Afferent Loop Syndrome Clinical Presentation

Updated: May 15, 2019
  • Author: Suresh Kumar Nayudu, MD; Chief Editor: BS Anand, MD  more...
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Acute ALS

Acute ALS is caused by complete obstruction of the afferent loop. However, it is rare and may either occur within a few days postoperatively or present unexpectedly several years after a Billroth II gastrectomy as described by Ballas et al [24]  and Valdivielso Cortázar et al. [25] In both circumstances, this condition is caused by an acute obstruction of the afferent limb due to herniation or volvulus of the afferent loop posterior to the efferent limb. Patients with acute ALS typically present with a sudden onset of epigastric and/or right or left upper quadrant abdominal pain, with associated nausea and vomiting.

With acute ALS, the vomitus is not bilious because the biliary and pancreatic secretions remain trapped in the obstructed bowel loop. If the afferent loop is not decompressed, the patient becomes acutely ill and can subsequently develop peritonitis and shock if intestinal perforation or infarction ensues.

Chronic ALS

Chronic ALS is caused by partial obstruction of the afferent loop and may be more difficult to diagnose than acute ALS. Approximately 10-20 minutes to an hour postprandially, the patient experiences abdominal fullness and epigastric pain. These symptoms usually last from several minutes to an hour, although they occasionally may last as long as several days.

Projectile bilious vomiting is a classic manifestation of ALS with partial obstruction. The distended afferent loop decompresses forcefully, providing rapid relief of symptoms. Note that the vomitus usually contains no food which passes through the unobstructed efferent limb. Vomiting may occur after each meal or only occasionally. [26] Also, symptoms in the immediate postprandial period may be minimized if the patient assumes a recumbent position.

Prolonged chronic ALS with stasis and bacterial overgrowth can be further complicated by steatorrhea, diarrhea, and vitamin B-12 deficiency anemia. These effects are primarily due to bacterial deconjugation of bile salts. The aforementioned factors, in addition to bypassing the duodenum and proximal jejunum, can result in iron deficiency anemia.


Physical Examination

Physical examination can reveal one or more of the following findings:

  • An ill-defined mass in the right upper abdominal quadrant may be present in one-third of patients with acute ALS.

  • Localized midepigastric or right upper abdominal quadrant tenderness

  • Peritonitis and/or a rigid abdomen if necrosis or perforation of the bowel wall has occurred

  • Jaundice

  • Signs of pancreatitis (eg, upper abdominal pain radiating to the flank or back)