Medicine chapters
Intestinal and peritoneal tuberculosis
How tuberculosis affects the bowel and peritoneum, the classic ileocaecal and ascitic presentations, how to tell it from Crohn disease, and how it is confirmed and treated.
- Abdominal TB is common in Pakistan; the ileocaecal region is the commonest bowel site, and the peritoneum is the other main target.
- Suspect it in a patient with fever, night sweats, weight loss, abdominal pain, altered bowel habit, a right iliac fossa mass, ascites or subacute obstruction; the main mimic is Crohn disease.
- Ascites is a lymphocytic exudate with high protein, low SAAG (<11 g/L) and high ADA; histology shows caseating granulomas; treat with 6 months of standard ATT, keeping surgery for complications.
On this page
Overview
Abdominal tuberculosis includes TB of the gut, the peritoneum, the abdominal lymph nodes and the solid organs. It is common in Pakistan and across South Asia, and it is a frequent cause of chronic abdominal pain, ascites and subacute bowel obstruction in our hospitals.
It is a great mimic. The two key exam tasks are to recognise the presentation and to distinguish TB from Crohn disease, because steroids or anti-TNF drugs given wrongly for "Crohn" can make TB spread.
How TB reaches the abdomen
- Swallowing infected sputum from active pulmonary TB (ulcerative bowel disease).
- Drinking unpasteurised milk infected with M. bovis (hyperplastic disease); rare where milk is pasteurised.
- Blood-borne spread from a primary focus or miliary TB (common route to the peritoneum).
- Lymphatic spread from mesenteric nodes, and direct spread from the fallopian tubes.
Risk is higher with HIV, malnutrition, diabetes, cirrhosis, peritoneal dialysis and anti-TNF or steroid treatment.
Only about half of patients with intestinal TB have evidence of pulmonary TB on chest X-ray, so a normal chest film does not exclude abdominal TB.
Forms of abdominal TB
- Intestinal (gastrointestinal) TB: ileocaecal region most often; also jejunum, ileum, colon; rarely stomach, duodenum, oesophagus, anus.
- Peritoneal TB (tuberculous peritonitis).
- Mesenteric lymph node TB.
- Solid organ TB (liver, spleen).
Intestinal TB
Why the ileocaecal region?
The terminal ileum has abundant lymphoid tissue (Peyer patches), food stays there longer (stasis), and digestion is almost complete, giving more contact between bacilli and mucosa.
Pathological types
| Type | When it occurs | Features |
|---|---|---|
| Ulcerative | Virulent organism, poor host resistance (often with active lung TB) | Transverse ulcers with undermined edges, following the lymphatics around the bowel; tubercles on the serosa; may perforate |
| Hyperplastic | Strong host resistance, low virulence (classically from milk) | Thick fibrous bowel wall, strictures, a mass in the right iliac fossa, shortening that pulls the caecum up under the liver |
| Ulcero-hyperplastic | Mixture | Ulcers plus mass and stricture |
Healing of transverse ulcers by fibrosis produces short, often multiple, strictures.
Clinical features
- Constitutional: low-grade evening fever, night sweats, weight loss, anorexia, malaise.
- Chronic or colicky abdominal pain, distension.
- Alternating diarrhoea and constipation; sometimes malabsorption.
- Right iliac fossa mass (hyperplastic type).
- Anaemia.
- Acute presentations (about a third): subacute or acute small bowel obstruction (colicky pain, distension, vomiting), perforation with peritonitis, or bleeding.
- Perianal TB fistulas can occur: often multiple with undermined edges and watery discharge.
An acute right iliac fossa presentation may be appendicitis, Crohn ileitis, Yersinia, amoebic or TB, or caecal cancer. In an older patient with a right-sided mass, anaemia and weight loss, exclude caecal carcinoma.
Peritoneal TB (tuberculous peritonitis)
The second most common form overall, and often found with bowel or nodal disease.
| Type | Presentation |
|---|---|
| Wet (ascitic) | Ascites, often with fever and weight loss; the commonest type |
| Dry (adhesive / plastic) | Dense adhesions cause subacute intestinal obstruction; the abdomen feels doughy |
| Fibrous (loculated) | Pain, distension, ill-defined tender masses of matted bowel and omentum ("abdominal cocoon") |
Thickened, rolled-up omentum may be felt as a transverse mass.
A "doughy" abdomen with ascites or a vague mass in a young patient with fever and weight loss is the textbook clue to tuberculous peritonitis.
Investigations
Blood and general tests
- Raised ESR/CRP, anaemia (often normocytic), low albumin.
- Chest X-ray: may show active or healed TB (about half).
- Sputum for AFB and GeneXpert (Xpert MTB/RIF) if there is cough.
- HIV test in every patient.
- Tuberculin test or interferon-gamma release assay support infection but cannot prove active disease; they are often positive in healthy people in Pakistan.
Ascitic fluid in TB peritonitis
| Test | Typical finding |
|---|---|
| Appearance | Straw-coloured, clear |
| Protein | High (an exudate, above about 20–25 g/L) |
| SAAG | Low (less than 11 g/L) |
| Cells | Lymphocytes predominate |
| Adenosine deaminase (ADA) | Raised; a useful supportive test |
| AFB smear | Almost always negative |
| Culture | Slow (weeks) and often negative |
Serum albumin 32 g/L, ascitic albumin 25 g/L
SAAG = 32 − 25 = 7 g/L → low gradient (under 11) → not portal hypertension; think TB, malignancy, pancreatitis or nephrotic syndrome
Compare cirrhosis: serum 30, ascites 12 → SAAG = 18 g/L (high, portal hypertension)
Peritoneal carcinomatosis also gives a low-SAAG, high-protein ascites. Look for malignant cells (cytology) and for raised ADA and lymphocytes to separate them.
Imaging
- Ultrasound: ascites (sometimes with fine septations), thick bowel wall, enlarged mesenteric nodes, matted loops.
- CT abdomen: thickened ileocaecal wall, enlarged nodes with central low density (necrosis), thick smooth or nodular peritoneum and omentum, ascites.
- Barium meal follow-through / small bowel enema (or CT/MR enterography):
- Narrowed, rigid terminal ileum and contracted caecum.
- Pulled-up (subhepatic), conical caecum, with the ileum running straight up into it instead of joining at an angle.
- Short, multiple strictures with dilated bowel between them.
- Wide-open, gaping ileocaecal valve with narrowed terminal ileum (Fleischner sign) and rapid emptying of the ileocaecal segment (Stierlin sign).
- Plain abdominal X-ray in acute obstruction: dilated small bowel loops and fluid levels.
Tissue diagnosis
- Colonoscopy with biopsies of the terminal ileum and caecum: transverse ulcers, nodules, strictures, a deformed ileocaecal valve.
- Laparoscopy for peritoneal disease: tubercles scattered over the peritoneum, adhesions, ascites; peritoneal biopsy gives the diagnosis.
- Histology: caseating granulomas with Langhans giant cells; acid-fast bacilli may be seen with a Ziehl–Neelsen stain.
- Culture and GeneXpert on tissue confirm TB and detect rifampicin resistance.
A histological diagnosis is ideal but not always possible. When suspicion is high and other causes are excluded, antituberculous treatment can be started and the response watched.
TB versus Crohn disease
| Feature | Intestinal TB | Crohn disease |
|---|---|---|
| Ulcers | Transverse, along lymphatics | Longitudinal, deep, fissuring, aphthous; "cobblestone" mucosa |
| Distribution | Ileocaecal; short strictures | Skip lesions anywhere from mouth to anus |
| Granulomas | Large, confluent, caseating | Small, non-caseating, scattered |
| Ileocaecal valve | Often gaping/destroyed | Often narrowed |
| Perianal disease | Uncommon | Common (fistulas, fissures, abscesses) |
| Fistulas to skin/bladder | Uncommon | Common |
| Chest X-ray | May show TB | Normal |
| Ascites | Common | Uncommon |
| Necrotic mesenteric nodes on CT | Suggest TB | Uncommon |
| AFB, culture, GeneXpert | May be positive | Negative |
| Course | Responds to ATT | Relapsing; needs immunosuppression |
In Pakistan, always exclude TB before diagnosing Crohn disease, and always screen for latent TB before steroids or anti-TNF drugs.
"TB ulcers go Transverse; Crohn ulcers Cut lengthwise."
Management
Antituberculous therapy (ATT)
- First-line drugs: isoniazid (H), rifampicin (R), pyrazinamide (Z), ethambutol (E).
- Standard drug-sensitive regimen: 2 months HRZE + 4 months HR = 6 months, as for pulmonary TB.
- Some clinicians extend treatment in severe or slow-responding disease; follow the current National TB Control Programme (NTP) Pakistan guidance, which can change.
- Give pyridoxine with isoniazid; monitor liver function (hepatotoxicity of H, R and Z).
- Send tissue for GeneXpert/culture where possible, as drug-resistant TB occurs.
- Nutritional support and correction of anaemia are part of treatment.
Surgery
Surgery is for complications, ideally combined with full ATT under joint medical and surgical care.
| Situation | Approach |
|---|---|
| Subacute obstruction from strictures | Often settles on ATT alone; if not, strictureplasty or limited ileocaecal resection once disease is controlled |
| Acute obstruction in a very sick patient | Resuscitate; do the least needed to save life (for example ileotransverse bypass), then definitive resection later |
| Perforation | Resuscitate, resect the affected segment; exteriorise (stoma) if contamination is heavy or the patient is unstable |
| Diagnostic doubt | Laparoscopy and biopsy |
| Abscess, bleeding, fistula | Drainage or resection as needed |
Resections should be conservative, as in Crohn disease.
Paradoxical reaction
Strictures may narrow further as they heal with fibrosis during ATT, causing obstruction even though the infection is responding.
Expect: the commonest site (ileocaecal), why the terminal ileum is affected, ulcerative versus hyperplastic types, transverse ulcers, the doughy abdomen, ascitic fluid findings (exudate, lymphocytes, low SAAG, raised ADA), barium signs (pulled-up caecum, narrowed terminal ileum), caseating granulomas, differences from Crohn disease, the 6-month ATT regimen, screening for TB before anti-TNF drugs, and the place of surgery for obstruction and perforation.
Quick revision
- Commonest gut site: ileocaecal (lymphoid tissue, stasis).
- Ulcerative type: transverse ulcers; hyperplastic type: stricture and RIF mass.
- Normal chest X-ray does not exclude it.
- TB peritonitis: wet, dry, fibrous; doughy abdomen.
- Ascites: exudate, lymphocytes, SAAG under 11, raised ADA; AFB smear usually negative.
- Barium: pulled-up caecum, narrowed terminal ileum, short strictures.
- Histology: caseating granulomas with Langhans giant cells; Crohn: non-caseating.
- ATT 2HRZE + 4HR; check current NTP guidance.
- Surgery only for complications; obstruction may settle on ATT.
Written by The House Job from standard references (Kumar and Clark's Clinical Medicine; Bailey & Love's Short Practice of Surgery).
FAQ
Why is the ileocaecal region the commonest site of intestinal TB?
It is rich in lymphoid tissue, contents move slowly there, and absorption is high, so swallowed bacilli have more time and contact with the mucosa.
What ascitic fluid findings suggest tuberculous peritonitis?
A straw-coloured exudate with high protein, a low serum–ascites albumin gradient, lymphocyte predominance and a raised adenosine deaminase.
How can ileocaecal TB be told apart from Crohn disease?
TB tends to show transverse ulcers, caseating granulomas, necrotic nodes, ascites and positive AFB or GeneXpert, while Crohn shows skip lesions, longitudinal ulcers, perianal disease and non-caseating granulomas.
Is surgery needed for intestinal TB?
Usually not; ATT is the main treatment, and surgery is kept for obstruction that does not settle, perforation, abscess, bleeding or diagnostic doubt.