Endoscopic ultrasound features of mediastinal tuberculosis

We read with interest the article by Fritscher-Ravens et al. [1] on the utility of endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) in differentiating between tuberculosis and sarcoidosis in patients with granulomatous mediastinal lymphadenopathy. We compliment the authors for conducting such a good study and agree with them that EUS-FNA has a high diagnostic yield for mediastinal tubercular lymphadenopathy; this has also been our experience [2] [3]. Also the ability of EUS-FNA to differentiate between sarcoidosis and tuberculosis, both granulomatous diseases, would be of great help for clinicians treating these two diseases that require different therapies.

We also read with interest about the echo features on EUS that could help in differentiating tubercular lymphadenopathy from nontubercular causes of lymph node enlargement. Fritscher-Ravens et al. [1] reported that tubercular lymph nodes were significantly smaller than the lymph nodes seen in sarcoidosis. There were inhomogeneous hyperechoic areas with or without acoustic shadowing in the lymph nodes in patients with tuberculosis, while none of the patients with sarcoidosis had these features. In our study, we compared the EUS features of mediastinal lymph nodes in 22 patients with tuberculosis with those in 20 patients with nontubercular mediastinal lymphadenopathy [2]. However, in our study there were only three patients with sarcoidosis. We found that there was no significant difference in the size of mediastinal lymph nodes between tubercular and nontubercular etiology. Hyperechoic foci in the lymph nodes were seen in 77.2 % of patients with tubercular mediastinal lymphadenopathy and in 5 % of patients with nontubercular mediastinal lymphadenopathy (P = 0.00) ([Fig. 1]).

Fig. 1 Endoscopic ultrasound (EUS) showing hyperechoic foci in the tubercular lymph node.

Patchy anechoic or hypoechoic areas were seen in 40.9 % patients with tubercular mediastinal lymphadenopathy whereas none of the patients with nontubercular mediastinal lymphadenopathy presented these (P = 0.01) ([Fig. 2]).

Fig. 2 a, b Endoscopic ultrasound (EUS) showing patchy hypoechoic areas in tubercular lymph node.

By aspirating caseous material from these patchy anechoic or hypoechoic areas we also demonstrated that they represented caseous necrosis in the lymph nodes. Also acid-fast bacillus (AFB) positivity on cytological examination was observed in aspirates from these patchy anechoic areas suggesting that they could probably be the sites of active multiplication of Mycobacterium tuberculosis. The hyperechoic foci probably represent speckled calcification or patchy fibrosis in the lymph nodes. However histopathological studies are needed to confirm the histopathological counterpart of the hyperechoic foci on EUS in mediastinal lymph nodes.

Therefore, it appears that patchy anechoic or hypoechoic areas and hyperechoic foci in the mediastinal lymph nodes on EUS are important signs of mediastinal tubercular lymphadenopathy, and EUS-guided FNA is a useful modality for diagnosis of mediastinal tuberculosis.

References

• 1 Fritscher-Ravens A, Ghanbari A, Topalidis T et al. Granulomatous mediastinal adenopathy: can endoscopic ultrasound-guided fine-needle aspiration differentiate between tuberculosis and sarcoidosis?.  Endoscopy. 2011;  43 955-961
• 2 Rana S S, Bhasin D K, Srinivasan R et al. Endoscopic ultrasound (EUS) features of mediastinal tubercular lymphadenopathy.  Hepatogastroenterology. 2011;  58 819-823
• 3 Rana S S, Bhasin D K, Sharma V et al. Dysphagia as the first manifestation of tuberculosis.  Endoscopy. 2011;  43 Suppl 2 UCTN E300-E301