Tuberculous empyema

Clinical History

A patient presented with a two-week-history of a cough, pyrexia, poor appetite and vomiting.

Imaging Findings

This 2 year and 10 month old girl presented initially to her GP with coryzal symptoms for which she was put on a course of Amoxycillin. Her cough and pyrexia persisted, and she became anorexic. She was admitted to the hospital, where administration of intravenous Cefuroxime was started, and she was then transferred to this hospital for further treatment and investigation, as she was found to have a large right pleural effusion. In the previous 14 months, she had been in contact with two adults, who had proven to have active pulmonary tuberculosis (TB). After the initial contact, she had 2 normal chest X-rays (CXR) taken, a Grade II Heaf test was done and she was treated prophylactically with Rifampicin. After the second contact, she had again undergone a normal CXR examination and a Grade II Heaf test and she was not given prophylactic treatment. After being transferred, she was found to be feeling miserable, pyrexial, with cervical lymphadenopathy and had a reduced air entry with a dull percussion note at the right base. Computed Tomography (CT) was performed, which showed a large right sided higher attenuation pleural effusion (Hounsfield Units 20-25), as well as a partial collapse and consolidation of the right lower lobe. Two soft tissue nodules were seen within the left lower lobe, one of which was pleural based, and superior mediastinal lymphadenopathy was also noted. The CT findings, along with a positive Mantoux test, helped diagnose TB empyema as a very likely cause. She underwent Video Assisted ThoracoScopic (VATS) drainage of her pleural effusion on the same day. Follow-up CXRs showed a diminished right sided pleural effusion and improved aeration of the right lower lobe. She was discharged 9 days after surgery, and was put on anti-tuberculous medication and is being followed up in the outpatient ward.

Discussion

Out of all new cases of TB, 5%–6 % are seen in patients under the age of 15 years. Sixty percent of these are observed in children under the age of 5 years, with a significant number occurring in immunocompromised children. Annually, TB accounts for nearly half a million paediatric deaths worldwide. Most children are infected by an infected adult carrier, rather than the infection spreading from one child to another, and it is postulated that this is so because children produce less sputum. Approximately 76% of primary TB infection is pulmonary, whereas only 3.3% is pleural. Primary infection can be split into 5 different groups depending on the clinical and radiological findings. Group 1: asymptomatic patients, when a 'routine' skin test when done is positive. The child is usually keeping well, and the CXR is likely to be normal. Group 2: Endobronchial TB, when the child presents with symptoms similar to another child with an inhaled foreign body. This is either due to compression of bronchi by lymphadenopathy or an endobronchial granuloma. The CXR will show signs of air trapping or atelectasis and possibly lymphadenopathy. Group 3: Pleural involvement. These children are usually over 2 years old and present with fever, signs of pneumonia and chest pain. CXR findings include pleural effusion and a primary parenchymal lesion. CT is helpful in distinguishing between exudate and transudate, by measuring the Hounsfield Units (HU) of the effusion. In our case, the HU of the effusion was consistent with an exudate. A further biochemical analysis was supportive of this, with a high LDH and protein value, and few organisms seen within the fluid. Other biochemical tests that can be used are those that measure the lysozyme and ADA (adenosine deaminase) levels which are usually high in a TB exudate. Group 4: Progressive primary pulmonary TB when caseation and rupture of the primary focus occurs. The child is unwell and the CXR shows parenchymal lesions as well as lymphadenopathy. Group 5: Miliary TB, when the primary TB reactivates and disseminates with a typical CXR showing multiple small nodular opacities throughout the lungs, sometimes with mediastinal and/or hilar lymphadenopathy. Imaging in those patients with pleural TB is mainly achieved using plain radiography in the first instance, which will show the effusion, as well as any lung parenchymal involvement or lymphadenopathy. An ultrasound examination can be helpful in detecting loculated effusions, another sign that the effusion is likely to be exudative, and also in marking the site for drainage or aspiration, if required. More frequently, particularly when there is suspected exudative effusion, surgical drainage, either open or VATS, which is used more commonly nowadays, is performed. This is followed by a CT to determine the effusion size and HU and to look at the rest of the lungs. MRI is not often used in this context, because although the effusion is seen clearly, the lung parenchyma is not visualised clearly enough. Nuclear medicine is not an imaging technique used in cases of pleural tuberculosis. It is actually to be used only where there suspected bony TB involvement.

Differential Diagnosis List

Final Diagnosis

Tuberculous empyema.

URL:	https://www.eurorad.org/case/3141
DOI:	10.1594/EURORAD/CASE.3141
ISSN:	1563-4086