NEW YORK, Aug 06 (Reuters Health) -- Up to a fourth of appendices removed during appendectomy confound surgeons by appearing perfectly healthy and normal. Now, researchers say they have identified neuroimmune dysfunction as the probable cause of appendix pain in these cases.
Hypersensitivity to specific neural compounds "might cause abdominal pain" in about 15% to 25% of appendicitis cases, according to European researchers led by Dr. Markus Buchler of the University of Berne, Switzerland. Their findings are published in the August 7th issue of The Lancet.
About 6% of individuals will experience appendicitis during their lifetimes. The illness is characterized by acute abdominal pain, usually triggered by inflammation of the small intestinal appendage.
Nevertheless, a minority of appendectomies result in the removal of normal-sized, apparently healthy specimens. Because "every surgeon would like to avoid unnecessary appendectomies," Buchler's team focused on identifying the cause of pain in these cases.
To do so, they compared tissues from 16 inflamed appendices to tissues from 15 normal-looking specimens.
According to the investigators, 'normal' organs differed from inflamed organs in one important respect -- an increased density of nerve fibers reactive to two immune-system neuropeptides, SP and VIP.
SP and VIP are both strongly associated with the production of pain linked to inflammation. Buchler and colleagues believe that increased nervous sensitivity to either of these compounds could trigger the pain associated with appendicitis -- without the usual inflammation.
These findings were supported by the fact that 13 of the 15 patients with 'normal' appendices "were symptom-free after operation, even though their appendix appeared normal at (laboratory) examination."
Based on these findings, the authors believe that 'neuroimmune appendicitis' should now be listed as a unique disorder, apart from inflammatory appendicitis.
SOURCE: The Lancet 1999;354:461-466.
