Peritoneal Tuberculosis and Closed-Loop Small Bowel Obstruction: Radiologic Insights, Pathophysiology, and Management

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 Keywords: Peritoneal tuberculosis, Closed-loop small bowel obstruction, Abdominal tuberculosis, CT imaging, Small bowel ischemia, Radiology case review, Peritoneal thickening, Omental caking

1. Introduction

Peritoneal tuberculosis (PTB) and closed-loop small bowel obstruction (SBO) represent a rare yet critical diagnostic combination that challenges even experienced radiologists and surgeons. 

While peritoneal tuberculosis is an insidious manifestation of Mycobacterium tuberculosis infection, typically mistaken for peritoneal carcinomatosis due to its nonspecific imaging features, closed-loop small bowel obstruction constitutes a surgical emergency with high risk of ischemia and necrosis.


This article reviews a classic case of a 64-year-old man with peritoneal tuberculosis–induced adhesional closed-loop SBO, illustrating the imaging findings, pathophysiology, epidemiology, differential diagnosis, and evidence-based management based on recent WHO and radiologic literature.

2. Pathophysiology

Peritoneal Tuberculosis

Peritoneal tuberculosis occurs when Mycobacterium tuberculosis disseminates hematogenously or via direct spread from an intra-abdominal focus, such as intestinal or fallopian tuberculous lesions. Within the peritoneum, macrophages and T-helper cells initiate a type IV hypersensitivity reaction, producing epithelioid granulomas and Langhans-type giant cells. The hallmark of this granulomatous inflammation is central caseous necrosis, leading to fibrosis and adhesion formation, which may subsequently cause mechanical obstruction of the small bowel.

Microscopically, confluent granulomas with epithelioid histiocytes, multinucleated giant cells, and caseation necrosis define the lesion. These adhesions, when organized, can constrict bowel loops, resulting in the “closed-loop” phenomenon.

Closed-Loop Small Bowel Obstruction

A closed-loop obstruction occurs when a segment of bowel is occluded at two adjacent points, forming an isolated loop. Venous congestion develops first, followed by arterial compromise and ischemia. The process rapidly leads to bowel wall necrosis, perforation, and peritonitis if untreated. Common causes include adhesions, internal hernias, and volvulus. In tuberculosis-related SBO, fibrotic peritoneal adhesions act as constricting bands, creating a dangerous closed-loop configuration.

3. Epidemiology

Globally, tuberculosis remains one of the top ten causes of death from infectious diseases. 

The WHO Global Tuberculosis Report (2024) highlights a resurgence in TB incidence following the COVID-19 pandemic, with approximately 10 million new cases annually.

Peritoneal tuberculosis constitutes only 1–3% of extrapulmonary TB cases, but its prevalence is higher in endemic regions such as South and East Asia, sub-Saharan Africa, and parts of Eastern Europe.

Risk factors include HIV infection, diabetes, chronic renal failure, and immunosuppressive therapy (especially TNF-α inhibitors). 

Closed-loop SBO itself is most commonly caused by postoperative adhesions but may also occur in tuberculosis-induced fibrosis or internal herniation.

4. Clinical Presentation

Patients with peritoneal tuberculosis often present insidiously with vague abdominal pain, fever, anorexia, weight loss, and ascites. Occasionally, as in the present case, acute abdominal symptoms occur due to fibrotic adhesions causing bowel obstruction.


Physical examination may reveal abdominal distension, tenderness, or signs of peritonitis in severe cases. 

Laboratory findings include elevated ESR, CRP, and hypoalbuminemia. Ascitic fluid typically shows high protein concentration and low SAAG (serum–ascites albumin gradient), with predominance of lymphocytes.


When the obstruction is acute and closed-loop in nature, symptoms escalate rapidly: cramping abdominal pain, bilious vomiting, and cessation of flatus or stool passage, often accompanied by localized tenderness.

5. Imaging Features

Contrast-enhanced CT remains the diagnostic cornerstone for both conditions.

CT Findings in Peritoneal Tuberculosis

  • Ascites: Either free-flowing or loculated (“wet type”).

  • Peritoneal thickening: Smooth or nodular enhancement.

  • Omental caking: Seen in fibrotic type, mimicking carcinomatosis.

  • Mesenteric nodularity and adhesions causing bowel fixation or obstruction.

  • Hepatic or splenic calcified granulomas, suggesting chronic tuberculous infection.

  • Associated chest findings: Micronodules or cavitary lesions support a tuberculous etiology.

CT Findings in Closed-Loop Small Bowel Obstruction

  • C- or U-shaped dilated loop with radial orientation (“whirl sign”).

  • Two closely approximated transition points (beak sign)—pathognomonic of closed-loop configuration.

  • Mesenteric vessel engorgement and bowel wall thickening, suggesting venous congestion.

  • Reduced bowel wall enhancement indicates ischemia or necrosis risk.

  • Peritoneal or mesenteric fluid often coexists.

6. Imaging Figures and Interpretations

Figure 1. (Axial CT, contrast-enhanced arterial phase)


Figure 2. (Axial CT, non-contrast)
Two closely spaced transition points are visible with compressed bowel wall between them—an adhesional band is suspected. The upstream bowel is distended, and downstream segments are collapsed.


Figure 3. (Axial CT, non-contrast)

Bowel wall thickening adjacent to the obstructed loop with surrounding mesenteric edema and ascites, implying inflammatory or ischemic change.


Figure 4. (Axial CT, non-contrast)
Diffuse peritoneal thickening with enhancement and small amounts of ascitic fluid; hepatic and splenic calcified granulomas indicate chronic tuberculosis.


Figure 5. (Axial CT, lung window)
Cavitary pulmonary lesion and micronodules, consistent with active pulmonary tuberculosis.


Figure 6. (Histopathology)
Peritoneal biopsy demonstrates confluent epithelioid granulomas with Langhans-type giant cells and central caseous necrosis, confirming tuberculous granulomatous inflammation.

7. Differential Diagnosis

The most challenging distinction is between peritoneal tuberculosis and peritoneal carcinomatosis.


Both exhibit ascites, omental thickening, and nodular peritoneal enhancement on CT. However, certain features favor tuberculosis:

  • Smooth, diffuse peritoneal thickening (vs. irregular nodularity in carcinomatosis)

  • Splenic or hepatic granulomas with calcification

  • Coexistent pulmonary TB findings

  • Positive ascitic fluid ADA or AFB culture

Other differentials include infectious peritonitis, Crohn’s disease, and fungal peritonitis. Definitive diagnosis requires peritoneal biopsy or AFB/PCR testing of ascitic fluid.

8. Diagnosis and Treatment

Diagnosis

  • CT imaging: Suggestive features, especially when combined with pulmonary or splenic TB.

  • Ascitic fluid analysis: Lymphocytic exudate, high ADA (>40 IU/L).

  • Histopathology: Caseating granulomas confirm diagnosis.

  • Microbiology: AFB culture or nucleic acid amplification (NAAT).

Treatment of Peritoneal Tuberculosis

According to the 2024 WHO guidelines, standard treatment for drug-sensitive peritoneal tuberculosis includes:

  • 2 months of intensive phase: Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), and Ethambutol (E).

  • 4 months of continuation phase: Isoniazid and Rifampicin (2HRZE/4HR regimen).
    Shorter four-month regimens may be considered for select patients under updated protocols.

  • In cases complicated by SBO or perforation, surgical intervention is mandatory for decompression and resection of nonviable bowel segments.

Treatment of Closed-Loop SBO

  • Urgent surgery is indicated if ischemia, peritonitis, or non-resolving obstruction is suspected.

  • Conservative therapy (nasogastric decompression, fluid resuscitation) is only appropriate in select, non-ischemic cases.

  • Early CT identification of reduced enhancement, mesenteric swirl, or peritoneal fluid predicts ischemia and mandates prompt surgical exploration.

9. Prognosis

With timely diagnosis and appropriate anti-tuberculous therapy, peritoneal tuberculosis carries a favorable prognosis.


However, delayed recognition or the presence of closed-loop obstruction with ischemia substantially worsens outcomes.


Mortality in surgical cases of ischemic SBO ranges between 10–30%, primarily due to delayed intervention.


For tuberculosis, the emergence of multidrug-resistant TB (MDR-TB) and immunosuppression remain key prognostic determinants.

10. Key Learning Points

  • Closed-loop SBO is a radiologic and surgical emergency; two closely located transition points and mesenteric swirl are diagnostic.

  • Peritoneal tuberculosis can closely mimic malignancy but should be suspected in the presence of calcified granulomas or concurrent pulmonary TB.

  • Histologic confirmation remains the diagnostic gold standard.

  • Early multidisciplinary coordination (radiology, surgery, infectious disease) is crucial for improved outcomes.

Quiz

Question 1: A 64-year-old man presents with acute abdominal pain and vomiting. CT shows radial dilatation of bowel loops with two adjacent transition points and mesenteric vessel engorgement. What is the most likely diagnosis?
A. Simple paralytic ileus
B. Closed-loop small bowel obstruction with ischemia risk
C. Peritoneal carcinomatosis
D. Bacterial enteritis

Question 2: Which diagnostic test provides the most definitive confirmation of peritoneal tuberculosis?
A. Serum CA-125
B. Colonoscopy
C. Peritoneal biopsy or ascitic AFB/PCR test
D. Abdominal ultrasound

Question 3: Histology reveals confluent granulomas with caseous necrosis and Langhans-type giant cells. What is the most likely etiology?
A. Mycobacterium tuberculosis infection
B. Crohn’s disease
C. Sarcoidosis
D. Fungal infection

Question 4: Which CT feature best predicts bowel ischemia in closed-loop SBO?
A. Mesenteric fat stranding alone
B. Decreased bowel wall enhancement
C. Ascites without wall thickening
D. Omental caking

Question 5: Which statement about peritoneal tuberculosis is TRUE?
A. It always requires surgical management
B. It presents exclusively as dry fibrotic form
C. It can mimic peritoneal carcinomatosis on imaging
D. It never coexists with pulmonary tuberculosis

Answer & Explanation

1. Answer: B. Explanation: Two close transition points and vascular congestion are hallmark features of closed-loop SBO requiring urgent surgical assessment.

2. Answer: C. Explanation: Imaging findings overlap with malignancy; only tissue biopsy or microbiologic confirmation can establish the diagnosis.

3. Answer: A. Explanation: The presence of central caseation and Langhans giant cells is typical for tuberculous granuloma.

4. Answer: B. Explanation: Reduced enhancement on contrast CT indicates ischemic compromise and impending necrosis.

5. Answer: C. Explanation: CT features of PTB and peritoneal carcinomatosis overlap; pulmonary involvement supports TB diagnosis.

References

[1] World Health Organization, Global Tuberculosis Report 2024, Geneva: WHO, Oct. 2024.
[2] M. Zins, I. Millet, and P. Taourel, “Adhesive Small Bowel Obstruction: Predictive Radiology to Improve Patient Management,” Radiology, vol. 296, no. 3, pp. 480–492, Sep. 2020.
[3] I. Millet et al., “Value of CT findings to predict surgical ischemia in small bowel obstruction: A systematic review and meta-analysis,” Eur. Radiol., vol. 25, pp. 1823–1835, 2015.
[4] H. K. Ha, J. I. Jung, M. S. Lee et al., “CT differentiation of tuberculous peritonitis and peritoneal carcinomatosis,” AJR Am. J. Roentgenol., vol. 167, pp. 743–748, 1996.
[5] E. V. Muñoz et al., “Computed tomography findings of peritoneal tuberculosis: Systematic review of seven patients,” Clin. Imaging, vol. 28, no. 5, pp. 340–343, 2004.
[6] E. K. Paulson et al., “Review of Small-Bowel Obstruction: The Diagnosis and Management,” Radiology, vol. 276, no. 2, pp. 325–336, 2015.
[7] A. Koff, “Diagnosing Peritoneal Tuberculosis: A Review,” Case Review, 2020.
[8] M. Miranda et al., “The Tuberculous Granuloma: An Unsuccessful Host Defense?,” Front. Immunol., 2012.

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