The role of bronchoscopy in childhood tuberculosis
Lionel Donato – Clément Ammouche
Hôpitaux Universitaires de Strasbourg (France)
In children, primary tuberculosis clearly differs from the forms found in adults.
Diagnosis and management guidelines should not be extrapolated. Although a key
element in the diagnosis, mycobacteriological identification is seldom achieved in
children. The younger the patients, the more significant the mediastinal involvement.
Substantial airway obstruction sometimes requires specific therapeutic procedures.
The flexible bronchoscope (FB) is usually employed for bacteriological sampling
purposes and for the assessment and follow-up of endobronchial tuberculosis (ETB).
The rigid tube is more suitable for endobronchial debulking maneuvers. Current
indications for bronchoscopy in childhood TB remain controversial. They obviously
depend on the skills and habits of the endoscopist but also on the institutional
environment, available modalities of sedation, paediatric anesthesiologists, dedicated
bronchoscopy suite and equipment. Technological advancements in the imaging
techniques also tend to balance the indications.
FB is useful too when the diagnosis is unclear, as TB can mimic other conditions
such as asthma, pneumonia, inhaled foreign bodies, and congenital malformations.
More specifically, ETB is an endoscopic differential diagnosis of foreign body
inhalation when substantial granuloma formation is generated.
Mycobacteriological studies:
Mycobacteria detection and isolation can be challenging in children with pulmonary
TB. Whatever the specimen collection methods the overall identification rate is poor,
partly due to the low density of bacilli but also in relation to the fact that toddlers and
preschools have no spontaneous ability to expectorate. Patients with latent forms are
usually culture negative. Bacterial sampling is systematically performed in children
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with a more patent disease (i.e. with clinical or radiological manifestations) in order
to:
-
apply rapid diagnostic tests: i) in patients with confusing symptoms; ii) when
resistant strains are suspected in the contamination source
-
evaluate the patient’s infectivity (presence of acid-fast bacilli on smears;
bacterial density semi-quantitative estimation)
-
obtain cultures to identify the strains and to establish an antibiogram (drug
resistance ?)
Unfortunately, these goals are difficult to achieve. Repeated gastric aspirates have
been described as the gold standard for specimen collection since children swallow
rather than expectorate sputum. The yield of this method has been demonstrated
superior to the one of bronchoalveolar lavage (BAL) [1]. Sputum induction, stimulated
by hypertonic saline nebulization, is proposed as an efficient and low-cost alternative
to include the youngest patients. Yet some authors counterbalance its advantages
with the increased risk of transmission due to induced coughing and the spreading of
droplets, requiring respiratory protection measures that may not be available in many
resource-limited
regions.
Other
methods
include
bronchial
brushing
and
transbronchial needle aspiration biopsy (TBNA), but there is quite no data in the
pediatric literature. Several studies have compared the performances of selected
collection methods but no global analysis is available regarding the advantages vs
drawbacks in the whole set. Choosing the most appropriate one depends on various
factors including the geographical burden of the disease and economical constraints.
Compared to gastric aspirates and induced sputum, the yield of BAL has been shown
to be very low when performed in unselected cases [2]. This is not surprising in
paucibacillary latent TB with minimal parenchymal involvement and intact mucosa.
Moreover the BAL procedure is usually performed only once and the specimen
collection involves a very limited area of the lungs. The sensitivity of BAL is higher in
the active forms of the disease and is manifold increased when DNA amplification
methods are applied [3]. Although never demonstrated it is clear that BAL sensitivity
is maximal when directly performed on visible mucosal changes (ulcerations,
caseating lesions) or into large parenchymal infiltrates guided by chest CT-scan.
Finally, combining different sampling methods increases the overall detection rate.
For instance, gastric aspirates obtain an advantage by being scheduled on the days
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immediately following bronchoscopy, as the procedure itself improves the
bacteriological yield of gastric specimens [4].
In our experience, BAL can demonstrate co-infection with usual microorganisms such
as Haemophilus influenzae particularly when ETB lesions are observed. This could
explain the fact of why some children with primary TB temporarily improved with nonspecific antibiotics, have delayed diagnosis.
Although traditionally considered dangerous in toddlers, TBNA is in fact feasible
provided it is guided by careful CT study of the mediastinum (fig.1). The place of the
procedure remains to be specified; it could be an option to a surgical approach when
facing mediastinal lymphadenopathy of an unknown nature; or when central necrosis
is seen on a chest CT-scan but where cultures are negative. Indications are still very
few but probably underestimated.
Endobronchial tuberculosis assessment:
In untreated toddlers, tuberculous mediastinal lymph nodes behave like locally
spreading malignant tumors. Dissemination follows the lymphatic ways; the nodes
have the potential of invading any adjacent structure with preferential tropism to the
central airway. ETB bronchoscopic findings can be classified as follows:
-
extrinsic compression: mild < 50%; severe > 50%.
-
bronchial wall invasion with mucosal inflammatory changes and edema;
granuloma formation; mucosal ulceration and perforation (caseating matter
emission).
-
long-term after-effects: scar fistula orifice, single or complex; bronchomalacia
due
to
cartilage
destruction;
circumferential
stenosis;
and
ultimate
bronchiectasis development.
There is an unresolved debate on the respective place of radiology vs endoscopy in
detecting endobronchial involvement. Several semi-recent publications focus on
underestimation by X-ray – including chest CT-scan – compared to flexible
bronchoscopy [2]. Nevertheless these studies provide little information about the
usefulness of detecting minor lesions, as this does not modify the treatment regimen.
More recent radiological techniques using 3D-rendering methods allow accurate
detection of ETB, thus potentially restricting the need for FB examination [5].
However there is a serious limitation regarding dosimetry when serial studies are
needed in children with active disease.
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The following principles are still widely admitted:
1. in children with no symptoms and normal chest X-ray there is no need for
additional investigation if the diagnosis is made clear.
2. CT-scan is indicated first when the chest X-ray demonstrates hilar
enlargement or mild parenchymal involvement; FB is next discussed if
bronchial wall abnormalities or airway patency impairment are suspected.
3. CT-scan and bronchoscopy are both performed in the case of huge
lymphadenomegaly, atelectasis or emphysema, and extended parenchymal
infiltrates.
4. FB is indicated whatever the radiological status when bacteriological studies
are positive.
There is a large agreement for early detection of ETB in order to prevent late
sequelae. Antituberculosis drugs show variable effect on lymph node volume;
significant enlargement remains sometimes visible for several years irrespective of
the antibacterial efficacy. Systemic corticosteroids are added to the 3 or 4 drugs
regimen at the early phase of the process when severe extrinsic compression or
endobronchial granulation are observed. Serial FB examinations are carried out in
order to assess the response - ranging from one to several weeks - and to keep an
eye on the occurrence of fistulization that can be promoted by steroids. Failure or
worsening lead us to consider interventional procedures in order to restore the airway
patency.
Interventional bronchoscopy:
Intractable airway obstruction can produce definitive pulmonary destruction. Surgical
adenotomy has been proposed in order to relieve compression but carries the risk of
severe postoperative complications. Tuberculous-infected tissues are weak in nature,
bleed easily and show a strong tendency to break in the adjacent connective
structures (including vessels) with no clear cleavage plane. Impairment of nutritional
status often acts as a pejorative factor. Therefore, endoscopic debulking should
always be attempted first.
FB is not the most appropriate tool for this purpose except for suctioning mucus or
caseum plugs. The rigid bronchoscope can be used by itself as a mechanical drill, by
rotating and guiding the bevel through the narrowing structure. Various working
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instruments can be passed through the tube including endoscopic forceps and
scissors, suction tubes, balloon-catheters, electrocautery probes, and laserconducting optical fibres. Purely mechanical disobstruction maneuvers have the
drawback of poor visualization due to induced bleeding and carry the risk of
imprecise tissue resection (wall laceration, perforation, vascular injury). Interestingly,
some laser beams exhibit specific properties that fit these constraints. The CO2 laser
is one of them but it is cumbersome for use into the lower pediatric airway. In our
experience the KTP laser is more suitable as the beam is carried on by optical fibres,
the contact of which causes soft tissue coagulation and necrosis with shallow
penetration and very precise cutting action (fig.2). Moreover the KTP wavelength
interacts specifically with hemoglobin and thus provides perfect hemostasis. It is
therefore a choice piece in the endoscopic armamentarium, allowing accurate
photoresection of obstructive granulomas including tuberculous ones [6].
Cicatricial
stenoses
can
be
dilated
using
long-shape
balloon
catheters.
Tracheobronchial stenting for post-tuberculous bronchomalacia has already been
described but only in adult patients.
References:
1. Abadco DL, Steiner P. Gastric lavage is better than bronchoalveolar lavage
for isolation of Mycobacterieum tuberculosis in childhood pulmonary
tuberculosis. Pediatr Infect Dis 19992;11:735-8.
2. Bibi H, Mosheyev A, Shoseyov D et al. Should bronchoscopy be performed in
the evaluation of suspected pediatric pulmonary tuberculosis ? Chest
2002;122:1604-8.
3. Gomes-Pastrana D, Torronteras R, Caro P et al. Diagnosis of tuberculosis in
children using a polymerase chain reaction. Pediatr Pulmonol 1999;28:34451.
4. Singh M, Ashan Moosa NV, Kumar L et al. Role of gastric lavage and
broncho-alveolar lavage in the bacteriological diagnosis of childhood
pulmonary tuberculosis. Indian Pediatr 2000;37:947-51.
5. Arlaud K, Gorincour G, Bouvenot J et al. Could CT scan avoid unnecessary
flexible bronchoscopy in children with active pulmonary tuberculosis ? A
retrospective study. Arch Dis Child 2010;95:125-9.
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6. Donato L, Tran TMH, Mihailidou E. Interventional bronchoscopy. In Priftis KN,
Anthracopoulos MB, Eber E, et al (eds). Paediatric bronchoscopy. Prog
Respir Res. Basel, Karger 2010, vol.38 pp 64-74.
Legend of figures:
Figure 1: Intermediate bronchus obstruction in an 18-month-old child with
primary tuberculosis
a. subcarinal enlargement with no contrast enhancement; note the central
necrosis into the lymph nodes and the close relationship with the right
pulmonary artery (anterior).
b. fine needle puncture through a rigid tube; the child is supine and the right
mainstem is right-sided on the picture; the needle is carefully kept away from
the anterior wall.
Figure 2: endoscopic laser photoresection of tuberculous lymphadenopathy
a. complete bronchus obstruction with right middle and lower lobes atelectasis
b. bronchus recanalization leading to right lung reventilation; the KTP fibre can
be seen at the bottom of the endoscopic picture (green light).
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