Time-course ultrasonographic observation of a mesenteric pseudocyst of the sigmoid colon: report of a case.

A 35-year-old woman was referred to our hospital for investigation of lower abdominal pain and a feeling of fullness. At her first consultation, a transvaginal ultrasonography (US) revealed a homogeneous cystic mass in the lower abdomen. Over a period of 8 months the US findings of the content of this mass changed from fine and faint internal echoes to moderate amounts of irregularly contoured internal echoes. At laparotomy, the cystic mass, which measured 3.0 x 3.0 x 3.5 cm, appeared to arise in the sigmoid mesocolon and tightly adhered to the appendix. The cyst was unilocular and contained a slightly yellow gelatinous fluid. Microscopically, its wall was fibrous and lacked an epithelial lining, suggesting that it was a so-called pseudocyst arising from the sigmoid mesocolon. To our knowledge, this is the first case report documenting the time-course ultrasonographic observations of a mesenteric pseudocyst. Our findings suggest that the time-elapsed ultrasonographic changes might have been dependent on the interval between the onset of cystic formation and the US examination.