Afferent loop syndrome

Did You Know?

• The treatment plan depends on the type of obstructive lesion, the blockage site (inframesocolic or supramesocolic), and the patency of hepaticojejunostomy and pancreaticojejunostomy anastomoses.
• In early afferent loop syndrome, a fluid-filled tubular formation crossing the abdominal midline between the superior mesenteric artery and the aorta is often seen on CT.
• Patients with afferent limb perforation leading to peritonitis and shock have a poor prognosis.

Signs and symptoms

Acute afferent loop syndrome commonly presents with nonbilious vomiting, nausea, and abrupt right upper quadrant abdominal pain. Chronic cases feature postprandial epigastric discomfort lasting minutes to an hour, abdominal distension, and bilious projectile vomiting that quickly relieves symptoms. Steatorrhea and diarrhea may worsen intestinal stasis in persistent disease. Bacterial deconjugation of bile salts can lead to iron deficiency anemia or vitamin B12 deficiency. Patients often avoid eating to prevent postprandial pain, resulting in significant weight loss. Physical findings include right upper quadrant or epigastric tenderness; about one-third of acute cases have a palpable abdominal bulge. Signs of pancreatitis, such as obstructive jaundice or radiating abdominal pain, may appear. Guarding and a rigid abdomen suggest intestinal perforation with peritonitis.

Causes

Afferent loop syndrome arises from benign or malignant obstructive lesions. Benign causes follow three pathways: intraluminal blockage from anastomotic stricture, foreign body impaction, bezoars, or enteroliths; intramural mechanical obstruction due to radiation enteritis or marginal gastrojejunostomy ulcer scarring; and external compression from internal hernia, volvulus, entrapment, kinking of the afferent loop, postoperative adhesions, or intussusception. An antecolic afferent loop longer than 30 to 40 cm risks kinking, volvulus, and adhesion-induced entrapment. A retrocolic afferent loop with improperly closed mesocolic defects increases internal herniation risk. Malignant causes typically involve locoregional tumor recurrence at the anastomotic site or gastric remnant, peritoneal carcinomatosis, or regional lymphadenopathy.