Tuberculous peritonitis is a chronic diffuse peritoneal infection caused by Mycobacterium tuberculosis. It can occur at any age but is more common in young and middle-aged individuals, with a male-to-female ratio of approximately 1:2.
Etiology and Pathogenesis
The condition is often secondary to pulmonary tuberculosis or tuberculosis in other parts of the body. The primary route of infection is direct spread from tuberculous lesions within the abdominal cavity, while a minority of cases result from lymphatic or hematogenous dissemination, leading to miliary tuberculous peritonitis.
Pathology
Based on pathological features, tuberculous peritonitis can be classified into exudative, adhesive, and caseous types, with the first two being more common. These types may coexist in some cases.
Exudative Type
The peritoneum shows hyperemia and edema, with fibrin exudates on its surface. Yellowish (or grayish-white) small nodules that may coalesce are often present. Ascitic fluid is typically straw-yellow or slightly bloody, and occasionally chylous.
Adhesive Type
Extensive fibrous tissue proliferation and protein deposition lead to significant thickening of the peritoneum and mesentery. Adhesions between intestinal loops may result in intestinal obstruction.
Caseous Type
This type often evolves from the exudative or adhesive forms and may exhibit features of both. It is characterized by caseous necrosis, often involving mesenteric lymph nodes and forming tuberculous abscesses. Lesions may extend to adjacent organs, resulting in fistulas or sinuses when they penetrate hollow organs or the abdominal wall.
Clinical Manifestations
Clinical features vary depending on the primary lesion, route of infection, host response, and pathological type. The onset is typically insidious, with mild symptoms in the early stages that are easily overlooked. In rare cases, the onset may be acute, presenting with acute abdominal pain or sudden high fever.
Systemic Symptoms
Symptoms of tuberculous toxemia are common, primarily including low-grade or moderate fever, often with a remittent or persistent fever pattern. Diaphoresis may also occur. High fever with pronounced toxemia is more frequently observed in the exudative or caseous types, or in patients with severe tuberculosis, such as miliary pulmonary tuberculosis or caseous pneumonia. In advanced stages, malnutrition is common, leading to weight loss, edema, anemia, glossitis, angular stomatitis, and symptoms of vitamin A deficiency.
Abdominal Pain
Pain is usually located around the umbilicus, in the lower abdomen, or diffusely across the abdomen. It is often dull and persistent but may also be intermittent. Occasionally, it may present as an acute abdomen, caused by rupture of caseous necrotic lesions in mesenteric lymph nodes or other intra-abdominal tuberculous foci, or by acute perforation of intestinal tuberculosis.
Abdominal Distension
A sensation of bloating and abdominal distension is common, often accompanied by visible abdominal swelling. This is usually due to intestinal dysfunction caused by tuberculous toxemia or peritonitis. Ascites is often present, typically in small to moderate amounts.
Abdominal Wall Rigidity
A doughy or stiff sensation of the abdominal wall may be noted. This is attributed to irritation of the peritoneum or chronic inflammation leading to peritoneal thickening, increased muscle tension, or adhesions between the abdominal wall and intra-abdominal organs. However, this is not a specific finding. Abdominal tenderness is generally mild, but significant tenderness with rebound pain may suggest caseous tuberculous peritonitis.
Abdominal Mass
Abdominal masses are more commonly observed in the adhesive or caseous types, often located around the umbilical region. These masses are typically formed by thickened omentum, enlarged mesenteric lymph nodes, adherent intestinal loops, or accumulations of caseous necrotic purulent material. They vary in size, have irregular borders, and an uneven surface, with a nodular texture, limited mobility, and may be tender.
Other Symptoms
Diarrhea is common, typically occurring 3–4 times per day, with stools often being mushy. This is usually caused by intestinal dysfunction associated with peritonitis. Alternating diarrhea and constipation may also occur. Complications such as intestinal obstruction, intestinal fistulas, and intra-abdominal abscesses may develop.
Laboratory and Other Examinations
Blood Tests
Mild to moderate anemia may be present. In cases with acute dissemination of abdominal tuberculosis or caseous disease, white blood cell counts may be elevated. Erythrocyte sedimentation rate (ESR) is often accelerated during active disease.
Tuberculin Test and Interferon-Gamma Release Assay (IGRA)
A strongly positive tuberculin test supports the diagnosis. IGRA has a high negative predictive value and sensitivity but limited specificity.
Ascitic Fluid Analysis
Ascitic fluid is often straw-yellow exudate that may coagulate naturally after standing. In some cases, it appears turbid or slightly bloody, and rarely chylous. The specific gravity is typically above 1.018, protein qualitative tests are positive, and protein levels exceed 30 g/L. White blood cell counts are usually greater than 500×106/L, predominantly lymphocytes or monocytes. However, in cases of hypoalbuminemia, protein levels in ascitic fluid may decrease. A serum-ascites albumin gradient (SAAG) < 11 g/L is helpful for diagnosis. Adenosine deaminase (ADA) activity in ascitic fluid is often elevated, but malignancies should be excluded. An increase in ADA isoenzyme ADA2 provides greater specificity for this condition. Routine bacterial cultures of ascitic fluid have a low positivity rate, but concentrating the fluid for Mycobacterium tuberculosis cultures or animal inoculation can significantly improve detection rates.
Abdominal Imaging
Ultrasound, CT, and MRI often reveal thickened peritoneum, ascitic fluid, intra-abdominal masses, or fistulas. Abdominal X-rays may show calcified mesenteric lymph nodes. Contrast studies may demonstrate intestinal adhesions, intestinal tuberculosis, fistulas, or extraluminal masses.
Laparoscopy
Laparoscopy is useful in cases where the diagnosis is unclear. Scattered or clustered gray-white nodules may be observed on the peritoneum, omentum, or visceral surfaces, along with loss of normal serosal luster and fibrous or sheet-like adhesions in the abdominal cavity. Histopathological examination of biopsied tissue can confirm the diagnosis. Laparoscopy is contraindicated in cases of extensive peritoneal adhesions.
Diagnosis
The following features should raise suspicion for tuberculous peritonitis:
- Young to middle-aged patients with a history of tuberculosis infection or contact, along with evidence of tuberculosis in other organs.
- Prolonged fever of unknown origin accompanied by abdominal pain, distension, ascites, abdominal wall rigidity, or abdominal masses.
- Ascitic fluid characterized as exudate, predominantly lymphocytic, with negative routine bacterial cultures and significantly elevated ADA (especially ADA2).
- Imaging findings of intestinal adhesions, peritoneal thickening, intestinal obstruction, or scattered calcifications.
- Strongly positive tuberculin test or positive IGRA.
A clinical diagnosis can often be made in typical cases, and confirmation is achieved if anti-tuberculosis treatment is effective. For atypical cases, laparoscopy with biopsy may be performed after excluding contraindications.
Differential Diagnosis
Conditions Primarily Presenting with Ascites
Malignant Abdominal Tumors
These include peritoneal metastatic carcinoma, malignant lymphoma, and peritoneal mesothelioma. The presence of cancer cells in ascitic fluid confirms the diagnosis. When cytology is negative, imaging, endoscopy, or other examinations may help identify the primary lesion.
Cirrhotic Ascites
This is typically transudative with SAAG ≥ 11 g/L and ascitic fluid albumin < 25 g/L, accompanied by characteristic signs of decompensated liver cirrhosis. In cases of spontaneous bacterial peritonitis, ascitic fluid may become exudative, but neutrophils predominate, and routine bacterial cultures are positive. When lymphocytes predominate, bacterial cultures are negative, and there is a history or evidence of tuberculosis, the possibility of cirrhosis complicated by tuberculous peritonitis should be considered.
Other Causes of Ascites
These include chronic pancreatitis-associated ascites, connective tissue diseases, Meigs syndrome, Budd-Chiari syndrome, and constrictive pericarditis.
Conditions Primarily Presenting with Abdominal Masses
Abdominal masses should be differentiated based on their location and characteristics from abdominal tumors (e.g., hepatocellular carcinoma, colorectal cancer, ovarian cancer) and Crohn's disease.
Conditions Primarily Presenting with Fever
Tuberculous peritonitis should be distinguished from other diseases causing prolonged fever.
Conditions Primarily Presenting with Acute Abdominal Pain
Acute peritonitis caused by rupture of caseous necrotic lesions or intestinal obstruction due to tuberculous peritonitis should be differentiated from other causes of acute abdomen.
Treatment
Early administration of appropriate and full-course anti-tuberculosis chemotherapy is essential to achieve recovery, prevent recurrence, and avoid complications.
Nutritional Support
Nutritional support should be enhanced to improve the patient’s nutritional status.
Anti-Tuberculosis Therapy
The treatment regimen follows the principles outlined for pulmonary tuberculosis. In cases with adhesions or caseous lesions, where extensive fibrous proliferation hinders drug penetration into the lesions, combination therapy is required, and the treatment duration may need to be appropriately extended.
Abdominal Paracentesis
For cases with a large volume of ascites, drainage of ascitic fluid may be performed to alleviate symptoms.
Surgical Treatment
Indications for surgery include:
- Complete or partial intestinal obstruction that does not improve with medical treatment.
- Acute intestinal perforation or intra-abdominal abscess unresponsive to antibiotic therapy.
- Intestinal fistulas that fail to close despite anti-tuberculosis chemotherapy and enhanced nutritional support.
- Diagnostic uncertainty where malignancy cannot be excluded, necessitating exploratory surgery.
Patient Education
Patient education is similar to that for intestinal tuberculosis.
Prevention
Early diagnosis and active treatment of tuberculosis in the lungs, intestines, mesenteric lymph nodes, fallopian tubes, and other sites can help prevent this condition.