Matrix metalloproteinase levels in peritoneal effluents were increased in a patient with appendicitis undergoing continuous ambulatory peritoneal dialysis.

A differential diagnosis of common bacterial peritonitis and appendicitis is difficult in continuous ambulatory peritoneal dialysis (CAPD) patients, and thus the definite diagnosis of appendicitis is often delayed. In this case, a 60-year-old man undergoing CAPD was at first diagnosed with bacterial peritonitis but not appendicitis, and antibiotics were administered. The number of leukocytes in the peritoneal effluent decreased mildly, but the level of C-reactive protein continued to be high and the pain aggravated. When the catheter was removed, suppurative appendicitis was confirmed for the first time. Levels of matrix metalloproteinase (MMP)-2 and -9 in peritoneal effluents were markedly high. Appendicitis should be diagnosed as early as possible because MMPs directly injure the peritoneum via degradation of extracellular matrix proteins. Future studies in a greater numbers of cases of appendicitis are required.