© Georg Thieme Verlag KG Stuttgart · New York
Rectal tuberculosis: the great mimic
03 August 2007 (online)
Gastrointestinal tuberculosis (TB) is a diagnostic challenge in the absence of pulmonary infection. Gastrointestinal TB can involve any part of the alimentary tract from the mouth to the anus, the distal ileum being the most common site . Lesions above and below this site are rare.
A 72-year-old gentleman complaining of constipation, abdominal pain, and a 2-month history of loss of appetite and weight loss was referred to our gastroenterology department.
Examination revealed pallor; vital signs including pulse, blood pressure, and respiratory rate were within normal limits. Abdominal examination demonstrated tenderness in the left iliac fossa, but no mass could be palpated. Digital rectal examination revealed a hard, palpable, fixed mass around 7 cm from the anal verge.
Examination of other systems gave unremarkable findings. On the basis of the history and clinical findings a provisional diagnosis of rectal carcinoma was made. Abdominal ultrasonography and chest radiography did not show any abnormality. Colonoscopy showed an irregular, ulcerated, nodular mass in the rectum around 1.5 cm in size ([Figure 1]) while the rest of the colon appeared normal.
Histopathological investigation revealed chronic inflammatory cells in the mucosa showing a number of scattered epithelioid histiocytic granulomas with central necrosis ([Figure 2]), and Ziehl-Neelsen staining showed numerous acid-fast bacilli ([Figure 3]). On the basis of these findings rectal tuberculosis was diagnosed, and the patient was started on an antituberculosis treatment regime with regular follow-up.
Figure 1 a, b Rectal mass.
Figure 2 Granuloma with central necrosis.
Figure 3 Multiple acid-fast bacilli.
Intestinal TB commonly occurs in the second and third decades of life; only 2 % of cases present after the age of 60 years .Only half of the patients have an abnormality in the chest radiograph or have active pulmonary tuberculosis . Between 30 % and 50 % of intestinal cases reported did not reveal acid-fast bacilli on Ziehl-Neelsen staining .
This case shows that tubercular involvement of the rectum is rare. It can closely mimic carcinoma of the rectum, and its diagnosis can be challenging.
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L. Kamani FCPS, MRCP(UK)
Department of Medicine
Aga Khan University Hospital