Afferent Loop Syndrome


Afferent loop syndrome (ALS) which is also known as afferent limb syndrome is a complication caused by a stomach surgery specifically following Billroth II gastrectomy procedure.

afferent loop syndrome


If a person had or is about to have this procedure, one must be aware that afferent syndrome can possibly occur after the stomach surgery. During the operation, the surgeon will bypass or remove the greater region of the stomach and is connected to the first part of the remaining jejunum in a side-to-side technique. The section where the jejunum and stomach are attached to each other is called anastomosis. A resection of the antrum or the lower region of the stomach is usually done after the Billroth II procedure.

Symptoms of Afferent Loop Syndrome

Symptoms depend on which type of Afferent loop syndrome is present. They are classified into two:

  • Acute obstruction occurs within the first week after surgery. This is a result from a complete blockage that commonly happens early after the surgical procedure and can be very dangerous unless prompt reoperation is done.
  • Chronic obstruction occurs within weeks or several years after surgery. This is the partial blockage of the afferent loop that could be more difficult to diagnose rather than acute afferent loop syndrome.

Clinical symptoms will begin to emerge when the bile and pancreatic secretions fill the afferent loop and are not able to pass the anastomosis.  These may include:

  • Epigastric pain and fullness particularly after eating a meal
  • Nausea
  • Severe and unexpected vomiting of bilious fluid that could ease the abdominal pain afterwards
  • Diarrhea
  • Steatorrhea which is the presence of abnormal fat quantities in feces
  • Low red blood cell count


An afferent loop is made up of the duodenal stump. Afferent loop syndrome is caused by a partial or complete obstruction on the area where the surgery was done or along the jejunal region of the afferent loop. After a surgical procedure, the pancreatic and bile juices get into the afferent loop. All these juices will then circulate downstream and have to pass the anastomosis before entering the digestive system. ALS occurs when something blocks the flow of the juices past and up to the anastomosis site.

Common possible causes are:

  • An incorrectly made anastomosis
  • Tumor that returns again and obstructs the afferent loop
  • Twisting or curving of the afferent loop
  • Internal hernias or the projection of the viscera through the mesentery or peritoneum but staying in the abdominal cavity
  • Ulceration scars at the area where the afferent loop connects the stomach


Basic X-rays and blood tests can contribute to the diagnosis of afferent loop syndrome but the best tests are:

  • Computerized Tomography (CT) scans – An imaging test that could show the fluid-filled, inflamed afferent loop
  • Gastrointestinal Endoscopy (GI) – A procedure wherein a physician makes use of an endoscope to see the GI tract lining. This can help by showing the obstruction of the afferent limb.


Surgery is the best treatment approach for afferent loop syndrome. For patients with acute obstruction, an emergency surgery might be done to prevent loop rupture. The kind of surgery that may be done will vary on what’s causing the blockage.

In some patients, the anastomosis may have to be done again and corrected. If the afferent loop is narrowed and scarred, the best option is to remove it.

Before taking the gastrectomy surgery, know all the complications first and ask the physician to explain everything such as the risks and benefits of the surgery before the procedure.


After a corrective and proper method done, the prognosis of afferent loop syndrome is typically very good, except for those individuals who have advanced or recurrent malignancy.

Life Expectancy

The patient who is diagnosed earlier to have the condition with medical interventions done, have greater chances of being completely cured and being able to live a normal life. Mortality rates for acute afferent loop syndrome patients are up to 57%, mostly due to a delayed diagnosis that led to bowel rupture and peritonitis.


  4. Han K, Song HY, Kim JH, et al. Afferent loop syndrome: treatment by means of the placement of dual stents. AJR Am J Roentgenol. 2012 Dec. 199(6):W761-6.
  5. Ballas KD, Rafailidis SE, Konstantinidis HD, et al. Acute afferent loop syndrome: a true emergency. A case report. Acta Chir Belg. 2009 Jan-Feb. 109(1):101-3.
  6. Zissin R. CT findings of afferent loop syndrome after a subtotal gastrectomy with Roux-en-Y reconstruction. Emerg Radiol. 2004 Feb. 10(4):201-3.

Leave a Reply

Your email address will not be published. Required fields are marked *