Medical Management of Nutritional Complications

Medical Management of Nutritional Complications

David Hughes


For many decades, it has been known that the dietary health of a population is associated with the incidence of disease. International guidelines produced by the World Health Organisation and other governmental bodies advise a balanced diet. Bariatric and metabolic surgery can alter this balance through inhibiting the absorption of nutrients and altering an individual’s choice of food. Therefore, all post‐bariatric surgical patients require lifelong monitoring and appropriate nutritional supplementation to prevent deficiencies that could lead to disease.

Each metabolic and bariatric surgical procedure poses a separate nutritional challenge in regard to nutrient absorption or food avoidance. Therefore, post‐surgical dietary recommendations and supplementation are tailored to each surgical procedure.

It is important to consider an individual’s presurgical nutritional status in order to avoid making pre‐existing nutritional deficits worse in the post‐operative period. All pre‐operative patients should be screened for nutritional deficiencies prior to bariatric surgery, and all identified deficiencies should be corrected. Occasionally, pre‐surgical nutritional deficiencies require further investigation to determine their aetiology, e.g. iron deficiency anaemia, which could be due to dietary iron insufficiency from veganism or due to gastrointestinal malignancy (Figures 23.1 and 23.2).

The incidence of multiple nutritional deficiencies in the obese population is relatively high due to the combination of the consumption of high‐calorie foods that have low nutritional value and immobility. Immobility leads to the lack of natural light that in turn results in vitamin D deficiency. As vitamin D, iron and B12 deficiencies are common in pre‐surgical candidates, it is advisable to commence multivitamins with mineral supplements prior to bariatric surgery.

Peri‐Operative Nutrition

Prior to bariatric surgery, it is recommended that patients undergo a pre‐operative diet that helps reduce the fatty content of their liver in order to reduce its size by 10–20%. A reduction in the size of the liver aids the ability to lift the liver during surgery and reduces the risk of peri‐operative complications. Liver‐shrinking diets usually involve a very low calorie diet with limited nutritional content so prophylactic vitamins and mineral supplementation are required. These pre‐operative low‐calorie diets can be particularly problematic for people with type II diabetes. The sudden reduction in the total oral intake of carbohydrates could potentially lead to hypoglycaemia in those patients on medications.

In the post‐operative period, there is a gradual reintroduction of a nutritionally balanced diet. Initially, patients are started on a liquid diet moving up to a pureed diet and then soft solids, before hopefully moving onto a normal balanced diet. Advice and guidance is usually required from a specialist dietitian to ensure adequate intake of all major food groups and nutrients occurs with a special focus on fluid intake. This is because there is a high incidence of post‐operative nausea, vomiting and constipation. Without adequate fluid intake, patients can then easily get dehydrated, which is a particular risk to those patients on antihypertensive agents or who have pre‐existing conditions, such as diabetes or chronic kidney disease.

Schematic illustration of balance diet consisting of appropriate quantities of water, carbohydrates, protein, fat, essential vitamins and minerals.

Figure 23.1 Balance diet consisting of appropriate quantities of water, carbohydrates, protein, fat, essential vitamins and minerals.

Source: Peggy Greb, USDA ARS / Wikimedia commons; Source: Assad / Adobe Stock; Source: Serghei Velusceac / Adobe Stock; Source: gawriloff / Adobe Stock; Source: Africa Studio / Adobe Stock

Schematic illustration of risk of nutrient malabsorption.

Figure 23.2 Risk of nutrient malabsorption.

The majority of post‐operative nutritional complications usually occur within the first 12 months post‐surgery. It is therefore essential that patients are regularly followed up by a specialist MDT team with access to specialist dietitians, physicians, surgeons and nutritional support nurses. Usually, nutritional deficiencies are mild and can be corrected by oral supplementation, but occasionally nutritional deficiencies can be so extreme that parenteral nutritional support is required.

Nutrient Supplementation Post‐Bariatric Surgery

As all forms of bariatric surgery can affect absorption of fluid/micronutrients, it is appropriate that regular post‐operative monitoring of nutritional status is implemented. It is essential that appropriate supplementation is instigated post‐operatively, and monitoring for compliance is undertaken at the appropriate intervals. Data concerning the likelihood of developing a nutritional deficiency has been taken from recent European guidelines and has been formatted in Table 23.1 in regard to the need of requiring supplementation. There are a few variations on the recommended post‐bariatric surgery dietary supplementation depending on the difference in national associations, but the majority agree that supplements are needed if there is a moderate need.

Table 23.1 Pre‐operative nutritional screening.

Dietary history (frequency, quality and quantity): Fruit and vegetables
Blood tests Full blood count
Vitamin B12
Vitamin D
Liver function tests

The majority of national associations also recommend that for the first couple of years after bariatric surgery patients undergo frequent monitoring of their nutritional status through blood tests. The purpose is twofold, firstly to ensure nutritional deficiencies are being adequately corrected and secondly to detect indolent post‐surgical complications. Recommended frequency of nutritional monitoring is displayed in Table 23.2.

Individual Nutritional Deficiencies

Protein Deficiency

Severe protein deficiencies are usually separated by aetiology into those with

  1. impaired intestinal absorption,
  2. poor diet resulting in malnutrition,
  3. secondary to non‐intestinal diseases.

Severe protein deficiency can result in the development of anaemia, ascites and loss of lean body mass. Ascites can occur due to reduced colloid osmotic pressure causing fluid to leak in the extracellular space. Prior to diagnosing impaired intestinal absorption, it is important to ensure that other non‐intestinal diseases such as liver disease, nephrotic syndrome and cardiac failure are excluded. This is typically performed by checking for normal urinary protein excretion, cardiac contractile function and evidence of hepatic cirrhosis.

Impaired intestinal protein absorption could be due to impaired dietary intake of protein or excessive loss of intestinal protein through a protein losing enteropathy. However, protein losing enteropathies are usually present with diarrhoea and abdominal pains. Biochemically, there is usually a low level of both albumin and globulin as the enteropathy is independent of the molecular weight of the proteins. Protein losing enteropathy is usually related to either mucosal damage, such as erosive disease (e.g. inflammatory bowel disease/NSAID‐related) or non‐erosive disease (e.g. Eosinophilic gastritis, hypertrophic gastritis or SLE) or less commonly lymphatic impairment. Investigations such as a faecal alpha‐1 antitrypsin clearance ([24 hour stool volume] × [stool alpha‐1 antitrypsin]/[serum alpha‐1 antitrypsin]) or nuclear medicine investigations with technetium labelled albumin scintigraphy. Whatever the cause, treatment usually involves enteral protein supplementation or parenteral protein supplementation in extreme cases.

Table 23.2 Likelihood of requiring nutritional supplementation.

Sleeve gastrectomy Gastric bypass Adjustable gastric band Biliopancreatic diversion +/− duodenal switch
Multiple vitamin and mineral Moderate Moderate Low High
Iron Moderate High Low High
Vitamin B12 Moderate Moderate Low Moderate
Calcium and Vitamin D Moderate Moderate Low High


Microcytic anaemia that occurs post‐bariatric surgery is very common with an incidence between 10 and 25% and presents with symptoms of fatigue. It is commonly caused by the combination of decreased dietary iron intake and impaired absorption due to reduced gastric hydrochloric acid. Oral iron supplementation usually corrects the deficiency, but care must be taken in regard to timing with other medications. Patients are commonly on calcium supplements that can inhibit the absorption of oral iron. The simple addition of vitamin C can increase the bioavailability of iron that can be absorbed. As vitamin C prevents the formation of insoluble iron compounds that cannot be absorbed and increases the bioavailability of ferrous iron, it aids cellular uptake of iron. If oral iron supplementation is not effective and ongoing iron deficiency anaemia is present, then intravenous iron preparations may be utilised. Care should always be taken in considering differential diagnosis for iron deficiency anaemia, including peptic ulcers and malignancy.

Vitamin B12 (aka Cobalamin)

Vitamin B12 absorption in the gut is primarily through binding with intrinsic factor. However, very small amounts are also absorbed passively. Deficiency in vitamin B12 usually results in megaloblastic anaemia, fatigue and peripheral neuropathy. The body usually stores large volumes of vitamin B12, and therefore deficiencies after bariatric surgery sometimes do not become apparent until >12‐month post‐surgery. Routine prophylactic oral or intramuscular supplementation is recommended in post‐bariatric surgery procedures except for gastric banding. Oral doses as high as 1000 μg per day are usually required if chosen over intramuscular supplementation. As higher levels of B12 are found in meat and dairy products, then the risk of vitamin B12 deficiency is also higher in vegetarians or vegans.

Ca and Vitamin D

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May 14, 2023 | Posted by in GENERAL SURGERY | Comments Off on Medical Management of Nutritional Complications

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