Bariatric surgery sequelae

Introduction

Obesity and inactivity are responsible for 30,000 deaths per year in England and 365,000 deaths per year in the US. [1] [2] [3] [4] The incidence of severe obesity is increasing at a rapid rate and this has resulted in a drastic increase in bariatric operations worldwide. Successful obesity surgery has been shown in large-scale prospective trials to result in improved quality of life and a decreased risk of death for morbidly obese people. [5] [6] [7] [8] [9] [10] In addition, bariatric surgery is being investigated as a possible primary therapy for type 2 diabetes. [11] [12] The International Diabetes Foundation published a statement in 2011 supporting the use of bariatric surgery in severely obese people with type II diabetes. [13] [14] The mechanism of action of bariatric surgery is not fully understood at present but is felt to include gastric volume restriction, malabsorption, and hormonal changes. [15]

After bariatric surgery, patients may present to clinics, emergency departments, or a hospital other than the one where they had the operation. Thus, it is necessary to be knowledgeable about the common complications. [16] The obese abdomen may be difficult to examine and can mask typical signs of sepsis. Careful attention to vital signs, examination findings, and any deviation from expected post-operative course is essential.

Types of surgical procedures

The most commonly performed operations include:

• Roux-en-Y gastric bypass (RGB)[B Evidence]

• Adjustable gastric banding, a common example of which is the Lap-Band®[A Evidence][B Evidence]

• Sleeve gastrectomy.[B Evidence]

These may be performed through open or laparoscopic techniques.

Less common or historical operations include:

• Biliopancreatic diversion (BPD) with or without duodenal switch (DS)[C Evidence]

• Vertical banded gastroplasty[C Evidence]

• Magenstrasse-Mill procedure (of historical interest)

• Jejunoileal bypass.

Expected weight loss

Weight loss after bariatric surgery is difficult to predict, as it may be affected by pre-operative weight, post-operative diet, activity level, and patient compliance. Post-surgical weight loss is typically measured as percentage of initial excess body weight lost, with excess weight calculated as initial body weight minus ideal body weight. One systematic review of bariatric surgery reported long-term (2 years or more) excess weight loss of 49% for adjustable gastric band, 63% for gastric bypass, and 73% for biliopancreatic diversion with duodenal switch. [12] Fewer long-term data are available for sleeve gastrectomy, but a 2010 study from Belgium reported 6-year weight loss of 53%, greater than adjustable gastric band but less than gastric bypass. [17]

Gastric bypass: description

Roux-en-Y gastric bypass has historically been the most common bariatric operation worldwide, comprising 80% of all bariatric procedures performed in the US as of 2003. [18] [19] However, it lost much of its pre-eminence to the adjustable gastric band in the 2000s and to the sleeve gastrectomy today.

• Bypass may be performed through either laparoscopic technique or open surgical technique. The laparoscopic technique uses 5 to 7 abdominal access incisions 5 mm to 15 mm in length, whereas the open technique generally requires a vertical midline incision. The laparoscopic approach involves less postoperative pain, faster recovery, and fewer wound-related complications. [20]

• A surgical stapler is used to divide the stomach into 2 sections. The upper section is typically referred to as the gastric pouch and is 15 to 30 mL in volume, based on the lesser curvature of the stomach (right side). It excludes the gastric fundus.

• Using a stapler that both staples and divides tissue, the jejunum is transected 20 cm to 100 cm from its origin at the ligament of Treitz. The proximal end is connected 75 cm to 150 cm "downstream" from the distal segment - or "Roux limb". Roux-en-Y gastric bypass diagramCopyright ©2008 Daniel M. Herron, MD; used with permission The Roux limb is connected to the gastric pouch, thus creating a Y-shaped intestinal anatomy.

• The distal stomach is completely excluded from the alimentary path. Its secretions, along with those from the liver and pancreas, drain through the biliopancreatic limb (20 cm to 100 cm long).

• Food passes from the oesophagus into the gastric pouch, before passing through the proximal anastomosis to enter the Roux limb or alimentary limb (75 cm to 150 cm long). At the distal anastomosis, the ingested food joins the digestive secretions in the common channel (150 cm to 400 cm long).

• Weight loss and metabolic improvements result through several different mechanisms, including gastric volume restriction, mild malabsorption, and hormonal effects. [21]

• The gastric remnant and biliopancreatic limb are inaccessible during standard upper endoscopy or colonoscopy, and ERCP cannot be performed.

Gastric bypass: early complications

Early complications are considered to be those occurring within 30 days of surgery. Reported mortality rates after RGB vary from 0.2% in a large case series to 2% in US state-wide registries. [22] [23] Laparoscopic RGB has been compared with open RGB and found to have a lower incidence of wound infection, ventral hernia, and pulmonary effects. [20] Early complications of gastric bypass include enteric leak or sepsis, DVT and pulmonary embolus (PE), GI haemorrhage, compartment syndrome, or early obstruction. Best practice guidelines have been published recommending specific surgical techniques, equipment, and hospital resources for facilities performing weight loss surgery in order to minimise such complications. [24] [25] [26]

• Enteric leak or sepsis

  • The American Society for Metabolic and Bariatric Surgery (ASMBS) has published guidelines on the prevention and detection of enteric leaks after gastric bypass. [27]

  • Leaks may occur at the proximal anastomosis (gastric-jejunostomy), distal anastomosis (jejunojejunostomy), pouch staple line, gastric remnant staple line, or other areas along the stomach, plus small and large bowel. Rates of GI leak range from 2% to 3% and are not affected by choice of laparoscopic versus open approach. [28] [29]

  • Symptoms include abdominal pain, back or shoulder pain, and anxiety or feeling of impending doom.

  • Signs include tachycardia >110-120 beats per minute, fever (>38.5°C [101.3°F]), respiratory distress (SOB or tachypnoea >20 breaths per minute), or a post-operative recovery that differs from expected course. Traditional signs of abdominal sepsis such as tenderness, rebound pain, or guarding may be unreliable or absent in the obese abdomen.

  • Imaging findings are commonly falsely negative, although a positive upper GI series or CT scan may be helpful in diagnosing enteric leak. A negative study does not eliminate enteric leak from the differential diagnosis.

  • Treatment includes broad-spectrum intravenous antibiotics and resuscitation, which should be started early. If the diagnosis is in doubt, surgical exploration as soon as possible is advisable. Re-exploration may be performed using laparoscopic or open techniques.

  • Operative intervention generally includes irrigation of peritoneal cavity, sewing over of leak site with placement of omental patch, placement of drain(s) near leak site, and insertion of feeding access into gastric remnant or jejunum.

• DVT and PE

  • DVT with subsequent PE may be the most common cause of death post-bariatric surgery. [30] Approximately 1% to 2% of patients will develop PE, with a mortality rate of 0.2% to 0.6%. [31] [32] Predisposing factors are present in all bariatric patients, including obesity, general anaesthesia, and impaired mobility. Additional risk factors include age less than 50 years, previous DVT/PE, smoking history, revisional operation, open surgery, and anastomotic leak. [33]

  • No formal recommendations exist for prophylaxis in bariatric surgery. The American College of Chest Physicians' evidence-based guidelines recommend thromboprophylaxis with low-molecular-weight heparin, low-dose fondaparinux, or low-dose unfractionated heparin for patients undergoing major general surgery. [34] In the UK, the National Institute for Health and Clinical Excellence has published guidelines for reducing the risk of DVT/PE in hospitalised patients. [35] Additionally, the American Society for Metabolic and Bariatric Surgery has published a position statement on prophylactic measures to reduce the risk of DVT/PE in bariatric patients. [36]

  • Preventative measures include early mobilisation, sequential compression devices, and unfractionated or low-molecular-weight heparin (note: dosing for heparin is different in obese patients). [37] For very high-risk patients, a temporary inferior vena cava filter and/or continuation of chemoprophylaxis for 14 days or more post-surgery is recommended. [38]

  • Diagnostically characteristic findings of DVT/PE (SOB, chest pain, tachycardia) are not specific and may also suggest the diagnosis of enteric leak. Lower extremity DVT is usually diagnosed by Doppler ultrasound. CT angiography is effective in making the diagnosis of PE. The diagnosis of DVT with CT angiography is less well described in this situation.

• GI haemorrhage

  • GI haemorrhage may present as an upper GI bleed with haematemesis, or as a lower GI bleed with bright red blood per rectum. The reported incidence of GI bleeding ranges from 1% to 4%. [28] Upper GI bleeding typically originates from the proximal anastomosis or the gastric pouch staple line. Lower GI bleeding typically originates from the distal anastomosis or the bypassed stomach (gastric remnant). As with any abdominal operation, intraperitoneal bleeding may occur from a staple line or from surgical injury to the spleen, mesentery, or omentum.

  • Management of postoperative GI bleeding includes:

    • Review of medications and discontinuation of any that enhance bleeding, such as heparin or non-steroidal anti-inflammatory drugs

    • Observation, if the patient is in a stable condition and bleeding is not excessive [39]

    • Endoscopy and/or immediate re-exploration under general anaesthesia should be considered if the patient is not in a stable condition or is bleeding excessively and persistently.

• Compartment syndrome, characterised by

  • Intra-abdominal oedema and elevation in intra-abdominal compartment pressure above 25 mm Hg, causing end-organ failure as a result of venous outflow obstruction. This may result in abdominal sepsis, bleeding, or bowel obstruction. Oliguria and renal failure may be the first manifestations.

  • Respiratory failure can occur because of interference with diaphragmatic excursion.

  • Diagnosis of compartment syndrome is achieved by measuring bladder pressure via pressure transducer, with a Foley catheter attached to 3-way stopcock. After the bladder is emptied, 50 cc of saline is introduced and the catheter is clamped. The pressure inside the catheter lumen is transduced and measured. Pressure greater than 25 mm Hg will require surgical decompression by opening the abdomen.

• Early obstruction

  • Early obstruction is uncommon but needs to be recognised and treated promptly, because of the risk of disrupting a fresh anastomosis or staple line. [40]

  • Obstruction at the proximal anastomosis may occur because of oedema at the gastric-jejunostomy. This typically resolves with time and may be treated expectantly.

  • Early obstruction most commonly occurs at the distal anastomosis because of kinking of the bowel approximately 2 weeks after surgery. [40] Occlusion of the biliopancreatic limb may not be visible on plain radiographs, and abdominal CT is required for diagnosis. View imageView image In a stable patient, CT-guided percutaneous decompression of the gastric remnant may temporise the situation and permit non-operative treatment. If this is not possible, revision of the distal anastomosis or bypass of the obstruction with a Braun "omega"-type loop may be necessary.

• Wound infection

  • Wound infection is reported in up to 20% of open gastric bypasses. [41]

  • Wound infection rate was found in one study to be lower in laparoscopic RGBs (1%) than in open RGBs (10%). [20]

Gastric bypass: late complications

Late complications are considered to be those occurring more than 30 days after surgery. They include:

• Vomiting due to stricture

  • Stricture of the proximal anastomosis is the most common complication of RGB. Reported incidence ranges from 0.6% to 27%. [42]

  • Symptoms generally appear 3 to 6 weeks after surgery and include increasing intolerance of solids and ultimately liquids. There may additionally be associated dysphagia, nausea, and vomiting. [43]

  • Diagnosis is based on history and confirmed with endoscopy. Simultaneous endoscopic balloon dilatation to 10 mm to 15 mm results in immediate symptomatic relief. Patients may be immediately restarted on a diet of pureed food. Many strictures require 2 or more dilatations. [44]

  • Upper GI contrast swallow is not generally necessary and may delay therapeutic endoscopic treatment or result in aspiration of contrast.

• Internal abdominal hernia

  • Abdominal pain in post-bypass patients should always suggest the possibility of internal hernia, particularly if it occurs 3 months or more after surgery. Incidence is approximately 3%. [45]

  • Pain is typically epigastric and may radiate to the back. Symptoms may be acute or chronic, and may mimic biliary colic.

  • Patients may complain of multiple similar episodes of pain. They may also have undergone ultrasound, upper GI series, or CT, which can be negative even in the presence of an internal hernia. [46]

  • Three potential hernia spaces in the gastric bypass patient are:

    • Peterson hernia space, located behind the Roux (alimentary) limb

    • Distal mesentery space, located between the 2 leaves of mesentery at the distal anastomosis

    • Mesocolic space, located in gastric bypasses with a retrocolic Roux limb (placed through an iatrogenic opening in the mesocolon). The bowel may herniate through this space.

  • Pain occurs because the bowel becomes entrapped in one of these spaces and blood supply is compromised. If ischaemia is persistent, necrosis of the intestine will occur. View image

  • Definitive diagnosis can only be made through laparoscopic or open surgical exploration. Bowel must be reduced from the herniated position, and necrotic intestine must be resected. All hernia spaces should be closed with continuous permanent suture material.

• Marginal ulcer

  • Marginal ulcers are a common source of pain or perforation after gastric bypass.

  • Aetiology is unclear. They are likely to be related to acid exposure, smoking, or the presence of foreign bodies (e.g., staples or permanent suture material) at the proximal anastomosis. [47]

  • Ulcers generally form just distal to the gastric-jejunostomy.

  • Symptoms range from minor intermittent epigastric pain to severe generalised abdominal pain if perforation occurs.

  • Marginal ulcer formation is strongly associated with fistulae from the low-pH gastric remnant to the gastric pouch. [48]

  • Ulcers are easily diagnosed with upper endoscopy.

  • Simple ulcers may be treated with acid reduction therapy. Suture material at the ulcer site should be removed endoscopically if possible. The presence of a gastrogastric fistula between the pouch and gastric remnant requires surgical revision.

• Incisional hernia

  • Incisional hernia formation in open gastric bypass patients is very common, occurring in 20% of patients. [49]

  • Hernia formation is very uncommon in laparoscopic gastric bypass surgery, occurring in less than 1% of patients. [50]

• Cholelithiasis

  • Cholelithiasis may occur in 32% of patients after surgically induced weight loss and may result in biliary colic or acute cholecystitis. [51]

  • Some bariatric surgeons routinely perform cholecystectomy at the time of gastric bypass. Others perform it only in the presence of documented cholelithiasis. However, many surgeons leave asymptomatic gallbladders in place, regardless of whether or not gallstones are present.

  • Prophylactic ursodiol (300 mg orally twice daily) during the first 6 months after surgery reduces the risk of postoperative gallstone formation to between 2% and 6%. [51] [52]

  • Indications for cholecystectomy include symptomatic cholelithiasis, acute or chronic cholecystitis, or history of gallstone pancreatitis.

  • Because gastric bypass anatomy precludes ERCP, a cholangiogram should be performed at the time of cholecystectomy to identify the presence of common bile duct stones.

  • In patients with abdominal pain after gastric bypass, cholelithiasis does not eliminate the possibility of internal hernia and it may be difficult to determine whether their pain is a manifestation of symptomatic cholelithiasis or undiagnosed internal hernia. If the patient is taken to the operating theatre for cholecystectomy, the gastric bypass anatomy should be carefully evaluated and any internal hernias repaired at that time.

Gastric band: description

• This is probably the most popular procedure other than gastric bypass.

• A number of brands of adjustable gastric band (AGB) device are commercially available and approved by the FDA. Laparoscopic adjustable gastric bandCopyright ©2008 Daniel M. Herron, MD; used with permission

• The vast majority of AGB operations are performed via laparoscopic approach. In general, open surgery is used only when technical considerations preclude a laparoscopic approach. Typically, 5 to 6 incisions, each 5 mm to 15 mm, are used for laparoscopic access. One incision is enlarged to allow attachment of the access port to the abdominal wall.

• The AGB is placed around the superior portion of the stomach, just beneath the gastro-oesophageal junction. The inner portion of the band includes a toroidal balloon that can be inflated with saline, injected through the subcutaneous access port. Injecting saline into the port tightens the band, and removing saline loosens the band.

• The mechanism of action is due to gastric volume restriction.

• Many different types of band device exist, with different saline capacities. In general, bariatric surgeons tighten bands just enough to result in restriction of intake, but not so tight as to cause vomiting, discomfort, or oesophageal widening (pseudoachalasia). Saline capacity may range from 4 mL to 15 mL.

• The access port is usually clearly visible on plan abdominal radiograph, and can typically be palpated on examination of the abdomen.

• On radiographs, the band generally appears to be rotated about 20-40 degrees from horizontal, with the left side higher than the right. View image Bands that are angulated differently may have slipped from their normal position. A vertically-oriented band suggests a band slippage with the posterior stomach prolapsed through the band, whereas a horizontally-oriented band suggests an anterior slippage.

• For band adjustments, the skin is prepared with an antibacterial agent, typically alcohol or povidone-iodine. The port can then be accessed with a special, non-coring, Huber-type needle. Use of a standard hollow-bore needle to access the port may result in permanent damage to the access port. If the port cannot be palpated, fluoroscopic guidance may be required.

• After band placement, the stomach remains accessible to upper endoscopy, although it may be necessary to remove some or all of the fluid from the band beforehand.

Gastric band: early complications

Early complications are those that occur less than 30 days after surgery. Adjustable gastric bands are generally placed around the body of the stomach just distal to the gastro-oesophageal junction, using laparoscopic surgical technique.

• Surgical injury to the stomach or intra-abdominal oesophagus may result in immediate or early GI leak and sepsis.

• Early GI leak requires immediate reoperation with removal of the band, closure and patch of the injury, and drainage.

• Surgical oedema at the site of the band may result in early surgical obstruction in 1.5% of patients. [53] Obstruction due to oedema may be treated with band removal.

• Venous thromboembolism is the most common cause of death in gastric band patients. [54] Mechanical and/or pharmacological DVT prophylaxis should be used routinely.

Gastric band: late complications

• Breakage of the access port or connecting tubing may occur in up to 8% of gastric band patients. [55]

• Band slippage, also referred to as gastric prolapse, may occur in 5% or more of patients. [53] Abdominal plain films show a normal band angle of approximately 20 to 40 degrees from horizontal, with the left side higher than the right side. View image Significant deviation from this appearance strongly suggests slippage or prolapse. This usually results in partial or complete obstruction of the stomach and associated abdominal pain. Deflation of the band may relieve symptoms. Persistent symptoms after deflation may indicate vascular compromise of the stomach, requiring urgent surgical revision or removal of the band.

• Patients with obstruction or pain should have all the fluid in the band removed. The access port is localised by palpation or fluoroscopy and accessed with a Huber-type non-coring needle. Different bands may hold from 4mL to 15 mL of saline.

• Gastric bands occasionally erode through the gastric wall and lead to infection. [56] [57] This should be suspected in a patient with cellulitis at the site of the access port, because the infection may track along the tubing to the level of fascia or skin. Erosion is diagnosed with endoscopy and treated with antibiotics and band removal.

• Band patients may develop oesophageal dilatation, or pseudoachalasia, in the long term. This is initially treated with band deflation, followed by band removal if necessary. [58]

• The access port may rotate, precluding percutaneous access. Such a complication would require surgical revision. The overall incidence of port-related complications was reported to be 11.2% in a European study of 1791 patients over 12 years. [59]

Biliopancreatic diversion (BPD) with or without duodenal switch: description

The BPD, sometimes referred to as the Scopinaro procedure, is only moderately restrictive but causes substantial malabsorption. Like the Roux-en-Y gastric bypass, the BPD involves reduction of the stomach volume and surgical division of the small bowel with Y-shaped reconstruction. However, the stomach pouch remains much larger than in the Roux-en-Y gastric bypass, the amount of bowel bypassed is much greater, and the common channel is much shorter (50 cm to 100 cm). This results in less restriction but far greater malabsorption than with the gastric bypass. Biliopancreatic diversion with duodenal switch (BPD-DS)Copyright ©2008 Daniel M. Herron, MD; used with permission

• In BPD, the stomach volume is reduced by resecting the antrum of the stomach (antrectomy).

• The biliopancreatic diversion with duodenal switch (BPD-DS) is a modification of the BPD. The antrum is left intact while the greater curvature (left side) of the stomach is resected. This results in a banana-shaped "sleeve gastrectomy" 100 cc to 200 cc in volume. The distal end of the pouch is formed by dividing the first portion of the duodenum several centimetres distal to the pylorus. This modification is intended to reduce dumping syndrome and ulceration of the anastomosis.

• The biliopancreatic limb is inaccessible to upper endoscopy or colonoscopy. ERCP cannot be performed.

Biliopancreatic diversion with or without duodenal switch: complications

• Surgical complications of BPD or BPD-DS are similar to those of gastric bypass. Overall mortality is approximately 1%. [60]

• Nutritional complications related to protein and fat malabsorption are substantially more common than in gastric bypass patients and may require surgical revision in 1% of patients. [60]

Sleeve gastrectomy: description

• Laparoscopic sleeve gastrectomy (SG), also referred to as vertical sleeve gastrectomy, is rapidly gaining in popularity due to its technical simplicity and minimal long-term metabolic effects. [61] [62] [63]

• In SG, the greater curvature (left side) of the stomach is resected, leaving a narrow, banana-shaped stomach in place. The small intestine is not involved in this operation, so there is no alteration to the alimentary path.

  Sleeve gastrectomyCopyright ©2008 Daniel M. Herron, MD; used with permission

• This operation has several significant advantages over the gastric band. First, it results in better weight loss than the adjustable gastric band. Second, there is no foreign body implanted within the abdomen. Third, there is no need for frequent adjustments. For these and other reasons, many surgeons feel that this is the best surgical option for a patient at high risk for poor compliance or limited follow-up.

• After sleeve gastrectomy, the remaining portion of the stomach is accessible endoscopically. ERCP may be performed if needed. This is in contradistinction to the gastric bypass or biliopancreatic diversion, where a significant portion of the stomach or small intestine is unreachable endoscopically, thus precluding routine ERCP in most circumstances.

Sleeve gastrectomy: complications

• There are no surgical anastomoses in the SG. However, the long staple line may leak (0.7% risk) or bleed (0.7%). [64] [65] Leakage may be more difficult to treat than in gastric bypass but may respond to endoscopic stenting. [66] [67]

• Patients may develop nausea and vomiting in the early post-operative period, generally 1 to 2 weeks after surgery. This may be caused by post-operative oedema or kinking of the stomach. Symptoms usually improve if upper endoscopy is performed, as it serves to minimally dilate and straighten the pouch. If a frank stricture is seen, it will probably respond to endoscopic balloon dilatation.

• Persistent nausea without mechanical obstruction may respond to medical therapy. First-line anti-nausea therapy would include prochlorperazine or ondansetron. If this is ineffective, the antidepressant medication mirtazapine may be used for its gastrointestinal stimulatory effect. Additionally, a patient who has difficulty swallowing saliva may benefit from hyoscyamine, an anticholinergic.

• Dilatation of the sleeve may occur over time, leading to decreased restriction, increased oral intake, and weight regain. In these cases, surgical revision may be indicated. [68]

• Overall readmission rate for SG patients is about 5%. [60]

Vertical banded gastroplasty (VBG)

• A surgical stapler is fired parallel to the lesser curvature, creating a vertically oriented 30 mL pouch. The outlet of the pouch is restricted by placement of a synthetic band.

• This operation was very common in the 1980s, but has since declined as long-term outcome studies demonstrated a success rate of only 25%. [21] [C Evidence]

• By 2002, vertical banded gastroplasty represented only 7% of bariatric procedures performed in the US. [18]

Jejunoileal bypass

• Jejunoileal bypass was the earliest commonly performed bariatric operation. It was first described in the 1950s.

• This operation involved the anastomosis of the proximal jejunum to the distal ileum, thereby essentially short-circuiting the small bowel, decreasing absorption and leaving a long segment of bypassed bowel.

• This operation is no longer performed, owing to unacceptable long-term complications, including protein malnutrition, hepatic injury, electrolyte imbalances, and renal stone formation. [69]

Metabolic and nutritional complications

Patients who have undergone bariatric operations are at increased risk of nutritional deficiency, because of the restrictive and/or malabsorptive effects of the surgery. [70] There is no standard regimen for nutritional supplementation after bariatric surgery. Many bariatric surgeons recommend that gastric bypass patients supplement a small-volume, high-protein, low-fat diet with a multivitamin, calcium citrate or carbonate, and iron. [71] [72] [73] A typical post-gastric bypass regimen would include:

• Multivitamin with iron, twice daily. Chewable supplements may be better tolerated than swallowed pills.

• Calcium supplementation. Calcium citrate is generally preferred over calcium carbonate due to its better absorption in gastric bypass patients. [74] Supplements with additional vitamin D may be beneficial due to the high incidence of vitamin D deficiency in the bariatric surgery population. [75]

• Iron supplementation. Iron polysaccharide complex may be better tolerated and absorbed than ferrous sulphate.

• Vitamin B12 (cyanocobalamin).

Bariatric operations that bypass the duodenum or jejunum (i.e., gastric bypass and biliopancreatic diversion with or without duodenal switch) reduce absorption of iron, calcium, and other divalent cations, and so require more supplementation than non-bypass operations. Since no intestine is bypassed in the sleeve gastrectomy and adjustable gastric band procedures, these patients may be maintained with minimal supplementation, such as a daily multivitamin with or without additional calcium.

It should be emphasised that any supplementation regimen such as the one outlined above is merely a starting point, and that all bariatric patients need to be followed with regular bloodwork to assess their vitamin status. With these results available, supplementation regimens may be customised for each patient as needed.

Extensive multi-society guidelines have been published recommending best practices for perioperative nutritional and metabolic support of bariatric patients. [76] [77] [78] [79] [70]

• Severe vomiting after bariatric surgery may result in vitamin B1 deficiency and Wernicke's encephalopathy. Neurological symptoms include ataxia, confusion, and blurred vision. Patients should not be treated with dextrose-containing intravenous fluids as this may result in permanent neurological injury. Instead, normal saline or Ringer's lactate solution should be used with added thiamine and multivitamin. [80]

• Protein deficiency may be seen after malabsorptive procedures that involve bypassing large portions of small intestine. Physical examination may demonstrate oedema, alopecia, and asthenia. Laboratory studies may show hypoalbuminaemia and anaemia. Incidence approaches 13% after RGB and 18% following BPD-DS. [71] Milder cases may respond to increased oral protein intake. Severe cases may require total parenteral nutrition or surgical revision.

• Iron deficiency is most likely in bariatric procedures such as gastric bypass and BPD-DS, in which the duodenum is bypassed. Rates may be as high as 50%. [71] Mild cases will respond to oral supplementation, whereas more severe cases require intravenous replacement.

• Vitamin B12 and folate may become deficient when the proximal small bowel is bypassed. Supplementation is generally recommended after RGB and BPD-DS. Vitamin D deficiency is very common and is associated with calcium deficiency and secondary hyperparathyroidism. [81] [82] This can be reduced with calcium citrate and vitamin D supplementation. Moderate sunlight exposure is also helpful.

• Certain medications, specifically those that are fat-soluble or that undergo enterohepatic circulation, may be poorly absorbed or metabolised after bariatric surgery. [83] [84]

Bariatric surgery and the pregnant patient

Bariatric patients are generally recommended to avoid pregnancy during the period of rapid weight loss following bariatric surgery. Limited guidelines regarding this issue have been published by the American College of Obstetricians and Gynecologists. [85] Both negative and positive effects of bariatric surgery on fertility and pregnancy outcomes have been reported. [86] [87]

Weight loss failure

• Initial evaluation

  • Inadequate weight loss or weight regain may occur in 10% or more of bariatric patients. [31] [88] [89] [90] Evaluation of these patients requires a systematic approach.

  • Initial evaluation includes a detailed nutritional and activity history. This should include a thorough review of postoperative behavioural compliance with diet, nutritional supplementation, exercise, and follow-up programmes.

  • Surgical anatomy should be assessed with upper GI series and upper endoscopy to ensure that the procedure remains intact.

• Non-intact surgical anatomy

  • Upper GI series and endoscopy may reveal that the original surgical anatomy is no longer intact. Examples of this include:

    • Excessively large gastric pouch (estimated volume >30 mL) after RGB. This usually leads to weight regain as a result of the decrease in gastric volume restriction, and may result in vomiting due to poor pouch emptying.

    • Formation of gastrogastric fistula after RGB. This often leads to marginal ulcer formation as well as weight regain.

    • Prolapse of stomach through a gastric band, resulting in an excessively large pouch.

  • These reasons for weight loss failure generally require reoperation to re-establish the desired surgical anatomy. Bariatric revisional surgery carries a substantially higher risk of morbidity and mortality than primary surgery.

Bariatric patient with abdominal pain

Approach to a bariatric patient with abdominal pain:

• After initial evaluation and resuscitation, the patient’s bariatric surgeon or the local bariatric surgeon on call should be contacted immediately.

• The date of surgery should be ascertained, as the causes of pain vary based on the post-operative period.

• Bloodwork: a complete blood count with differential will be helpful to determine if there is infection, inflammation, or haemorrhage. Serum electrolytes are useful in a patient who has had poor oral intake. Amylase/lipase and liver function tests will help to diagnose pancreatitis, cholecystitis, or hepatobiliary problems. Coagulation studies may be useful in a patient with a malabsorptive operation, as vitamin K deficiency may elevate the prothrombin time.

• New-onset abdominal pain in the first 2 weeks after surgery raises the concern of enteric leak, typically from a staple line or anastomosis. CT scan with oral contrast will be useful in identifying leakage, intra-abdominal fluid, or abscess. Upper GI series with water-soluble contrast is very helpful in identifying a leak from the stomach or proximal jejunum, but may be less useful for distal leaks. Generally, enteric leak requires immediate return to the operating theatre for washout, repair of the leak, drain placement, and placement of enteral feeding access. Well-contained leaks in a stable patient may occasionally be managed non-operatively.

• Epigastric or right upper quadrant pain in a bariatric patient 3 months or more post surgery is suggestive of cholecystitis or marginal ulcer. Abdominal ultrasound is the single best study for evaluating the gallbladder. Upper endoscopy will reveal gastritis or marginal ulcer if present.

• Gastric band patients with acute abdominal pain may be suffering from an acute band slip or gastric prolapse, which can be diagnosed with upper GI series radiographs.

• If the patient is 3 months or more post surgery, abdominal pain may also be due to an internal hernia. While this may be seen on CT scan, it is very possible that all imaging will be negative. Immediate surgical consultation should be obtained to determine whether surgical exploration is warranted.

• Rapid onset of pain in the absence of any prior symptoms is strongly suggestive of perforated marginal or gastric remnant ulcer.

• Chronic intermittent pain in the epigastrum radiating to the back is strongly suggestive of internal hernia and should be diagnosed with surgical exploration if no other pain source is identified.

Bariatric patient with nausea and vomiting

Approach to a bariatric patient with nausea and vomiting:

• Nausea and vomiting in the first week after gastric bypass may be suggestive of anastomotic oedema, which typically resolves spontaneously. If the patient is more than 2 weeks post surgery, anastomotic stricture is the most likely diagnosis. This can be diagnosed and treated with upper endoscopy and balloon dilatation.

• A gastric band patient with nausea and vomiting should have the band loosened immediately. If this fails to relieve the symptoms, upper GI series should be obtained urgently to assess for continued obstruction, suggestive of band slip or gastric prolapsed.

• Nausea and vomiting is common in post-operative sleeve gastrectomy patients. Upper endoscopy will demonstrate whether a mechanical obstruction is present, and may also be therapeutic by gently dilating an oedematous or kinked sleeve.