Discussion
In the present review, we summarize the safety and diagnostic utility of the minimally invasive endosonographic modalities, EBUS-TBNA and EUS-B-FNA in children. We found that EBUS-TBNA and EUS-B-FNA have an excellent safety profile as the major complication rate is minimal. The overall diagnostic yield (61%) is similar to the diagnostic yield of EBUS-TBNA in adults in real-world settings.(21) The excellent sampling adequacy has important clinical relevance. The findings highlight that when used as first-line investigations for evaluation of mediastinal lymphadenopathy in children, invasive surgical procedures may be avoidable in a majority of them.
Wurzel et al. reported the first case of EBUS TBNA in children using an adult EBUS-TBNA bronchoscope (2009), for the diagnosis of Sarcoidosis. (7) After this, few studies and case reports have highlighted the use of broncho-endosonographic modalities in children and interest in this field has grown. There are particular concerns regarding the use of EBUS-TBNA and EUS-B-FNA in children. The available EBUS bronchoscopes have an outer diameter of 6.9 – 7.4 mm. Recently, a thinner EBUS bronchoscope has become available (6.3 mm diameter). The diameter of all the available EBUS scopes is larger than that of the conventionally used flexible bronchoscopes in children (usually 2.8-4.2 mm). Therefore, the performance of EBUS-TBNA is challenging in younger children with a smaller trachea.(16) Introduction of the EBUS bronchoscope through the oesophagus to perform mediastinal lymph node aspiration, a technique described as transesophageal bronchoscopic ultrasound-guided fine-needle aspiration (EUS-B-FNA) approach has been one of the most significant additions for pediatric mediastinal lymphadenopathy. (6) The first description of this modality in children was to sample the subcarinal lymph node in a 3-year-old child. (16) EUS-B-FNA allows successful sampling from oesophagal accessible lymph node stations (like subcarinal, lower left paratracheal and para-oesophagal) in children as young as one year.(17) This approach has the advantage of being complementary to the traditional EBUS and can be the sole approach in small children. Avoidance of tracheal entry during EUS-B-FNA minimizes the risk of impairment of ventilation and desaturation. The available literature suggests that traditional adult EBUS scopes can be easily used through the tracheal route in children more than 12 years of age or weighing more than 50kg.
Sedation and anaesthesia constitute an essential aspect of optimization of procedure comfort. In adults, EBUS-TBNA is routinely performed under moderate sedation, although deep sedation/GA is optional. In children, ensuring adequate anaesthesia is vital for safety and procedural success. As the scope for error during needle manipulation during sampling is minimal, a comfortably sedated child with proper ongoing ventilation is ideal. The sedation practices reported in the studies on EBUS in children are varied. While many operators have used general anaesthesia, studies have shown that the procedure can be very well be performed using moderate to deep sedation without an artificial airway.(13) While using general anaesthesia, either an LMA (laryngeal mask airway) or an endotracheal tube may be used. The diameter of the EBUS scope varies from 6.3–7.4 mm, hence the minimum size of endotracheal tube required for easy passage of the scope would be around 8 mm. This could be problematic in small children. Also, the use of an endotracheal tube may cause difficulty in accessing the upper and lower paratracheal lymph nodes.(14) An appropriately sized supraglottic airway (Laryngeal Mask Airway) can help circumvent this problem. The minimum size of the LMA recommended is 2.0 (IGel LMA). While using an artificial airway, the scope may be required to be removed intermittently to enable ventilation. While using general anaesthesia, inhalational sevoflurane and neuromuscular blockade using intravenous atracurium can be used. (18) Administration of anaesthesia and monitoring by a trained anesthesiologist is ideal.
Various gauge EBUS-TBNA needles are available like 21G, 22G, 19G and 25G. Most of the published literature in children describes the use of either a 21G or a 22G needle. The reported yield of either of the two needles in adults is similar. 19 G needles may allow one to obtain larger specimens. However, currently, no data is available with the use of 19G and 25G EBUS-TBNA needles in children. We believe that Rapid on-site evaluation (ROSE) by a pathologist is ideal during EBUS-TBNA/EUS-B-FNA in children as it may allow minimization of needle punctures and reduce the total duration of procedure thereby minimizing the duration and risks of anaesthesia.
EBUS was developed in adults mainly for staging and diagnosis of lung cancer. However, since then, the diagnostic utility of EBUS is established in many other benign diseases like Sarcoidosis. In children, tuberculosis and lymphoma constituted the two most common pre-clinical diagnosis. EBUS-TBNA has excellent diagnostic performance for Tuberculous mediastinal lymphadenopathy. (22) EBUS-TBNA can be a useful initial minimally invasive diagnostic modality in lymphoma if it is combined with immunophenotyping and molecular analysis. (23)
The pooled diagnostic yield of EBUS-TBNA in the meta-analysis was 61% which approximates the diagnostic yield of EBUS-TBNA in adults (around 63%) in real-world settings. (21) The excellent sampling adequacy (98%) signifies that representative lymph nodal tissue is nearly always obtained. The data for determination of sensitivity, specificity, positive and negative predictive values and diagnostic accuracy were not provided in any study due to lack of a detailed follow-up. Gilbert et al. reported that EBUS TBNA helped in avoiding invasive surgical biopsy in 62% of cases. (15) In addition to the risk of complications, invasive procedures entail more cost.
Overall endosonographic procedures (EBUS-TBNA/EUS-B-FNA) have an excellent safety profile and favourable cost-benefit. The complication rate is low, approximately 0.05%. (24) Although EUS-B-FNA is complimentary to EBUS TBNA, it has a small risk of oesophagal perforation (0.02%) which may occur due to puncture of the node as the needle traverses the oesophagal wall. (25) Ideally, these procedures in children should be performed by experienced bronchoscopists who are regularly performing these procedures in adults. Paediatric bronchoscopists can quickly gain skills in this modality with training.