A 93-year-old Japanese man who presented with gluteal and coccygeal pain was referred to our hospital. Furthermore, discharging were observed in his fistula in the posterior peri-anal region. He had neither fever nor respiratory symptoms.
He had history of pulmonary TB at 25 years of age, and underwent surgery for the removal of complex anal fistula at 75 years of age at another institution.
Based on clinical examination, there were two fistulous orifices between the anus and coccyx with purulent discharge (Fig. 1). He did not present with cough, fever, weight loss, and anorexia. The chest radiograph result was normal, and hematologic examination showed no abnormalities, except for a slight elevation in C-reactive protein level.
Fistulography showed a complex supra-elevator track that is connected to the pre-sacral area and another track ending blindly behind the rectum. The connection between the track and the rectum or anus was not identified on fistulography (Fig. 2). A computed tomography (CT) scan of the whole body reveled a lytic destruction of the sacrum (S3-5) and coccyx, with a low-density area in front of the sacrum, suggesting fluid collection (Fig. 3A). No abnormality was found in the lungs and other vertebrae on CT scan. Colonoscopy findings showed normal colorectal mucosa and no evidence of fistula.
Based on these radiological findings and the past medical history of the patient, the recurrence of complex anal fistula with osteomyelitis, or metastatic bone tumor of unknown origin, was suspected.
Bacterial examination of the fistula discharge showed normal bacterial culture and was negative for acid-fast bacilli (AFB). However, real-time polymerase chain reaction (PCR) using COBAS TaqMan MTB test (Roche Molecular Systems, the USA) was used to test the cold abscess fluid, and results showed that the patient was positive for Mycobacterium tuberculosis. AFB test and PCR were negative for sputum. However, the T-SPOT.TB (Oxford Immunotec, the UK) blood test result was positive. Thus, the diagnosis of isolated sacrococcygeal TB was confirmed.
The patient was treated with rifampicin, isoniazid, and ethambutol for 2 months, followed by rifampicin and isoniazid for 7 months. The patient's pain resolved, and the purulent drainage stopped within the first 2 months of treatment. Based on the physical findings, closure of the fistula was not achieved. However, the PCR test result for PCR DNA turned to be negative. A follow-up CT scan was carried out during treatment, and results showed that fluid collection in front of sacrum had disappeared (Fig. 3B).