Malabsorption

Malabsorption is when we have impaired ability of the GI tract to absorb nutrients. It may be global if there is dysfunction of intestinal cells, or it could be partial if there is an external agent interfering with absorption.

It is a broad topic, however, in this topic we will cover:

We will then focus a little bit on bile-acid malabsorption and the implications of this.

COELIAC DISEASE

Read more on coeliac disease in it’s relevant CCC:

Coeliac disease

LACTOSE INTOLERANCE

Pathophysiology

Lactose is a disaccharide (glucose + galactose) found in milk and dairy products. It occurs due to a deficiency in lactase, which is the enzyme used to break down lactose. With a decreased ability to digest lactose, we get an increase in fermentation of lactose which leads to gas formation causing bloating. It is also produces osmotically active substances which causes diarrhoea.

⚠️ Risk factors

😷 Presentation

Symptoms present after lactose ingestion.

🔍 Investigations

1. Lactose elimination trial - this is the test of choice. Resolution of symptoms following elimination is diagnostic of lactose intolerance.
2. FBC - no test to identify lactase deficiency, but if anaemia is present it is more likely another disease leading to the GI symptoms.

🧰 Management

🏆 Lactose-free diet is curative. If this is not possible or not tolerated by the patient, there are oral lactase supplements available which may permit the diet.

If it is secondary to other GI disease, then treatment of underlying disease is of course most important.

Consider vitamin D and calcium supplementation as these can be markedly reduced when removed from the diet → osteopenia.

SMALL BOWEL BACTERIAL OVERGROWTH SYNDROME

Small bowel bacterial overgrowth syndrome (SBBOS) is a disorder caused by excessive bacteria in the small bowel. It often is a result of other conditions that cause decreased intestinal motility, impaired gastric acid and bile secretion, and IgA deficiencies.

An increase in bacteria leads to increased gas production and bloating.

Bacteria also cause bile acid inactivation, leading to fat accumulation and osmotic flow of water, causing diarrhoea.

Intrinsic factor degradation will lead vitamin B12 deficiency.

⚠️ Risk factors

• Diabetes mellitus
• Neonates with GI abnormalities
• Scleroderma

🧰 Management

🥇 If there is an underlying disorder, then it needs to be corrected.

Antibiotic therapy

• Rifaximin - as it has a low chance of resistance.
• Co-amoxiclav or metronidazole is also effective in most.

WHIPPLE’S DISEASE

Whipple’s disease is a rare, chronic infectious disease of the GI tract that is caused by trophyrema whipplei and leads to malabsorption. T. whipplei is a gram-positive, periodic acid-Schiff positive bacillus. It is transmitted through the faecal-oral route. It is often carried asymptomatically, but there are hypotheses that immunodeficiency or genetic predisposition will lead to establishment of the infection.

It not only causes GI symptoms, but rapidly disseminates throughout the body causing multisystem effects.

⚠️ Risk factors

😷 Presentation

Presents with a triad of:

1. Diarrhoea
2. Weight loss - present in 92% of patients.
3. Arthralgia

🔍 Investigations

🧰 Management

INFLAMMATORY BOWEL DISEASE

Read more on IBD in it’s relevant CCC:

BILE ACID MALABSORPTION

This is another cause of chronic diarrhoea. It may be due to excessive bile acid production or may be due to secondary causes such as seen in Crohn’s, cholecystectomy, SBBOS, coeliac disease.

As bile acids are important for absorption of lipids and fat soluble vitamins, it can lead to steatorrhoea and vitamin deficiencies (A, D, E, K).

🔍 Investigations

🧰 Management

• Bile acid sequestrant
• Colestyramine