What is afferent loop syndrome?

Afferent loop syndrome is a problem that can occur after some kinds of stomach surgery. It’s also known as afferent limb syndrome. 

The small intestine loop has 2 loops. The loop going to the upper stomach is the afferent loop. The loop carrying food away from the stomach is called the efferent loop. Afferent loop syndrome can occur after some types of gastrojejunostomy. One type is the Billroth II gastrectomy. During the procedure, a surgeon will remove or bypass the lower part of the stomach and attach the remaining upper part of the stomach to a loop of small intestine. The new connection is the anastomosis.

What causes afferent loop syndrome?

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

Common causes of afferent loop syndrome include:

• A problem with an anastomosis after gastrojejunostomy, such as an ulcer

• Twisting of the afferent loop 

• Scar tissue near the afferent loop after surgery

• Cancer that blocks the afferent loop 

 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 right side of your abdomen

• Nausea and fullness, especially after eating

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

How is afferent loop syndrome diagnosed?

Your healthcare provider may diagnose afferent loop syndrome based on your symptoms after surgery. You may have a CT scan. This may show the swollen afferent loop. You may also have an upper endoscopy. This can show blockage of the afferent loop.

How is afferent loop syndrome treated?

Treatment is almost always surgery. For acute afferent loop syndrome, emergency surgery may be needed. This is to prevent a tear of the loop. 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 removed.

When should I call my healthcare provider?

Call your healthcare provider right away if you have symptoms of afferent loop syndrome.

Key points about afferent loop syndrome

• Afferent loop syndrome is a problem that can occur after some kinds of stomach surgery. It’s also known as afferent limb syndrome. 

• It occurs when something traps the flow of digestive juices in the afferent loop. Fluid pressure builds up in the loop 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 provider if you have questions.