An emergency medicine physician asked me to comment on the use of prophylactic antibiotics in patients having surgery for acute appendicitis and acute cholecystitis. He said in hospitals where he has worked in three different areas—New York, Miami and San Francisco—surgeons are using Imipenem for cholecystitis and Zoysn for appendicitis.

He wondered why those drugs were chosen and offered a few theories. They are as follows:

1) Surgeons are trying to avoid resistant bugs, so they’re using bigger guns

2) There is more pressure to reduce post-op complication numbers, so they’re using bigger guns

3) It’s easier to give one antibiotic to cover multiple bacterial types, instead of, say, cipro/flagyl or cefoxitin/flagyl

4) Patients do better with these big gun antibiotics

5) Residents are being taught incorrectly, and are just developing bad habits

Yes, it is mandated that everyone needs a dose of prophylactic antibiotics within an hour of surgery for appendicitis and cholecystitis. Of course, there are nuances.
Appendicitis is a disease involving an inflamed, eventually infected appendix so the use of antibiotics is possibly therapeutic and not simply prophylactic.
For acute cholecystitis, a similar argument can be made. The problem here is that it is often difficult to tell acute cholecystitis (with possibly infected bile) from biliary colic (pain caused by a gallstone impacted in the neck of the GB) without infection. Sometimes the GB ultrasound says acute cholecystitis, the surgeon says acute cholecystitis and the path report says chronic cholecystitis. There are many other permutations of those three observations. (e.g., US-biliary colic, surgeon-biliary colic, path-acute cholecystitis, etc.)
Note: I do not routinely culture peritoneal fluid in appendicitis or bile in cholecystitis because by the time the culture report comes back, most patients have been home for two days. There is evidence to support not culturing either fluid.
Honestly, I’m not so sure that people with early acute appendicitis really need antibiotics. Unless the appendix is perforated, I use only one preop dose. There are also similar differences in the imaging reports, surgeon description and path reports for this disease too.

I doubt that patients with biliary colic benefit from antibiotics either. The problem is that one may not discover that acute cholecystitis is present until one is in the abdomen. The same issue occurs with appendicitis where an unsuspected perforation may be found at surgery.

At least for now, at least one pre-op dose of an appropriate antibiotic seems reasonable.
Where I practiced for the last few years, we did not use Imipenem for GBs and only occasionally is Zosyn used for appys. Most of us use Unasyn for both except in the penicillin-allergic patient. For that patient, we use Levaquin and Flagyl. The problem with the latter two drugs is that they each are supposed to be infused over an hour. This is not always possible because the surgery may be started within an hour in certain circumstances, such as when an operating room happens to be vacant and the patient is ready to go. It’s a rare event, but it does happen.
There is no evidence that patients with either disease, who usually present from home, have resistant bacteria, and postoperative complications, especially infections, are not common with either disease. There is no evidence that patients do better with “big gun” antibiotics. In fact, most of the evidence that prophylactic antibiotics are even needed in these two operations comes from the pre-laparoscopic era. Wound infections are extremely uncommon with laparoscopic appendectomies and cholecystectomies. This is probably due to the fact that the wounds are small and in most cases, the specimen is removed in a plastic bag so the infected organ does not touch the subcutaneous tissue.
If residents are being taught to use “big gun” antibiotics for these two diseases, I agree it’s incorrect. There is little hope of changing this.

It is similar to the unfounded practice of giving everyone who is NPO a proton pump inhibitor. There is no scientific rationale for it. Yet everyone does it, and no amount of discussion will convince people to stop.

Skeptical Scalpel is a recently retired surgeon and was a surgical department chairman and residency program director for many years. He is board-certified in general surgery and a surgical sub-specialty and has re-certified in both several times. For the last two years, he has been blogging at and tweeting as @SkepticScalpel. His blog has had more than 340,000 page views, and he has over 4200 followers on Twitter.