Abdominal tuberculosis mimicking a disseminated appendicular malignancy

A 50-year-old female presented with right-sided flank pain for 3 weeks duration. She had associated low backache, fatigability, loss of weight and appetite for the past 3 months. Physical examination revealed left cervical lymph node enlargement and hepatosplenomegaly. Routine lab investigations showed an elevated total WBC count of 13,700 WBCs per microliter (normal range is 4500 to 11,000 WBCs per microliter), C-reactive protein of 82 mg/L (normal range is below 3 mg/L) and ESR - 80 mm/hr (normal range for women is 0-29 mm/hr).

On ultrasound of the abdomen showed a tubular blind-ending bowel-related structure (caliber of 1.2 cm) in right iliac fossa with thickened wall. There was no free fluid or fluid collections in RIF. (Figure 1).

Contrast-enhanced CT of the abdomen showed a distended appendix (measures approximately 1.85 cm in calibre) replaced by a soft tissue density mass associated with periappendiceal fat stranding and enlarged ileocecal lymph nodes (measures 1 cm in short-axis diameter). (Figure 2a, 2b, 2c, 2d).

There was mild hepatosplenomegaly (craniocaudally the right lobe of liver measures 16 cm and spleen measures 12 cm).

Her spleen showed a mixed echogenic mass (approximately measures 7.9 x7cm) with absent colour Doppler flow. (Figure 2a). On CT abdomen there was a solitary lobulated non enhancing hypodense mass within the splenic parenchyma (measures approximately 6.8x7.9 cm, mean HU 21). (Figure 3a, 3b).

The D12 vertebral body was sclerotic without associated soft tissue, collections or significant endplate erosions. (Figure 4).

On imaging, a presumptive diagnosis of disseminated primary appendicular malignancy and a differential diagnosis of abdominal tuberculosis were considered.

Colonoscopy showed polypoidal mucosa in caecum surrounding the appendicular opening and histopathological examination revealed granulomatous colitis most likely tuberculosis.

Background:

Tuberculosis is an aerosol infection caused by mycobacterium tuberculosis and commonly affects the lung. However, there has been a significant increase in extrapulmonary manifestations in the past decade. Abdominal involvement may occur in the GI tract, peritoneum, lymph nodes or solid viscera.

Clinical Perspective:

Abdominal tuberculosis is regarded as a great mimicker of other pathology which may lead to diagnostic delays and development of complications. Gastrointestinal involvement usually occurs secondary to pulmonary TB with no evidence of pulmonary disease seen radiologically in most cases. The most common site of GI involvement is ileocecal region (90%) due to abundant lymphoid tissue. Appendicular involvement is quite rare, usually secondary to TB elsewhere in abdomen and therefore the diagnosis is usually made after the histopathological examination.[1,2].

Imaging Perspective:

CT is the mainstay for investigating possible abdominal tuberculosis.GI involvement may show wall thickening of cecum and terminal ileum with mesenteric lymphadenopathy. However, the characteristic findings include asymmetrical thickening of ileocecal valve, medial wall of cecum and central low attenuation in lymph nodes. Perforation and fistulas are the most frequent gastrointestinal complications and the small bowel and the colon are the most common sites. Other complications include vascular complications, intussusception and obstruction of the small bowel[1,3].

Hepatosplenic TB is common in patients with disseminated disease and is either micronodular- military or macronodular. Miliary involvement is seen in patients with miliary pulmonary tuberculosis and is characterized by innumerable 0.5-2 mm nodules which may not be detected at CT. Macronodular hepatic tuberculosis is uncommon and show either diffuse hepatomegaly with low attenuation lesions or a single tumour-like mass.

On ultrasound splenic involvement may show multiple regular hypoechoic nodules or irregular hypoechoic/mixed echoiec lesions (represent splenic abscess).CT findings in splenic involvement are isolated splenomegaly, single or multiple hypodense focal lesions, splenic abscess with or without splenic calcifications  [4,5].

Skeletal involvement occur in approximately 1-3% patients, spine being commonest (50%). Most common site being upper lumbar/lower thoracic with vertebral body more commonly involved than posterior elements. More than one vertebral involvement is seen. Typical form shows destruction of two adjacent vertebral bodies and opposing end plates, destruction of the intervening intervertebral disc and a paravertebral or psoas abscess [3].

Abdominal TB is generally responsive to medical treatment, and early diagnosis and management can prevent unnecessary surgical intervention. However, abdominal TB should be considered a surgical problem in the acute and chronic abdomen[4,6].

Conclusion:

Diagnosing abdominal tuberculosis remains a great challenge even for experienced clinicians and radiologists and a high index of suspicion is essential for reaching its diagnosis. However, TB should be considered in the list of differential diagnoses in areas of high prevalence and in immunocompromised patients.