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DISEASE · CATS

IBD in cats: what the blood tests show and how it is diagnosed

Inflammatory bowel disease (IBD), now often called chronic enteropathy, is a long-lasting inflammation of the gut. It causes vomiting, diarrhea or weight loss for weeks. No single blood test proves it: the vet first rules out other causes, then often needs biopsies to tell it from low-grade lymphoma.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Chronic enteropathy means gut signs lasting at least 3 weeks once other diseases have been ruled out. Weight loss is the most common sign, and many cats have no diarrhea. Blood work checks the thyroid, kidneys, liver and pancreas, and measures vitamin B12 (cobalamin) and folate. A low B12 or a mildly low albumin is common, but the same changes occur in low-grade lymphoma. Some cats improve with a diet trial alone. Others need intestinal biopsies, the only way to separate inflammation from lymphoma.

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What IBD is, and what it is not

Vets now group these cats under “chronic enteropathy”: gut signs that last at least 3 weeks, once causes outside the gut, hormonal or metabolic diseases and infections have been excluded [1]. Its inflammatory form is called lymphoplasmacytic enteritis: an infiltrate of lymphocytes and plasma cells in the intestinal wall [1].

It is a diagnosis of exclusion [3]. Some cats turn out to have a food-responsive enteropathy, which improves with a diet change alone; vets separate it from other forms with a diet trial [1, 5]. Low-grade intestinal lymphoma looks very similar and is the main disease to rule out: see lymphoma in cats.

In cats, the picture is not dominated by diarrhea. Weight loss is the most common sign and is often missed; vomiting, poor or increased appetite and lethargy are also seen [1]. Cats can lose muscle along the spine while keeping belly fat [1].

What the vet rules out first

Possible causeTest usedTo know
Parasites and infectionsFecal analysisPart of the standard workup [1].
HyperthyroidismTotal T4Recommended in the workup; it can also exist alongside gut disease [1]. See hyperthyroidism in cats.
Kidney, liver and other metabolic diseaseBlood count, chemistry panel, urinalysisAlways needed before calling it a chronic enteropathy [1].
PancreatitisfPLI (Spec fPL) and ultrasoundOften found together with gut inflammation [1]. See pancreatitis in cats.
Exocrine pancreatic insufficiencyfTLIShould be checked in cats with chronic gut signs [1].
FeLV and FIVBlood testFor cats that go outdoors or live with other cats [1].

What the blood work shows

  • Vitamin B12 (cobalamin): absorbed at the end of the small intestine. It was low in 18% to 80% of cats with chronic enteropathy across studies [1], and in 49 of 80 cats tested for suspected gut disease in an older study [9]. A normal B12 does not rule out gut disease [1].
  • Folate: absorbed at the start of the small intestine, so B12 and folate together hint at where the disease sits. Both low and high folate occur, and a hemolyzed sample can raise it [1].
  • Albumin: often low, usually only mildly; reports range from 14% to 100% of cats [1]. Severe protein loss through the gut is extremely rare in cats [1]. Total protein is often normal or even high because globulins rise [1]. See albumin and globulin.
  • Liver enzymes (ALT, ALP) and phosphorus: sometimes abnormal; with total protein, they are part of a score used to rate disease activity [1, 7]. See high liver enzymes in cats.
  • Blood count: may show anemia from iron deficiency [1].

None of these values tells IBD apart from low-grade lymphoma, and there is no cancer marker in the blood [1]. To read the whole report, see cat blood work explained.

How to read the cobalamin line

Here is an example line from a cat with months of vomiting and weight loss.

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
COB Cobalamin (vitamin B12)160ng/L> 200L
  1. Abbreviation COB, B12 or Cbl, depending on the laboratory.
  2. Result 160 ng/L in this illustrative line: low.
  3. Unit ng/L, the same as pg/mL.
  4. Laboratory interval In a 2021 study, 200 ng/L was the lower limit of the reference interval; below it, B12 was counted as low [2]. Each laboratory sets its own limit.
  5. Flag L: below the interval. Points to disease of the small intestine or pancreas. In that study, it was low in 19% of cats with IBD and 57% of cats with low-grade lymphoma [2].

How IBD is confirmed

  • Diet trial: the cat eats only a selected-protein (elimination) or hydrolyzed diet. In one study, 16 of 55 cats (29%) were food sensitive and 11 more (20%) improved on the elimination diet [5]. In another, 15 of 33 cats responded to a hydrolyzed diet within 6 weeks [6].
  • Ultrasound: checks the intestinal wall, lymph nodes and nearby organs [1]. It cannot tell IBD from lymphoma, and it can look normal despite real disease [1].
  • Intestinal biopsies: needed to characterize the inflammation and rule out lymphoma, by endoscopy or surgery [1, 3]. Immunohistochemistry and clonality testing (PARR) help in doubtful cases, yet some cases stay ambiguous [1].
  • Clues, not proof: cats with lymphoma tend to be older (median age 13 vs 8 years) and to have had signs for longer [1].

Triaditis: inflammation of the gut, pancreas and bile ducts at the same time. It was found in 8 of 27 cats (30%) with symptoms in one study [4].

Outlook

The outlook depends on the cause. Cats with a food-responsive enteropathy usually do well long term with diet management [8]. In cats that need medication, response varies: some relapse often, and a few do not respond [8]. The activity score falls when treatment works, which helps follow progress [7]. In a study of 100 cats with chronic gut signs and a thickened intestine, 99 had a diagnosable small-bowel disease: these signs should not be dismissed [10].

Related articles

Lymphoma in cats

The main disease to rule out, with the same blood clues.

Read the article

Hyperthyroidism in cats

Weight loss with a hearty appetite: the T4 test.

Read the article

En français : la MICI du chat.

Questions to ask your veterinarian

  1. Have parasites, hyperthyroidism, kidney and pancreas disease been ruled out?
  2. Are vitamin B12 and folate low, and should B12 be supplemented?
  3. Is the albumin low, and what are the globulins doing?
  4. Should we try a diet trial first, and for how long?
  5. Are biopsies needed to rule out low-grade lymphoma?
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Frequently asked questions

What blood tests are done for IBD in cats?

A blood count, chemistry panel, total T4, vitamin B12 and folate, often fPLI and fTLI for the pancreas, plus urine and stool tests [1].

Is IBD in cats the same as lymphoma?

No, but low-grade lymphoma looks very similar on blood tests and ultrasound; biopsies are needed to tell them apart [1, 3].

Can a blood test diagnose IBD in cats?

No. Blood tests rule out other causes and give clues such as a low B12, but there is no specific marker [1].

Can a diet change help a cat with IBD?

Sometimes. Some cats improve on an elimination or hydrolyzed diet alone [5, 6].

What is triaditis in cats?

Inflammation of the intestine, pancreas and bile ducts at the same time; it was found in 30% of cats with symptoms in one study [4].

Sources

  1. Marsilio S et al. ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats. J Vet Intern Med. 2023;37(3):794-816. doi.org/10.1111/jvim.16690
  2. Freiche V et al. Clinical, laboratory and ultrasonographic findings differentiating low-grade intestinal T-cell lymphoma from lymphoplasmacytic enteritis in cats. J Vet Intern Med. 2021;35(6):2685-2696. doi.org/10.1111/jvim.16272
  3. Jergens AE. Feline idiopathic inflammatory bowel disease: what we know and what remains to be unraveled. J Feline Med Surg. 2012;14(7):445-458. doi.org/10.1177/1098612X12451548
  4. Fragkou FC et al. Prevalence and clinicopathological features of triaditis in a prospective case series of symptomatic and asymptomatic cats. J Vet Intern Med. 2016;30(4):1031-1045. doi.org/10.1111/jvim.14356
  5. Guilford WG et al. Food sensitivity in cats with chronic idiopathic gastrointestinal problems. J Vet Intern Med. 2001;15(1):7-13. pubmed.ncbi.nlm.nih.gov/11215916
  6. Kathrani A et al. The effect of a hydrolyzed protein diet on the fecal microbiota in cats with chronic enteropathy. Sci Rep. 2022;12(1):2746. doi.org/10.1038/s41598-022-06576-y
  7. Jergens AE et al. A clinical index for disease activity in cats with chronic enteropathy. J Vet Intern Med. 2010;24(5):1027-1033. doi.org/10.1111/j.1939-1676.2010.0549.x
  8. Ewald N et al. Chronic enteropathies in cats: diagnostic and therapeutic approach (in German). Tierarztl Prax Ausg K Kleintiere Heimtiere. 2021;49(5):363-376. doi.org/10.1055/a-1584-9705
  9. Simpson KW et al. Subnormal concentrations of serum cobalamin (vitamin B12) in cats with gastrointestinal disease. J Vet Intern Med. 2001;15(1):26-32. pubmed.ncbi.nlm.nih.gov/11215907
  10. Norsworthy GD et al. Diagnosis of chronic small bowel disease in cats: 100 cases (2008-2012). J Am Vet Med Assoc. 2013;243(10):1455-1461. doi.org/10.2460/javma.243.10.1455

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

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