Peritoneal tuberculosis (TB) is the most common abdominal form of extrapulmonary TB, characterized by involvement of the peritoneum, omentum, and mesentery by Mycobacterium tuberculosis. It constitutes 3-5% of all TB cases and is more common in developing countries, HIV-positive patients, and immunosuppressed individuals. Three clinico-pathological forms are defined: wet type (exudative ascites), dry type (adhesions, fibrosis), fibrotic type (omental thickening, masses). Classic CT findings include smooth peritoneal thickening, rim-enhancing (centrally necrotic) lymph nodes, omental cake, ascites, and jejunal/ileal bowel wall thickening. Elevated serum ADA (adenosine deaminase) and positive PPD test aid diagnosis. Treatment with 6-9 month anti-tuberculous therapy (HRZE regimen) is effective.
Age Range
20-55
Peak Age
35
Gender
Equal
Prevalence
Uncommon
Peritoneal TB develops from spread of M. tuberculosis to the peritoneal cavity. Spread may be hematogenous (most common), direct passage from intestinal mucosa, via fallopian tubes, or from retroperitoneal lymph nodes. Tubercle bacilli are phagocytized by peritoneal macrophages but survive intracellularly. Activated CD4+ T-lymphocytes trigger granuloma formation — caseating granulomas are the histological signature of TB. Caseous necrosis forms from accumulation of cell debris when tubercle bacilli in the center are killed by immune response. Rim enhancement on CT reflects vascularized granulomatous tissue surrounding the necrotic center retaining iodinated contrast — the necrotic center does not enhance because it is avascular. Peritoneal thickening represents granuloma accumulation and fibrotic response. High-protein exudative ascites results from increased vascular permeability due to peritoneal inflammation. Omental cake reflects omental thickening from granulomatous infiltration and fibrosis. ADA enzyme is secreted by activated T-lymphocytes and elevated levels in ascitic fluid are a sensitive marker for peritoneal TB.
Central low density (caseous necrosis) and peripheral rim enhancement in mesenteric/retroperitoneal lymph nodes on CT. This pattern is very specific for TB lymphadenitis and distinguishes from sarcoidosis's homogeneously enhancing, non-necrotic lymph nodes.
Mesenteric and retroperitoneal lymph nodes show central necrosis (low density) and peripheral rim enhancement. This pattern is very specific for TB lymphadenitis. Lymph nodes are usually 1-3 cm and may form conglomerate masses. Necrosis represents caseous material.
Report Sentence
Mesenteric and retroperitoneal lymph nodes show central necrosis and rim enhancement; finding consistent with TB lymphadenitis.
Smooth, diffuse thickening and enhancement of parietal and visceral peritoneum. Thickening is usually smooth-contoured — nodular thickening is less frequent and may overlap with carcinomatosis. Peritoneal enhancement reflects granulomatous inflammation.
Report Sentence
Smooth, diffuse thickening and enhancement of parietal and visceral peritoneum are seen; finding consistent with TB peritonitis.
On non-contrast CT, ascitic fluid shows higher density (>20 HU) than simple transudative ascites. High protein content and fibrin accumulation contribute to density increase. Thin septa or fibrin bands may be seen within ascitic fluid. Ascites distribution may be localized or diffuse.
Report Sentence
High-density (... HU) ascitic fluid is seen in the peritoneal cavity; consistent with exudative ascites and TB peritonitis should be considered.
Omental thickening and nodularity — 'omental cake'-like appearance. In TB, omental cake is usually smoother-contoured and less nodular than in carcinomatosis. Granulomatous nodules and calcifications may be seen within omentum. Omental enhancement indicates active inflammation.
Report Sentence
Omental thickening, nodularity, and enhancement are seen (omental cake); finding consistent with TB peritonitis, carcinomatosis should be considered in the differential.
Peritoneal thickening shows intermediate to low signal on T2-weighted images — reflecting predominance of fibrotic component. T2 hyperintensity may be seen in active inflammatory areas. Necrotic lymph nodes show central hyperintensity and peripheral hypointensity on T2. Ascitic fluid is T2 hyperintense.
Report Sentence
Peritoneal thickening shows intermediate to low signal on T2-weighted sequence; may be consistent with fibrotic component-predominant TB peritonitis.
Septated or localized ascites in the peritoneal cavity on US — fibrin bands seen as thin septa. Peritoneal thickening may appear as echogenic band. Omental thickening seen as hyperechoic mass. Mesenteric lymph nodes appear hypoechoic and enlarged.
Report Sentence
Septated ascites is seen in the peritoneal cavity; combined with fibrin bands and peritoneal thickening may be consistent with TB peritonitis.
Criteria
Free or localized high-density ascites predominant. Most common form. Peritoneal thickening accompanies. Diagnostic paracentesis: ADA >40 U/L.
Distinct Features
High-density ascites + peritoneal thickening + necrotic LAP on CT; septated ascites on US.
Criteria
Peritoneal adhesions and fibrotic bands predominant. Little or no ascites. Risk of bowel obstruction. Difficult access for laparoscopic biopsy.
Distinct Features
Peritoneal thickening and fibrotic bands on CT; bowel loops matted (adherent); minimal ascites.
Criteria
Omental and mesenteric masses (omental cake) predominant. Carcinomatosis and lymphoma differential critical. Biopsy usually mandatory.
Distinct Features
Omental cake + necrotic LAP on CT; smoother contoured than carcinomatosis omental cake; calcification may be present.
Distinguishing Feature
In carcinomatosis lymph nodes usually enhance homogeneously (no rim pattern); rim-enhancing necrotic lymph nodes are specific for TB. Carcinomatosis has primary tumor history.
Distinguishing Feature
In sarcoidosis lymph nodes enhance homogeneously without necrosis; central necrosis and rim enhancement are specific for TB. Bilateral hilar LAP accompanies sarcoidosis.
Distinguishing Feature
In lymphoma lymph nodes enhance homogeneously, show sandwich sign, and necrosis is generally absent; rim enhancement and necrotic center are specific for TB.
Distinguishing Feature
Sclerosing mesenteritis shows misty mesentery and fat ring sign; TB peritonitis features peritoneal thickening, necrotic LAP, and ascites — different CT patterns.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
3-monthPeritoneal TB is an infectious disease requiring urgent treatment. Diagnosis uses ascitic fluid analysis (ADA >40 U/L, lymphocyte-predominant exudate), peritoneal biopsy (laparoscopic preferred — caseating granuloma is gold standard), AFB staining, and culture. Standard treatment is 6-9 month anti-TB therapy (2 months HRZE + 4-7 months HR). Treatment response is monitored with CT — ascites resolution, peritoneal thickening decrease, and lymph node shrinkage are expected. In HIV-positive patients, concurrent ART should be started. Mortality is high without treatment; cure rate is >90% with treatment.
Peritoneal TB can mimic carcinomatosis and diagnosis may be delayed. Ascitic fluid analysis (elevated ADA, lymphocyte predominance) and peritoneal biopsy are diagnostic. Anti-tuberculosis treatment is curative. Common in immunosuppressed patients (HIV, dialysis).