An 82-year-old man presented with a three-day history of abdominal distention and nausea. His family had a history of tuberculosis, and his past surgical history included strangulated small bowel obstruction 35 days prior. Then, he underwent release surgery without bowel resection (Figure 1).
Abdominal ultrasound sonography revealed ascites around the small intestine in the encapsulated area. Abdominal computed tomography further showed a mass of jejunum in the encapsulated area with ascites and calcified nodules (Figure 2).
We aspirated ascites comprising serous blood. Cytology, culture, including Mycobacterium tuberculosis, and other ascites laboratory data did not indicate malignancy or tuberculosis. A blood test did not confirm tuberculosis nor other malignancy; interferon-gamma release assays, CA125, and other tumor markers were unremarkable. Then, serum albumin and C-reactive protein were 2.5 g/dL and 6.4mg/dL, respectively. The nasogastric tube did not improve the ileus, and he underwent surgery. The small intestine was enveloped in dense fibrous tissue with calcified nodules and became a contiguous mass like sclerosing encapsulating peritonitis (SEP), also known as an abdominal cocoon (Figure 3).
This section, which lacked peristalsis without signs of obstruction, was resected. Histopathological evaluation of the capsule, nodules, and resected bowel did not reveal an apparent cause of abdominal cocoon; chronic dense fibrous tissue without caseous granuloma. Thus, we diagnosed an idiopathic abdominal cocoon. While tuberculosis peritonitis was most likely, we did not confirm the cause of the abdominal cocoon.