The body's natural defenses work better after "keyhole" gut surgery than after open surgery, a new study shows.

Thanks to new surgical tools, doctors now can perform many kinds of operations without having to make the large incisions typical of open surgery. These minimally invasive surgical techniques are often called keyhole surgery because they require only small cuts into the body.

In trained and experienced hands, these techniques sometimes work even better then older techniques. Why? One reason is that the less-invasive techniques keep the body from shutting down its own natural disease-fighting systems, find Matthias W. Wichmann, MD, and colleagues at Ludwig-Maximilians University, in Munich, Germany.

"Our findings ... help explain the reported lower rate of infectious complications in these patients," Wichmann and colleagues write in the July issue of the Archives of Surgery.

The researchers studied 70 patients with various diseases of the colon or rectum. Half underwent open surgery. The other half underwent keyhole surgery.

Read WebMD's "'Keyhole' Surgery Effective for Colon Cancer"

Patients who undergo surgery usually have a surge in inflammation -- a response to trauma that causes body tissues to redden and swell dangerously. There was less of this reaction in patients who underwent keyhole surgery.

And that's not all. While the body's highly specialized, specific immune responses shut down after both kinds of surgery, the less-invasive surgery left the body's more general first-line immune defenses more intact.

"Post-operative immune dysfunction is important for patients ... because it influences the rate of infectious complications as well as the growth of disseminated tumor cells," Wichmann and colleagues write. "In patients with cancer, better preserved post-operative immunity could result in better long-term [cancer] results."

Read WebMD's "Learn More about Laparoscopic Surgery"

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCE: Wichmann, M.W. Archives of Surgery, July 2005; vol 140: pp 692-697.