Malabsorption in dogs: symptoms, causes and treatment

Overview

Malabsorption describes impaired digestive function rather than one specific disease. It may affect fats, proteins, carbohydrates or vitamins. The use of several nutrients is often impaired at once.

Digestion occurs in stages: food breaks down inside the intestine, nutrients cross the lining and then move into the body. In maldigestion, the problem is food breakdown before absorption itself. Small intestinal lining disease can impair nutrient uptake or onward transport. Distinguishing these causes guides treatment choice.

Fat digestion and absorption involve pancreatic lipase and micelles, small fat-carrying structures formed with bile salts.

Causes

Enzyme and bile salt deficiency impair digestion

The pancreas secretes a large proportion of the enzymes needed to break down food. In exocrine pancreatic insufficiency, or EPI, it secretes insufficient enzymes. Symptomatic insufficiency generally develops only after around 85–90% of exocrine pancreatic tissue is lost. Fat utilisation is particularly impaired, but protein and starch utilisation also decline.

The most common cause of EPI in dogs is atrophy of enzyme-producing pancreatic tissue. Advanced chronic pancreatitis can also cause insufficiency. Fat absorption may also decline when cholestasis or bile duct obstruction prevents enough bile salts entering the intestine.

The lining, microbes and lymphatic vessels may be affected

Chronic inflammatory enteropathy can reduce the absorbing surface or function of intestinal cells. An intestinal tumour or Giardia infection, for example, can also be responsible. Shortening of intestinal villi reduces the surface available for nutrient absorption. Lining damage can also impair enzymes that digest milk sugar.

Imbalance of intestinal bacteria, called dysbiosis, may further impair nutrient utilisation. Bacteria can compete for nutrients. They can also alter bile salts needed for fat processing. In lymphangiectasia, dilation of intestinal lymphatic vessels, fat transport can be disrupted. Protein and fat may also leak into the intestine.

Within intestinal cells, fats are packaged into chylomicrons that enter the lymphatic vessel in the villus and then reach the bloodstream.

Risk factors

Predisposing factors depend on the disease underlying malabsorption. Chronic inflammatory enteropathy can affect many breeds. Recognised predispositions include German Shepherd Dogs, Soft-Coated Wheaten Terriers and Shar Peis. No sex predisposition to this form of enteropathy has been established.

Rare inherited cobalamin malabsorption differs from the usual broader impairment of nutrient absorption. This selective vitamin B12 malabsorption is recognised in breeds including Giant Schnauzers, Australian Shepherds, Beagles and Border Collies. In older dogs, end-stage chronic pancreatitis can cause enzyme deficiency.

Congenital pancreatic underdevelopment is a rare cause of enzyme deficiency. Selective inherited cobalamin malabsorption can occur without the usual intestinal signs.

Typical symptoms

Severity depends on disease duration and the extent of lining damage. Not every affected dog has visible diarrhoea.

• Your dog loses weight or muscle mass.
• Stools are repeatedly loose and may be passed in larger quantities.
• Appetite increases while weight falls.
• Your dog eats faeces or other material unsuitable as food.
• With severe inflammation, appetite may instead decrease.
• The abdomen or limbs may swell as blood protein falls.

Diarrhoea lasting more than 3 weeks is considered chronic. A good appetite and relatively lively behaviour do not exclude malabsorption. Conversely, nausea, poor eating or marked swelling can indicate more severe disease.

Complications and consequences

Nutrient deficiencies and protein loss worsen health

Prolonged malabsorption can reduce weight and muscle condition. Cobalamin deficiency can impair metabolism and reduce appetite. Diarrhoea causes water and electrolyte losses. Reduced blood albumin can allow fluid to accumulate in the abdomen or tissues.

Protein-losing enteropathy, or PLE, means protein loss through the intestine. Dogs with PLE have an increased risk of blood clots. This risk can remain high even when other signs are controlled.

Chronic inflammation or small, ongoing intestinal blood losses can cause anaemia. Fat-soluble vitamin utilisation may decline if fat digestion is impaired.

The outlook varies between diseases

During follow-up of dogs with EPI, around 60% had a good response to enzyme replacement. A further 17% had a partial response. These figures describe pancreatic insufficiency patients rather than every cause of malabsorption.

In follow-up studies of dogs with PLE, more than 50% died within 12 months of diagnosis. Severe weight loss, refusal to eat and low albumin are poor prognostic signs. In chronic inflammatory enteropathy, the proportion responding to diet is 38–89%.

Diagnosis at the vet

Blood tests distinguish pancreatic and intestinal causes

Investigation begins with dietary and symptom histories and a physical examination. Your vet assesses weight, muscle condition and any swelling. Basic tests often include a blood count, biochemistry, urinalysis and a faecal sample. These look for parasites and exclude other diseases causing diarrhoea or weight loss.

Pancreatic enzyme production is investigated with a cTLI blood test. The sample is generally taken after an 8–12-hour fast according to your vet's instructions. With the assay described, cTLI at or below 5.5 micrograms per litre supports an EPI diagnosis. Results of 5.6–7.5 micrograms per litre are equivocal and assessed alongside signs.

An equivocal cTLI can be rechecked after 1–2 months. At 7.6–10.8 micrograms per litre, EPI is less likely and other causes are investigated. For repeating an unclear result, your vet may advise a longer fast of 12–18 hours before sampling. Enzyme replacement does not distort cTLI results.

A dog with intestinal disease but no pancreatic insufficiency may also partly benefit from enzyme replacement. Response alone therefore does not confirm EPI. Once EPI is confirmed, cTLI does not need repeated measurement to monitor response.

Vitamins, ultrasound and biopsies complete investigation

Measuring cobalamin, or vitamin B12, and folate helps assess small intestinal function. Low cobalamin can occur with intestinal disease or pancreatic insufficiency. High folate and low cobalamin do not provide an unequivocal dysbiosis diagnosis.

Ultrasound assesses the intestinal wall, lymph nodes and other abdominal organs. Endoscopic biopsies can identify inflammation, lymphangiectasia, shortened villi or tumour changes. However, biopsy inflammation does not always reveal the original cause. Dietary trials may precede biopsies in an otherwise well dog that is eating. Supportive care and further investigation in a severely affected dog are not delayed for lengthy treatment trials.

Increased faecal alpha1-proteinase inhibitor can reveal protein loss in dogs at least 1 year old, even while albumin remains normal.

Treatment

Pancreatic insufficiency needs enzyme replacement

Pancreatic enzyme replacement with food is the foundation of EPI treatment. Treatment is generally lifelong. The preparation is mixed into food because giving it directly into the mouth can damage the lining.

Cobalamin deficiency is corrected because it can impair the response to enzyme replacement. Other confirmed deficiencies and concurrent intestinal disease are also addressed. Medicines and supplements are chosen following veterinary investigation.

Dietary trials are central to intestinal disease treatment

For chronic inflammatory enteropathy, the selected complete food is fed exclusively for at least 2 weeks. Options include hydrolysed or novel-protein diets, or another nutrient profile suited to the signs. If the first option fails and your dog's condition allows, properly conducted trials of at least 3 different diets may be considered. Response is monitored at least weekly during the trial.

A diet that resolves signs is continued for at least 12 weeks before a possible change to another food. A dog with PLE may benefit from continuing a successful diet long term. Among 24 dogs with lymphangiectasia responding poorly to corticosteroids or relapsing during treatment reduction, fat restriction helped 19, or 79%.

Inflammation responding inadequately to diet may need immunosuppressive medication. Empirical antibiotics, meaning use without an established need, are not recommended for suspected chronic enteropathy. Confirmed parasites or another specific underlying cause receive appropriate treatment.

Weight and blood results show treatment response

Monitoring assesses weight, muscle condition, stools and quality of life. Early in chronic enteropathy treatment, assessment may take place around every 1–2 weeks. Cobalamin, inflammation and intestinal protein loss are also monitored as needed. Biopsy changes do not necessarily disappear at the same rate as your dog's signs.

Prevention

Diet cannot prevent every cause of malabsorption, as inherited disorders or intestinal disease may underlie it. Adequate dietary cobalamin prevents deficiency caused by low vitamin intake. Continuing suitable therapeutic food forms part of managing food-responsive enteropathy.

Antibiotics are not started solely for prolonged diarrhoea without investigating the cause. Testing for intestinal parasites forms part of investigating prolonged diarrhoea. Continuity of treatment for diagnosed pancreatic insufficiency is essential for nutrient utilisation.

Dairy products may be avoided when feeding a dog with diarrhoea, because lining damage can reduce lactose tolerance.

Important for dog owners

Record weight, appetite, stool quantity and consistency, and any vomiting in one diary. Include every treat, chew, supplement and food given by other family members. Bring previous test results and food packaging details. Agree when the dietary trial's effectiveness and your dog's weight will be assessed.

Follow the agreed dietary trial consistently and report any departures before the response is interpreted. Ask for practical instructions on mixing the enzyme preparation and monitoring any vitamin deficiency. Contact your vet sooner if your dog stops eating, deteriorates or develops abdominal swelling. Treatment aims include improved weight and muscle condition, stools and quality of life.

Frequently asked questions

Can a dog lose weight despite being constantly hungry?

With malabsorption, weight can fall despite a good or even ravenous appetite. Nutrients in food are then not being made available to the body normally. Pancreatic insufficiency and small intestinal disease are possible causes. Simply increasing food portions therefore does not replace investigation of the underlying cause.

Is malabsorption the same as pancreatic insufficiency?

Pancreatic insufficiency is one cause of malabsorption. It causes inadequate food breakdown because too few enzymes are available. Small intestinal inflammation, lining damage or lymphatic problems can have a similar outcome. Pancreatic function is checked with a cTLI blood test before investigating intestinal disease more closely.

Does a low B12 always mean pancreatic insufficiency?

Low cobalamin, or vitamin B12, can occur with pancreatic insufficiency or small intestinal disease. Some breeds also have a recognised inherited selective cobalamin malabsorption disorder. Deficiency can additionally result from insufficient dietary intake. The result is therefore interpreted alongside other investigations.

How quickly should a dietary trial help?

In a chronic enteropathy dietary trial, the selected food is fed exclusively for at least 2 weeks. Response is monitored at least weekly. At least 3 different dietary trials may be considered in an otherwise well dog. A food that resolves signs is continued for at least 12 weeks before any change. A severely affected dog is investigated and treated sooner.

Can malabsorption be cured?

The outlook depends on the underlying disease. Some dogs with chronic inflammatory enteropathy have their signs controlled through diet alone. Pancreatic insufficiency generally requires lifelong enzyme replacement. Severe protein loss, refusal to eat and substantial weight loss worsen the outlook.