We describe a 35-year-old woman with colonic phlebitis of unknown orig
in accompanied by effusion of serum protein into the peritoneal cavity
. Abdominal ultrasonography and computed tomography showed massive asc
ites and edematous wall thickness of the colon. Laboratory examination
of the peritoneal fluid showed a high concentration of protein, proba
bly due to nonselective efflux of serum protein. The main histopatholo
gical finding was extensive edema of the submucosa with vasculitis in
the colon. This kind of phlebitis with massive ascites, but without sy
stemic involvement, and with the ascitic fluid almost identical to the
serum protein level, has not been reported previously.