Lab Evaluation of GI Tract

Question 1

What’s a specific test for myasthenia gravis?

Answer 1

Demonstrating circulating anti-bodies against acetylcholine receptors in serum

Question 2

What tests can be used for Helicobacter-like organisms for patients with chronic gastritis?

Answer 2

• special stain (Warthin-Starry stain)
• PCR
• FISH
• indirect with urease test on gastric biopsy

Question 3

What tests can be used for parvovirosis?

Answer 3

• in-house ELISA test –> detects the CPV-2 antigen in feces
• false positive possible with recent vaccination
• PCR = higher sensitivity, but not as clinically useful when animal is already very sick

Question 4

What tests can be used for Salmonella spp for diarrhea?

Answer 4

• fecal culture –> but is not routinely shed in the feces
• PCR
• enriched culture followed by PCR

Question 5

What tests can be used for pathogenic Campylobacter spp?

Answer 5

PCR
- C. jejuni and C. coli = causes diarrhea

Question 6

What tests can be used for C. difficile and C. perfringens?

Answer 6

C. difficile
- ELISA for toxin A (enterotoxin) and toxin B (cytotoxin)
- positivity doesn’t always correlate with disease

C. perfringens
- ELISA for enterotoxin
- positivity also does not correlate to infection
- it’s a commensal organism

Question 7

What tests can be used for enteroinvasive E. coli?

Answer 7

FISH
(recall histiocytic ulcerative colitis, Boxers)

Question 8

Which endoparasite can be detected on fecal smear?

Answer 8

• Giardia
• Tritrichomonas foetus
  both have low sensitivity, so negative smear does not rule out infection

Question 9

Which endoparasite can be detected with fecal float?

Answer 9

• helminths
• Giardia

Question 10

Which endoparasite can be detected immunofluorescence?

Answer 10

• Giardia
• Cryptosporidium

Question 11

Which endoparasite can be detected by ELISA?

Answer 11

Giardia lamblia. Highly sensitive, but not as specific (< Immunofluorescence), esp in treated animals

Question 12

How does small intestinal disease, esp in the proximal intestine, affect folate absoprtion?

Answer 12

• folate = water soluble vitamin B (vitamin B9)
• plentiful available in commercial diets
• mostly supplied as folate polyglutamate
• needs to be digested to folate monoglutamate for absorption –> this is done via folate deconjugase
• once it’s in the form of folate monoglutamate, can it can be absorbed by specific glutamate carrier
• if there is proximal SI disease or diffuse SI disease also involving the proximal portion, the folate deconjugase and folate carrier can be destroyed, lead to decrease in absorption\
• clinical signs are noted in chronic patients as the body does have a large store of folate

Question 13

Where is folate absorbed?

Answer 13

proximal small intestine

Question 14

Where is cobalamin absorbed?

Answer 14

ileum, distal small intestine

Question 15

What can cause an increase in folate / cobalamin?

Answer 15

small intestinal dysbiosis

Question 16

What conditions can affect cobalamin absoprtion?

Answer 16

• distal small intestinal disease or diffuse SI disease involving the ileum
• exocrine pancreatic insufficiency

Question 17

How is cobalamin absorbed?

Answer 17

• plentiful available in commercial diets
• but could be lacking if owner is feeding vegetarian/ vegan diets
• cobalamin is bound to animal protein –> the protein is digested by pepsin and HCl in the stomach –> free cobalamin
• the free cobalamin is immediately bound to R-protein, which is produced by the gastric mucosa
• once in the duodenum, the exocrine pancreas secrets protease, digests the R-protein
• it then is bound to an intrinsic protein, which is also secreted by the exocrine pancreas
• on the intrinsic protein/ cobalamin complex can be absorbed by the specific receptors in the ileum

Question 18

How is measurement of fecal alpha1-proteinase inhibitor useful in GI disease?

Answer 18

• it’s of similar size to albumin, but it’s not digested –> ie. will survive the GI tract
• used as a surrogate for PLE
• used in patients with hypoalbuminemia without overt GI signs, and extra-GI causes of hypoalbuminemia has bee ruled out
• can be used for breeds at risk for PLE (Norwegian Lundehund, soft coated Wheaten terriers, Yorkies) intended for breeding that have no GI signs

Question 19

What’s the utility of measuring C reactive protein?

Answer 19

It’s increased in GI disease
- best used for monitoring IBD response to therapy

Question 20

Are there any tests of GI permeability?

Answer 20

historically had used simple sugars, more recent years have been trying with iohexol –> but need more studies
- no assay available for routine GI permeability testing