Biliary tract infections: a guide to drug treatment

Initial therapy of acute cholecystitis and cholangitis is directed towards general support of the patient, including fluid and electrolyte replacement, correction of metabolic imbalances and antibacterial therapy. Factors affecting the efficacy of antibacterial therapy include the activity of the agent against the common biliary tract pathogens and pharmacokinetic properties such as tissue distribution and the ratio of concentration in both bile and serum to the minimum inhibitory concentration for the expected micro-organism. Antimicrobial therapy is usually empirical. Initial therapy should cover the Enterobacteriaceae, in particular Escherichia coli. Activity against enterococci is not required since their pathogenicity in biliary tract infections remains unclear. Coverage of anaerobes, in particular Bacteroides spp., is warranted in patients with previous bile duct-bowel anastomosis, in the elderly and in patients in serious clinical condition. In patients with acute cholecystitis or cholangitis of moderate clinical severity, monotherapy with a ureidopenicillin--mezlocillin or piperacillin--is at least as effective as the combination of ampicillin plus aminoglycoside. In severely ill patients with septicaemia, an antibacterial combination is preferable. Therapy with aminoglycosides, mostly for Pseudomonas aeruginosa-related infections, should not exceed a few days because the risk of nephrotoxicity seems to be increased during cholestasis. Relief of biliary obstruction is mandatory, even if there is clinical improvement with conservative therapy, because cholangitis is most likely to recur with continued obstruction. Emergency invasive therapy is reserved for patients who fail to show a clinical response to antibacterial therapy within the first 36 to 48 hours or for those who deteriorate after an initial clinical improvement. Immediate surgery is indicated for gangrenous cholecystitis and perforation with peritonitis. Long-term administration of antibacterials is required for recurrent cholangitis, as seen in bile duct-bowel anastomosis. Oral cotrimoxazole (trimethoprim/sulfamethoxazole) is the preferred agent. Wound infection rates after biliary tract surgery can be significantly reduced by preoperative administration of prophylactic antibacterials. Newer generation beta-lactams have not proven to be of greater benefit than older agents such as cefuroxime or cefazolin. Antibacterial prophylaxis before endoscopic retrograde cholangiopancreatography (ERCP) should be reserved for patients with obstructive jaundice, since the risk of infectious complications seems to be strongly associated with this clinical condition. Failure to achieve full biliary drainage is the most important factor in predicting septicaemia, and prophylaxis should be prolonged until the bile duct is unobstructed. Piperacillin, cefazolin, cefuroxime, cefotaxime and ciprofloxacin are effective for this indication.