GASTROINTESTINAL TRACT

1. GASTROINTESTINAL TRACT

2. 1. EXOCRINE PANCREAS • Exocrine pancreatic abnormalities that can be detected by laboratory tests: • Pancreatic inflammation • Exocrine pancreatic insufficiency (EPI)

3. PANCREATIC INFLAMMATION - Associated with a variety of systemic signs in dogs & cats. - During inflammation, pancreatic enzymes gain access via the lymphatics into blood where their activity is increased. - Pancreatic inflammation systemic signs = anorexia, vomiting, pyrexia, abdominal pain etc. - Laboratory tests: Amylase Lipase Trypsin-like Immunoreactivity (TLI)

4. AMYLASE • Cytoplasmic enzyme • Mainly derived from the pancreas and small intestine in healthy animals. • Amylase is excreted or inactivated via the kidneys • SPECIES DIFFERENCES: • Only pigs have salivary amylase. • Not a useful test in horses or ruminants.

5. LIPASE • Cytoplasmic enzyme. • Derived from the pancreas in healthy animals. • Lipase is excreted or inactivated via the kidneys. • SPECIES DIFFERENCES: • Not a useful test in horses or cattle • Should always be measured in conjunction with amylase.

6. TRYPSIN-LIKE IMMUNOREACTIVITY (TLI) Species specific (canine = cTLI, feline = fTLI) Increased in: - Pancreatic inflammation • Peak in TLI can occur 1-2 days before peak of amylase & lipase activities • Greater increases in dogs with severe disease - Decreased renal clearance TLI is more specific than amylase and lipase for pancreatic inflammation.

7. Other test results that can indicate pancreatic inflammation - Leukocytosis/Neutrophilia - Hypocalcaemia (especially cats) - Azotaemia (pre-renal - dehydration) - Hyperlipidaemia (Defective lipase activity altering lipid metabolism) - ↑ liver enzymes & bilirubin (2° hepatocellular damage/cholestasis) - Hyperglycaemia (Secondary diabetes mellitus) - Coagulation disturbances

8. Exocrine Pancreatic Insufficiency (EPI) - Clinical signs associated with maldigestion= weight loss, polyphagia, diarrhoea (fatty faeces) - Characterised by a decrease of exocrine pancreatic enzymes resulting in maldigestion. - Trypsin-like immunoreactivity (TLI) is the test of choice: Low TLI = EPI - Highly sensitive and specific

9. Other tests • Faecal trypsin test • Is rarely used since development of TLI • Faecal pancreatic elastase • Detects faecal pancreatic elastase in faeces • Species specific ELISA for dogs • Stable in faeces during intestinal transport • Low Concentration = severe EPI • High sensitivity and specificity but is time consuming

10. 2.GASTROINTESTINAL TRACT

11. LABORATORY TESTS - The most commonly performed tests are: • Serum Folate/vitamin B12 (cobalamin) • Rumen fluid analysis • Serum Proteins • D-Xylose absorption test

12. Folate is absorbed in the proximal intestine Vit B12 is absorbed in the distal intestine under the action of pancreatic factors Small intestinal bacteria bind Vit B12 and synthesise folate SERUM FOLATE/VITAMIN B12

13. SERUM FOLATE/VITAMIN B12 Interpretation folate and vitB12 indicates small intestinal bacterial overgrowth (SIBO) folate indicates proximal SI disease vitB12 indicates distal small intestinal disease or absence of pancreatic factor Sensitivity and specificity for SIBO are low

14. RUMEN FLUID ANALYSIS - 10 ml of fluid is required for analysis • Analysis must be performed immediately - Laboratory tests: • Gross evaluation • pH • Microscopic examination • Methylene blue test • Bacteria and protozoa will be immobilised and perhaps killed if the sample ages or cools, so it should be examined as soon as possible, and kept warm (37 0C) in the meantime. • Approximately 10 ml fluid is needed for the methylene blue decolourisation test

15. GROSS EVALUATION CLINICALLY HEALTHY ANIMALS • Physical characteristics: brown-green colour aromatic smell • Sediment formation: < 8 min In diseases such as rumenal acidosis or atony the fluid may become discoloured (grey to black) and foul-smelling, and fail to sediment on standing.

16. pH May be the most useful laboratory test - Use pH meter or pH papers - Normal pH =5.5-7 - pH < 5.5 • Acute, severe carbohydrate overload • pH is very low if abomasal fluid is collected instead of ruminal fluid, as may occur in left-sided abomasal displacement - pH > 7.0 • decreased fermentation • protein overload • urea toxicosis • ruminal alkalosis • dilution with saliva

17. Fluid from a healthy rumen has numerous actively-motile small, medium and large protozoa Fluid from an acidotic or atonic rumen has few or no active protozoa MICROSCOPIC EXAMINATION - A drop of still-warm rumenal fluid is placed on a warmed glass slide, a cover-slip is applied & it is examined at low power (10X) microscopically, after lowering the microscope condenser

18. - MB is mixed with ruminal fluid. - In health, active bacteria & protozoa decolourise (reduce) the methylene blue within 3-6 minutes. - Prolonged decolourisation time indicates decreased microbial activity, and occurs in ruminal acidosis and atony METHYLENE BLUE (MB) TEST Decolourised ruminal fluid Ruminal fluid + MB

19. D-XYLOSE ABSORPTION TEST - Used to test intestinal absorption in horses (and dogs) - Assesses ability of intestine to absorb monosaccharides • Abnormalities in monosaccharide absorption are assumed to reflect concurrent abnormalities in the absorption of proteins and lipids - Sample submission: •Heparinised plasma, timed sampling - Laboratory method: • D-Xylose determination by colorimetric methods

20. D-XYLOSE ABSORPTION TEST IN HORSE • Test method used in horses: • overnight or 18-24 h fast • per os: 0.5 g D-xylose/kg of body weight • heparin plasma samples at 0, ½,1, 1½, 2, 2½, 3, 3 ½ and 4 h after D-xylose administration • Interpretation • In healthy horses plasma D-xylose concentration peaks within in 60-120 min of D-xylose administration • Delayed of the D-xylose absorption may reflect delayed gastric emptying, increased intestinal transit time and/or impaired intestinal absorption • The peak concentration and the time of the peak value is dependent in some extent on the length of fasting, diet composition and the laboratory method used