Afferent loop syndrome

Overview

Afferent Loop Syndrome (ALS) is a rare complication that occurs after certain types of gastric surgery, particularly procedures involving a gastrojejunostomy or a Billroth II reconstruction. It involves obstruction or impaired drainage of the afferent limb, the segment of small intestine that carries bile and pancreatic secretions to the site of the stomach connection. The syndrome can be acute or chronic and leads to the accumulation of digestive fluids, causing pain, distension, and sometimes infection or perforation if untreated.

Causes

ALS is a postoperative complication that arises when there is a mechanical or functional obstruction of the afferent loop. Causes include:

• Surgical adhesions or kinking of the bowel

• Anastomotic strictures (narrowing at the surgical connection site)

• Internal hernias

• Tumor recurrence (in patients operated on for gastric cancer or pancreatic cancer)

• Volvulus (twisting of the bowel)

• Radiation-induced fibrosis (from prior abdominal radiotherapy)

Symptoms

The symptoms of afferent loop syndrome depend on whether the obstruction is partial (chronic) or complete (acute).

Chronic ALS:

• Postprandial abdominal pain

• Bloating or fullness after eating

• Vomiting (which may relieve symptoms temporarily)

• Weight loss

• Steatorrhea (fatty stools)

Acute ALS:

• Sudden severe abdominal pain

• Fever and signs of infection or sepsis

• High-output vomiting, possibly with bile

• Jaundice (if bile drainage is obstructed)

• Signs of peritonitis in case of perforation

Diagnosis

Timely diagnosis of afferent loop syndrome is essential to avoid complications. Diagnostic approaches include:

• Clinical history and physical exam: Especially in patients with prior gastric surgery

• Abdominal CT scan: May show fluid-filled dilated afferent loop or signs of obstruction

• Upper GI contrast studies (e.g., barium swallow): To visualize loop anatomy and obstruction

• Endoscopy: May help exclude anastomotic ulcer or stricture and assess obstruction site

• Lab tests: May show elevated liver enzymes, bilirubin, or signs of infection (in acute cases)

Treatment

Treatment depends on the severity and cause of the obstruction:

Conservative Management (for mild or transient cases):

• NPO (nothing by mouth) and nasogastric decompression

• IV fluids and electrolyte replacement

• Antibiotics if infection is suspected

Definitive Treatment (for persistent or severe cases):

• Surgical correction: To relieve obstruction, revise the anastomosis, or resect the affected bowel segment

• Endoscopic or percutaneous drainage: In select cases to relieve the pressure temporarily

• Stent placement: May be used in cases of tumor-related obstruction

Prognosis

The prognosis for afferent loop syndrome varies depending on the underlying cause and timeliness of treatment:

• Chronic ALS may improve significantly with surgical correction or symptom management.

• Acute ALS can lead to serious complications like perforation, peritonitis, and sepsis if not treated promptly.

With appropriate surgical intervention and supportive care, long-term outcomes are generally favorable. However, recurrence is possible if structural abnormalities persist or in cases involving malignancy.