to our Department of%aediatrics for wor,up studies and eventual treatment between =33 and >444( Fone of thepatients had been e"posed to BCG vaccination( #ll patients underwent a thorough history

including e"posure tracing.+ physical e"amination+ frontal and lateral chest radiographs+and sonographic study of the mediastinum( The radiographic 8ndings consideredrepresentative of TB included nonspeci8c locali*ed in8ltrates+ hilar adenitis+ locali*edhyperaeration+ atelectasis+ segmental lesions+ cavitation+ calci8cation+ and locali*ed pleuraleusion(CTof the chest was performed in selected patients at the discretion of the physiciansin charge(

0ltrasonography of the mediastinum was performed with high-resolution equipment'ogiq 944+ General 2lectric. using a 7-M/* conve" probe( The presence of one or moremasses with an ovoid or round shape and hypoechoic appearance in the anterior or middlemediastinum was recorded( The anterior mediastinum included the prevascular region+occupied by the thymus gland and the middle mediastinum+ the right paratracheal+ supra-aortic+ aortopulmonary+ and subcarinal regions( En 0 the normal thymus has a bilobulatedappearance and homogeneous echote"ture with some echogenic strands( 6t is hypoechoic

relative to the thyroid gland and has a smooth+ well-de8ned margin due to its 8brouscapsule( 6t is a soft organ that does not compress neighbouring vascular structures+ acharacteristic that can help the radiologist to dierentiate it from mediastinal masses( Thenormal thymus can vary considerably in position+ e"tension+ si*e and con8guration( 6n smallchildren+ the organ can e"tend from the cervical region to the diaphragm( During respirationand particularly when the child is crying+ the thymus can be above the manubrium andsimulate a cervical mass(

The mediastinum was accessed via the suprasternal and left parasternal approaches<9?( @hen using the suprasternal approach+ the patient was placed in a supine decubitusposition with a cushion under the bac, and the nec, slightly e"tended( The transducer was



placed above the manubrium and titled caudally( To obtain an oblique sagittal view+ theprobe was placed laterally to encounter the space between the trachea and thesternocleidomastoid muscle( Hor the left parasternal approach+ the patient was placed in aleft lateral decubitus position to move the mediastinum downwards and increase the si*e ofthe anatomic acoustic window( Hive standard sonographic slices were used to visuali*e thecomplete anterior and middle regions of the mediastinum( Three sonographic slices were

obtained with the suprasternal approach oblique coronal+ coronal+ and oblique parasagittal.and two with the left parasternal approach a"ial and parasagittal views.( The obliquecoronal view through the suprasternal approach was used to visuali*e the paratrachealregion and to study the aortopulmonary region; the coronal view was useful for visuali*ingthe vessels+ particularly the IC; the oblique parasagittal view visuali*ed theaortopulmonary region( The a"ial and parasagittal views through the left parasternalapproach were used to study the subcarinal and prevascular regions(

6n all the cases+ the number and si*e long a"is. of lymph nodes were determined( The following groups were established arbitrarily no adenopathy or lymph nodes K=4 mm indiameter negative+ group 4.; a single lymph node L=4 mm positive + group =.; a singlelymph node L=7 mm positive + group >.; a single lymph node L>4 mm positive +group A.; more than one lymph node L=7 mm positive+ group .( 6n the case ofclearly matted nodes+ the si*e of the whole mass was considered( @hen possible+ the si*e ofeach of its components was measured( Hor each patient+ the results of chest radiography+ 0of the mediastinum+ and chest CT were compared(

)esultsEf the A> patients who had 0 studies of the mediastinum+ 345 had recent contact

with a person with con8rmed pulmonary TB( Enly == A(5. children had clinicalmanifestations such as fatigue+ low-grade fever+ mild cough+ weight loss+ night sweats+chills+ and failure to thrive( The remaining >= children were asymptomatic+ but with apositive tuberculin s,in test( %ulmonary radiographic 8ndings were suggestive of TB in >=children+ negative in nine+ and uncertain in two( @ith regard to 0 of the mediastinum+ therewere 8ve children in group 4+ =7 in group =+ two in group >+ four in group A+ and si" in group( CT of the chest was performed in si" children( Details of 8ndings of chest radiography+mediastinal 0 and chest CT are shown in Table = and in Higs( =+ >( 6n the group of ninechildren with normal 8ndings on chest radiography+ 0 of the mediastinum con8rmedlymphadenopathy in si" cases 11(95. and was negative in the remaining three( Ene ofthese three patients had a normal chest CT scan and in the other two+ CT e"amination wasnot performed( #ll patients but two with compatible radiological 8ndings of TB had visiblemediastinal lymph nodes on 0( Therefore+ 34(75 =3 out of >=. of patients with pathologicimages in the chest radiographs+ had visible mediastinal lymphadenopathy in theultrasonographic study( 6n the two patients with doubtful radiological images+ultrasonography con8rmed the diagnosis of tuberculous lymphadenopathy in two(

The chest CT e"amination+ which was carried out in si" patients+ con8rmed theresults of 0 in four( 6n one patient with normal radiographic 8ndings and absence ofmediastinal adenopathy+ the CT scan was also negative+ whereas in the other patient withuncertain radiographic 8ndings and mediastinal lymphadenopathy in the ultrasounde"amination+ the CT scan was negative( This patient+ however+ was given antituberculoustreatment and his clinical symptoms resolved and radiological images cleared( 6n 8ve of si"NA(A5. patients a concordance between results of mediastinal ultrasonography and CTe"amination was observed(

The case of a patient with lymphadenopathy in the right paratracheal region usingthe suprasternal approach is shown in Hig( A( 6n this case+ results of 0 were con8rmed by CTHig( A.( 6n the case of a =-yearold patients with active TB involving the left upper lobe+ thesuprasternal approach revealed a lymph node+ =(N cm in diameter+ in the aortopulmonaryregion Hig( .( # lymphadenopathy in the subcarinal space was detected in a patient withnormal chest roentgenogram using the left parasternal approach Hig( 7.(



DiscussionMost TB infections in children and adolescents are asymptomatic when the tuberculin

s,in test is positive( 6n the present series+ only A(5 of patients had nonspeci8c symptoms+such as fever+ cough+ weight loss+ and failure-to-thrive pattern in young infants( #ll patientswere referred for evaluation because of the tuberculin s,in test and in 345 of them+ a recente"posure to an adult with active disease was present( 6t should be noted that there were two

patients aged between =7 and =9 years of age( Despite the fact that these patients wereadolescents+ they were referred for evaluation to our department because =N years is theupper age limit assigned to pediatrics by our health care system( En the other hand+ the factthat A> patients with a tentative diagnosis of TB had been referred for wor,-up studiesduring the study period indicates that although signi8cant progress has been made in thecontrol of TB in developed countries+ this communicable disease has not yet beeneradicated( Hurthermore+ children with primary tuberculous infection are the reservoir fromwhich future cases will emerge(

Ene of the maOor practical problems in diagnosing TB in children is that isolation ofMycobacterium TB from gastric aspirates or sputum is dicult <N?( putum for acid-fast stainand culture is rarely available from infants and children( Eptimal collection of gastricaspirates requires hospitali*ation to sample the swallowed secretions that accumulateovernight( /owever+ the sensitivity of acid-fast stain for gastric contents is usually below

=45( The low yield of positive cultures from gastric aspirates is a result of the small numberof organisms in primary TB in childhood and possible inadequate techniques for collection ofgastric washings( Therefore+ the diagnosis is frequently based solely on detecting typicalradiographic abnormalities in a child with a reactive tuberculin s,in test and with history ofcontact of an infectious case( The Mantou" method is helpful in supporting the diagnosis(#lthough a reaction of P=4 mm induration is the usual cut-point for de8ning a signi8cantreaction+ a reaction of P7 mm is considered signi8cant for symptomatic children and forrecent contacts with infectious cases <3?( /owever+ a negative reaction in a child who hassigns and symptoms compatible with TB does not rule out the diagnosis( 6n the presentseries+ indurations ranged between 3 and >N mm(

'ymphadenopathy+ with or without parenchymal abnormality+ is the radiologicalhallmar, of primary TB in children <=4?( Children less than A years of age show a higherprevalence of lymphadenopathy and a lower prevalence of parenchymal abnormalitiescompared with children :=7 years <7?( 6n early childhood+ lymphadenopathy as the soleradiological manifestation of disease was seen in 35 of cases versus 35 in late childhoodand adolescence according to data reported by 'eung et al( <==?( Bronchi in infants are ofsmaller calibre and more easily compressed by enlarging hilar lymph nodes( #s the hilarlymph nodes enlarge+ bronchial obstruction may occur and signs of air trapping maydevelop( #lthough hilar lymphadenopathy may be the only suggestive 8nding of TB in thechest radiographs+ in the present study+ 11(95 of patients with chest radiographsconsidered unrevealing showed mediastinal lymphadenopathy in the ultrasounde"amination( 'ymph nodes can sometimes be dicult to visuali*e on frontal plainradiographs( Eccasionally+ lymphadenopathy is visible only on the lateral 8lm <=>?( #pical-lordotic views may aid in visuali*ing lesions obscured by the heart( @hen nolymphadenopathy is present on the standard radiographic e"amination of the chest+ specialimaging techniques such as CT may be of particular value <=A?( 6t has been shown that CTscan may reveal mediastinal adenopathies which are not evident on the chest radiograph<1?( 0ltrafast CT scanning+ however+ is costly+ not available in many institutions+ includesradiation+ and may require the use of sedation in young children( 6n contrast+ 0 is much lesse"pensive+ the use of sedatives or contrast medium is not necessary+ and can be easilyobtained both in the hospital and in primary care settings( #lthough subcarinal adenopathyhas recently been reported to be the most common site of lymphadenopathy in children with

TB <=?+ we have detected small adenopathies more frequently in the paratracheal regionand aortopulmonary window because of a better echographic access( 6n the subcarinalregion+ we have documented large lymph nodes due to limitations in the echographic accessand artifacts e(g(+ the oesophagus.(



#s far as we are aware+ no previous study regarding the usefulness of mediastinalultrasonography for the diagnosis of lymphadenopathy in TB in children has been published(Hor this reason+ the present results cannot be compared to those reported by others(

Conclusions6n the present series of A> patients with positive tuberculin s,in test+ 34(75 of those

with chest radiographic images compatible with TB had coincident 8ndings in themediastinal ultrasonographic study( En the other hand+ 11(95 of those with normal chestradiography had evidence of mediastinal lymphadenopathy on 0( 6n all cases but one+ 0and CT 8ndings agreed( 6n view of the usefulness of 0 of the mediastinum for the diagnosisof lymphadenopathy in children with TB+ this non-invasive method could also be of value inthe control and follow-up of children receiving antituberculous chemotherapy(

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