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home - Miscellaneous - Infection - TB Written by Dr Sebastian Zeki

TB

Risk Factors:Cirrhosis.HIV infection.Diabetes mellitusUnderlying malignancy.Following treatment with anti-tumor necrosis factor (TNF) agents.CAPD. From hematogenous spread from a primary lung focus from latent state or from active pulmonary or miliary TB Less likely is spread from infected small intestine or contigu-ously from tubercu-lous salpingitis Visceral peritoneum Parietal peritoneum Visceral and parietal peritoneum become increasingly studded with tubercles. Visceral peritoneum Parietal peritoneum Fibroadhesive Disease (Dry form) Ascites develops secondary to "exudation" of proteina-ceous fluid from the tubercles, similar to the mechanism leading to ascites in patients with peritoneal carcinoma-tosis.> 90 % of patients with TB peritonitis have ascites at the time of presentation, It develops within 1 year of developing CAPD.The most common features are ascites (93 %), abdominal pain (73 %), and fever (58 %). The diagnosis usually requires a targeted peritoneal biopsy performed under direct visualization.If laparoscopy non-diagnostic, should have a mini-laparotomyLaparoscopic findings:1)visceral and parietal peritoneum is studded with multiple whitish nodules or tubercles.2) Enlarged lymph nodes, 3)"Violin-string" fibrinous strands4) Omental thickening.Targeted biopsies reveal caseating granulomas in up to 100 % of patients and are positive for acid fast bacilli in 74 % of patients. Gold-standard= culture growthTuberculin skin testing with purified protein derivative (PPD) - +ve in 70 % but -ve doesnt exclude.Patients with a known previous skin reaction to TB maybe anergic at the time of PPD reading.Radiologic imagingCan get: peritoneal thickening, omental caking, and the presence of ascites with fine mobile septations on ultrasound and CT imaging.Peritoneal fluid analysisLymphocytic ascites (in CAPD, it may be neutrophilic)Exudate with (SAAG) is <1.1 g/dL. unless have cirrhosis when SAAG is >1.1g/ dLAFB stain sensitivity is 5%Culture positive in 20% and takes 6w to come back (50% dead in 6 weeks of presentation)- increase sensitivty with larger volume (>1L) but impracticalPolymerase chain reaction- may be more useful but sensitivity not establishedAdenosine deaminase(ADA)ADA is a purine-degrading enzyme involved in maturation and differentiation of lymphoid cells.ADA levels had high sensitivity (100 %) and specificity (97 %) using cut-off values from 36 to 40 IU/L; the optimal cut-off value was 39 IU/L.Lower sensitivity in patients with cirrhosis (30 %) due to the characteristically poor humoral and T cell mediated response of cirrhotic patients.As a result, ADA measurement has its greatest utility in settings where TB peritonitis is suspected in non-cirrhotic patients.T-cell based testing for mycobacterium TB (ELISPOT)Measures gamma producing T-cell responses to early secreted antigenic targets of mycobacterium TB, has sensitivity and specificity for extrapulmonary TB as 94 and 88 %, respectively. TreatmentFever usually resolves within one week of commencing anti-tuberculous treatment.> 90 % of patients have improvement in abdominal ascites within weeks of initiating treatment.The role of steroids is still not established but it may help in preventing adhesions. TB Peritonitis Clinical Manifestations Lab results:Mild to moderate normochromic normocytic anaemia in most patients (mean hemoglobin concentration 9.9 g/dL)- in 50%.A normal leukocyte count- present in most patients.CA-125-not helpful.Old TB- visible on chest x-ray in only 33 %. PrognosisThere is a mortality of 25%.Advanced age, delay in initiating therapy, and underlying cirrhosis have been associated with higher mortality rates.Some develop complications (such as small bowel obstruction) related to adhesions. Diagnosis 20% have no risk factors Written by Dr Sebastian Zeki

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