Roux Y gastric bypass is a well established metabolic bariatric surgery and is widely performed worldwide with low complication profile

But it is associated with chronic abdominal pain in the longer term

• The incidence is about 14-3 to 34.2%
• 1/3 of the patients do not have an explanation for their pain

The known causes of abdominal pain after gastric bypass are listed below.

Marginal ulcers   Ulcers formed at the gastro-jejunal anastomosis   The risk factors include a larger gastric pouch, circular stapled anastomosis (2-3 fold increase rate), permanent sutures (2.6 vs 1/3%), smoking (4.6 fold increase), use of NSAIDs (3.1 fold increase), steroids and immunosuppressants (4.6 fold increase)   Proton pump inhibitors (PPI) medications *For prophylaxis has been found to decrease marginal ulcer risk from 7.3 to 1.2% and a 3 months course post op is recommended *For ulcer treatment faster healing of the gastric ulcers has been seen with opening the PPI capsules instead of swallowing them whole   Upper GI endoscopy can be done after 8-12 weeks to monitor the ulcer healing and treatment response   Failure of ulcer healing may require long term PPI or revision surgery Surgery treatment is indicated for complicated ulcers involving bleeding, perforation, stricture, gastro-gastric fistula   Up to 24% of marginal ulcer present with overt or occult bleeding *Endoscopy treatment is often fairly successful *Angiographic embolization has been used for failed endoscopic treatment *Surgical treatment include resection of the ulcer and creation of a new gastro-jejunostomy or reversal of the RYGBP   Recurrence rate for marginal ulcer after surgical repair are high (up to 1/3 of cases) even with risk factor reduction Long term PPI medication is often needed

Intussusception May occur at the jejuno-jejunostomy in an antegrade or retrograde (more common) fashion *The range has been reported to be 0.15 to 4.7% with the pooled incidence rate reported to be 0.62% *Note incidental intussusception has also been observed in asymptomatic patients   Symptoms are mainly abdominal pain, nausea and vomiting and the complication includes small bowel obstruction and strangulation (necrosis, perforation)   CT scan often reports target sign centred around the jejuno-jejunostomy, mesenteric vessel crowding, proximal small bowel dilatation, fat stranding and free fluid   The longer small bowel anastomotic length has a higher risk for intussusception   Intussusception length greater than 10cm on CT is often associated with small bowel obstruction requiring emergency surgery   Surgical exploration is also warranted when clinical suspicion is high   Surgical management include: *Simple reduction alone *Reduction with imbrication or plication of the jejuno-jejunostomy or pexy the BP limb to the common channel *Resection and revision of the jejuno-jejunostomy   Recurrence rate following surgical treatment range from 3.6 to 26.5% with a pooled recurrence rate of 22%, lowest rate with the revision of the jejuno-jejunostomy

Internal hernia   Routine closure of mesenteric defects during RYGBP reduces the risk of internal hernia by about 70%, important not to kink the small bowel during the mesenteric defect closure *Unfortunately mesenteric defects may re-open with time especially with massive weight loss   About half of the patients present with severe acute pain and half with intermittent, chronic milder pain   Colicky abdominal pain associated with nausea and vomiting are the most common presenting symptoms   Higher odds to have an internal hernia include post prandial pain radiating to the back, localized peritonitis and elevated white cell count   The incidence of internal hernia ranges from *4 to 17% without mesenteric defect closure *0-7% with mesenteric defect closure   The risk factors include rapid weight loss, younger age, pregnancy (especially in the 2nd or 3rd trimester) and non closure of mesenteric defects at the time of the bypass surgery   CT scan often report mesenteric swirl sign, SMV bird beak sign, clustered small bowel loops, small bowel located behind the SMA and mesenteric oedema   CT scan has a positive predictive value of 81% and a negative predictive value of 96% A normal CT scan does not exclude internal hernia, highlighting the importance of maintaining a high level of clinical suspicion in symptomatic patients   Surgical management include: *Reducing the herniated small bowel contents by tracing it from the ileo-caecal valve and closing all mesenteric defect *A non absorbable running suture is preferred for the defect closure, the use of clips, fibrin glue and mesh have also been described   Recurrence rate of internal hernia has been reported up to 40-50%  when the defect is re-opened

Bile reflux gastritis   Bile reflux gastritis after gastric bypass is characterized by inflammation of the gastric mucosa due to bile backflow from the duodenum back into the remnant bypassed stomach   But the pathophysiology remains unclear *The exclusion of nutrient flow to the bypassed stomach may impair mucosal function, alter the gut microbiome and affect motility which may lead to retrograde pooling causing chemical damage to the gut mucosa due to the bile toxicity   One study reported the prevalence to be 2.7%   Symptoms include epigastric pain, LUQ/RUQ pain, left shoulder pain, nausea and vomiting   The diagnosis is made with a combination of HIDA scan, fibre optic bilirubin monitoring and gastroscopy   HIDA scan has a high accuracy (PPV 88%, sensitivity 88%)   Treatment includes *ursodiol, which has demonstrated efficacy in reducing the bile cytotoxic effects and reducing symptoms by 80% *resection of the remnant bypassed stomach which reported 90% symptom resolution

Dumping syndrome   Dumping syndrome is a common complication following gastric bypass which can occur in up to 40% of patients   These symptoms are often distressing to patients *Early dumping is characterized by symptoms 10-30 minutes after a meal, which leads to abdominal cramps, nausea, diarrhoea or tachycardia *Late dumping can occur 1-3 hours after a high carbohydrate meal, associated with reactive hypoglycaemia   Symptoms may be assessed using the Dumping Symptom Rating Scale, Sigstad, Milne score or the Arts dumping questionnaire   Investigations include *Oral glucose tolerance test (ingesting 50 or 64g of glucose solution) and then measuring the blood glucose level, haematocrit, pulse rate and blood pressure at 30 minutes interval for 3 hours after ingestion *Hydrogen breath test   Management involves *Dietary modification to avoid/reduce the volume of food ingested, reduce carbohydrate and post pone fluid intake for 30 minutes after a meal *Pharmacotherapy include acarbose and somatostatin *Endoscopic management include stomal outlet reduction *Surgical intervention such as RYGBP reversal for refractory symptoms

Small intestine bacterial overgrowth   SIBO is caused by an increase in number and/or abnormal bacteria in the small intestine responsible for digestive symptoms   Symptoms include abdominal pain, nausea, bloating and chronic diarrhoea The long term effects of SIBO leads to malnutrition and vitamin malabsorption/deficiencies Investigation includes *A breath test to measure the exhaled hydrogen or methane following oral intake of a mixture of glucose + water *Small bowel aspirate and culture, with bacterial count >10 units/mL   Treatment includes metronidazole or rifaximin

Candy cane syndrome   Candy cane syndrome is rare but is increasingly recognized complication of RYGBP resulting from an elongated blind loop of jejunum at the gastrojejunostomy, increasing intra luminal pressure and small bowel dilatation *Intussusception of the blind loop into the gastric pouch may also contribute causing non specific GIT bleeding and acute pain   Food is trapped and leads to symptoms such as abdominal pain, nausea, vomiting, reflux and weight loss   Investigations include gastroscopy and imaging test which reveal the characteristic candy cane sign   Management option include: *Surgical resection which has been shown to resolve 73-100% of the cases *Endoscopic marsupialization, endoscopic sutures, lumen apposing stents have been described

Biliary pathology   Gallstone formation can occur after metabolic bariatric surgery due to cholestasis and increased bile lithogenicity   In one meta analysis there is a 35% increase in incidence of symptomatic gallstones following RYGBP compared to sleeve gastrectomy   One study reported 1.9% incidence in symptomatic gall stone during the 12 months follow up period   One retrospective analysis reported the rate of interval cholecystectomy was more than 2x the reported rate from previous ASMBS guidelines   Biliary hyperkinesia has also been described in a small case series as a cause of recurrent abdominal pain *The gall bladder ejection fraction were >95% with a normal ultrasound scan without sludge/stones *Cholecystectomy has been successful in addressing these symptoms after ruling out other pathologies

Vascular disorders   These relates to mesenteric ischaemia secondary to atherosclerosis   The risk factors include dyslipidaemia, T2DM, hypertension, smoking and cardio-vascular co-morbidities found in 23% of the patients with chronic abdominal pain   Vascular disorders result in compromise intestinal micro circulation or abdominal mesenteric angina   Portomesenteric and splenic vein thrombosis are both rare complications requiring anticoagulation with an incidence of 0.4% and mortality 3.6%   Portomesenteric vein thrombosis is more common than splenic vein thrombosis, reported in 41.5% of patients, diagnosed usually in the first year after surgery

Gastro-oesophageal reflux disease   RYGBP bypassed the acid producing stomach, creates a low pressure proximal alimentary limb and diverts bile away from the oesophagus *However reflux can persist or develop after RYGBP causing abdominal pain   The prevalence of reflux after RYGBP has been reported between 20-30% of patients with symptoms, one study reported 21.1% prevalence with 12 years follow up (22% has persistent reflux whilst 25% develop de novo symptoms) despite having RYGBP   The risk factors include *Technical factors include a large gastric pouch with acid retaining cells, short Roux limb (<60cm) increase the risk of bile reflux (60% of these patients report bile reflux), hiatus hernia, impaired motility of the Roux limb (found in 20-25% of patients) causing prolonged acid exposure ***The antegrade intestinal anastomosis and longer Roux limb is more beneficial against post op reflux *Patient factors include weight regain, anastomotic strictures, patients with pre-existing reflux and T2DM   PPI often provides symptom relief for 60-70% of patients with acid related reflux and 30% for bile reflux or technical issues *H2 receptor antagonist and sucralfate is less effective than PPI     Investigation for bile reflux include Bravo capsule, high resolution manometry or impedance test catheter (multi channel intraluminal impedance)   Surgical revision is an option for patient unresponsive to medical therapy, which includes *Elongating the Roux limb and reducing the gastric pouch size, which reported to improve the symptoms in 70-80% of cases *Hiatus hernia repair has about 75% success rate *Fundoplication using the remnant stomach *Other treatments include magnetic sphincter augmentation to improve lower oesophageal sphincter pressure     GOR disease following RYGBP is a complex, multifactorial issue affecting a significant minority of patients

Summary

Chronic abdominal pain after gastric bypass is a challenging problem

Chronic epigastric abdominal pain needs investigation to exclude marginal ulcer, gastro-oesophageal reflux and bile reflux gastritis

Chronic right upper quadrant pain needs ultrasound to check for gallstones

Generalized non specific abdominal pain may be due to vascular pathology needs investigation for internal hernia, small bowel obstruction, intussusception, mesenteric or portomesenteric vein thrombosis

Rare causes include SIBO and dumping syndrome