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Case Report | Discussion

Case report:

A 35 year-old-man, truck driver by profession, who was a known alcoholic and chronic smoker, also gave history of exposure to unprotected intercourse. He presented with sudden onset right sided chest pain, breathlessness , accompanied by high grade fever and cough since the past one week.

On examination, he was found to have decreased air entry on the right side.

The frontal chest radiograph showed mediastinal widening with a minimal, right-sided pleural effusion. The lung fields were clear.

Fig 1

In view of the acute presentation, the patient was suspected to have spontaneous esophageal rupture, which was ruled out by contrast study of the esophagus, which showed no leak.

An ultrasound of the abdomen and chest revealed a loculated pleural effusion on the right side with splenomegaly. The loculated effusion was aspirated under ultrasound guidance, which showed straw colored fluid , which was then sent for histopathology and biochemistry.

A CT scan of the chest showed multiple hypodense collections in the right hemithorax, which appear to be sub pleural. They are loculated and show an uniform wall. There is no abnormal enhancement. Underlying lung parenchyma appears normal.

Fig 2

Fig 3

This was diagnosed as a mediastinal collections of indeterminate etiology and percutaneous pigtail (8F) catheter drainage was done under CT guidance. Approximately 450cc was drained.

Fig 4

A follow up CT scan performed after two days revealed recurrence of the collection with pigtail seen insitu.

Fig 5

Fig 6

Cytological studies of the fluid were negative for pus cells, organisms and malignancy.

However, adenosine deaminase levels were 41.6 IU/L (normal 36 IU/L) and the patient tested positive for HIV.

Thus we arrived at a diagnosis of atypical presentation of tuberculosis in an immunocompromised patient presenting as a mediastinal abscess.

Discussion

Tuberculous infection is an important cause of morbidity and mortality in an immunocompromised patient especially those infected with HIV.

Radiographic findings mimic reactivation tuberculosis. Reticulonodular opacities are present in the apical and posterior segments of the upper lobes or superior segments of the lower lobes. Cavitation and necrotic mediastinal lymphadenopathy are often present.

Mycobacterium presentation during advanced HIV infection, resembles primary tuberculosis.

In a small percentage of patients, the presentation may be of miliary tuberculosis due to hematogenous spread of tuberculosis.

Among patients infected with HIV, unifocal or multifocal alveolar infiltrates and mediastinal lymph adenopathy are the most common manifestations.

However, unusual radiographic manifestations of tuberculosis are more common in the immunocompromised patient, than in the general population.

Abscesses in the mediastinum usually result from downward extension of an abscess in the neck, perforation of the esophagus or rarely from perforation of the trachea or by direct extension from lung abscesses. Osteomyelitis of the spine, upward extension of a retroperitoneal abscess almost always produce absesses in the posterior mediastinum.

Anterior displacement of the trachea is clearly demonstrable on lateral views of the neck, which disclose a widening of the prevertebral space.

Mediastinal abscesses in the lower mediastinum are almost always due to perforation or spontaneous rupture of the esophagus. In which case the mediastinum abscess often show a fluid level, which can be differentiated from a hiatus hernia by a barium swallow. In the absence of a fluid level, an abscess needs to be differentiated from a paramediastinal effusion unless it extends on both sides.

An abscess confined to the mediastinum rarely shows a fluid level, however fluid level may be present once the abscess perforates into the lung.

Perforation of a mediastinal abscess into the pleura results in a pyopneumothorax or an empyaema, which can become chronic. A persistent sinus may form following drainage of the empyaema because of underlying infection in the mediastinum.

Besides appropriate anti tuberculous treatment, percutaneous abscess drainage is beneficial for accelerated symptomatic relief.