How do you decide which patients get antibiotics before their endoscopic procedures and which do not? Perhaps you consider the patient's risk factors and the procedure she's about to undergo. Or perhaps you've developed your own protocols. Whatever you do, the scientific evidence backing it is probably pretty slim - controlled studies on the effectiveness of prophylactic antibiotics are rare. To strengthen your footing, I set out to find the most recent indications for administrating antibiotics to endoscopy patients. I pored over journals, committee recommendations, statistics, verdicts and testimony from gastroenterologists from over the past two decades. Here's what I found out.

Calculated risks
Some physicians prefer a conservative approach to antibiotic prophylaxis, while others are more aggressive. Shifting recommendations make it difficult to maintain a strong protocol. The present consensus is reasonably straightforward regarding the best standard of care for endoscopy patients requiring prophylactic antibiotics.

For the most common procedures performed in an endoscopy suite, such as esophogastroduodenoscopies and colonoscopies, there's a relatively low (4 percent) risk of infection. Most patients won't need antibiotics, but cirrhotic patients presenting with gastrointestinal bleeding should always receive antibiotic prophylaxis.

In other situations, you'll need to make a case-by-case assessment for patients with one or more high-risk factors. These include:

• a prosthetic heart valve;
• a history of endocarditis;
• a recently (within one year) implanted systemic-pulmonary shunt or synthetic vascular graft (infection of vascular grafts has a high rate of morbidity and mortality that decreases with time)
• severe neutropenia (<100x109/liter) and
• complex cyanotic congenital heart disease.

In contrast, the risk of infection is much higher for esophageal dilation (45 percent) or sclerotherapy (as high as 50 percent). Here, everyone with high-risk factors or cirrhosis should receive antibiotics. Further, you should consider offering prophylaxis to those with a moderate risk factor such as:

• a mitral valve prolapse with insufficiency;
• rheumatic valvular or congenital cardiac lesion;
• hypertrophic cardiomyopathy;
• ventriculo-peritoneal shunt;
• transplant patients on high-dose steroids; and
• moderate neutropenia (100-500x109/liter).

Other procedures may also call for more stringent measures based on the odds of developing an infection. For example, the chances of infection from variceal banding is 6 percent, but antibiotics should be given to all high-risk patients and considered for those at low risk due to the variety of infectious culprits. Laser therapy patients may have up to a 34-percent risk of infection, but you should administer antibiotics only to high-risk patients since the only threats come from the normal flora of the patient's skin and mucous membranes.

The ounce of prevention
In each case, the course of treatment is the same: parenteral ampicillin/vancomycin with parenteral gentamycin before the procedure. Add parenteral metronidazole for neutropenic patients. These drugs can prevent endocarditis, symptomatic bacteremia and bacterial colonization in cardiac and non-cardiac prosthetics. Other invasive procedures, such as endoscopic ultrasound-guided fine needle aspiration, require an agent such as parenteral levofloxacin. Researchers caution against medicating patients who don't meet criteria for prophylactic antibiotics. Besides the financial burden, unnecessary antibiotic administration can result in allergic drug reactions, drug resistance or antibiotic-related colitis. Keep up with developments; it's clear that more research is needed into what defines high-risk patients.