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Efferent Loop Syndrome After Gastric Bypass Surgery

Efferent Loop Syndrome After Gastric Surgery

Efferent loop syndrome is one of two "loop syndromes" that can occur after some types of gastric surgery. In a loop syndrome, a portion or "limb" of the small intestine becomes blocked.

This blockage can happen because of a hernia within the small intestine, which becomes trapped and blocked. It can also happen because of blockage from an adhesive band or kinking because of scarring or poor reconstruction during the weight-loss surgery. In some cases, part of your intestine may slide inside another part of the intestine (called intussusception), causing an efferent loop blockage.

Facts about efferent loop syndrome

Of the two types of loop syndromes, the other type, afferent loop syndrome, is the more common. Efferent loop syndrome is quite rare. Surgeons have improved gastric surgery, so both types of loop syndromes are now less common.


When efferent loop syndrome occurs, it is usually within the first few weeks after surgery. But it can also develop even years after weight-loss surgery.

As a result of the blockage, secretions such as bile and other secretions from the pancreas build up in the intestines and begin to cause problems. Rarely, a rupture of the intestinal wall can occur.

You may have the following symptoms:

  • Extreme, often cramping, abdominal pain

  • Nausea

  • Distended abdomen and pain relieved only by vomiting

  • Vomiting large quantities of bile, a green digestive fluid

Contact your doctor immediately if you have any of these symptoms any time after your weight-loss surgery.


If your doctor suspects that you have efferent loop syndrome as a result of a gastric bypass procedure, he or she may perform a physical exam, upper GI radiography, or a CT scan to look for the blockage. Doctors will generally use an endoscope, a thin, lighted tube with a tiny camera at the end, passed through your mouth and into your intestines to confirm the diagnosis.


Surgery is required to correct efferent loop syndrome and restore the intestines to healthy working order. Depending on how severe the efferent loop syndrome has become, the surgery may have to repair lesions, fix a hernia, close any anatomical defects, repair the intestine, and possibly make changes or repairs to the gastric surgery itself.