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Tuberculosis 115
Computed Tomographic Scan Imaging Bacterial Infection with Infecton
Ileocaecal tuberculosis is usually hyperplastic and well evaluated on A new radioimaging agent, Tc-99m ciprofloxacin (Infecton) has been
a computed tomography (CT) scan. Circumferential thickening of used to detect deep-seated bacterial infections, such as intraabdominal
caecum and terminal ileum, adherent loops, large regional nodes, and abscesses. Patients with suspected bacterial infection have been sub-
mesenteric thickening can together form a mass centred around the jected to Infecton imaging and microbiological evaluation, reporting
ileocaecal junction. A CT scan can also pick up ulceration or nodularity an overall sensitivity of 85.4% and a specificity of 81.7% for detecting
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within the terminal ileum, along with narrowing and proximal dilata- infective foci. Sensitivity was higher (87.6%) in microbiologically
tion. Involvement around the hepatic flexure of the colon is common. confirmed infections. Infecton may aid in the earlier detection and treat-
Complications of perforation, abscess, and obstruction can also be ment of deep-seated infections, and serial imaging with Infecton might
seen. Tubercular ascitic fluid is of high attenuation value (25–45 HU) be useful in monitoring clinical response and optimising the duration
due to its high protein content. Thickened peritoneum and enhancing of antimicrobial treatment.
peritoneal nodules may be seen. A smooth peritoneum with minimal Colonoscopy
thickening and marked enhancement after contrast suggests tuberculous Although the appearance is nonspecific, colonoscopy has been used for
peritonitis, whereas nodular and irregular peritoneal thickening sug- the diagnosis of colonic or ileocaecal tuberculosis. Most commonly,
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gests the presence of peritoneal carcinomatosis. Omental thickening ulcers, strictures, or oedematous and polypoid mucosal folds are seen.
is well seen often as an omental cake appearance. 22 Mucosal pinkish nonfriable nodules of variable sizes with ulcerations
Lymph nodes may be interspersed. The four patterns of contrast in between the nodules in a discrete segment of colon, most often in the
enhancement of tuberculous lymph nodes on the contrast-enhanced caecum, are pathognomic. Areas of strictures, pseudopolypoid oedema-
CT (CECT) have been described as (in order of frequency): (1) tous folds, and a deformed and oedematous ileocaecal valve may be seen.
peripheral rim enhancement, (2) nonhomogenous enhancement, (3) Multiple biopsies should be taken from the edge of the ulcers. The
homogenous enhancement, and (4) homogenous nonenhancement. tissue should also be examined for AFB smear and culture, as the
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Different patterns of contrast enhancement may be seen within the same histology may not be characteristic.
nodal group, possibly related to the different stages of the pathological Endoscopic biopsy specimens may be subjected to PCR for
process. Caseating lymph nodes are seen as having hypodense centres detection of AFB. The limitations of colonoscopic biopsy are that
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and peripheral rim enhancement. The presence of nodal calcification previous antitubercular therapy can alter the histology, and that
in the absence of a known primary tumour in patients from endemic granulomas are often found in the submucosa. Of 82 patients with GI
areas suggests a tubercular aetiology. CT findings can help differentiate tuberculosis, colonoscopy was diagnostic in only 47. 31
it from other inflammatory and neoplastic diseases, particularly Laparoscopy
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lymphoma and Crohn’s disease. In tuberculosis, the mesenteric,
mesenteric root, celiac, porta hepatic, and peripancreatic nodes are Laparoscopy is a very useful investigation in doubtful cases. Visual
characteristically involved, reflecting the lymphatic drainage of the appearances have been found to be more helpful than histology, culture,
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small bowel. The tuberculous involvement of the pancreas may show or guinea pig inoculation.
as well-defined hypoechoic areas on ultrasonography and as hypodense The laparoscopic findings in peritoneal tuberculosis can be grouped
necrotic regions within the enlarged pancreas. CT is more accurate into three categories: (1) thickened peritoneum with tubercles, (2)
than ultrasound in detecting abnormalities such as periportal and thickened peritoneum without tubercles, and (3) fibroadhesive
peripancreatic lymph nodes and bowel wall thickening. However, peritonitis with markedly thickened peritoneum and multiple thick
bowel wall dilatation can be better appreciated on ultrasound than on a adhesions fixing the viscera.
CT scan. Magnetic resonance imaging (MRI), when compared to a CT Markers for Treatment Response
scan, provides no additional information. 25 ESR tends to fall with response to antitubercular treatment. A signifi-
Cytology and Biochemistry of Ascitic Fluid cant decrease in the concentrations of C-reactive protein (CRP), cerulo-
The ascitic fluid in abdominal tuberculosis is clear or straw-coloured. plasmin, haptoglobin, and alpha-1-acid glycoprotein has been seen with
Its glucose concentration is less than 30 mg/dl, and its high protein con- antitubercular treatment.
tent is >3 g/dl, with a total cell count of 150–4000/cu mm, usually more Differential Diagnosis
than 1,000/cu mm (consisting predominantly of lymphocytes (>70%)). Hypertrophic intestinal tuberculosis may mimic malignant neoplasms
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The ascites-to-blood glucose ratio is less than 0.96. The serum ascitis such as lymphoma or carcinoma. The ulcero-hypertrophic form may
albumin gradient is less than 1.1 g/dl, and adenosine deaminase levels mimic inflammatory bowel disease. The nodal form may closely
are above 36 U/l. Adenosine deaminase (ADA) is increased in tuber- mimic lymphomas. The ascitic form can be difficult to distinguish from
culous ascitic fluid due to the stimulation of T-cells by mycobacterial malignant peritoneal disease and sometimes ascites due to chronic liver
antigens. In coinfection with HIV, the ADA values can be normal or disease. In cases of hepatosplenomegaly, all other causes need to be
low. High interferon levels in tubercular ascitis have been found to be excluded before considering a tubercular aetiology. Sometimes, when
useful diagnostically. Combining both ADA and interferon estimations all investigations are negative and TB is strongly suspected, a lapa-
may further increase the sensitivity and the specificity. The AFB smear rotomy may be indicated.
and culture are positive in only 10–15% cases, but the yield rises dra- Treatment
matically by culturing a litre of fluid concentrated by centrifugation.
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Fluorescent staining with auramine-O is superior to Ziehl-Neelsen Laparotomy
staining with regard to the positivity and the ease of detection. In chil- In circumstances where the clinical suspicion of intraabdominal disease
dren, AFB may be recovered from stomach wash, keeping in mind that is strong, but results of investigations are equivocal, a diagnostic lapa-
scant saprophytic mycobacteria may also be present as normal flora. rotomy may be a safer option for abdominal tuberculosis. Where clini-
PCR conducted with ascites fluid has produced DNA sequences cal suspicion is strong and imaging features are suggestive, a therapeu-
compatible with tuberculosis. PCR can be a rapid and reliable tic trial of antitubercular treatment (ATT) may be justified. However,
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method for identification of peritoneal tuberculosis; acceleration of the laparotomy is definitely indicated where the diagnosis is in doubt and
diagnostic decision-making process prevents exposure to unnecessary if the malignancy cannot be ruled out with certainty. In many patients,
surgery and allows early initiation of antituberculosis treatment. it may not be possible to rule out malignancy, even at laparotomy. A