Afferent Loop Syndrome

Updated: May 15, 2019
Author: Suresh Kumar Nayudu, MD; Chief Editor: BS Anand, MD 



Afferent loop syndrome (ALS) is a purely mechanical complication that infrequently occurs following the construction of a gastrojejunostomy. Creation of an anastomosis between the stomach and jejunum leaves a segment of the small bowel, most commonly consisting of the duodenum and proximal jejunum, lying upstream from the gastrojejunostomy. This limb of the intestine transfers bile, pancreatic juices, and other proximal intestinal secretions toward the gastrojejunostomy and is thus termed the afferent loop. See the images below.

Afferent limb syndrome. Kinking of the afferent li Afferent limb syndrome. Kinking of the afferent limb at the gastrojejunostomy.
Afferent limb syndrome. Tracing of kinking of the Afferent limb syndrome. Tracing of kinking of the afferent limb at the gastrojejunostomy.

For patient education resources, see Digestive Disorders Center, as well as Peptic Ulcers and Anatomy of the Digestive System.

Relevant Anatomy

The afferent loop consists of the duodenal stump, the remainder of the duodenum, and the segment of jejunum proximal to the gastrojejunostomy. The clinically relevant portion of the loop pertaining to ALS is the jejunal portion of the afferent limb. The jejunal limb is subject to adhesion formation, internal herniation, volvulus, anastomotic obstruction, and other etiologies of ALS, as described below.



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.


An afferent loop is composed of the duodenal stump, the remainder of the duodenum, and the segment of jejunum located proximal to a Billroth II–type gastrojejunostomy. ALS is caused by complete or partial mechanical obstruction at the gastrojejunostomy or at a point along the jejunal portion of the afferent loop.

Passage of food and gastric secretions through the gastrojejunostomy and into the efferent loop triggers the release of secretin and cholecystokinin. These enteric hormones stimulate the secretion of bile, pancreatic enzymes, and pancreatic bicarbonate and water into the afferent loop. Under gastrointestinal hormonal influence, up to 1-2 L of pancreatic and biliary secretions can enter the afferent loop each day.

Symptoms associated with ALS are caused by increased intraluminal pressure and distention due to the accumulation of enteric secretions in a partially or completely obstructed afferent limb. ALS is one of the main causes of duodenal stump blowout in the early postoperative period and is also an etiology for postoperative obstructive jaundice, ascending cholangitis, and pancreatitis due to the transmission of high pressures back into the biliopancreatic ductal system.[1] High luminal pressures and distention increase bowel wall tension in the afferent loop (in accord with the Laplace law) and can lead to ischemia and gangrene with subsequent perforation and peritonitis.

Secondarily, prolonged stasis and pooling of secretions with partial obstruction facilitate bacterial overgrowth in the afferent loop.[2] Bacteria deconjugate bile acids, which can lead to steatorrhea, malnutrition, and vitamin B-12 deficiency leading to megaloblastic anemia.

A variety of investigations have been performed to confirm the diagnosis of bacterial overgrowth and include jejunal aspiration, 14 carbon D-xylose breath testing, hydrogen breath testing using glucose or galactose, and 14 carbon-glycocholic breath testing. However, as none of these investigations have been standardized, treatment is often initiated clinically when there is a high index of suspicion. Although the mechanism behind iron deficiency is complex, iron deficiency can also develop due to the bypassing of the proximal small bowel and achlorhydria which impairs iron solubility.

The severity at presentation mainly depends on the degree and duration of obstruction.

History of the Procedure

The surgical procedures 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[3]

  • Late dumping syndrome[4]

  • Postvagotomy diarrhea[5]

  • Chronic gastric atony[6]

  • Roux stasis syndrome[7]

  • Small gastric remnant syndrome[8]

  • Alkaline reflux gastritis[9]

  • Afferent loop syndrome[10]

  • Efferent loop syndrome[10]

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.[11] The first detailed description in the English literature of the etiology, clinical presentation, and treatment of ALS was contributed by Wells and Welbourn in 1951.[12]


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)[13]

  • Volvulus of the intestinal segment

  • Enteroenteral or enterogastric intussusception

  • Kinking of the afferent limb at the gastrojejunostomy (see the following images)

    Afferent limb syndrome. Kinking of the afferent li Afferent limb syndrome. Kinking of the afferent limb at the gastrojejunostomy.
    Afferent limb syndrome. Tracing of kinking of the Afferent limb syndrome. Tracing of kinking of the afferent limb at the gastrojejunostomy.
  • Scarring due to marginal (stomal) ulceration[14]

  • Recurrence of cancer at or near the anastomotic site

  • Enteroliths in the afferent limb[15, 16, 17, 18]

  • Bezoars in the afferent limb or at the anastomosis[19]

  • 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 30-40cm in length.

  • 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.

Bushkin and Woodward reported an equal incidence of ALS in patients with short, retrocolic afferent limbs.[20] However, according to Eagon and coworkers, most authors opine that longer, redundant, and antecolic afferent limbs are more prone to kinking, volvulus, and entrapment by adhesions.[10]


United States and international data

In the United States, ALS affects approximately 1% of patients undergoing gastric resection and Billroth II gastrojejunostomy. This figure may be an underestimation because this complication is probably underdiagnosed. Overall, the incidence of this complication decreased dramatically during the final quarter of the 20th century as elective gastric surgery for complications of peptic ulcer disease underwent a logarithmic decline.[21, 22]

Internationally, rates for the development of this complication appear to be similar in other nations.

Sex- and age-related demographics

According to Tovey et al, one or more of the postgastrectomy syndromes is more likely to occur in female patients.[23]

ALS favors no particular age group on a per capita basis.


After a proper corrective procedure, the prognosis is usually very good, except in cases of advanced or recurrent malignancy.


Mortality rates of up to 57% have been reported for acute ALS. Mortality is most frequently associated with a delay in the diagnosis that leads to bowel infarction or rupture and peritonitis. Patients in whom a timely diagnosis is made or who present with chronic manifestations of the disease can undergo corrective surgery with acceptably low morbidity and mortality rates. 


Patients undergoing surgery for ALS are at risk of developing any of the following complications:

  • Wound infection

  • Wound dehiscence with or without evisceration

  • Urinary tract infection

  • Atelectasis

  • Pneumonia

  • Anastomotic disruption

  • Anastomotic stricture

  • Marginal ulceration

  • Intra-abdominal abscess formation

  • Cholangitis

  • Delayed gastric emptying/gastroparesis

  • Internal or enterocutaneous fistulae

  • Small bowel obstruction

  • Dumping syndrome

  • Alkaline reflux gastritis

  • Roux stasis syndrome

  • Cardiac arrhythmias

  • Deep venous thrombosis

  • Pulmonary embolism




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)



Diagnostic Considerations

Important considerations

Note that a delay in the diagnosis of ALS can result in serious consequences, particularly with acute ALS, because diagnostic delay can lead to bowel perforation or gangrene, with resultant intra-abdominal sepsis.

Other problems to be considered include the following:

  • Bile reflux gastritis

  • Pancreatic pseudocyst or cystic tumor

  • Mesenteric cyst

  • Mesenteric lymphoid hamartoma

  • Intra-abdominal abscess

  • Cystic metastases

Differential Diagnoses



Laboratory Studies

Complete blood count

Blood should be drawn for a complete blood count (CBC). Areas of interest include the hemoglobin and hematocrit values, white blood cell (WBC) count, and red blood cell (RBC) characteristics (eg, mean corpuscular volume, cell size, iron content).

These studies aid in confirming the diagnosis of anemia (hemoglobin and hematocrit), the possibility of infection or acute illness (WBC count), and a possible cause for anemia related to ALS (eg, vitamin B-12 deficiency anemia, iron deficiency anemia).

Liver function tests and pancreatic enzymes

Elevated levels of serum bilirubin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, amylase, and lipase may be detected when biliary and/or pancreatic duct obstruction is prominent.

Occasionally, abnormalities of these hepatic and pancreatic products are early clues to the diagnosis in the proper patient scenario (eg, those with a Billroth II gastrojejunostomy).[27]

Electrolyte panel

Serum electrolytes should be examined, especially in patients with prolonged vomiting and possible dehydration. These conditions can lead to hyponatremia or hypernatremia, hypokalemia, and hypochloremia. Metabolic alkalosis may be present.


Serum albumin levels should be measured, especially because ALS requires surgical correction.

In patients with chronic ALS and significant malnutrition, a period of preoperative specialized nutritional support might be appropriate.

Carbon 14 xylose breath test

When bacterial overgrowth is present, a carbon 14 xylose breath test reveals an increased concentration of hydrogen in exhaled gas following a glucose-containing meal. This test is mainly helpful in diagnostic dilemmas and has no role in acute ALS.


Imaging studies may be of greater utility in patients with chronic ALS in which the diagnosis is often elusive. Although imaging tests are often performed in patients with acute ALS, the vast majority of such patients require urgent surgery regardless of the results of the imaging tests.

Upper gastrointestinal series

Findings from an upper gastrointestinal series may suggest the diagnosis when orally administered contrast agents fail to provide adequate opacification of the afferent loop. However, test results are not specific because nonopacification of the afferent loop is not unusual in normally functioning Billroth II anastomoses.

Plain abdominal radiography

Plain abdominal radiographs can be helpful by demonstrating abnormal bowel gas patterns or air-fluid levels, but these findings are not specific to the diagnosis of ALS.

Abdominal Ultrasonography

Ultrasound may demonstrate a peripancreatic cystic mass or a fluid-filled tubular structure in the right upper abdominal quadrant that may cross the midline.

Kitamura and associates performed ultrasound as an adjunct to percutaneous small bowel drainage in patients with ALS.[28] They used ultrasound to identify a segment of the afferent limb in apposition to the abdominal wall in 3 patients with ALS. In each case, the small bowel segment was successfully cannulated and decompressed.

Derchi and colleagues reported their experience with ultrasound in 4 patients with ALS caused by tumor recurrence at or near a Billroth II gastrojejunostomy.[29] In each case, ultrasound was able to define the distended afferent limb as a fluid-filled structure with a multilayered wall and effacement of the mucosal folds. The investigators described being able to trace the obstructed afferent loop from the hepatic hilum to the anastomosis with the stomach.

Lee and coworkers reviewed the sonographic findings of ALS in 7 patients.[30] In their group of patients, the etiology of ALS was internal herniation in 3, recurrent cancer in 2, marginal ulceration in 1, and a new primary cancer at the anastomosis in 1. The obstructed afferent limb appeared as a dilated, fluid-filled structure in the upper abdominal quadrants, which crossed the midline. These investigators also described the ability to trace this distended bowel loop to the area of the gastrojejunostomy.

Matsusue and colleagues published their experience with ultrasound in 3 patients with ALS.[31] In their report, the salient features of ALS on ultrasound images included a dilated intestinal loop without accompanying gas echoes in the upper abdomen and associated echolucent, edematous swelling of the pancreas.

Nuclear Imaging Studies

Hepatobiliary scintigraphy

These investigations have been used with limited success in diagnosing chronic ALS. Normally, the radionuclide should pass from the afferent limb into the stomach or distal small bowel. Failure to do so may suggest the possibility of an afferent loop obstruction, although the medical usefulness of these studies remains to be determined.

Muthukrishnan and colleagues used technetium-99m (99m Tc) mebrofenin hepatobiliary scintigraphy to examine 2 patients with gastrojejunostomies who presented with bilious vomiting.[31] Findings from previous studies, including endoscopy and ultrasonography, had been nondiagnostic. The scintigraphic technique identified duodenal and extrahepatic biliary dilation in these patients, consistent with chronic ALS

Lai and coworkers performed99m Tc hepatoiminodiacetic acid scanning on a patient with a gastrojejunostomy and obstructive jaundice.[32] The main findings included a dilated afferent loop and dilated biliary radicles.

Sivelli and colleagues reported their experience with99m Tc hepatoiminodiacetic acid scanning in 50 patients with Billroth II gastrojejunostomies and postgastrectomy syndromes.[33] Based on clinical findings, 18 of these patients were thought to have ALS. In this subgroup, abnormal afferent loop emptying was demonstrated in 8 and atonic gallbladder distension without afferent loop abnormalities was found in 10. The authors stressed that clinical symptoms associated with ALS are not pathognomonic and that hepatobiliary scintigraphy can aid in the differential diagnosis of ALS and other conditions such as biliary dyskinesia.

Computed Tomography Scanning

Abdominal computed tomography (CT) scanning helps in the visualization of the obstructed segment directly and yields detailed information regarding the biliary tree, pancreas, and other structures. Yilmaz et al reported that CT scanning should be the radiographic study of choice in the diagnosis of ALS.[34, 35]

Zissin and coworkers reported salient CT scan features of ALS.[36] They described the typical appearance as that of a U-shaped, fluid-filled tubular structure crossing the midline of the abdomen between the abdominal aorta and the superior mesenteric artery.

Kim and coauthors demonstrated the accuracy of CT scanning not only in detecting ALS but also in predicting the underlying pathology causing the condition.[37] They performed helical CT scans on 18 patients presenting with ALS. CT scanning helped correctly predict locally recurrent gastric cancer or carcinomatosis as the cause in 16 patients and adhesion formation and internal herniation as the cause in the other 2 patients.

Gayer and colleagues described CT scan findings in 5 patients with ALS.[38] The afferent limb appeared as a dilated (average 5.3 cm diameter), fluid-filled tubular mass. Valvulae conniventes were observed in all cases, and intraluminal air was detected in 80%. The dilated loop was confined to the subhepatic area in 60%, but it crossed the midline in the other patients. Biliary dilation was identified in all patients, and radiographic evidence of pancreatitis was discovered in one. Notably, orally administered contrast opacified the afferent limb in just one patient.

Gale and coworkers stated that the afferent limb can appear as multiple, uniformly sized, peripancreatic cystic masses on CT scans.[39] This description was confirmed by Swayne and Love, who added that the cysts featured attenuation numbers consistent with water density.[40]

The initial description of ALS on CT scans was offered by Kuwabara and associates in 1980.[41] They characterized an obstructed afferent limb as a U-shaped cystic mass in continuity with the biliary system, appearing posterior to the superior mesenteric artery.

Magnetic Resonance Imaging and Magnetic Resonance Cholangiopancreatography

Chevallier and associates described a case of a 77-year-old man presenting with obstructive jaundice.[42] Magnetic resonance imaging (MRI) revealed biliary and pancreatic ductal dilation and a dilated afferent limb. A mass was visualized between the afferent loop and gastric remnant. Endoscopy with biopsy proved this mass to be an adenocarcinoma that was completely obstructing the afferent limb.

A variety of investigators have used magnetic resonance cholangiopancreatography (MRCP) to diagnose ALS.[43, 44, 45, 46] For example, McKee and coworkers described the use of MRCP in ALS manifesting with cholangitis.[43]

Upper Endoscopy

Esophagogastroduodenoscopy offers the advantage of direct visualization of the gastrojejunostomy and portions of its afferent and efferent limbs. The anastomosis can be inspected for kinking or marginal ulceration. A twist near the anastomosis suggests volvulus or internal herniation. Worrisome masses in the region of the anastomosis can be identified, and biopsy samples can be taken. In addition, enteroliths may also be present, which may mimic mitotic disease on imaging studies and can only be diagnosed with upper endoscopy as described by Yavuz et al.[47]

According to Eagon et al, esophagogastroduodenoscopy is helpful in discriminating between ALS and alkaline reflux gastritis, which is an important entity in the differential diagnosis.[10]

Radiographically Guided Interventional Techniques

The cornerstone of treatment in ALS remains corrective surgery. Occasionally, patients are too debilitated to withstand operative therapy or recurrent cancer may preclude a successful reoperation.

In 2002, Kim and associates published their results with palliative percutaneous tube enterostomy in patients with ALS who presented with a chief complaint of jaundice.[48] In each case, the dilated afferent loop was successfully cannulated and decompressed. Bilirubin levels returned to reference ranges in 5 (71%) of 7 patients.

Lee and coworkers described 2 patients with ALS due to recurrent gastric cancer who were deemed inoperable.[49] Both patients underwent percutaneous transhepatic drainage of the duodenum followed by weekly infusions of 5-fluorouracil and leucovorin. In both cases, afferent limb patency was reestablished, and the drainage catheters were subsequently removed. At the time of the report, the patients remained free of symptoms 16 and 17 months after drainage, respectively.

Caldicott and associates published the case report of a man who had undergone partial gastrectomy and later presented with distal common bile duct and duodenal obstruction due to an inoperable carcinoma of the head of the pancreas.[50] Using percutaneous transhepatic techniques, the patient was effectively palliated by placement of metallic stents across the biliary and duodenal strictures.

Yoshida and coauthors reported the case of a 77-year-old man presenting with fever, right upper quadrant abdominal pain, and jaundice 2 years after a distal gastrectomy for cancer.[51] CT scanning revealed a dilated afferent limb and intrahepatic biliary tree. ALS secondary to recurrent gastric cancer was diagnosed. The authors accessed the afferent limb via the ampulla of Vater, using percutaneous transhepatic biliary drainage techniques. One week after the initial drainage, a sheath introducer was inserted distal to the point of obstruction, and the stenotic area was successfully reopened with metallic stents. A double pigtail catheter was also deployed to prevent stent migration.

The same investigators further refined the above technique for afferent loop obstruction caused by recurrent gastric carcinoma.[52] Yoshida et al simultaneously deployed an expandable metal biliary stent percutaneously together with a double-pigtail catheter endoscopically to prevent migration of the metal stent.

Chevallier and colleagues described a patient in whom a malignant distal afferent loop obstruction developed 19 months after undergoing pancreaticoduodenectomy with Roux-en-Y reconstruction for pancreatic cancer.[53] The obstruction was too distal to be palliated by stent deployment via the transbiliary route. Successful palliation was achieved by percutaneous jejunostomy and stenting.

Song et al reported their experience with metallic stents in 39 consecutive patients who had undergone gastrojejunostomy.[54] The investigators reported that although placement of these stents was technically successful in 90% of patients, stent migration was more common with fully covered stents (4 of 24 cases) compared with no migration with the bare or partially covered stents. In addition, recurrent ALS occurred 10 days after stent placement in 1 patient. Tumor ingrowth occurred in 1 of 4 bare stents and tumor overgrowth in 1 of 29 partially covered stents requiring a second metal stent.



Medical Therapy

Acute ALS

In patients with acute ALS, a favorable outcome is correlated with an expedient diagnosis and corrective surgery. Medical therapy has no role, although nasogastric tube drainage may temporarily provide relief of symptoms while patients are resuscitated before surgery. Kim et al reported a case of a 67-year-old patient with ALS and coexisting acute pancreatitis who was not considered to be an ideal surgical candidate.[55] As a result, the patient was treated with an endoscopically placed nasogastric/enteric tube, with excellent relief of symptoms.

Chronic ALS

Patients with chronic ALS can be severely malnourished and anemic. These patients may benefit from preoperative specialized nutritional support or transfusion before undergoing corrective surgery. However, surgery should not be delayed if symptoms and signs consistent with complete obstruction develop.

Surgical Therapy

The treatment of ALS is surgical. Conservative measures can be temporarily used to resuscitate the patient, but the definitive treatment is corrective surgery. When ALS is caused by recurrent or unresectable malignancies, successful palliation is frequently accomplished using interventional radiologic techniques. Several references are provided in the preceding section.

Surgical correction is accomplished by deconstructing the Billroth II gastrojejunostomy and restoring gastrointestinal continuity with an alternate method. Several procedures have been described, but the two predominant operations are Billroth I gastroduodenostomy and Roux-en-Y gastrojejunostomy.

Interestingly, based on their retrospective study of 19 patients with postgastrectomy syndromes of whom 3 had ALS, Borrelli et al reported that a significant proportion of patients required minor surgical intervention.[56] The authors raised the question that in selected patients, laparoscopic surgery may be considered.

Vettoretto and associates reported a case of afferent loop obstruction caused by an adhesive band following distal gastrectomy and reconstruction for gastric cancer.[57] The authors performed diagnostic laparoscopy and laparoscopic lysis of adhesions, resulting in resolution of the ALS.

Aimoto and colleagues described two cases of malignant ALS in patients who had undergone pancreaticoduodenectomy.[58] In both patients, recurrence of the pancreatic cancer was found at laparotomy. Bypass procedures were performed in each case to achieve palliation.

Korean investigators have suggested that placement of partially covered self-expandable dual stents may be effective in patients who develop afferent loop syndrome following different types of surgical procedures.[59] The investigators retrospectively evaluated data from 13 consecutive patients who underwent placement of dual-stents (15 dual stents, 1 fully covered esophageal stent) via either the percutaneous transhepatic biliary drainage tract (n = 9) or the perioral route (n = 4). The stent placements were technically successful in all 13 patients, with 12 of 13 achieving postprocedure normalization of their blood tests and bowel decompression. The single patient that showed no change following stent placement subsequently underwent surgical jejunojejunostomy.[59]


Early consultation with a surgeon is mandatory.

Indications and Contraindications


Surgery is indicated in most cases of ALS. Recently, successful management of ALS in cases of advanced or recurrent malignancy using image-directed percutaneous drainage techniques has been reported. The fact remains that ALS is a purely mechanical complication consisting of varying degrees of obstruction of the afferent loop and will not resolve without surgery or other interventional techniques.


Surgical correction of ALS has no absolute contraindications. Relative contraindications include severe debilitation or extensive intra-abdominal malignancies. Patients with these conditions can be effectively treated with nonsurgical drainage procedures as described in Treatment.

Preoperative Details

The patient is properly identified. The patient (or a legal representative) is counseled about the operation and signs the informed consent documents.

Intravenous access is established, and intravenous fluid resuscitation is begun. A nasogastric tube is placed to decompress the stomach, and preoperative antibiotics are administered.

Intraoperative Details

Billroth I gastroduodenostomy

This procedure creates a direct anastomosis between the stomach and duodenum. It is the most physiologic procedure and is therefore the operation of choice. Several factors may preclude its use, including previous subtotal gastrectomy or extensive scarring around the duodenum. In these situations, the surgeon may be unable to gain enough mobility on the stomach and duodenum to create an anastomosis without excessive tension.

Roux-en-Y gastrojejunostomy

For a Roux-en-Y gastrojejunostomy, the jejunum is divided several centimeters distal to the ligament of Treitz. The proximal portion of the distal jejunal segment is anastomosed to the stomach. The distal end of the Roux limb is anastomosed to the distal jejunal segment. This jejunojejunostomy is created approximately 40 cm downstream from the gastrojejunostomy in order to minimize the possibility of developing alkaline (bile) reflux gastritis.

Van Stiegmann and Goff described a variant of this operation in which the jejunum is not divided.[60] This is the so-called uncut Roux-en-Y gastrojejunostomy. The procedure was developed to avoid Roux stasis syndrome, which was thought to be caused by interruption of the jejunal intestinal pacesetting potentials.

In an uncut Roux procedure, a loop gastrojejunostomy is fashioned. The afferent limb of this loop is occluded—but not divided—by a staple line. A jejunojejunostomy is made between the afferent and efferent jejunal limbs just proximal to the occluding staple line. This operation has not gained wide acceptance, partially because of the problem of dehiscence of the occluding staple line, as reported by Mulholland and colleagues.[61]

Other surgical procedures

The following remedial operations have also been used:

  • Revision of the gastrojejunostomy

  • Side-to-side enteroenterostomy

  • Jejunal segment interposition (between the gastric remnant and duodenum to create a modified Billroth I–type anastomosis)

  • Resection of the redundant portion of the afferent jejunal loop

Poor candidacy for surgery

In patients who are poor surgical candidates, such as those with disseminated unresectable malignancies, percutaneous transhepatic biliary or direct transperitoneal catheter placement and drainage can be performed for palliation of afferent loop syndrome.[48, 62, 63, 64, 65, 66] However, percutaneous transhepatic biliary drainage of an obstructed afferent loop may precipitate cholangitis and septic shock as a result of increased intrabiliary pressure and reflux of the infected duodenal contents into the bile duct.[48, 66, 67] An additional catheter should be placed into the bile duct in cases of biliary stasis.[66]

Postoperative Details

Intravenous fluids

Resuscitative and maintenance intravenous fluids are provided postoperatively. These are usually administered as a balanced salt solution (eg, lactated Ringer solution). If the patient has hypochloremic metabolic alkalosis due to nasogastric suctioning or other causes, normal saline can be substituted. Intravenous fluid support is continued until the patient successfully resumes oral intake.


Early activity, including arising from the bed to a chair and ambulating frequently, is encouraged.

Diet and nutrition

Patients are kept nil per os (NPO) for varying durations depending on the preference of the operating surgeon. Because correction of ALS entails reoperative gastric and small bowel surgery, many surgeons choose to advance patients' diets slowly.

Following nasogastric tube removal, patients can be started on liquids and advanced to a full diet as tolerated. Postgastrectomy diet counseling by a registered dietitian is helpful. Patients may find that they tolerate 5-6 smaller feedings per day better than the traditional 3 meals.

Depending on the patient's preoperative nutritional status, a period of specialized nutritional support might be warranted. This can range from enteral tube feedings to peripheral hyperalimentation to total parenteral nutrition. In addition, multivitamin and iron supplementation may be indicated.


A nasogastric tube is typically left in place postoperatively. Ensuring that the tube functions continuously and remains unclogged is crucial. Criteria for removal of the nasogastric tube include diminishing output and return of bowel function as manifested by bowel sounds or the passage of flatus.

A Foley catheter remains in place in the early postoperative period to monitor the hydration status and to serve as a guide for fluid resuscitation. Once the patient is stabilized and no further major fluid shifts occur, the catheter can be removed.

Pulmonary toilet

Instruct patients to cough and to take frequent deep breaths. The incentive spirometer is an important adjunct and should be used every 1-2 hours while the patient is awake. Early mobilization of the patient assists with maintaining good pulmonary toilet.


Vital signs are monitored per protocol. Intake and output records are kept to monitor intravenous fluids given, oral intake, and urine and nasogastric tube outputs. Pulse oximetry may be used to measure oxygen saturation.


Unless bowel perforation has occurred, a single dose of antibiotics as prophylaxis against wound infection usually suffices. Patients with abdominal catastrophes, such as bowel perforation or infarction, require a full course of antibiotic therapy aimed at gut flora.

Pain control

An epidural catheter can be placed by anesthesia personnel for postoperative pain control. Alternately, a patient-controlled anesthesia regimen can be ordered.

Deep venous thrombosis prophylaxis

Prophylaxis against deep venous thrombosis is crucial because deep venous thrombosis and pulmonary embolism are significant sources of postoperative morbidity and mortality. Available modalities include subcutaneous heparin, subcutaneous fractionated heparin preparations, and sequential compression stockings.

Aspiration precautions

The head of the bed can be kept elevated at 30-45° or sometimes higher in elderly patients or during sleep.


The operating surgeon should monitor patients to ensure that wound healing is complete and that no signs of infection arise. Patients are questioned about eating and elimination habits and are weighed to ensure that proper nutritional status is maintained.

Gastric emptying

Patients with persistent delayed gastric emptying or gastroparesis may report early satiety, epigastric fullness, nausea, or vomiting. Abdominal pain may be present. According to Gustavsson and associates, up to 30% of patients undergoing revision with a Roux-en-Y gastrojejunostomy develop one or more of these symptoms.[7] This has been termed Roux stasis syndrome.

The workup for Roux stasis syndrome or simple gastric atony begins with upper gastrointestinal contrast studies to exclude a source of mechanical obstruction. Upper endoscopy can help determine if the patient has a mechanical problem (eg, anastomotic stricture). Radionuclide imaging is useful to confirm the diagnosis.

Conversely, patients may develop signs and symptoms of dumping syndrome following corrective surgery. While the diagnosis is primarily made based on clinical findings, radionuclide imaging helps confirm the diagnosis by demonstrating rapid gastric emptying.

Treating altered gastric emptying

For delayed gastric emptying, agents such as erythromycin and metoclopramide have been used with varying degrees of success. Patients with dumping syndrome can be given a low-carbohydrate diet and are instructed to limit fluid intake during meals. A somatostatin analog administered before meals has been successful in controlling dumping-related symptoms.


CBC count and RBC characteristics are monitored. Patients with loss of parietal cell mass and bypass of the proximal small bowel may require supplemental iron and vitamin B-12.


Questions & Answers


What is afferent loop syndrome (ALS)?

What is the anatomy relevant to afferent loop syndrome (ALS)?

What are the types of afferent loop syndrome (ALS)?

What is the pathophysiology of afferent loop syndrome (ALS)?

Which surgical procedures are associated with afferent loop syndrome (ALS)?

Which postgastrectomy syndromes are associated with afferent loop syndrome (ALS)?

What is the clinical onset of afferent loop syndrome (ALS)?

Which postoperative conditions cause afferent loop syndrome (ALS) in patients with gastrojejunostomy?

What are the risk factors for afferent loop syndrome (ALS)?

What is the prevalence of afferent loop syndrome (ALS)?

Which patient groups have the highest prevalence of afferent loop syndrome (ALS)?

What is the prognosis of afferent loop syndrome (ALS)?

What are the mortality rates of afferent loop syndrome (ALS)?

What are the possible complications of afferent loop syndrome (ALS)?


Which clinical history findings are characteristic of acute afferent loop syndrome (ALS)?

Which clinical history findings are characteristic of chronic afferent loop syndrome (ALS)?

Which physical findings are characteristic of afferent loop syndrome (ALS)?


What is the disease course of untreated afferent loop syndrome (ALS)?

Which conditions should be considered in the differential diagnoses of afferent loop syndrome (ALS)?

What are the differential diagnoses for Afferent Loop Syndrome?


What is the role of a complete blood count (CBC) in the workup of afferent loop syndrome (ALS)?

What is the role of liver function and pancreatic enzyme testing in the workup of afferent loop syndrome (ALS)?

What is the role of an electrolyte panel in the workup of afferent loop syndrome (ALS)?

What is the role of serum albumin testing in the workup of afferent loop syndrome (ALS)?

What is the role of a carbon 14 xylose breath test in the workup of afferent loop syndrome (ALS)?

What is the role of imaging studies in the workup of afferent loop syndrome (ALS)?

What is the role of upper GI radiography in the workup of afferent loop syndrome (ALS)?

What is the role of plain abdominal radiography in the workup of afferent loop syndrome (ALS)?

What is the role of ultrasound in the workup of afferent loop syndrome (ALS)?

What is the role of hepatobiliary scintigraphy in the workup of afferent loop syndrome (ALS)?

What is the role of CT scanning in the workup of afferent loop syndrome (ALS)?

What is the role of MRI and MRCP in the workup of afferent loop syndrome (ALS)?

What is the role of upper endoscopy in the workup of afferent loop syndrome (ALS)?

What is the role of radiographic interventions in the treatment of afferent loop syndrome (ALS)?


What is the role of medical therapy in the treatment of acute afferent loop syndrome (ALS)?

What is the role of medical therapy in the treatment of chronic afferent loop syndrome (ALS)?

How is afferent loop syndrome (ALS) treated?

Which specialist consultations are beneficial to the treatment of afferent loop syndrome (ALS)?

When is surgery indicated for afferent loop syndrome (ALS)?

What are the contraindications for the surgical treatment of afferent loop syndrome (ALS)?

What is included in the preoperative care of afferent loop syndrome (ALS)?

What is the role of Billroth I gastroduodenostomy in the treatment of afferent loop syndrome (ALS)?

What is the role of Roux-en-Y gastrojejunostomy in the treatment of afferent loop syndrome (ALS)?

Which surgical techniques have been used in the treatment of afferent loop syndrome (ALS)?

Which procedures are performed for the palliative treatment of afferent loop syndrome (ALS)?

What is the role of IV fluids following surgery to treat afferent loop syndrome (ALS)?

Which activity modifications are used in the treatment of afferent loop syndrome (ALS)?

Which dietary modifications are used in the treatment of afferent loop syndrome (ALS)?

How is a nasogastric tube managed following surgery to treat afferent loop syndrome (ALS)?

How is a Foley catheter managed following surgery to treat afferent loop syndrome (ALS)?

How is pulmonary toilet maintained following surgery to treat afferent loop syndrome (ALS)?

What is included in patient monitoring following surgery to treat afferent loop syndrome (ALS)?

What is the role of antibiotics following surgery to treat afferent loop syndrome (ALS)?

How is pain managed following surgery to treat afferent loop syndrome (ALS)?

What is the role of deep venous thrombosis prophylaxis following surgery to treat afferent loop syndrome (ALS)?

Which aspiration precautions are needed following surgery to treat afferent loop syndrome (ALS)?

What is included in the outpatient monitoring following surgery to treat afferent loop syndrome (ALS)?

How is gastric emptying monitored following surgery to treat afferent loop syndrome (ALS)?

How is altered gastric emptying following surgery to treat afferent loop syndrome (ALS) managed?

What is the role of hematopoiesis in the treatment of afferent loop syndrome (ALS)?