Formation of Abdominal Cerebrospinal Fluid Pseudocyst

: A 63-year-old man who underwent insertion of a lumboperitoneal shunt developed gait disturbance. He had undergone surgery for gastric cancer 7 years and for ileus 5 years previously. Head computed tomography (CT) revealed enlargement of the ventricles. Abdominal CT revealed a cyst in the abdominal region and the distal segment of the peritoneal shunt tube located within the cyst. Laparotomy revealed the cyst located between the small intestine, colon, and peritoneum. The anterior wall of the cyst was excised. The distal segment of the peritoneal shunt tube was replaced in the rectovesical pouch. Histological examination showed that the cyst wall consisted of inner fibrous tissue and outer fat tissue without epithelial lining, and invasion of lymphocytes. The diagnosis was pseudocyst. Only 29 cases of abdominal cerebrospinal fluid (CSF) pseudocysts have been reported in adults. Although the mechanism underlying the formation of abdominal pseudocyst remains to be clarified, several predisposing factors for cyst formation have been reported including changes in absorption of CSF due to inflammation or infection, peritoneal adhesions due to previous abdominal surgery, and increase in the protein content of the CSF. In our case, the medical history and histological features of the cyst wall indicated that formation of the abdominal pseudocyst was associated with previous surgery or inflammatory reaction.