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ABDOMINAL TUBERCULOSIS

Comprehensive MD Exam Answer — 15 Marks

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INTRODUCTION & EPIDEMIOLOGY

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I. INTESTINAL TUBERCULOSIS

Site of Involvement

• Abundant lymphoid tissue (Peyer's patches)
• Relative physiological stasis
• Minimal digestive activity → prolonged contact of AFB with mucosa

Pathogenesis

1. Direct mucosal invasion by ingested organisms (in swallowed sputum or contaminated milk/food) — most common
2. Transport via infected bile
3. Extension from adjacent organs
4. Haematogenous spread (miliary pattern)

Pathology (Gross & Microscopic)

• Ulcers are transverse and circumferential (unlike longitudinal ulcers in Crohn's)
• Ulcers are deep but do not usually penetrate the muscularis propria (contained perforation if it occurs)
• Healing → collagenous fibrosis → circumferential stricture (key complication)
• Serosa studded with nodules; mesenteric lymph nodes enlarged
• Skip areas with normal-appearing mucosa between diseased segments
• Histological hallmark: caseating granuloma
  • Granulomas in 50%–80% of mucosal biopsies
  • Caseation seen in 10%–30%
  • AFB detected in only ~5% of mucosal samples
  • Features specific for TB: caseation, confluent granulomas, lymphoid cuff around granulomas (meta-analysis, Du et al., 2014)

Clinical Features

• Age: 20–40 years; both sexes equally affected
• Symptoms arise from:
  1. Intestinal ulcero-constrictive disease → colicky pain, distension, obstruction, bleeding
  2. Chronic inflammation → fever (40–70%), weight loss (60–90%), night sweats, anorexia
  3. Adjacent tissue involvement → ascites, lymphadenopathy, tubo-ovarian disease
  4. Concurrent pulmonary TB → cough, haemoptysis
• Most common symptom: Abdominal pain (90%) — colicky if from intestinal lumen, diffuse/non-specific if mesenteric/peritoneal
• Diarrhoea in 20–30%; constipation in ~50%
• Lower GI bleeding in 10–15% (rarely massive)
• Palpable RLQ mass in 10–20% (adherent loops + lymph nodes + mesentery)
• Doughy abdomen in fibro-adhesive peritoneal involvement
• Signs: poor nutritional status, anaemia, low-grade fever, RLQ tenderness

Complications

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INVESTIGATIONS

Laboratory

• Haematology: mild anaemia, normal/raised WBC; ESR elevated
• Non-diagnostic individually; baseline monitoring required
• All patients screened for HIV

Imaging Studies

• Early: spasm, hyper-motility, mucosal oedema at ileocaecal valve
• Advanced: Fleischner's sign (inverted umbrella sign) — thickened ileocaecal valve with narrowing of terminal ileum; conical shrunken caecum pulled up from iliac fossa; swan-neck deformity; circumferential strictures; incompetent ileocaecal valve

• Gold standard for extra-luminal disease assessment
• Shows: intestinal wall thickening (unifocal/multifocal), stricture with proximal dilatation, mesenteric lymphadenopathy with central hypodensity (necrosis) and peripheral enhancement — seen in 40–70% (pathognomonic)
• CT-enterography/MR-enterography preferred for small bowel as intestinal lumen is adequately distended with negative contrast
• Active inflammation shows contrast enhancement; fibrotic strictures show no enhancement
• SAAG <1.1 g/dL with high protein ascites suggests TB peritonitis

Endoscopy (Colonoscopy with retrograde ileoscopy)

• Investigation of choice — ileocaecal area accessible in majority
• Classical findings: transverse circumferential ulcers with ill-defined sloping/overhanging edges, nodularity, strictures, markedly thickened bowel wall
• Pseudopolyps, flattening of folds, erosions in surrounding mucosa
• Obtain multiple biopsies for histopathology, AFB staining, culture, PCR

Microbiological Tests

• Mycobacterial culture: most specific (gold standard); sensitivity only 10–30% from mucosal biopsies
• AFB smear: positive in 25–36% of intestinal biopsies
• PCR (CBNAAT/Xpert MTB-RIF): sensitivity 20–64%; high specificity (97.9% in peritoneal fluid, 92% in peritoneal tissue); use cautiously (contamination, saprophytic mycobacteria)

Histopathology

• Granulomas in 50–80% of biopsies
• Features specific to TB (meta-analysis):
  • Caseating necrosis
  • Confluent granulomas
  • Lymphoid cuff around granulomas
  • Large granulomas (>400 µm), ≥5 granulomas per segment, submucosal granulomas

Diagnostic Criteria (INDEX-TB Guidelines, India 2017)

• Bacteriologically confirmed: positive microscopy, culture, or validated PCR (Xpert MTB/RIF)
• Clinically diagnosed: negative microbiological tests but strong clinical suspicion + compatible imaging/histopathology/ancillary tests/response to ATT

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II. PERITONEAL TUBERCULOSIS

Forms

1. Ascitic (wet) type — most common
2. Encysted (loculated) type
3. Dry (plastic/fibro-adhesive) type — no ascites; "doughy abdomen"

Clinical Features

• Subacute onset over weeks to months
• Abdominal pain (60–70%) — non-localised, from peritoneal/mesenteric inflammation
• Abdominal distension (absent in dry type)
• Fever, weight loss, night sweats, anorexia
• Rebound tenderness rare (ascitic fluid prevents approximation of peritonea)
• "Doughy abdomen" in 5–10% (plastic type)
• Active pulmonary TB uncommon in peritoneal TB

Ascitic Fluid Analysis

Special Markers in Ascitic Fluid

• ADA (Adenosine Deaminase):
  • ADA >32 IU/L → high sensitivity and specificity for TB ascites
  • Meta-analysis: sensitivity 100%, specificity 97% at cut-off 36–40 IU/L
  • Can be elevated in malignant and cirrhotic ascites (false positives)
  • Reflects activated T-lymphocyte activity in closed compartment infection
• IFN-γ: Higher in TB ascites vs malignant/cirrhotic ascites
• CA-125: Elevated (mimics ovarian carcinoma); falls rapidly with ATT — useful monitoring marker
• Xpert MTB/RIF on ascitic fluid: Pooled specificity 97.9%, sensitivity 59.2% (Cochrane 2018)

Imaging

• Ultrasonography: First-line; shows echogenic debris with fine mobile strands/particulate matter in ascites; encysted loculated fluid; thickened nodular peritoneum
• CECT abdomen:
  • Attenuation of TB ascitic fluid: 20–45 Hounsfield Units (high)
  • Symmetrical peritoneal thickening with enhancement → TB peritonitis
  • Nodular/irregular peritoneal thickening → peritoneal carcinomatosis
  • Omental masses, matted bowel loops, thickened mesentery (>15 mm) with enlarged lymph nodes (central hypodensity = necrosis)

Laparoscopy — Gold Standard for Peritoneal TB

1. Thickened hyperaemic peritoneum + ascites + whitish miliary nodules (<5 mm) — 66% (most common)
2. Thickened hyperaemic peritoneum + ascites + adhesions — 21%
3. Markedly thickened parietal peritoneum + yellowish nodules + cheesy material + thick adhesions (fibro-adhesive type) — 13%

• Sensitivity of macroscopic appearance: 93%
• Combined with histopathology (caseating epithelioid granuloma/AFB): sensitivity 93%, specificity 98%
• Peritoneal biopsies must be sent for culture and sensitivity

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III. OTHER FORMS OF ABDOMINAL TB

Hepatobiliary TB

• Two forms:
  1. Miliary/disseminated → hepatomegaly, granulomas on liver biopsy; no specific LFT changes
  2. Localised hepatic TB: solitary/multiple tuberculomas; biliary ductal involvement → obstructive jaundice; porta hepatis lymph nodes → bile duct obstruction
• LFTs: elevated ALP, GGT; mild transaminases elevation
• Diagnosis: USG → CECT → MRCP/ERCP for biliary disease; liver biopsy

Pancreatic TB

• Uncommon; mostly from lymphatic/haematogenous spread
• Presents as pancreatic mass (mimics carcinoma)
• Head involvement → obstructive jaundice
• Diagnosis: FNAC + culture; EUS-guided biopsy

Oesophageal TB

• Direct extension from mediastinal lymph nodes/lung
• Upper oesophagus > lower
• Presents as dysphagia, odynophagia, tracheo-oesophageal fistula
• Upper GI endoscopy + biopsy; endosonography for mediastinal assessment

Gastroduodenal TB

• Rare (acidic environment protective)
• Duodenal > gastric involvement
• Presents with abdominal pain, vomiting, obstruction, GI bleeding
• Diagnosis: endoscopy + biopsy; CECT for extent; balloon dilation for strictures

Splenic TB

• Part of miliary/disseminated disease; isolated rare
• Splenomegaly ± single/multiple lesions on USG/CT
• Mostly immunocompromised; splenectomy rarely needed

Mesenteric Lymph Node TB (TB Lymphadenitis)

• Common component of abdominal TB
• CT: lymph nodes with central hypodensity (caseation) + rim enhancement — characteristic
• May present as RIF mass (mimics appendicular lump)

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IV. DIFFERENTIAL DIAGNOSIS — TB vs. CROHN'S DISEASE

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V. TREATMENT

Anti-TB Therapy (INDEX-TB Guidelines 2017)

2HRZE / 4HRE (daily) — 6 months total

• Rifampicin (R), Isoniazid (H), Pyrazinamide (Z), Ethambutol (E) for first 2 months
• Rifampicin (R), Isoniazid (H), Ethambutol (E) for next 4 months
• Strong recommendation (very low quality evidence)

• RCT (Makharia et al., Clin Infect Dis 2015; n=197): Thrice-weekly DOTS — complete response 91.5% (6 months) vs. 90.8% (9 months); no significant difference
• 6 months is adequate — no benefit with 9 months
• No role for adjunctive corticosteroids in abdominal TB (unlike TB meningitis)

Nutritional Management

• High-fibre diet avoided in intestinal strictures
• Nutritional assessment and correction of deficiencies
• Gastroduodenal obstruction: liquid diet initially; endoscopic balloon dilation

Endoscopic Treatment

• Balloon dilation of gastroduodenal, colonic, and small intestinal strictures
• Endoscopic mucosal resection for lesions requiring larger tissue sample

Surgical Indications

• Stricturoplasty or resection with end-to-end anastomosis
• Limited ileocaecal resection / right hemicolectomy
• Bypass surgery (entero-enterostomy) is NOT recommended — leads to blind loops, obstruction, malabsorption
• Elective surgery should be deferred until 4–6 weeks of ATT; ATT must continue post-surgery

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VI. MONITORING & FOLLOW-UP

• Counsel regarding drug side effects, especially hepatotoxicity (monitor LFTs)
• Fever and constitutional symptoms improve within weeks; may take up to 8 weeks for full resolution
• Intestinal pain improves as inflammation resolves and luminal diameter widens
• Repeat colonoscopy at end of 6 months (especially empirically treated cases) to confirm complete mucosal healing
• Active unresponsive stricture (from MDR-TB or treatment failure) vs. fibrotic stricture: distinguish by contrast enhancement on CT-enterography (active = enhancement; fibrotic = no enhancement)
• Non-response: suspect non-adherence, alternative diagnosis, or MDR-TB

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SUMMARY TABLE — KEY NUMBERS TO REMEMBER

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• Sharma SK, Mohan A (Eds). Textbook of Tuberculosis and Nontuberculous Mycobacterial Diseases, 3rd Ed. Chapter 15 — Makharia GK. Abdominal Tuberculosis, pp 208–218.
• Sharma SK, Ryan H, Khaparde S, et al. INDEX-TB Guidelines. Indian J Med Res 2017;145:448–63.
• Makharia GK et al. Intermittent directly observed therapy for abdominal tuberculosis: RCT. Clin Infect Dis 2015;61:750–7.
• Sleisenger & Fordtran's GI and Liver Disease, 11th Ed. Section on Tuberculosis of the Intestinal Tract.
• Murray & Nadel's Textbook of Respiratory Medicine. Intestinal & Peritoneal Tuberculosis sections.