What is afferent loop syndrome?

This uncommon problem can occur after some kinds of stomach surgery when the first part of the small intestine is brought up to the stomach and connected to the stomach. The connection is called an anastomosis. Fluids from the pancreas and bile duct flow through the first part of the small intestine up to the stomach. If a partial or complete blockage happens in this part of the small intestine (also known as the afferent limb of the small intestine), then problems can occur. This afferent loop syndrome can cause abdominal or back pain, nausea, and vomiting. If the obstruction is severe, this could affect the pancreas, the bile duct and liver, the duodenum, and the afferent limb.

What causes afferent loop syndrome?

After surgery, your bile and digestive fluids enter the afferent limb. The fluids then flow toward the upper stomach. They need to pass through the anastomosis and then enter the part of the small intestine that empties from the stomach (called the efferent limb). Afferent loop syndrome occurs when something traps the flow of these juices in the afferent limb. Fluid pressure builds up in the afferent limb and causes discomfort and nausea. If the pressure builds up, the bile and pancreatic fluid may then suddenly empty into the upper stomach. This can cause symptoms, such as vomiting.                                                                                                                                              

Common causes of afferent loop syndrome include:

• A problem with the anastomosis, the connection between the small intestine and the stomach. This could be an ulcer at the anastomosis. There might be a narrowing at the anastomosis that has caused the blockage.

• Twisting of the afferent limb

• Scar tissue (adhesions) near the afferent limb after surgery

• Cancer that blocks the afferent limb

• Foreign bodies, such as a bezoar, a mass of impacted food 

Afferent loop syndrome can occur anywhere from days to years after surgery. If it occurs soon after surgery, it’s called acute afferent loop syndrome. If it occurs weeks or years after surgery, it’s called chronic afferent loop syndrome.

What are the symptoms of afferent loop syndrome?

The most common symptoms are:

• Abdominal pain, especially in the upper part of your abdomen

• Nausea and fullness, especially after eating

• Sudden, severe vomiting of fluid with bile in it that suddenly eases the pain

• Chronic afferent loop syndrome may result in weight loss because of pain after eating.

How is afferent loop syndrome diagnosed?

Acute afferent loop syndrome happens early after stomach surgery. There may be a sudden onset of upper abdominal pain. Nausea is usually present, and vomiting may occur. If a leak from the anastomosis occurs, then peritonitis or shock may result, with a fast heart rate and lower blood pressure. Labs should be checked, and an abdominal CT scan will help to diagnose an afferent loop syndrome. This may show the swollen afferent limb. Surgery may be needed to relieve the obstruction.

Chronic afferent loop syndrome, which shows up months to years after surgery, may also be diagnosed with an abdominal CT scan. An upper endoscopy may also examine the anastomosis to look for obstruction, an ulcer, or tumor.

How is afferent loop syndrome treated?

For acute afferent loop syndrome, emergency surgery may be needed. This is to prevent a leak at the anastomosis at the staple line of the duodenum, or ischemia or perforation of the afferent limb. The type of surgery will depend on what's causing the blockage. In some cases, the anastomosis may need to be redone. Scar tissue may need to be divided, freeing up the blockage.

For chronic afferent loop syndrome, a nasogastric tube might be placed to decompress the stomach and the afferent limb. Supplemental nutrition may be needed if there has been significant weight loss. Antibiotics may be recommended if there has been bacterial overgrowth in the partially obstructed afferent limb. Upper endoscopy helps to diagnose any narrowing at the anastomosis. Surgery is most likely recommended if there is no malignancy present. Possible surgical procedures include revision of the small intestine loop, reconstruction of the anastomosis, or an additional anastomosis between the afferent limb and the efferent limb. If malignancy is present, surgical revision may not be the best approach. Instead, palliative procedures might be considered with endoscopic balloon dilation or stent placement or drains.

When should I call my healthcare provider?

Call your healthcare provider right away if you have symptoms of afferent loop syndrome, especially after recent stomach surgery.

Key points about afferent loop syndrome

• Afferent loop syndrome is a problem that can occur after some kinds of stomach surgery.

• It occurs when something traps the flow of digestive juices in the afferent limb. Fluid pressure builds up in the limb and causes discomfort and nausea.

• Common symptoms are abdominal pain, nausea, and sudden vomiting of fluid with bile in it.

• Treatment is almost always surgery. For acute afferent loop syndrome, you may need emergency surgery.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions, especially after office hours or on weekends and holidays.