Lab Eval of GI Disease - Dr. Summers

Question 1

What are indications for in-depth diagnostics based on history and PE?

Answer 1

hematemesis/ bloody stools
chronicity/ failure of symptomatic tx
abdominal pain
fever, tachycardia, respiratory probs, adominal distention, prolonged anorexia, melena, abnormal mucous membranes

Question 2

What should we consider when making a ranked differential list

Answer 2

history, signalment, PE findings, acute (less than 14d or chronic more than 3 weeks) , whether p has small or large bowel diarrhea

Question 3

What are common CBC findings of primary GI disease?

Answer 3

eosinophilia (wbcs)
Anemia (low hemoglobin or hematocrit)

Question 4

What are our top differentials for eosinophilia?

Answer 4

parasitic causes or eosinophilic gastroenteritis (form of IBD)

Question 5

What is a suspected cause of a mild normocytic normochromic non regenerative anemia?
(reduced total # of RBCs)

Answer 5

an anemia of chronic disease
remember that any source of infection in the body can suppress the immune system

Question 6

What type of anemia can we expect with acute blood loss?

Answer 6

mild to severe macrocytic hypochromic regenerative anemia

Question 7

What type of anemia can we expect with chronic blood loss?

Answer 7

iron deficiency anemia
mild to severe microcytic hypochromic nonregenerative anemia
remember hypochromic= not much hemoglobin

Question 8

You see an elevated BUN value on your patients biochemistry profile, what GI disease should you consider?

Answer 8

An overt GI bleed - HUGE

Question 9

What are the three differentials for hypocholesterolemia?

Answer 9

think malabsorptive and maldigestion
-GI disease
-Liver dz
-Addisions

Question 10

What should you always look for in a patient with panhypoproteinemia?

Answer 10

almost always GI disease.
hypoalbuminemia and hypoglobulinemia

PROTEIN LOSING ENTEROPATHY

Question 11

What are causes of hypochloremia?

Answer 11

vomiting- loss of HCl from GI contents
Diarrhea- secretory (Cl- secretion)
ex of dz: bacterial endotoxins

Question 12

What are causes of hypokalemia?

Answer 12

decreased intake (p is anorexic)
vomiting (bc loss of Cl- enhances K+ excretion in kidneys!)
secretory or exudative diarrhea (bc we have a loss of electrolyte rich fluid

Question 13

What are differentials for hypochloremic metabolic alkalosis?
(pH: over 7.45)

Answer 13

-loss of hydrogen chloride (i.e. loss of acid, think severe acute vomiting), therefore the body retains bicarbonate to maintain electroneutrality
-severe vomiting: Upper GI obstruction or GI stasis (stomach loses all motility)

Question 14

What are some differentials for Hyperchloremic metabolic acidosis?

Answer 14

-Loss of bicarbonate! (the body retains chloride with hydrogen to maintain electroneutrality
-GI causes: diarrhea (MOST COMMON), vomiting pancreatic/intestinal secretions rich in bicarb (cause is distal to the pancreatic duct)

-think about causes on the butt end of the animal

Question 15

Why is it uncommon to test for bacterial enteropathogens such as: Clostridium perfringens, clostridium difficule, campylobacter jejuni, salmonella and Escherichia Coli?

Answer 15

bc these are all normal flora that are found in pets w/o diarrhea. there are only specific strains that are problematic

Question 16

What are some clinical signs that may be associated with an enteropathogen?

Answer 16

mild and self limiting to acute hemmorhagic diarrhea, fever, melasie, vomiting

Question 17

What is required to diagnose C. perfringens-associated diarrhea?

Answer 17

PCR detection of C. perfringens enterotoxin genes

Isolation alone via culture/pcr alone is NOT enough to dx!

Question 18

What does diagnosis of Clostridium difficile require?

Answer 18

I need a positive result for both:
organism detection (culture, antigen ELISA, PCR) AND Toxin A and B detection via ELISA/ PCR

Question 19

How do I diagnose campylobacter and Salmonella? Why?

Answer 19

fecal culture or PCR- it is important to look at the clinical picture. These bacteria do NOT produce enterotoxins!

Question 20

When should I consider testing for a bacterial enteropathogen?

Answer 20

dogs/cats w/ acute onset of bloody diarrhea
dogs/ cats w/ diarrhea + a fever
diarrhea outbreaks in multiple animals and or people (densely populated shelter or kennel)
chronic diarrhea cases that have failed to respond to therapy

Question 21

What does Fluorescent in situ hybridization detect and what is it used to diagnose?

Answer 21

used to detect enteroinvasive E.Coli
used to diagnose granulomatous colitis! (aka boxer colitis)

e.coli invades the villi and can be found within the mucosa

Question 22

What are you looking to ID with giardia?

Answer 22

cysts

Question 23

What are you looking to ID in tritrichomonas?

Answer 23

trophozites

Question 24

What are you looking to ID in helmiths?

Answer 24

ova

Question 25

How can you rule out a parasitic cause?

Answer 25

you need to test multiple fresh fecal samples

Question 26

If you suspect giardia or tritrichomonas foetus what diagnostic test would you use?

Answer 26

stained fecal smear bc you can ID protozoan oocytes and trophozoites

Question 27

What should I check my sample for before staining my fecal stain?

Answer 27

motile trophozoites

Question 28

What is a drawback to stained fecal smears?

Answer 28

they have low sensitivity therefore you need PCR if you don’t see anything bc of the high rate of false negatives

Question 29

If I suspected my patient had giardia, roundworms or hookworms, what diagnostic test would I use?

Answer 29

Fecal flotation w/ centrifugation bc it can detect giardia cysts and a lot of helminths

Question 30

What is the preferred test to look for trematode ova (Heterobilharzia)

Answer 30

fecal sedimentation - they can detect helminth ova

Question 31

If I am concerned about giardia or/or cryptosporidium, what should I order to detect the fecal antigen?

Answer 31

Giardia and Cryptosporidium ELISA or IFA because it has high sensitivity and specificity

Question 32

What are my test options if I am worried about my patients cat having tritrichomonas foetus?

Answer 32

visualization of trophozoite on direct -wet mount
-pouch TF culture
Fecal PCR

Question 33

Where is serum folate absorbed?

Answer 33

(vitamin B9) is absorbed in the PROXIMAL small intestine by folate carriers

Question 34

What leads to hypofolatemia?

Answer 34

chronic proximal intestinal disease (duodenal disease)

Question 35

What is elevated serum folate concentrate a marker of?

Answer 35

dysbiosis
THIS DOES NOT MEAN TX WITH antibiotics

Question 36

When does hypocobalaminemia occur?

Answer 36

-chronic distal SI dz (ileum dz) bc of decreased absorption
-exocrine pancreatic insufficiency - we aren’t producing the intrinsic factor that B12 needs to be bound to be absorbed
-Small intestinal dysbiosis
-surgical removal of ileum

Question 37

Do normal serum folate and cobalamin concentrations allow us to exclude chronic GI disease?

Answer 37

NO.
(remember you need patients fasted to obtain a serum sample for testing)