Issue 137 Malabsorption after surgery

COVER STORY

MALABSORPTION AFTER SURGERY Rebecca Gasche Registered Dietitian, Countess of Chester Hospital NHS Trust Rebecca has a keen interest and specialises in gastroenterology dietetics. She currently works in the community setting in the Chester area, running clinics and group sessions to manage a wide range of gastroenterology conditions.

REFERENCES Please visit the Subscriber zone at NHDmag.com

The World Gastroenterology Organisation (WGO) describes malabsorption as defective mucosal up take and transport of adequately digested nutrients, including vitamins and trace elements.1 It can be caused by a number of conditions such as mucosal damage, pancreatic insufficiency, inflammatory bowel disease and intestinal resections.2 This article will discuss the effects of malabsorption post-surgery.

Many medical conditions can cause malabsorption. It may be generalised, or caused by a specific molecule.3 Examples of general causes of malabsorption include chronic pancreatitis, coeliac disease, inflammatory bowel disease (IBD), bile acid malabsorption and bacterial overgrowth or infections.

Malabsorption may also be specific to particular molecules, for example lactose in someone with lactose intolerance and fat malabsorption leading to malabsorption of fat soluble vitamins A, D, E and K.3 The most common cause of malabsorption in Western countries is villous atrophy caused by coeliac disease, an autoimmune condition in which the body reacts to gluten, resulting in damage to the villi in the small intestine and thus decreasing the surface area for absorption.3 Malabsorption can also occur following surgery, when there has been structural changes made to the digestive system. Bowel surgery can be as a result of a number of conditions, such as: diverticular disease, IBD (Crohn’s disease and ulcerative colitis), colorectal cancer, bowel obstruction, abdominal trauma and ischaemic bowel.3 Surgery of the pancreas may be as a result of cancer and bariatric surgery is used to reduce body mass index (BMI) of clinically obese patients.

NUTRIENT ABSORPTION

As displayed in Figure 1 overleaf, the majority of nutrients are absorbed in the small intestine, with the large intestine being responsible mostly for water absorption, short chain fatty acids and electrolytes. Most carbohydrates, proteins and fats are absorbed in the first 100cm of the small bowel. Many other nutrients can be absorbed by the ileum, but this depends on individual transit time.4 SURGERY

Surgery of the bowel Table 1 shows the different types of bowel surgery which may be performed as a result of cancer, IBD or other bowel conditions.5 Two types of stomas may be created depending on which part of the bowel has been resectioned: colostomy and ileostomy. Within these there are varying types of each stoma, as displayed in Table 2.

Surgery of the pancreas The pancreas - a small organ found behind our stomach and below our ribcage - has two main functions, which allow for the release of enzymes and hormones to aid the digestion of foods.

The exocrine function produces enzymes to break down carbohydrates, proteins and fats, and the endocrine function homes the islet cells responsible for the

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malabsorption,

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Aptamil Pepti-Junior is designed to be easy to digest and absorb for infants with malabsorption related conditions, such as: • Short bowel syndrome • Post gastrointestinal surgery • Liver disease • Chronic diarrhoea • Feed intolerance Complete nutrition suitable from birth for the dietary management of malabsorption related conditions in infants.

Discover more at eln.nutricia.co.uk Or for more information call our free Healthcare Professional Helpline on 0800 996 1234 REFERENCES: 1. Mabin DC, Sykes AE, David TJ. Arch Dis Child, 1995;73(3):208-10. 2. Pedrosa M, Pascual CY, Larco JI, et al. J Investig Allergol Clin Immunol, 2006;16(6):351-6. 3. Miraglia Del Guidice M, D’Auria E, Peroni D, et al. Ital J Pediatr, 2015;41(1):42 4. Keohane PP, Grimble GK, Brown B, et al. Gut, 1985;26(9):907-13. 5. Ammoury RF, Croffie JM. Pediatr Rev 2010;31(10):407-16.

6. Bach AC, Babayan VK. Am J Clin Nut, 1982;36(5):950-62. 7. Shaw V (ed). Clinical Paediatric Dietetics. 4th ed. Oxford: Wiley Blackwell, 2015.

IMPORTANT NOTICE: Aptamil Pepti Junior is a food for special medical purposes for the dietary management of malabsorption related conditions. It should only be used under medical supervision, after full consideration of the feeding options available including breastfeeding. Suitable for use as the sole source of nutrition for infants from birth, and/or as part of a balanced diet from 6-12 months.

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For Healthcare Professional Use Only

Figure 1: Absorption of nutrients across intestines

Many additional nutrients may be absorbed from the ileum depending on transit time.

Based on: Advanced Nutrition and Human Metabolism, fifth edition.

release of the hormones insulin and glucagon, to maintain blood glucose levels. Some patients require surgery to remove part of or their entire pancreas. Table 3 shows the different types of pancreatic surgery.

Bariatric surgeries Bariatric surgeries are carried out to aid obese patients with weight loss and these involve different procedures that both reduce gastric capacity and bypass areas of the small intestine.

Table 4 explains the different types of bariatric surgery in more detail.

MALABSORPTION POST-SURGERY

Bowel surgery The formation of a stoma in the small bowel causes a decrease in transit time, meaning that nutrients pass through the digestive system too quickly and can be malabsorbed. This can also

lead to weight loss and malnutrition. Studies show that malabsorption is common, especially in ileostomies and demonstrate that only 60-70% energy, 50-60% fat and 60-70% carbohydrate are absorbed.8,9 Dehydration is most commonly found when large amounts of the ileum have been removed and can often result in a readmission to hospital and acute renal failure.10 Postoperatively, the most common losses seen in ileostomy patients are fluids and sodium.

This is particularly seen in patients who have had a total colectomy, as this means that the entire colon has been removed, where most of the fluid and sodium is normally absorbed. Particularly within the first six to eight weeks, patients may lose 1200-2000ml fluid and 120-200mmol sodium/day. After eight weeks, the ileum then adapts to absorb and fluid losses reduce to 400-600ml/day.3 Due to the loss of sodium, patients are encouraged to add salt to their diet. www.NHDmag.com August/September 2018 - Issue 137

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NHD0818

CLINICAL Table 1: Bowel surgeries Right hemi-colectomy

Right half of the colon is removed.

Left hemi-colectomy

Left half of the colon is removed.

Abdomino-perineal resection

Rectum and anus removed, colostomy formed.

Anterior resection

Removal of cancer in the rectum.

Sigmoid colectomy

Sigmoid colon removed, two ends joined together.

Hartmann’s procedure

Sigmoid colon and upper rectum removed, end colostomy formed.

Total colectomy

Entire colon removed, permanent ileostomy or small bowel will be joined to rectum.

Pan proctocolectomy

Colon, rectum and anus removed, permanent ileostomy formed.

Table 2: Types of stoma3 Loop colostomy

The colon is sutured to the abdomen and there are two openings - one for intestinal waste and one for mucus produced by the GI tract.

End colostomy known as a Hartmann’s procedure

The sigmoid colon and upper rectum is removed, an end colostomy is formed.

Double barrel colostomy

Both ends of the colon are brought out onto the abdomen.

Temporary or loop ileostomy

A loop of the small intestine is brought to the skin, and the colon and rectum remain in situ. This is usually reversed 8-10 weeks later.

End ileostomy

The colon and rectum are removed and the end of the small intestine is brought through the skin.

Continent ileostomy

An internal pouch is created and the stoma is connected to a valve implanted in the skin, which can be emptied using a catheter.

Following a total colectomy, the absorption of other nutrients should be unaffected and the absorptive capacity of the small intestine remains intact. A small number (3-9%) of patients have been estimated to suffer from vitamin B12 deficiency and some patients may find absorption of bile acids are also affected.

This is thought to be due to reduced absorptive capacity due to ileal involvement, inadequate dietary intake or bacterial overgrowth.

The ileum contains B12 receptors and bile salt transporters, therefore, for those patients who have had ileal resection, they often suffer from B12 deficiency and fat malabsorption.

Fat malabsorption may lead to steatorrhea and deficiencies in fat soluble vitamins A, D, E and K.11 Colostomies have minimal impact on the digestion and absorption of nutrients and fluids and most patients are, therefore, encouraged to take a healthy balanced diet and keep to a healthy BMI.3 Following the formation of a colostomy, it is usually advised that the patient follows a low 16

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residue (low fibre) diet, to aid symptoms and reduce the risk of obstruction. After six to eight weeks, higher fibre foods may be reintroduced into the diet. Most colostomy patients should be able to return to a normal healthy diet, as there is no evidence for any particular diet to follow.

However, it is individualised as to what patients may be able to tolerate, particularly when it comes to some of the higher fibre foods.

Pancreatic surgery If a patient has part of, or all of their pancreas removed, this may affect production of pancreatic enzymes, which are vital for the digestion of proteins, fats and carbohydrates.

If the pancreas is unable to produce enough enzymes, or none at all, malabsorption will occur, as the body is unable to break down these nutrients for absorption. Patients may experience symptoms such as steatorrhoea, weight loss and fatigue. In this case, patients will need to be prescribed pancreatic enzyme replacement therapy (PERT).

Table 3: Pancreatic surgeries6 Whipple’s operation pancreaticoduodenectomy (PPPD)

Removal of the head of the pancreas, the duodenum, the gall bladder, part of the bile duct and surrounding lymph nodes.

Pylorus-preserving PPPD

Similar to the Whipple’s operation, but none of the stomach is removed.

The stomach valve (the pylorus), which controls the flow of food into the duodenum, isn’t removed either. The tail of the pancreas is joined to the small intestines or stomach.

Distal pancreatectomy

Removal of the body and tail of the pancreas and sometimes the spleen.

Total pancreatectomy

Removing the whole pancreas, the duodenum, the gall bladder, part of the bile duct and sometimes part of the stomach.

Table 4: The different types of bariatric surgery7 Laparoscopic adjustable gastric banding (LAGB)

A synthetic band is placed just distal to the gastroesophageal junction, creating a small gastric pouch with an adjustable opening.

Sleeve gastrectomy

Around 80% of stomach is removed, creating a long, banana-shaped pouch.

Roux-en-Y gastric bypass (RYGBP)

The top part of stomach is stapled, creating a small pouch and attaching it to middle part of small intestine. This encourages malabsorption by preventing the mixing of food and digestive enzymes.

Biliopancreatic diversion with duodenal switch (BPD/DS)

This surgery is in two parts. The first is similar to gastric sleeve surgery.

The second surgery redirects food to bypass most of the small intestine.

The surgeon also reattaches the bypassed section to the last part of the small intestine, allowing digestive juices to mix with food.

PERT works by mimicking the physiological conditions of a healthy pancreas, allowing the correct amount of enzymes to be delivered to the duodenum, where they are activated with food allowing it to be absorbed.12 Published treatment guidelines for chronic pancreatitis and pancreatic cancer recommend initiating patients on 40,000 to 50,000 lipase units per meal and 10,000 to 25,000 lipase units per snack,13 but this is often titrated to higher doses depending on symptom control.

In the case of partial pancreas resections, enzymes may be discontinued in the long-term follow-up, depending on the remaining pancreas function of the individual patient. Studies have shown that approximately 70% of pancreatic surgery patients will need lifelong PERT.14 Bariatric surgery As Table 3 demonstrates, bariatric surgery aims to aid weight loss, using techniques such as reducing gastric capacity and bypassing parts of the small intestine. This results in a reduction of

the total absorption surface area. As a result of this, post-operatively, bariatric surgery patients are at increased risk of developing nutrient deficiencies. In addition, these patients often also have a reduced dietary intake, vomiting and food intolerance.15 This can lead to the malabsorption of nutrients, in particular vitamin B12, folate, iron, calcium, vitamin D and fat soluble vitamins.

Some bariatric surgeries may induce fat malabsorption which can cause deficiencies of fat soluble vitamins, therefore, routine supplementation is recommended. Similarly, vitamin B12 and folate deficiency occurs commonly after bariatric surgery procedures, with reports suggesting rates as high as 45% after Roux-en-Y gastric bypass.16 This deficiency occurs due to the bypassing of portions of the small intestine, the main site of absorption.

Calcium and vitamin D deficiency after bariatric surgery has also been extensively investigated.17,18 Studies estimate that over 50% of post-operative patients develop low levels of vitamin D and that a progressive increase in www.NHDmag.com August/September 2018 - Issue 137

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Date of preparation: July 2018 ANUKANI180187

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CLINICAL

When seeing patients with a history of surgeries involving any part of the digestive system, it is important to consider the implications these may have. the incidence and severity of these deficiencies occurs with time after biliopancreatic diversion with duodenal switch (BPD/DS).

When looking at iron absorption, it is known that post-bariatric surgery patients have reduced iron intake secondary to a considerable reduction of their meat intake. Ruz et al19 showed a reduction of almost 50% of the total amount of meat per day consumed. In addition to this, the reduced gastric capacity caused by bariatric surgery reduces the production of hydrochloric acid. This affects malabsorption, as hydrochloric acid is used to convert iron into a more absorbable form and not enough

NETWORK HEALTH DIGEST

• HEF/HPN

hydrochloric acid limits the release of iron from the structural proteins.19 CONCLUSION

When seeing patients with a history of surgeries involving any part of the digestive system, it is important to consider the implications these may have. Whether it’s offering support immediately post-surgery, or making lifelong recommendations, a clear understanding of the areas of absorption in the gut and how the body breaks down nutrients can help healthcare professionals to advise patients on the correct diet and supplementation.

Coming in the October issue:

• Cow's milk allergy • PEG: nutritional support • Goat milk

• Malnutrition

• Non-diet nutrition • Probiotics and gut health • Free-from bites

Check whether you are eligible for a FREE subscription to Network Health Digest (NHD) at wwwNHDmag.com . . .

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