What is Afferent Loop Syndrome?
Afferent Loop Syndrome (ALS) is a rare issue that can come up after certain upper digestive tract surgeries. These surgeries involve linking some parts of the stomach or esophagus to the jejunum, which is a part of the small intestine. ALS is often associated with a surgery called Billroth II gastrojejunostomy, but it can also occur following similar procedures like Roux-en-Y gastrojejunostomy, Roux-en-Y esophagojejunostomy, and the Whipple procedure.
After undergoing these surgeries, a section called the afferent loop is formed. This loop, following a Billroth II reconstruction, includes parts of the stomach or duodenum, and a bit of the jejunum that’s close to where the new connection was made. In other surgeries, like Roux-en-Y gastric bypass, a part of the digestive system tied to the remaining stomach is linked to the small intestine.
The afferent loop’s job is to carry digestive juices like bile, pancreatic, and intestine secretions towards the new connection, be it a gastrojejunostomy or jejunojejunostomy. Meanwhile, the efferent loop handles ingested food and drink. Afferent Loop Syndrome occurs when something stops the flow in the loop, causing it to swell up due to the buildup of the digestive juices.
What Causes Afferent Loop Syndrome?
Afferent Loop Syndrome can happen when something blocks the pathway in the digestive tract, either in its main part or where it connects to another part. This blockage can be caused by adhesions, which can result in squeezing or twisting of the pathway, inner hernia, scarring from past ulcers at the gastrojejunostomy, or a comeback of the disease in patients who had cancer surgery. There can also be blockage because of foreign bodies, bezoars, or enteroliths. Other contributing factors could be afferent loop intussusception, a condition where one part of the intestine slides into another part, and radiation enteritis or inflammation caused by radiation therapy.
Longer afferent loops (more than 30 to 40 cm) are more likely to undergo volvulus, a condition where a part of the intestine twists around itself, or have adhesive formations that can result in trapping or twisting. Pathways located behind the colon (retrocolic afferent loops) are vulnerable to inner herniation through faults in the mesocolon, a part of the tissue that holds the colon in place.
The differing causes of Afferent Loop Syndrome determine the severity of its symptoms and what treatment is required. For instance, a blockage caused by a recurrent disease is likely to result in chronic symptoms and may need treatment with endoscopic or percutaneous decompression followed by additional chemo-radiation therapy. On the other hand, a bezoar or hardened mass of indigestible material stuck at the point of connection between two parts of the digestive tract will likely show up with sudden symptoms, and will most likely require surgical intervention.
Risk Factors and Frequency for Afferent Loop Syndrome
Afferent loop syndrome is connected to certain types of surgeries, such as those for stomach and duodenal ulcer diseases and stomach cancer. However, as medications have improved for treating ulcers and a bacteria called Helicobacter pylori, the need for such surgeries – and, by extension, cases of afferent loop syndrome – has gone down. There are however still high rates of stomach cancer in some places like China and Japan. This means that this syndrome can still be a risk in parts of the world with high rates of these diseases.
The rise in obesity has led to an increase in bariatric surgeries, or weight loss surgeries, being performed. One type called Roux-en-Y gastric bypass used to be more popular but has been overtaken by another, sleeve gastrectomy. These surgeries also pose a risk for afferent loop syndrome.
- About 1% of patients who undergo specific types of gastric surgeries like partial gastrectomy with Billroth II or Roux-en-Y reconstruction will experience afferent loop syndrome.
- Scientific studies have shown a similar incidence as high as 1% after a specific minimally invasive surgery, and a lower rate of 0.2% after open surgery.
- The risk of developing afferent loop syndrome is about the same whether the surgery was open or minimally invasive.
Although most patients show symptoms soon after surgery, some might experience symptoms many years later, even a decade or more. The incidence is especially higher, up to 13%, in patients who have a type of pancreatic surgery called pancreaticoduodenectomy, especially if they live more than three years after their surgery.
Signs and Symptoms of Afferent Loop Syndrome
Afferent loop syndrome is a condition that develops after certain types of stomach surgeries. Patients with afferent loop syndrome can experience symptoms that are either acute (sudden and severe) or chronic (long-term).
Acute symptoms usually occur soon after surgery. They include sudden abdominal pain, nausea and vomiting, tenderness in the upper right part of the abdomen or the central upper abdomen, muscle stiffness in the abdomen when touched, a possible lump in the upper abdomen, and yellowing skin or eyes which can be a sign of blocked bile ducts. In severe cases, signs of inflammation of the stomach lining (peritonitis) and severe infection throughout the body (septic shock) might be present.
- Sudden abdominal pain
- Nausea and vomiting
- Tenderness in the upper right part or central part of the abdomen
- Muscle stiffness in the abdomen when touched
- Possible lump in the upper abdomen
- Yellowing skin or eyes
- In severe cases, signs of peritonitis and septic shock
Chronic symptoms may not appear until months or even years after surgery. These often include discomfort after eating, weight loss, and in some cases, forceful vomiting of bile which provides temporary relief. The weight loss can happen due to various reasons – it may be due to an aversion to eating because of pain, poor absorption of nutrients due to bacterial overgrowth in the gut, or recurrent disease. The physical signs upon examination are usually similar to those in acute cases, but less severe.
- Discomfort after eating
- Weight loss
- Forceful bile vomiting that provides temporary relief
Testing for Afferent Loop Syndrome
Acute afferent loop syndrome with full blockage needs immediate surgery. If someone has chronic afferent loop syndrome, it could get worse and lead to a full blockage. This can result in a sudden worsening of symptoms. To diagnose and manage this condition early, doctors need to be alert when examining a patient with relevant surgical history who is experiencing sudden stomach pain.
Laboratory tests like the full blood count, lactate, liver function tests, pancreatic enzymes, and serum electrolytes can provide important information when evaluating the patient. But, the primary tool for diagnosing afferent loop syndrome is abdominal imaging with computed tomography (CT). A CT scan of the abdomen helps confirm the diagnosis by showing the blocked loop. It also provides information about the severity of the damage to the bowel and any complications like perforation, pancreatitis, and inflammation in the biliary tree. A CT scan is also useful in identifying the underlying cause of the obstruction, which could impact treatment.
Radiologists should understand the disease’s inner workings to better interpret the imaging findings. There are several signs to look out for in a CT scan, including the C-loop sign in the right upper part of the abdomen, which indicates a widened afferent limb. Other signs include the keyboard sign, which can help tell apart the dilated bowel from pancreatic pseudocysts. Magnetic resonance cholangiopancreatography (MRCP) is another tool that provides similar information. It can be used for patients who might be at risk from a CT scan’s iodinated contrast or ionizing radiation. MRCP can also be helpful in finding out the underlying cause in patients with a slow-onset or long-term presentation.
In patients with acute afferent loop syndrome, whether through a CT scan or MRCP, it’s important to note specific digestive system abnormalities. Signs of a blockage or leak (like an elevated heart rate of more than 120 bpm, fever, and stomach pain) could indicate aperforation in the afferent limb.
Abdominal radiographs (which are often normal except in cases of full pneumoperitoneum or a widely dilated afferent loop), ultrasound, and fluoroscopic upper GI barium tests have been largely replaced with CT imaging in critically ill patients with suspected afferent loop syndrome. In the early postoperative period, the main concern is a leak in the anastomotic site. These patients usually undergo fluoroscopic upper GI tests before imaging. Afferent loop syndrome may be suggested in fluoroscopic upper GI tests if contrast fails to enter the afferent limb or if it preferentially enters the afferent limb and is retained there.
Treatment Options for Afferent Loop Syndrome
The approach to managing afferent loop syndrome, a condition affecting the digestive system, often depends on what’s causing it. If it’s due to a non-cancerous condition, surgery is generally the ideal treatment. However, when cancer is present, initial treatment might focus on preparing for surgical intervention, which could aim to cure or relieve symptoms.
For a quick, temporary relief of symptoms, a nasogastric tube, a tube going through the nose into the stomach, can be used to drain the patient’s stomach while they’re prepared for surgery. This method can be useful to manage the condition temporarily before surgery or as a stand-alone treatment for some patients. In addition to this, those with chronic afferent loop syndrome might get nutritional support, blood transfusions, and antibiotics to help them get in better shape for surgery and reduce potential complications.
The type of intervention for non-cancerous afferent loop syndrome depends on the patient’s previous surgery and why the obstruction is happening. Some corrective surgical procedures that may be considered are converting a Billroth II to a Roux-en-Y (different types of surgical rearrangements of the intestines), creating a Braun anastomosis in a Billroth II (creating a new connection between two parts of the intestine), or removing and reconstructing redundant loops.
If the obstruction is in the upper part of the afferent loop, fixing it could be challenging due to the intense scarring in the area. For patients not suitable for surgery, alternative procedures might involve the use of endoscopic (minimally invasive by using a thin tube) methods.
Palliative (relief-oriented) treatment is usually the best way forward for patients with afferent loop syndrome caused by cancer who cannot undergo surgery. This generally includes methods to relieve the immediate blockage but doesn’t involve removing and reconstructing like in the case of benign obstructions. If patients have undergone a pancreaticoduodenectomy (a surgical procedure to remove the pancreas), there should be a particular focus on ensuring the patency (openness) of certain connections in the digestive system, as further obstructions can lead to worse outcomes.
What else can Afferent Loop Syndrome be?
When an individual undergoes a complex abdominal surgery, there’s a chance they might experience a condition called afferent loop syndrome along with other complications. After surgery, it’s typical for patients to feel abdominal pain and nausea, but these symptoms aren’t specific and can be associated with a range of issues. These could include:
- Postoperative ileus (a temporary halt in the bowel’s activity)
- Anastomotic leak (a leak in the intestine where two sections were sewn together)
- Partial blockage due to swelling at the point of surgery
- Bile reflux (when digestive fluid travels back up into the stomach and esophagus)
- Acute pancreatitis caused by the surgery
- Buildup of fluid after the operation
Also, feelings of nausea and vomiting may not necessarily be related to the surgery, but could be due to the painkillers or an imbalance in the body’s normal levels of biochemical substances. If patients report extreme abdominal pain or symptoms that worsen, they should be checked with imaging tests like X-rays or Ultrasound.
In cases where afferent loop syndrome becomes a chronic condition, the symptoms may not be distinct and could confuse it with:
- Internal hernias and adhesions without obstruction
- Reduced blood flow to the mesentery (tissue that connects intestines to the abdominal wall)
- Overgrown bacteria in the small intestine
- Chronic pancreatitis
- Biliary colic (severe pain in the abdomen due to gallstones)
- Disorders related to gallstones
What to expect with Afferent Loop Syndrome
Generally, patients with early or recurring cancer cases have a good outlook if they are diagnosed quickly and have surgery. However, the mortality rate for those whose diagnosis is delayed can range from 30% to 60%. The outcome can get worse for patients who experience a rupture of the afferent limb, leading to peritonitis and shock.
Possible Complications When Diagnosed with Afferent Loop Syndrome
Acute afferent loop syndrome is often followed by life-threatening complications, such as sepsis — a severe infection that can cause the body’s organs to fail. This can occur even if the patient gets early treatment before becoming infected. The risk of other complications related to the treatment is higher, especially for patients who had surgery for cancer.
Similarly, chronic afferent loop syndrome also poses a high risk of complications, especially for patients suffering from malnutrition and anemia. Here are some of the potential complications:
- Anastomotic leak: A hole that forms along the surgical joint between two body parts
- Recurrent adhesions or strictures: Repeat formation of scar tissue or narrowing of passageways in the body
- Fistula formation: An abnormal connection between two body parts
- Wound infection and dehiscence: Infected wound or wound that re-opens after surgery
- Deep venous thrombosis: Blood clot in a deep vein, often in the legs
- Pulmonary embolism: Blockage in one of the lungs’ arteries
- Aspiration on the induction of anesthesia: Breathing in foreign objects (such as food or drink) during the administration of anesthesia
Recovery from Afferent Loop Syndrome
After having upper gastrointestinal surgery, patient care is quite standard. The patient should not eat or drink anything (NPO), should receive continuous IV fluids, and needs adequate pain relief. Often a tube is placed through the nose to the stomach or intestine to provide relief by draining fluids or gas. It’s important for the patient to get up and move around as soon as they can to avoid blood clots (deep venous thrombosis), and they may also receive prevention treatments as necessary. The patient’s diet will gradually transition from clear liquids to soft foods, and eventually to solid meals. Future dietary changes should be based on the patient’s specific situation, including the type of surgery. If possible, these changes should be overseen by a knowledgeable and experienced nutritionist.
Preventing Afferent Loop Syndrome
Although it doesn’t happen often, people going through certain types of stomach surgeries, like Billroth II, Roux-en-Y, and pancreaticoduodenectomy, should be informed about the possibility of a condition called afferent loop syndrome. It’s important that these patients know that if they start experiencing symptoms of this syndrome, they should seek immediate medical care.
