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Thread: Afferent Loop Syndrome

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    Afferent Loop Syndrome


    Afferent loop syndrome (ALS) is a purely mechanical complication that infrequently occurs following construction of a gastrojejunostomy. Creation of an anastomosis between the stomach and jejunum leaves a segment of small bowel, most commonly consisting of duodenum and proximal jejunum, lying upstream from the gastrojejunostomy. This limb of intestine conducts bile, pancreatic juices, and other proximal intestinal secretions toward the gastrojejunostomy and is thus termed the afferent loop.
    Afferent loop syndrome is an uncommon complication following a Billroth II procedure and occurs in approximately 0.3% of cases . Most cases are due to mechanical obstruction of the afferent loop from adhesions, kinking at the anastomosis, internal hernia, stomal stenosis, malignancy, or inflammation surrounding the anastomosis . Obstruction of the afferent bowel with ongoing accumulation of biliary, pancreatic, and intestinal secretions results in afferent loop dilatation. The back pressure from the dilated afferent loop can cause biliary dilatation, gallbladder dilatation, and acute pancreatitis . The frequency of acute pancreatitis in afferent loop syndrome, however, has not been established in a large series, to our knowledge.

    Uncommonly, afferent loop syndrome can be secondary to preferential gastric emptying into the afferent loop rather than to mechanical obstruction. In this form of afferent loop syndrome, there is excessive accumulation of gastric contents, usually secondary to a left-to-right surgical anastomosis rather than a right-to-left connection . Another form of afferent loop syndrome that may have an upper gastrointestinal appearance similar to a left-to-right surgical anastomosis is obstruction of the efferent loop with preferential filling of the afferent loop. In the early postoperative period, anastomotic edema, hemorrhage at the origin of the efferent limb, or both can prevent gastric emptying and, similarly, result in fluid accumulation in the afferent loop.

    The clinical features of afferent loop syndrome are variable and depend on whether the afferent loop obstruction is acute or chronic. Most of the findings are relatively nonspecific and include abdominal pain, nausea and vomiting, postprandial fullness, and, rarely, postobstructive jaundice. The classic presentation of chronic afferent loop syndrome has been described as bilious vomiting with relief of the abdominal pain . This classic presentation presumably is due to intermittent release of pressure from the afferent loop into the stomach. In the case presented, the clinical presentation had a relatively lengthy list of differential considerations, including peptic ulcer disease, gastritis, gastric outlet obstruction, small-bowel obstruction, mesenteric ischemia, acute cholecystitis, and pancreatitis. The elevated amylase and lipase levels in this case supported the presence of acute pancreatitis.

    Prior to CT and ultrasonography (US), radiographic barium examinations of the upper gastrointestinal tract were the primary means of assessing for afferent loop syndrome. Two classic findings were described at radiographic upper gastrointestinal examinations. First, nonfilling of the afferent limb suggests afferent loop syndrome. However, this finding can be problematic in that some patients without afferent loop syndrome may have nonfilling of their afferent limbs. Second, preferential filling and retention of barium in a dilated afferent limb for at least 60 minutes is consistent with afferent loop syndrome.
    History of the Procedure

    The operations most commonly associated with this complication include distal or subtotal gastrectomies for peptic ulcer disease or gastric malignancies with Billroth II reconstructions, pancreaticoduodenectomies, and gastrojejunostomies performed to bypass other foregut pathology. The pathophysiology and signs and symptoms associated with ALS result from partial or complete obstruction of the afferent loop.

    ALS is included in the constellation of resectional gastric surgical complications known as the postgastrectomy syndromes. The following syndromes are included:

    Early dumping syndrome

    Late dumping syndrome

    Postvagotomy diarrhea

    Chronic gastric atony

    Roux stasis syndrome

    Small gastric remnant syndrome

    Alkaline reflux gastritis

    Afferent loop syndrome

    Efferent loop syndrome
    Patients with ALS may present with an acute, completely obstructed form or with a chronic, partially obstructed form. The syndrome can manifest at any time from the first postoperative day to many years after surgery. The acute form usually occurs in the early postoperative period (1-2 wk), but it has been described to occur 30-40 years after surgery.

    In 1942, McNealy first described acute ALS as a cause of early postoperative duodenal stump leakage. Lake is credited with recognizing the chronic form in 1948. Roux and coworkers coined the term afferent loop syndrome in 1950.42 The first detailed exegesis in the English literature on the etiology, clinical presentation, and treatment of ALS was contributed by Wells and Welbourn in 1951.52
    ALS manifests in acute and chronic forms. Acute ALS represents complete obstruction of the afferent loop and is a true surgical emergency. It must be diagnosed and corrected expeditiously. Chronic ALS is associated with partial obstruction. It is not a surgical emergency but does require corrective surgery.

    Postoperative conditions

    Each of the following postoperative conditions can cause ALS in a patient with a gastrojejunostomy:

    Entrapment or compression of the afferent loop by postoperative adhesions

    Internal hernia (eg, through a mesocolic defect)

    Volvulus of the intestinal segment

    Enteroenteral or enterogastric intussusception

    Kinking of the afferent limb at the gastrojejunostomy

    Scarring due to marginal (stomal) ulceration

    Recurrence of cancer at or near the anastomotic site

    Enteroliths in the afferent limb6

    Bezoars in the afferent limb or at the anastomosis

    Foreign bodies in the afferent limb or at the anastomosis
    Surgical technique

    Patients have an increased chance of developing ALS if one or more of the following conditions is met:

    The jejunal portion of the afferent limb is longer than 10-15 cm.

    The gastrojejunostomy is placed in an antecolic position instead of a retrocolic position.

    Mesocolic defects are not properly closed after construction of a retrocolic gastrojejunostomy.

    Acute ALS
    Acute ALS is caused by complete obstruction of the afferent loop. 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. 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 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 because it has progressed along the unobstructed efferent limb. Vomiting may occur after each meal or only occasionally.16 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.

    Medicolegal pitfalls

    The major medicolegal pitfall associated with ALS is a delay in diagnosis. This is most serious with acute ALS because diagnostic delay can lead to bowel perforation or gangrene with resultant intra-abdominal sepsis.

    Afferent limb syndrome. Normal anatomy and Billroth II gastrojejunostomy.

    Afferent limb syndrome. Roux-en-Y gastrojejunostomy.


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    Last edited by trimurtulu; 03-17-2009 at 07:07 AM.

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