bubble_chart Overview

Afferent Loop Syndrome refers to the stasis of bile or pancreatic fluid caused by obstruction of the afferent loop after Billroth II gastrectomy and antecolic anastomosis. There are two types: acute and chronic obstruction. The former is mostly complete obstruction, while the latter is reversible and partial obstruction.

bubble_chart Pathogenesis

Acute afferent loop obstruction usually occurs within 24 hours after surgery, but it can also develop days or even years postoperatively. The obstruction may be partial or complete, intermittent or permanent. After Billroth II surgery, approximately 1% of patients experience obstruction near the gastrojejunal site of the afferent loop, with antecolic anastomosis being more common than retrocolic anastomosis. In antecolic anastomosis, if the afferent loop is left too long, it may become trapped behind the efferent loop while passing through the space between the mesentery of the efferent jejunal loop and the transverse mesocolon, leading to strangulated obstruction. If the gastrojejunal anastomosis or the duodenal-jejunal flexure forms a crossed position—with the afferent loop posterior and the efferent loop anterior—the mesentery of the latter may compress the afferent loop, causing closed-loop obstruction of the afferent jejunal loop. In retrocolic anastomosis, the afferent loop may retract into the opening of the transverse mesocolon, resulting in obstruction.

Due to the blockage of pancreatic juice and bile outflow in the afferent loop, pancreatic juice and bile accumulate, causing acute dilation of the afferent loop and severe epigastric pain that radiates to the interscapular region. Frequent vomiting occurs, but the volume is small, and the vomitus does not contain bile. Symptoms are not relieved after vomiting. There is significant tenderness in the epigastrium, and sometimes the dilated afferent loop can be palpated. Excessive fluid accumulation in the afferent loop may lead to reflux of intestinal fluid into the pancreatic duct, increasing the risk of acute pancreatitis, with a rapid rise in serum amylase levels. In cases of complete obstruction, the dilated afferent loop may become necrotic and perforate, causing peritonitis and shock.

Chronic efferent loop obstruction typically develops weeks after surgery, but it can also occur a year or more postoperatively. This type is more common after Billroth II surgery when angulation exists, particularly in antecolic anastomosis. It is caused by the afferent loop protruding into the space behind the gastrojejunal anastomosis, though adhesions or jejunojejunal intussusception may also contribute. When bile and pancreatic juice accumulate in the afferent loop, causing dilation and stimulating peristalsis, the accumulated fluid is expelled into the stomach, resulting in vomiting of bile-containing liquid.

bubble_chart Clinical Manifestations

Patients typically present with strangulating high jejunal obstruction, often experiencing sudden projectile vomiting of bilious fluid approximately one hour after meals. Before vomiting, nausea, upper abdominal distension, and epigastric pain radiating to the back are common. Symptoms usually subside after vomiting until the next meal triggers another episode. Physical examination reveals tenderness in the upper abdomen, and occasionally, a dilated afferent loop may be palpable in the right upper quadrant.

bubble_chart Diagnosis

Based on the clinical presentation and the results of Dahlgren and Jordan tests, a diagnosis can be made after a Billroth II gastrectomy with antecolic anastomosis.

bubble_chart Treatment Measures

Acute afferent loop syndrome should be treated with early surgery; for chronic cases, surgical treatment is necessary when drug therapy is ineffective.