55 | Chronic diarrhoea in dogs and cats: is it always IBD?

PodcastGastroenterology
Written By Laura Jones

In this episode, we’re continuing our gastrointestinal series and diving into chronic enteropathies.

 

These are some of the most common gastrointestinal diseases we see in practice and some of the most misunderstood. Today, though, we’re changing that - looking at the types of chronic enteropathies we see, how they affect our patients, and how we diagnose, treat and nurse them.

So, what is a chronic enteropathy?

You’ll no doubt have heard the term ‘inflammatory bowel disease’ or IBD before. Previously, that has been used as a ‘catch-all’ term to describe chronic intestinal diseases - but that’s not technically true.

The term is definitely overused, and most of the time, when we say ‘IBD’, we actually mean chronic enteropathy - so that’s the term I’ll be using for the rest of this episode.

Chronic enteropathies are gastrointestinal diseases that cause clinical signs (such as diarrhoea, vomiting and anorexia) lasting at least 3 weeks, where other diseases (e.g. parasites, neoplasia) have been excluded.

There are several different types of chronic enteropathy:

  • Food-responsive enteropathy 

  • Antibiotic-responsive enteropathy (aka intestinal dysbiosis)

  • Immunosuppressant-responsive enteropathy (aka IBD)

  • Nonresponsive enteropathy

There is also a fifth type of chronic enteropathy, known as protein-losing enteropathy or PLE, which we can see on top. This is a severe enteropathy in which the patient’s underlying GI disease causes proteins to leak from the diseased gut. The disease carries a much more guarded prognosis, and these patients often need intensive nursing care - so much so that we’re actually going to cover PLE in a separate podcast episode next week.

Ok, so what about IBD? How does that fit into things?

Now, I am going to get back on my terminology soapbox for just a minute, and then I promise I will stop!

As you can see from the list I’ve just mentioned, many chronic enteropathies don’t need to be treated with steroids or other immunosuppressant medications. Food-responsive enteropathies, for example, respond to a change in diet, as the name suggests.

 Antibiotic-responsive enteropathies, again as the name suggests, respond to antimicrobials (side note - I am NOT suggesting we treat all diarrhoea patients with antibiotics - that is an entirely different soapbox moment which I won’t subject you to right now!).

My point is this: referring to every chronic enteropathy patient as having ‘IBD’ when many of them don’t need immunosuppression is misleading. 

IBD patients technically have immunosuppressant-responsive enteropathy - and to diagnose IBD, we must confirm that inflammatory cells are present in the intestinal tissue with intestinal biopsies.

We describe immunosuppressant-responsive enteropathies or ‘true’ IBDs based on the type of inflammatory cell present and the location. 

For example:

  • Lymphoplasmacytic enteritis is the infiltration of the intestinal tissue with lymphocytes and plasma cells

  • Eosinophilic enteritis is the infiltration with eosinophils

  • Neutrophilic enteritis is infiltration with neutrophils

  • Lymphoplasmacytic gastritis is the infiltration of the gastric mucosa with lymphocytes and plasma cells

  • And so on.

Patients can have inflammation in multiple areas of the GI tract. For example, biopsies of the stomach, small intestine, and large intestine may all document the infiltration of inflammatory cells in those tissues.

What causes a chronic enteropathy?

The underlying cause of chronic enteropathy is poorly understood. We do know that several factors can contribute to developing chronic enteropathy, including:

  • Changes in the permeability of the lymphatic tissue present in the GI tract (the gut-associated lymphoid tissue or GALT)

  • Genetic changes

  • Psychosomatic disorders (similar to irritable bowel syndrome in people)

  • Infectious agents

  • Parasitic agents

  • Dietary allergens

  • Changes in the intestinal microbiome

  • Gastrointestinal motility disorders

  • Adverse drug reactions

  • Immune-mediated changes

Research into many of these areas is ongoing, particularly the importance of the microbiome, which we discussed in more detail in episode 48.

We do know, though, that hypersensitivity (allergic-type) reactions to antigens in food, bacteria, mucous, and epithelial cells inside the intestine play an important role in chronic enteropathies. 

These reactions stimulate inflammatory cells, causing inflammation in the intestinal mucosa. This inflammation, in turn, impairs the mucosa’s ability to act as a barrier, allowing additional antigens and harmful substances to enter.

The disease doesn’t just impair the intestinal mucosa’s barrier ability, though—it also impairs absorption, meaning that our patients can’t effectively absorb nutrients from their food. This causes marked weight loss, poor body and muscle condition, and decreased levels of certain vitamins, such as vitamin B12.

Ok, that’s what chronic enteropathy is - but which patients are most at risk?

There is no particular breed, age or sex predisposition for chronic enteropathy in general. However, IBD (immunosuppressant-responsive enteropathies) is more commonly seen in German Shepherds, Yorkshire Terriers, Cocker Spaniels and purebred cats.

It can be seen in dogs as young as 1 year old, though the mean age for clinical disease in dogs and cats is around 6.

Typically, food-responsive enteropathies and antibiotic-responsive enteropathies are seen in younger patients compared with immunosuppressant-responsive enteropathies.

And what signs do we see in these patients?

Signs are chronic - they need to be to diagnose a chronic enteropathy; remember, we said at least 3 week’s duration - and they’re often cyclic or intermittent. They include:

  • Diarrhoea (which may be either small intestinal, large intestinal or mixed, depending on the type of enteropathy our patient has)

  • Vomiting

  • Hyporexia

  • Anorexia

  • Weight loss

If a patient has gastrointestinal ulceration alongside their chronic enteropathy, we can also see haematemesis, melena and cranial abdominal pain - and, as we discussed in episode 52, clinically significant anaemia can result in severe cases.

Patients with PLE have a whole host of other signs associated with their protein loss, but we’ll discuss these in more detail in the next episode, so you’ll have to wait to learn more.

Interestingly, patients with chronic enteropathy may also be at increased risk for developing GDV. Inflammation of the intestine can cause changes in gastric emptying and motility, predisposing a patient to gastric dilation and torsion.

In cats, we also know there is a correlation between chronic enteropathy, pancreatitis, and inflammatory liver and biliary disease, known as triaditis. 

There’s also a link between severe inflammatory enteropathy in cats and intestinal lymphoma - with some suggestions that their enteropathy can progress to small cell lymphoma. We’ll discuss that in a special episode later in this series, where resident cancer queen Inge, aka The Oncology RVN, will join us again to talk about all things GI neoplasia.

We know how chronic enteropathies affect our patients. But how will we diagnose them?

Chronic enteropathies are generally diagnosed by exclusion. 

This means we need to rule out all other causes of GI signs, including:

  • Bacterial disease

  • Parasitic disease

  • Neoplasia

  • Foreign bodies

  • Pancreatitis

  • Pancreatic insufficiency

  • Non-gastrointestinal diseases like Addison’s disease or CKD.

Our approach to diagnosis and treatment depends on the type of chronic enteropathy our patient has.

Generally, we diagnose our patients using a combination of clinical history, clinical signs, bloodwork and diagnostic imaging, and response to treatment. After this, we perform intestinal sampling, usually via endoscopy, if needed.

In many chronic enteropathy cases, bloodwork and diagnostic imaging don’t reveal any specific abnormalities, particularly if the patient has food-responsive or antibiotic-responsive enteropathy and remains clinically well. However, patients with severe disease or other forms of chronic enteropathy often have evidence of:

  • Hypoproteinaemia on bloods due to PLE

  • Hypokalaemia on bloods secondary to anorexia

  • Anaemia on bloods due to GI haemorrhage

  • Intestinal loop thickening or loss of layering on ultrasound

Food-responsive enteropathies are diagnosed by trial-treating and assessing response to a diet trial, and antibiotic-responsive enteropathies are diagnosed and treated by assessing response to appropriate antibiotics (generally tylosin or metronidazole). Their signs usually relapse when antibiotics are stopped.

Further diagnostics are indicated in patients who are severely clinically unwell, have evidence of protein loss or malabsorption on bloodwork, or do not respond to a diet or medication trial. 

This is typically a gastrointestinal endoscopy procedure, examining and collecting biopsies from the stomach and duodenum, and potentially their ileum and colon, depending on the patient’s blood results and clinical signs. Even if the mucosa looks normal on endoscopy, it’s still important to sample it because there is a poor correlation between how the mucosa appears to the eye and what it looks like under the microscope.

These samples are submitted for histology, which documents the type of inflammation present within the intestinal mucosa and guides immunosuppressive treatment.

Ok, so that’s your patient diagnosed. What about treatment?

Treatment options for chronic enteropathies include dietary changes, antibiotics, steroids and other immunosuppressive drugs.

In most cases, if the patient is clinically well and doesn’t have evidence of PLE, a diet trial +/- an antibiotic trial is initiated first.

Let’s talk diet.

When it comes to managing chronic enteropathies, our nutritional goals are:

  • To provide a complete and balanced, highly digestible, good-quality diet

  • To provide a diet that reduces antigenic stimulation and inflammation

  • To promote appetite and weight gain (where needed)

We achieve this by reaching for a diet containing either a novel protein or a hydrolysed protein source.

A novel protein source is one that our patient has never been exposed to before. This can be challenging to determine, especially if the patient’s dietary history is unknown; recently, we’ve seen a rise in insect-protein-based diets as a novel protein source, as many of the more ‘unusual’ meats (e.g., duck, venison, etc.) are being fed more commonly than before.

An easy alternative to finding a novel protein source is to opt for a hydrolysed protein diet. In these diets, the protein source undergoes a hydrolysis process where it is broken down into its building blocks - amino acids. This means the body’s immune system can’t recognise that protein source as ‘chicken’, for example - meaning it can’t react to it and cause inflammation.

Regardless of the protein source used, it should be highly digestible. This is because these patients have chronic gastrointestinal disease and struggle to absorb nutrients from food.

So that’s protein taken care of - but there are a few other nutrients we need to consider:

  • Fat restriction may be required if our patient has concurrent pancreatitis or protein-losing enteropathy

  • Dietary fibre levels may require manipulation depending on whether our patient has small-intestinal or large-intestinal diarrhoea.

We may also use probiotics within or alongside the patient’s diet to improve the intestinal microbiome and reduce inflammation in some cases.

Then there’s antibiotics.

As the name suggests, patients with antibiotic-responsive enteropathy will require antibiotics. However, there is a big difference between prescribing them to a patient with chronic antibiotic-responsive diarrhoea and blanket prescribing them to all acute diarrhoea patients - we definitely don’t want to do that!

Antibiotics are overprescribed in diarrhoea especially metronidazole. While there’s no evidence to support its use in acute diarrhoea patients, metronidazole is one of the antibiotics we use to manage chronic ARE patients - the other being tylosin.

Whilst we as nurses and technicians aren’t going to prescribe, we all have a responsibility to use antibiotics appropriately and safeguard their use - and that includes knowing when they’re indicated and when they aren’t.

And then there’s immunosuppressants.

Immunosuppressive agents are the mainstay of treatment for IBD cases, alongside dietary modification and supportive care.

If the immune system is wreaking havoc on our patient’s intestines, we need to intervene and stop it - and we’ll do this with steroids initially. Steroids, as we all know, come with side effects - such as PUPD, polyphagia and, ironically, GI signs - so it’s essential we taper our patient to the lowest effective dose.

If steroids alone aren’t enough to control the patient’s signs, we’ll reach for a second immunosuppressive agent - generally chlorambucil (which is cytotoxic) or cyclosporine.

What other treatments can we use?

Whilst long-term treatment is achieved with diet +/- immunosupressants or antibiotics depending on the patient, that’s not the only treatment we’ll use.

These patients can be significantly unwell and need intensive supportive care - especially if they have severe chronic enteropathy or PLE. IV fluid therapy to correct dehydration, antiemetics to manage nausea and vomiting, and analgesics in patients with abdominal pain are essential.

Alongside this, we’ll provide supportive nursing care, including:

  • Skin and coat care

  • Diarrhoea management

  • Nutritional assessment and assisted enteral nutrition

  • Fluid balance assessments

  • IV catheter management and care

  • Thorough patient monitoring

And much, much more.

So there you have it - that’s my take on treating and caring for chronic enteropathy patients. Though many of these patients are stable, the ones that aren’t really aren’t - they often need intensive supportive care and treatment. This means there is a lot we can do to support these patients and lots of skills we can use in the process.

Giving great care starts with understanding chronic enteropathies and how they impact our patients - which we now do!

Did you enjoy this episode? If so, I’d love to hear what you thought - screenshot it and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout out, and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
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56 | Help, my patient is losing protein! How to care for patients with protein-losing enteropathy
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54 | My top 4 considerations for nursing GI foreign bodies