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Puppy
with SIBO
Q: I emailed
you recently about my 5 month old puppy Jake, who had suspected colitis.
He has since had blood tests, and has been diagnosed with bacterial overgrowth
in his small intestine, and is on a course of antibiotics. Can you tell
me what the long-term prognosis is, as my vet is very vague about this, saying
he may get better, or he may not. Also, he has a problem with hiccups which
he has had since I got him, every morning without fail at about 5.00 am,
he gets a them, is this related to his digestive problems or is it something
I don't need to worry about? Donna
A: Dear Donna,
Small Intestinal Bacterial Overgrowth { SIBO for Short } is not an uncommon
problem in dogs. All dogs have naturally occurring bacteria in their gut
- the so-called gut flora. They normally live with these bacteria quite happily
until something happens to upset he delicate balance of the intestines.
There are many, many possible causes for this - a dietary upset, infection,
parasites, partial obstruction, pancreatic problems, inflammatory bowel diseases,
etc, etc. These conditions can allow the normal bacteria to overgrow and
add to the problem. So you then need to treat this bacterial overgrowth as
well as the underlying problem. German Shepherds are prone to getting SIBO
for no obvious reason and these cases are likely to keep flaring up again.
Normally SIBO is simple enough to treat with a long course of a suitable
antibiotic. The underlying cause in a puppy is most likely to be just an
upset gut due to eating the wrong thing, or something too rich, or a mild
infection. Make sure he has been wormed correctly. So the underlying problem
may already be settled in Jake. I cannot remember what breed he is - if he
is a Shepherd, then he may be a dog who will be prone to SIBO and need repeated
antibiotics, otherwise he should be fine once this bout has cleared up if
you keep an eye on his diet. As for the hiccuping - pups often get this and
it is nothing to worry about. I will say it is unusual to get it every morning
like that ! It can be associated with gulping food or water too quickly -
although I would not have thought he would be eating at 5am. It does signify
that he may be a greedy pup which would help explain his SIBO ! Most pups
grow out of it - hopefully he will too. He might be best on a complete dry
food and fed several times a day, even as an adult, to spread out the food
a bit.Your vet could advise you better about this as they know him. I hope
he is soon well again,
Maeve
Moorcroft MVB MRCVS( PetPlanet
Vet }
What's a Good Diet for Lab Puppy with SIBO?
Q: I have written to
you for advice a couple of times about my 6 month old Lab pup, Jake, who
has been diagnosed with SIBO, and you have been really helpful. The question
I have now is regarding diet. Jake has been on a tinned prescription diet
for about 6 weeks now, and this agrees with his stomach. Unfortunately this
is expensive and I cannot afford to feed him on this long term, he is insured,
but the insurance Co won't pay for it. The vet advised trying to wean him
off the prescription food onto a branded complete food, for sensitive stomachs,
which I did. However, this doesn't seem to agree with his stomach either,
and I had to take him to the emergency vet this week, as he had severe stomach
pains during the night. I have tried just about every type of canned meat
on the market (mainly chicken varieties), and cannot find one that he will
tolerate. I have now decided that it would be better to feed him myself with
natural ingredients. However, I need advice as I don't know what amount of
meat he should have (tripe and chicken have been suggested), and whether
he will need anything adding to this, such as mixer. I presume I will need
to give him vitamin supplements, but would like advice on what to give him.
Please help, any advice you give will be greatly received. I have tried talking
to the vet about this, but he isn't particularly sympathetic, and thinks that
I should just continue to give him his medication (antibiotics and steroids),
however, he has been taking these for about 6 weeks now, and I haven't seen
any improvement.
A: Dear Donna, You do seem to have quite a problem there with
Jake and I can sympathise with your frustrations. It does sound as if the
SIBO (Small Intestinal Bacterial Overgrowth) may be complicated by a dietary
intolerance in his case. Most SIBO cases clear up on 3-4 weeks on antibiotics
and a low-fat diet. Relapses are possible especially in german shepherds.
Jake seems to be taking a long time and the trouble he is having tolerating
different foods would also suggest that something else beside the SIBO is
going on. It may be that this is suspected anyway as steroids are not normally
required for SIBO, but would be used for Inflammatory Bowel Disease.Changing
to a natural diet is a good step to take but you will find yourself faced
with dozens of everyone's favourite recipes, all of which they will claim
is the only one to feed. Some are so intricate that people give up and then
feel guilty and some are deficient in particular nutrients over a period of
time, because of their lack of variety. So I'll just suggest things you can
use, give you proportions and supplements and let you decide what suits availability,
complexity and cost for yourself. Basic rough guide should be 4 parts starchy
food 2 parts protein and 1 part fruit and vegetable measured by weight on
an equal moisture content. That is, weigh the rice or whatever, cooked,
not dry. That's for a pup and young dog, for an old dog change to 6 parts
starch to 2 protein and 1 fruit and veg. Keep fat on the meat or add oil
to the mixture in the form of vegetable oils, raw eggs, raw chicken wings,
lambs liver and rabbit. Flax seed oil, rapeseed oil (sometimes called canola)
and borage oil (sometimes called safflower oil)are highest in omega 3 essential
fatty acids, but all vegetable oils have some. Also add Vitamin E to prevent
the oils and fats becoming rancid. Starting to sound complicated already,
but you don't have to do all this every day, just let it balance out over
a week and one day can be more meat, another more starch or more veg. Fruit
and veg can be fed as treats or liquidised and mixed in the rest of the
food. Food can be fed raw as long as the source and preparation is hygienic,
that's for your safety as well as for your dogs, but light cooking is also
fine as dogs have been around us humans long enough to have a wider tolerance
for different foods than their wild cousins. Supplements are best in the
form of balanced multivitamin and mineral mixes. Making your own up can
be done but when good quality ones are available there's no point. Only
use those made for dogs as the calcium and phosphorous ratio is different
in human supplements. Herb mixes such as Dorwest's Keepers Mix or Designing
Health's Missing Link will also cover most things plus adding extra herb
and vegetable substances to the diet. I do have a recipe for a herb mix but
I'm rambling on enough here already!! First, Starches:- Pasta, Semolina, Oats,
Barley, Rice, Rye and wheat-free rye bread, Tapioca, Millet, Boiled potatoes,
Flaked maize, Rice pudding made with soya milk. Wheat is avoided because
of gluten sensitivity but some dogs will be fine so wholemeal bread could
be used if they are. Proteins:- Fish, Eggs, Chicken, Beef, Lamb, Turkey, Tripe,
Rabbit, Quorn or Tofu, Yoghurt, Cottage cheese, Cheese and Pulses(also a
source of starch). Big raw marrow bones are fine. Vegetables:- Carrots and
other root vegetables, broccoli, beansprouts, lettuce, spinach, cauliflower,
runner beans and celery. Fruit:- Apples, pears, bananas, plums, dates, grapes,
mangoes, any berries in season and any dried fruit. Quantity overall should
be roughly the same volume as fed already and adjust up or down according
to weight gain or loss. Raw food takes longer for a dog to digest so once
daily feeding for an adult is fine, pups, old dogs and those prone to bloat
need more frequent smaller meals. Still sounds pretty off-putting but you
only have to pick some of these ingredients, those easiest and most reliable
to source locally. If you have a proper butcher, bones and off-cuts are
possible, if you're in a fishing area and have a relation on the boats, then
fish might be easiest. Anyway, back to Jake. Fish, tripe or lamb may be
your best bets to start with and rice, potato or maize as the starch. Raw
tripe is pretty off putting to us but provided the source is clean it's a
surprisingly easily digested food for dogs. Chicken could be fine as well
but some dogs don't tolerate it. If his selected protein food is chicken based
then try that. Introduce the vegetables gradually and liquidise them or lightly
cook them to make them easier to digest. In his case, keep things much the
same daily until you see how it's going then you can start to vary things
for him. Also add, just for Jake, Lactobacillus acidophilus, what's referred
to as a probiotic, to replace the friendly bugs killed by the antibiotics,
Vitamin B complex 10 to 20 mg daily, Folic acid 100 to 150 mg daily, proanthocyanadin
complex ( also called bioflavinoid) 50 to 100 mg daily, N-Acetyl Glucosamine
250 to 1000 mg daily (helps repair leaky gut syndrome and is an anti-inflammatory,
but may not be eay to find) and Glutamine 500 to 2000 mg daily, which is
a primary energy source for the mucosal cells of the digestive tract, these
are not animal licensed products so a visit to the health food shop is in
order, but don't panic if you can't find everything just get what you can.
Have the homoeopathic remedies Nux vomica, for indigestion, Carbo veg, for
bloated gas and Colocynth, for abdominal cramps to hand just in case. Better
still, consult a homoeopath and hopefully get Jake off the antibiotics and
steroids. (Don't stop your current vet's treatment without his supervision
or referral to another vet.) Remember that this is just advice and I can't
see Jake or know all the facts. Worth reading is Give Your Dog a Bone by
Dr Ian Billinghurst or The Natural Way for Dogs and Cats by Midi Fairgrieve.
As well as fresh foods its worth finding a tinned or dry food that he can
tolerate as back up if you're away and someone else has to feed him. Organic
foods like Yarrah, Naturediet, Pero, Nutra and hypoallergenic foods like
James Wellbelloved are worth a look, but get Jake stable on his fresh food
and off medication first before playing around. Phew!! I'll get this made
up in book form now I think. Best wishes to you and Jake
June
Third-Carter B.V.M.S., M.R.C.V.S., Vet.M.F.Hom. (Vet for PetPlanet)
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Bacterial Overgrowth in Dogs-More Common Than You
Think
(SIBO)
Roger M Batt
Masterfoods, Mars Inc.
Waltham-on-the-Wolds, Leicestershire, UK
The proximal small intestine
normally contains few bacteria.In small intestinal bacterial overgrowth
(SIBO) there is proliferation of abnormal numbers of bacteria in the lumen
of the upper small intestine. The definition of what is considered an abnormal
number of bacteria in the dog is still under discussion. It is classically
stated that in normal household pet dogs no more than 104 to 105 bacteria
per mL of juice are present in the lumen of the upper small intestine. Although
recent reviews have questioned the accuracy of this upper limit of normal,
some of the reported variation may reflect inclusion of dogs not from household
environments rather than pet dogs. However, it is generally accepted that
species normally present in the proximal small intestine of dogs include
E. coli, enterococci and lactobacilli, and that obligate anaerobic species
are rare. In dogs with SIBO there are not only increased numbers of intraluminal
bacteria, but the composition of the flora also changes to a predominantly
anaerobic one, resembling that of the colon.
SIBO in the dog has been infrequently reported, probably because of the
difficulty in establishing the diagnosis, and initial descriptions were limited
to its occurrence in German Shepherd Dogs. However, in recent years it has
been described as a common finding in dogs with chronic small intestinal
disease, either as a cause or a consequence of their disease. This condition
in the dog has been controversial because of difficulties in defining its
aetiology and pathogenesis. There have been suggestions that it be renamed
antibiotic-responsive diarrhoea (ARD) until more is known about its aetiopathogenesis.
However, this does not apply to all cases since it is not always associated
with diarrhoea; indeed, weight loss alone can be the only presenting sign.
Accumulated data on clinical cases indicate that SIBO should be considered
an important emerging syndrome that may occur in many breeds of dog. It
typically presents in young animals as chronic intermittent small bowel
diarrhoea, which may be accompanied by loss of body weight or failure to
gain weight. Clinical signs are variable and some animals may only exhibit
weight loss, while others may have intermittent vomiting or signs suggestive
of mild colitis.
Aetiology
SIBO may develop if the normal host defence mechanisms, such as gastric
acid secretion, intestinal peristalsis, the ileocaecal valve, intestinal
immunoglobulin secretion, and mucus barrier are impaired. In people, SIBO
is usually associated with intestinal stasis (blind loop syndrome). Small
intestinal dysmotility, as evidenced by reduced migrating motor complex activity,
is probably responsible for the prevalence of SIBO in elderly human patients.
In dogs, there is rarely evidence for stasis, and the cause of SIBO is often
unknown. A naturally developing enteropathy associated with SIBO was first
described in German Shepherd Dogs, and it has been postulated that this is
related to an apparent relative deficiency of IgA in this breed. SIBO may
also develop secondary to exocrine pancreatic insufficiency, and has been
reported in asymptomatic laboratory Beagles. We have documented SIBO by culture
of duodenal juice in over half of dogs with chronic intestinal disease; dogs
of many breeds are affected, although there is a predominance of German Shepherd
Dogs. Serum IgA levels in these dogs have been variable. Predisposing conditions
usually cannot be identified, although it remains important to rule out causes
of intestinal stasis, such as neoplasia and intussusception. Increased numbers
of pathogenic E. coli have been demonstrated in the duodenal juice of these
dogs, and these may also play a role in the development of this condition.
SIBO may furthermore be a secondary complication of many intestinal diseases
due to altered intestinal motility and/or local immunity; in addition,
malabsorption of nutrients may cause an environment favourable for bacterial
proliferation. Conversely, bacterial antigens gaining access to the lamina
propria also may cause an inflammatory reaction, although this tends to
be milder.
Pathophysiology
Bacteria or their secreted products can directly damage the mucosa or
indirectly impair absorption by competing for nutrients and by changing intraluminal
factors such as the concentration of conjugated bile acids. This results
in diarrhoea and steatorrhoea, competition with the host for nutrients, and
weight loss. Enterocyte damage is often not visible on light microscopy,
but may be demonstrated using biochemical or ultrastructural studies, or
by measurement of intestinal permeability. Increased mucosal production of
interleukin-6, a cytokine that plays a central role in the regulation of
inflammatory and immune reactions, has been demonstrated in people with SIBO,
suggesting heightened mucosal immune activity.
The species of bacteria in duodenal juice of dogs with SIBO varies markedly,
with coliforms, staphylococci, enterococci, and Clostridium and Bacteroides
spp predominating. Anaerobic overgrowth is most common, found in approximately
70% of dogs with SIBO. This is of clinical significance, since anaerobic
bacteria have a much greater potential to damage the intestinal brush borderand
cause malabsorption; in addition, anaerobes, especially Bacteroides, are
the major cause of bile salt deconjugation resulting in fat malabsorption
and steatorrhoea.
Diagnosis
Symptomatic SIBO typically presents in young animals as chronic intermittent
small bowel diarrhoea, which may be accompanied by loss of body weight
or failure to gain weight. Diarrhoea often has been present since puppyhood,
and gradually worsens. Some dogs also may have signs of a mild colitis,
due to colonic irritation by bacterial metabolites, and these dogs may be
erroneously diagnosed as having primary colitis. Weight loss may be severe,
and is in some dogs the only sign. Appetite is often reduced. Vomiting is
not typically associated with bacterial overgrowth; its presence suggests
concurrent inflammatory bowel disease. Some dogs with SIBO are presented
because of excessive intestinal gas.
Baseline investigation
CBC and biochemical profile should be performed to rule out systemic
disease. Faeces should be examined for parasites and cultured for enteric
pathogens. Abdominal radiography and especially ultrasound can be helpful
to rule out partial obstruction, particularly in young (intussusception)
or older (neoplasia) animals. Subsequently, exocrine pancreatic insufficiency
(EPI) should be ruled out by assay of serum TLI activity.
Serum folate and cobalamin
Assays of serum folate and cobalamin appear to be the most helpful aids
to the diagnosis of SIBO in the dog for use in general practice, although
they have poor sensitivity (i.e., many affected dogs do not have abnormal
test results). Normal serum vitamin concentrations do not exclude the possibility
of SIBO, because alterations depend on the type and numbers of organisms
present, the severity of any secondary mucosal damage that may interfere
with folate absorption despite high intraluminal concentration, and depletion
of body stores. If pancreatic function is normal (i.e., serum TLI is normal)
then finding a decreased serum cobalamin concentration or increased serum
folate is supportive of SIBO. If both of these are found together, SIBO
is extremely likely; however, this combination occurs infrequently. High
serum folate may also be a consequence of high folate intake, such as a
high-folate diet or coprophagia. Demonstration of low serum cobalamin is
the more useful finding, since it is less influenced by diet and coprophagia
and appears to relate more to the severity of clinical disease
Intestinal permeability
Measurement of intestinal permeability is a sensitive tool for the detection
of mucosal damage, but it does not tell you about the underlying cause.
However, these tests are useful to detect and assess the severity of mucosal
damage in dogs with overgrowth. Increased intestinal permeability can be
demonstrated using a differential sugar absorption test in 50-60% of clinical
cases with SIBO, even when there are no histologic abnormalities. In addition,
changes in intestinal permeability following antibiotics may be used to
monitor response to treatment. Normalization of intestinal permeability
following antibiotic therapy suggests successful treatment, and antibiotics
may be discontinued. Antibiotics possibly should be continued longer if
permeability remains high despite apparent response to treatment; in addition,
other causes of intestinal disease should be suspected and investigated
(e.g., dietary sensitivity). Persistent high permeability in dogs with a
poor clinical response should prompt one to look for underlying disease,
such as a primary inflammatory bowel disease.
Breath hydrogen testing
Breath tests measure the breath excretion of CO2 or hydrogen (H2) produced
by intraluminal bacterial metabolism of an administered substrate. They
appear to be the one of the most sensitive and specific tests available
for the diagnosis of SIBO, although they are not yet technically feasible
in most veterinary practices. The H2 breath test has been used most often
in both human and veterinary medicine. It has been used not only for diagnosis
of SIBO but also for detection of carbohydrate malassimilation and measurement
of oro-caecal transit time. The time after ingestion of the test substrate
at which increased breath H2 concentrations are first detected is used to
distinguish between SIBO and carbohydrate malabsorption. In SIBO, elevated
breath H2 concentrations occur within 1 to 2 hours after ingestion of the
test substrate. An H2 breath test using a multiple sugar solution has been
used successfully for detection of SIBO in dogs and has the advantage that
it simultaneously allows for quantification of intestinal permeability.
A limitation of breath H2 tests in people is that 15-20% of the human population
have intestinal flora that does not produce hydrogen, and therefore cannot
demonstrate a positive test result if bacterial overgrowth develops. The
same probably applies to the dog, since there are significant numbers of
dogs with culture-proven overgrowth but persistently negative breath tests.
The H2 breath test is more sensitive than serum folate and cobalamin
assay, and has been useful to identify cases of SIBO with a falsely negative
duodenal juice culture. A positive breath H2 test is very suggestive of
SIBO, and there is no need to culture duodenal juice in these cases. However,
a negative test does not rule it out, and culture of duodenal juice remains
necessary in these patients.
Culture of duodenal juice
Definitive diagnosis of SIBO is based on results of microbiologic culture
of duodenal juice, obtained usually at endoscopy or alternatively via intra-operative
permucosal aspiration. Juice culture is still the gold standard for the
diagnosis of SIBO, but it is technically difficult, time-consuming and expensive,
and it may still not identify all cases of SIBO (for example when this is
in the more distal portions of the small intestine or in isolated pockets).
However, intestinal biopsies can be taken at the same time as the juice collection,
and these are useful to rule out primary mucosal disease as the cause of
malabsorption. Duodenal biopsy in SIBO is often normal. Over 75% of clinical
cases with SIBO will have no histologic abnormalities, whereas mild to moderate
lymphocytic infiltrates occur in up to 25%. Mild lymphocytic-plasmacytic
enteritis can occur as a consequence of SIBO, and may resolve following appropriate
antibiotic treatment.
Duodenal bacterial counts may be influenced by environmental factors,
such as housing conditions (kennelled dogs tend to have higher bacterial
numbers, perhaps associated with coprophagia) and infective load (such as
endoparasites and naturally occurring enteropathogens in hot climates). This
should be taken into account when defining bacterial levels deemed diagnostic
of bacterial overgrowth.
Miscellaneous tests
Bacterial deconjugation of bile salts may result in increased serum concentrations
of unconjugated bile acids. Unlike the conjugated bile acids normally present
in the small intestinal lumen, these unconjugated bile acids (UBA) diffuse
across the intestinal mucosa into the blood. Dogs with SIBO have been shown
to have significantly higher serum concentrations of UBA. This test has
also proven useful to identify dogs with culture proven SIBO that did not
have abnormal serum vitamin concentrations. Until now, this test was technically
too complicated for routine use, but new developments should lead to this
becoming more available in the near future. It may therefore become a useful
addition to the battery of diagnostic tests required to diagnose SIBO.
Response to treatment with antibiotics may also help in the tentative
diagnosis of SIBO. However, lack of response does not rule it out, since
prolonged treatment may be required in some dogs before clinical improvement
is manifest.
Subclinical SIBO
SIBO can be a subclinical intestinal abnormality, as has been reported
in man, German Shepherd dogs and laboratory Beagles. Development of clinical
signs in these individuals probably depends on the nature of the bacterial
population (for instance, colonization with anaerobes is more likely to
result in signs) and the effect of the overgrowth flora on the local immune
system. These patients may be identified on basis of abnormalities in serum
folate and/or cobalamin concentrations, a positive hydrogen breath test,
or by culture of duodenal juice aspirated in the course of other investigations.
Treatment is not required as long as they are asymptomatic; however, they
are at risk for developing signs once the delicate balance in their intestinal
ecosystem is disturbed. Progressive decreases in serum cobalamin concentration
in dogs with asymptomatic SIBO often precede development of clinical signs.
Treatment
An attempt should be made to identify and correct an underlying cause,
such as partial obstruction due to intussusception, tumours or foreign
bodies. Detection of dysmotility is more difficult and often not feasible;
however, motility modifying agents such as cisapride or low-dose erythromycin
may empirically be used in refractory patients. In many dogs with SIBO a
cause cannot be found, and long-term oral antibiotic treatment is required.
Oxytetracycline (10-20 mg/kg TID for 28 days) is used initially, and may
need to be continued for extended periods if clinical signs recur on withdrawal
of medication. Its mechanism of action may involve more than just pure
antibacterial action (e.g., direct influence on the mucosa), although this
is not certain. Metronidazole (10-20 mg/kg TID) and tylosin (20 mg/kg BID)
are good alternative choices and are used if dogs fail to respond to oxytetracycline.
Broad-spectrum bactericidal antibiotics tend to be less effective.
Dietary management with a low fat diet may also be valuable, because
this can minimize the secretory diarrhoea, which is a consequence of bacterial
metabolism of fatty acids and bile salts. Since intestinal permeability
is often increased in SIBO, a restricted antigen diet may be of value to
reduce the incidence of secondary dietary sensitivities. Dietary supplementation
with fructo-oligosaccharides has been suggested as a means of modifying
bacterial counts in the small intestine in German Shepherd Dogs with asymptomatic
naturally occurring bacterial overgrowth. However, since these compounds
are more likely to affect the large rather than the small intestine, further
studies in clinical cases are required to assess the efficacy of prebiotics
in the management of canine SIBO.
Probiotics are a mixture of non-pathogenic bacteria, often containing
Lactobacillus, which can change intestinal pathobiology by preventing enteric
infections, modifying metabolic actions of intestinal bacteria, and promoting
nutrition. They also may promote local mucosal and systemic immune response.
Probiotics are extensively used in large animals, and have also been advocated
as a means of modulating gut flora in people with gastrointestinal disease.
Parenteral cobalamin (e.g., 500µg/month for 6 months) may help
dogs with apparent cobalamin deficiency. It may have to be given more frequently
if serum cobalamin levels remain subnormal. Persistently low serum cobalamin
levels are often associated with a poor clinical response to treatment.
Prolonged antibiotic therapy is often required in treatment of dogs with
idiopathic SIBO, and serial measurement of intestinal permeability and
breath H2 testing are helpful in monitoring response to treatment. Some
dogs with SIBO relapse as soon after antibiotics are discontinued. In these
patients long-term antibiotic treatment will be required, but empiric reduction
of the dose to well below the recommended level may be effective in controlling
signs.
In dogs with moderate to marked inflammatory bowel disease, corticosteroids
should be added to the treatment regimen if response to antibiotics alone
is inadequate. Corticosteroids are not recommended in the initial treatment
of dogs with lymphocytic/plasmacytic enteritis and SIBO because in our
experience they appear to worsen clinical signs associated with SIBO.
Chronic SIBO may cause permanent functional damage to the intestinal
mucosa. This may explain the poor response to treatment of some dogs, and
also the need for indefinite dietary management with controlled diets after
apparent successful antibiotic therapy in some dogs with chronic SIBO.
References
1. 1.Rutgers HC, Batt RM, Elwood CM, Lamport A. Small intestinal
bacterial overgrowth in dogs with chronic intestinal disease. J Am Vet
Med Assoc 1995;206:187-19
2. 2.Rutgers HC, Batt RM, Proud FJ, et al. Intestinal permeability
and function in dogs with small intestinal bacterial overgrowth. J Sm Anim
Pract 1996;37:428-434
3. 3.Bissett SA, Guilford WG, Spohr A. Breath hydrogen testing
in small animal practice. Comp Cont Educ 1997;19:916-931
4. Ludlow CL, Davenport DJ. Small intestinal bacterial overgrowth.
In: Bonagura JD, ed. Current Veterinary Therapy XIII. Philadelphia, WB
Saunders, 1999: 637-641
5. Melgarejo T, Williams DA, O'Connell NC, Setchell KD. Serum unconjugated
bile acids as a test for intestinal bacterial overgrowth in dogs. Dig Dis
Sci 2000; 45:407-414
Roger
M Batt Masterfoods, Mars Inc. Waltham-on-the-Wolds, Leicestershire, UK
Roger Batt qualified as a veterinarian from Bristol University in 1972
and obtained his PhD at the Royal Postgraduate Medical School in London.
In 1980 he moved to the University of Liverpool where he established a
comparative gastroenterology research group. In 1990 he was appointed Professor
of Veterinary Medicine at the Royal Veterinary College in London. In 1998
he moved to the Waltham Centre for Pet Nutrition to become Head of Research
and in 2001 was given the status of Visiting Professor at the University
of Bristol.
His research has focused on gastrointestinal disease in specific breeds
of dog. He has over 300 publications, and for his research has received a
1989 Ralston Purina Award from the American Veterinary Medical Association,
the 1990 Walter-Frei Prize from the University of Zurich, the 1991 Woodrow
Award from the British Small Animal Veterinary Association, and the 1997
Oscar W. Schalm Award from Davis, University of California. In 1993 he became
the first President of the European Society of Comparative Gastroenterology
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Small Intestinal Bacterial Overgrowth
Introduction
Small intestinal bacterial
overgrowth (SIBO) is characterized by an uncontrolled increase in the number
of bacteria (105 colonies/ml intestinal fluid) in the upper small intestine.
It is considered by some to be an important cause of diarrhea in small
animals. SIBO may occur secondary to a number of other intestinal
disorders, or be idiopathic.
Factors which can cause
Secondary SIBO include:
Ileus (impaired GI motility): Bacterial populations normally
increase in number proximally to distally in the GI tract. Peristalsis
is one important mechanism that limits bacterial populations in the upper
small intestine by flushing bacteria distally through the GI tract.
Conditions that cause ileus have classically been associated with bacterial
overgrowth. There are many causes of ileus, including intestinal
obstruction, neuropathy, abdominal surgery, peritonitis, pancreatitis,
uremia, hypokalemia, and endotoxemia. "Blind loop syndrome" refers
to an anatomical out-pouching of gut or a mesenteric hernia that
results in a localized ileus, which may then cause SIBO.
Increased substrate
Conditions which result in increased nutrients in the lumen of the
bowel can allow bacteria in the small intestine to overgrow by providing
substrate. This occurs with motility disorders, and maldigestive
disorders, such as exocrine pancreatic insufficiency (EPI).
Host malnutrition
A decrease in body condition can have deleterious effects on the
local gut immunity and mucus secretion. This may lead to uncontrolled
bacterial proliferation.
Idiopathic SIBO
Idiopathic SIBO is also referred to as antibiotic-responsive
SIBO, and is seen more commonly in young German Shepards than in any other
breed. Animals with idiopathic SIBO will have a decrease in signs
following the appropriate antibiotic regimen.
Pathophysiology
There are several mechanisms by which bacterial overgrowth causes clinical
signs:
Bacteria cause deconjugation of bile salts. These products are
then allowed to be reabsorbed from the intestinal lumen, making them unavailable
to participate in fat absorption. This inability to break down and
absorb fats causes both an osmotic and a secretory diarrhea since deconjugated
bile acids stimulate enterocyte secretion.
Bacteria cause hydroxylation of fatty acids. Hydroxylated fatty
acids inhibit fluid absorption, and may act synergistically with deconjugated
bile acids in stimulating enterocyte secretion. Fatty acids further
damage enterocytes by their detergent properties, which solubilize components
of the cell membrane. This enterocyte damage may result in some degree
of villous atrophy, which is sometimes seen in association with SIBO.
Bacteria change brush border enzyme activity. Increased bacterial populations
can also lead to maldigestion by causing changes in the enzyme activity
of the brush border cells, and disrupting the mucosal stage of digestion.
This change in the mucosal function is reversible with antibiotic therapy,
and does not cause any structural damage that would be evident on histopathology.
Bacteria compete for nutrients. Excess bacteria compete for nutrients
in the lumen of the bowel, resulting in malabsorption and weight loss.
Signalment
Idiopathic SIBO
Young, large-breed dogs and German Shepards seem to be more likely to
have idiopathic SIBO.
Idiopathic SIBO is not recognized in cats.
Secondary SIBO
This condition may be seen in all breeds and ages of dogs.
Clinical signs
Idiopathic SIBO
Dogs with idiopathic SIBO present with chronic intermittent small bowel
diarrhea, failure to thrive, stunted growth, or an increase in gas production.
Often the animals have an increased appetite manifested as polyphagia,
coprophagia, or pica.
Secondary SIBO
This is a sequela to a number of primary conditions including chronic
Giardia, EPI, motility disorders, intestinal obstruction, or dietary sensitivity.
Clinical signs usually pertain to the primary condition.
Gross Pathology
There are no gross lesions associated with SIBO.
Histopathology
Increased bacteria are not evident on tissue biopsy, and there are generally
no morphologic changes in SIBO. Occasionally, histopathology may
reveal villous atrophy or mild lymphocytic-plasmocytic inflammation.
In such cases, it is sometimes difficult to determine which came first
- the inflammation or the bacterial overgrowth.
Idiopathic SIBO Young, large-breed dogs and German Shepards seem
to be more likely to have idiopathic Sibo. Idiopathic SIBO is not recognized
in cats.
Secondary SIBO
This condition may be seen in all breeds and ages of dogs.
Diagnosis
The diagnostic gold standard is finding an increased bacterial colony
count in duodenal fluid culture via endoscopy. Colony counts >105
are considered indicative of SIBO. However, some dogs and cats have colony
counts as high as 107 -108 and are asymptomatic. In reality, the
test is technically complicated, time-consuming and expensive. Few
veterinarians have the capability of performing the test and in light of
the problems associated with interpretation, quantitative culture of duodenal
fluid is seldom done. Instead, veterinarians rely on indirect testing
- namely measuring serum folate and cobalamin levels (see below & your
clinical pathology notes).
Increased serum folate, secondary to bacterial synthesis, is commonly
associated with SIBO.
Decreased serum cobalamin is also associated with SIBO because bacterial
bind the vitamin cobalamin.
The colonic flora does not necessarily reflect what is happening in the
small intestine and, therefore, colonic or fecal cultures cannot be used
to diagnose SIBO.
NOTE: An increased serum folate and decreased serum cobalamin
is found in both SIBO and Exocrine Pancreatic Insufficiency. If EPI
has been ruled out by a normal TLI, elevated folate in conjunction with
decreased serum cobalamin is highly specific for SIBO. However, it
should be noted that these tests are not considered to be very sensitive
measures for SIBO. For more information, see folate and cobalamin.
For more information. . .
Textbook of Veterinary Internal Medicine: Disease of the dog and cat,
5th edition, eds. Ettinger and Feldman, pp 1223-1228.
Small Animal Medicine, eds. Nelson and Couto, pp 453.
Strombeck's Small Animal Gastroenterology, third edition, eds. Guilford,
Center, Strombeck, Williams, and Meyer, pp 370-373.
Copyright © 2007 Board of Regents, Washington
State University
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