Malabsorptive disorders and coeliac disease

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Chapter 11 MALABSORPTIVE DISORDERS AND COELIAC DISEASE

KEY POINTS

• Malabsorption may present with weight loss, bloating, diarrhoea and specific vitamin and nutrient deficiencies.
• Identification of the underlying cause and replacement of any nutrient deficiencies are the cornerstones of management.
• Coeliac disease, bacterial overgrowth, food-cobalamin malabsorption, pancreatic insufficiency and malabsorption after gastric surgery are commonly seen in clinical practice.
• Coeliac disease affects 1% of the population and is often undiagnosed as many patients are asymptomatic.
• IgA antibodies to tissue transglutaminase and endomysium have a high sensitivity and specificity for coeliac disease. The diagnosis is confirmed by endoscopic small intestine biopsy.
• Serological testing for coeliac disease is appropriate in cases of weight loss, iron or folate deficiency, osteoporosis, irritable bowel syndrome and in at-risk groups including first-degree relatives of diagnosed cases, type 1 diabetes, autoimmune thyroid disease and Down syndrome.
• A lifelong gluten-free diet is the only effective treatment and ameliorates the malabsorptive and neoplastic risks of coeliac disease.

INTRODUCTION

The body obtains nutrients from food by the absorption of food components that have been broken down by digestion. Malabsorption is the failure of the processes of digestion and absorption, and may present with weight loss, bloating, diarrhoea and a myriad of specific vitamin and nutrient deficiencies. Identification of the underlying cause and replacement of vitamin and nutrient deficiencies are the cornerstones of management (see Figure 11.1). An aetiologic classification of malabsorption is listed in Table 11.1 with the types commonly seen in clinical practice summarised in Table 11.2.

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FIGURE 11.1 Management of malabsorption.

TABLE 11.1 Classification of malabsorption

Pancreatic insufficiency

Chronic pancreatitis
Cystic fibrosis
Pancreatic carcinoma

Mucosal disease

Coeliac disease
Crohn’s disease
Tropical sprue
Short bowel syndrome
Post radiotherapy
IgA deficiency and common variable immunodeficiency
Amyloidosis
Bile salt deficiency

Bacterial overgrowth
Biliary obstruction
Chronic cholestatic liver disease
Other

Post gastric surgery
Intestinal lymphangiectasia

TABLE 11.2 Common types of malabsorption in clinical practice

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PANCREATIC INSUFFICIENCY

Pancreatic disease resulting in pancreatic lipase activity to less than 10% of normal will cause steatorrhoea and weight loss as a result of fat malabsorption. Common causes of pancreatic insufficiency include cystic fibrosis, chronic pancreatitis, pancreatic resection and, occasionally, pancreatic carcinoma.

Steatorrhoea is characterised by offensive pale floating stools that are difficult to flush and although often most marked in pancreatic disease, steatorrhoea can also be a feature of biliary or diffuse intestinal mucosal disease.

Testing for pancreatic insufficiency

The measurement of stool fat in a 72 hour stool collection while consuming 80–100 g of fat per day is the best validated test for pancreatic insufficiency. Excretion of more than 7 g of fat per day suggests steatorrhoea. Of note, severe diarrhoea of any cause can result in up to 14 g of stool fat daily, while a low-fat diet can result in less than 7 g of fat per day in patients with fat malabsorption.

Treatment

Treatment is with pancreatic enzyme supplements. At least 30,000 units of pancreatic lipase are given with each meal with some experts suggesting 90,000 units. The addition of a proton pump inhibitor reduces enzyme denaturation by gastric acidity.

BILE SALT DEFICIENCY

A deficiency of the detergent-like activity of bile salts in the absorption of fat is commonly found in bacterial overgrowth, Crohn’s disease of the terminal ileum, surgical resection of the terminal ileum, bile salt transporter defects at the terminal ileum, chronic biliary obstruction and chronic cholestatic liver disease such as primary biliary cirrhosis and primary sclerosing cholangitis.

Bacterial overgrowth

In health, the bacteria that are cultured from the small intestinal lumen are transiently present in counts of less than 104

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