What is the difference between an external biliary drainage catheter and an internal or external biliary drainage catheter?
External drains end within the bile ducts above the site of obstruction. The obstructed biliary tree is decompressed by draining the bile externally into a drainage bag. Internal/external drains cross the site of obstruction and end within the small bowel. Bile may drain externally into a drainage bag or internally from the biliary tree through side holes in the catheter into the small bowel. Internal/external drains are advantageous because they can be capped externally to allow for internal drainage to the small bowel only. Internal/external drainage catheters are placed whenever it is possible to cross the site of obstruction because drainage to the bowel is more physiologic than external drainage, and the catheters also are easier to care for. Internal drainage prevents loss of bile salts and electrolytes and allows the bile to aid in fat metabolism within the bowel. It is important to monitor the volume status and electrolytes of patients when draining bile externally. These patients can lose a large volume of fluids rich in electrolytes.