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Unexplained weight loss and a palpable abdominal mass in a middle aged woman

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Q1: What does the barium enema study (figs 1 and 2; p 341) show?

A small bowel study showed normal stomach and upper small bowel and a somewhat featureless terminal ileum. The caecum and right hemicolon appeared abnormal and a barium enema was suggested. The barium enema (figs 1 and 2) shows classic radiographic features of ileocaecal and colonic tuberculosis1 confirming a diffusely abnormal terminal ileum with a long stricture affecting the caecum, ascending colon, and proximal portion of the transverse colon with shortening of these bowel segments. The left hemicolon appears normal.

Q2: What is the differential diagnosis and what test should be performed to confirm the diagnosis?

The main differential diagnosis is between ileocolonic Crohn's disease or tuberculosis. While an intestinal lymphoma or colonic malignancy could produce similar radiological findings, the extent of the colonic involvement in a relatively asymptomatic patient is against these. Other infections—for example, gastrointestinal amoebiasis, actinomycosis or yersinia, though rare, are possible causes.

The patient was further investigated with a colonoscopy. This revealed ulceration and narrowing at the level of the mid-transverse colon that could not be crossed. Biopsy samples were taken both for standard histological assessment and for tuberculosis culture. Haematoxylin and eosin stains of the biopsy samples showed acutely inflamed granulation tissue but normal underlying colonic mucosa with no evidence of an underlying inflammatory bowel disease, infection or neoplastic process. Ziehl-Neelsen stains were negative for acid-fast bacilli; however, three weeks following the colonoscopy a positive tuberculosis culture was reported. Mycobacterium tuberculosissensitive to isaniazid, rifampicin, and ethambutol was grown.

Q3: What treatment would you initiate?

The treatment of Crohn's disease and abdominal tuberculosis differ widely. Blind treatment with steroids may lead to deterioration in a patient with tuberculosis. Fortunately, our patient had only mild symptoms allowing the delay of definitive treatment until the results of tuberculosis culture were available. A nine month course of standard antituberculous treatment was started (rifampicin 450 mg daily, isoniazid 300 mg daily, pyrazinamide 1.5 g daily, and pyridoxine 10 mg daily) and was tolerated without any side effects. Her pyrazinamide was stopped after two months.

The inflammatory markers fluctuated over the next nine months but showed a general downward trend. Her weight increased progressively to 46 kg, parallelling her improved exercise tolerance and general clinical condition. A repeat colonoscopy to the caecum was normal with no evidence of residual fibrous scarring. Follow up computed tomography showed thickened bowel loops in the right iliac fossa with some calcification visible in the mesenteric nodes. She remains well 18 months after treatment.

Discussion

Abdominal tuberculosis remains rare, and its incidence over the last decade has remained stable despite variation in reported rates of pulmonary tuberculosis.2 It is more common in patients with AIDS. As with pulmonary tuberculosis most reported cases in the UK are immigrants. Our patient had never travelled outside the UK but may have been exposed to tuberculosis at the same time as her brother. Another possible source was her neighbours, both recent immigrants, who were found through contact tracing to have active pulmonary tuberculosis.

Her chest radiograph was normal on two occasions. Reports suggest that 20% of patients with abdominal tuberculosis have coexistent pulmonary disease on chest radiography at presentation, but reported rates vary widely (6%–86%). Non-specific symptoms at presentation are not unusual and a high index of suspicion is required to make the diagnosis. In addition to weight loss (66%), abdominal pain (85%), diarrhoea (20%), fever (35%–50%), weakness, nausea, vomiting, melaena, or rectal bleeding may be presenting features. An abdominal mass, usually in the right lower quadrant, is palpable in 25%–50% of patients.3 Investigations typically show a normal white cell count. Mild anaemia is common with inflammatory markers characteristically raised. Abdominal ultrasound or computed tomography may confirm an abdominal mass or enlarged lymph nodes but are often unhelpful in distinguishing the underlying cause. Laparoscopy and biopsy can be helpful but are safer if ascites is present, reducing the risk of bowel perforation.

Our case illustrates the value of colonoscopy, biopsy, and culture in establishing the diagnosis. Classical caseating granulomas on routine histology or Ziehl-Neelsen staining may give an immediate answer but may be negative. Fine needle aspiration cytology at colonoscopy may improve the diagnostic yield when nodular lesions are seen.4 The major disadvantage with tuberculosis culture of biopsy samples is the time taken to get the result. Because of this new “rapid culture” methods have been developed. Approximately 85% of patients will have a positive purified protein derivative or Mantoux test, but a negative result does not exclude the diagnosis. Enzyme linked immunosorbent assay, soluble antigen fluorescent antibody, or polymerase chain reaction based tests have been developed but reduced specificity limits their routine use.

Such extensive colonic involvement is unusual. The ileocaecal region is most commonly involved (75%). Involvement of the transverse colon is less common.1 2 The abnormality seen on the initial barium meal investigation remains unexplained. Oesophageal tuberculosis is very uncommon, but usually affects the upper half of the oesophagus. It may present with disruption of normal peristalsis secondary to intramural thickening, though thickened mucosa or ulceration is usually visible on endoscopic examination.

Pathologically three gross appearances of intestinal tuberculosis are described; ulcerative, hypertrophic, or ulcerohypertrophic, although there is considerable overlap.3 Fibrous strictures may develop. Mesenteric lymph nodes are often involved and may calcify. Of the complications, intestinal obstruction is the most frequently encountered (20% of cases). Massive gastrointestinal bleeding is less common. Perforation of the bowel or fistula formation also occur and are associated with a poorer prognosis.

The use of short course chemotherapy for abdominal tuberculosis has not been evaluated in controlled trials but both six and nine month regimens are probably as effective as they are in pulmonary disease. Success rates of 95% have been reported.2 Occasionally, when investigations have failed to determine the underlying diagnosis, the decision to treat with antituberculous therapy is based on a high index of clinical suspicion alone. This can pose a difficult clinical dilemma, particularly as the main differential diagnosis is Crohn's disease, which may require treatment with steroids.

Final diagnosis

Abdominal tuberculosis.

References

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