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A man with abdominal pain

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Q1: What does the chest radiograph show (fig 1 in questions, p 741)?

Figure 1

 Pathway of steroid hormone synthesis.

The chest radiograph shows a homogenous round opacity in the left upper zone with erosions of the second, third, and fourth ribs.

Q2: What are the findings on computed tomography of the chest (fig 2 in questions; p 741)?

Chest computed tomography reveals erosion of the second, third, and fourth ribs with soft tissue mass in the extrapleural space. In addition there is erosion of thoracic vertebrae. Differential diagnosis includes secondaries in the rib and tuberculosis of the rib with an abscess in the extrapleural space.

Q3: What are the findings on computed tomography of the abdomen (fig 3 in questions; p 741)?

Abdominal computed tomography shows erosion of the lumbar vertebrae, with bilateral thick walled cysts suggestive of bilateral psoas abscess. Aspiration of the abdominal cyst revealed turbid straw coloured fluid with a protein content of 76 g/l. Staining for acid fast bacilli was negative and cytology showed few lymphocytes in an eosinophilic background. At thoracotomy, a tumorous mass (fig 1 below) measuring 10 × 10 cm was seen adherent to the second, third, and fourth ribs on the left side with mass effect on the upper lobe of the lung. Cut section was fleshy. Histology confirmed a tuberculous granulomatous lesion; acid fast bacilli were identified.

The patient was started on isoniazid, rifampacin, ethambutol, and pyrazinamide. There was significant improvement in the general condition within one month of initiation of treatment, with spontaneous regression of the cystic swelling of the abdomen.

Discussion

Bone and joint tuberculosis is a common form of extrapulmonary tuberculosis and takes fourth place among all sites.1 In spinal tuberculosis, thoracic and lumbar spine are the most frequent locations.2 Rib tuberculosis is an uncommon form of osteoarticular tuberculosis2and constitutes 5% of all cases of bone and joint tuberculosis.3 The case reported has tuberculosis involving the rib and lumbar vertebrae with bilateral psoas abscess.

Skeletal tuberculosis may occur as a progressive primary infection particularly in children or as reactivation of a quiescent primary focus after immunosupression.4 It is the foremost inflammatory process affecting the ribs.3 In the thoracic region, the lung may be invaded through adhesions of pleura.5 In the lumbar region, cold abscess can collect beneath the psoas fascia, iliac muscle and this can extend to inguinal region beyond the inguinal ligament.

The onset of musculoskeletal tuberculosis is usually insidious and local pain is the most common and earliest symptom followed by impairment of function and swelling. A painless cold abscess may be the only presentation, as was seen in the present case. A single site of tuberculous involvement is the rule; multiple locations are rare6 and it is common in the immunocompromised state.7

The combination of rib destruction and an extrapleural rib soft tissue opacity makes tuberculosis a highly likely diagnosis.8 The rib erosion and the soft tissue mass closely simulates secondaries of the rib. In a report by Adil et al, two of their four patients had a pseudotumorous lesion.9

Computed tomography of the chest is useful in diagnosis of osseous tuberculosis. Bone sclerosis, associated soft tissue abscess, osteolytic lesion, and a sequestrum suggests chest wall tuberculosis.10 Twenty five percent of computed tomography guided biopsy specimens from bony elements, contiguous pleura, and paraspinal masses were non-contributory in a series reported by Ali et al.11 In a study by Omari et al, 50% of biopsy samples were positive for acid fast bacilli; 64% had granulomatous lesions on histopathological examination.12 Fine needle aspiration cytology from lesions is not always diagnostic. In the present case, aspiration from the psoas abscess was negative for acid fast bacilli. The histopathological and microscopic examination of the biopsy material from the rib cage confirmed the diagnosis of tuberculosis.

Surgery has a limited role in the management of osseous tuberculosis. It is often indicated for correction of neurological deficit, spinal instability/deformity, or for draining an abscess not responding to treatment.11 At times it is indicated for confirmation of diagnosis, as was necessary in the present case.

In summary, while evaluating a patient with a destructive spinal lesion, there should be a heightened index of suspicion for spinal tuberculosis. Rib tuberculosis can present as a pseudotumorous lesion.

Final diagnosis

Multiple osseous tuberculosis.

References

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