Lab Eval of GI Disease - Dr. Summers Flashcards
What are indications for in-depth diagnostics based on history and PE?
hematemesis/ bloody stools
chronicity/ failure of symptomatic tx
abdominal pain
fever, tachycardia, respiratory probs, adominal distention, prolonged anorexia, melena, abnormal mucous membranes
What should we consider when making a ranked differential list
history, signalment, PE findings, acute (less than 14d or chronic more than 3 weeks) , whether p has small or large bowel diarrhea
What are common CBC findings of primary GI disease?
eosinophilia (wbcs)
Anemia (low hemoglobin or hematocrit)
What are our top differentials for eosinophilia?
parasitic causes or eosinophilic gastroenteritis (form of IBD)
What is a suspected cause of a mild normocytic normochromic non regenerative anemia?
(reduced total # of RBCs)
an anemia of chronic disease
remember that any source of infection in the body can suppress the immune system
What type of anemia can we expect with acute blood loss?
mild to severe macrocytic hypochromic regenerative anemia
What type of anemia can we expect with chronic blood loss?
iron deficiency anemia
mild to severe microcytic hypochromic nonregenerative anemia
remember hypochromic= not much hemoglobin
You see an elevated BUN value on your patients biochemistry profile, what GI disease should you consider?
An overt GI bleed - HUGE
What are the three differentials for hypocholesterolemia?
think malabsorptive and maldigestion
-GI disease
-Liver dz
-Addisions
What should you always look for in a patient with panhypoproteinemia?
almost always GI disease.
hypoalbuminemia and hypoglobulinemia
PROTEIN LOSING ENTEROPATHY
What are causes of hypochloremia?
vomiting- loss of HCl from GI contents
Diarrhea- secretory (Cl- secretion)
ex of dz: bacterial endotoxins
What are causes of hypokalemia?
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
What are differentials for hypochloremic metabolic alkalosis?
(pH: over 7.45)
-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)
What are some differentials for Hyperchloremic metabolic acidosis?
-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
Why is it uncommon to test for bacterial enteropathogens such as: Clostridium perfringens, clostridium difficule, campylobacter jejuni, salmonella and Escherichia Coli?
bc these are all normal flora that are found in pets w/o diarrhea. there are only specific strains that are problematic
What are some clinical signs that may be associated with an enteropathogen?
mild and self limiting to acute hemmorhagic diarrhea, fever, melasie, vomiting
What is required to diagnose C. perfringens-associated diarrhea?
PCR detection of C. perfringens enterotoxin genes
Isolation alone via culture/pcr alone is NOT enough to dx!
What does diagnosis of Clostridium difficile require?
I need a positive result for both:
organism detection (culture, antigen ELISA, PCR) AND Toxin A and B detection via ELISA/ PCR
How do I diagnose campylobacter and Salmonella? Why?
fecal culture or PCR- it is important to look at the clinical picture. These bacteria do NOT produce enterotoxins!
When should I consider testing for a bacterial enteropathogen?
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
What does Fluorescent in situ hybridization detect and what is it used to diagnose?
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
What are you looking to ID with giardia?
cysts
What are you looking to ID in tritrichomonas?
trophozites
What are you looking to ID in helmiths?
ova
How can you rule out a parasitic cause?
you need to test multiple fresh fecal samples
If you suspect giardia or tritrichomonas foetus what diagnostic test would you use?
stained fecal smear bc you can ID protozoan oocytes and trophozoites
What should I check my sample for before staining my fecal stain?
motile trophozoites
What is a drawback to stained fecal smears?
they have low sensitivity therefore you need PCR if you don’t see anything bc of the high rate of false negatives
If I suspected my patient had giardia, roundworms or hookworms, what diagnostic test would I use?
Fecal flotation w/ centrifugation bc it can detect giardia cysts and a lot of helminths
What is the preferred test to look for trematode ova (Heterobilharzia)
fecal sedimentation - they can detect helminth ova
If I am concerned about giardia or/or cryptosporidium, what should I order to detect the fecal antigen?
Giardia and Cryptosporidium ELISA or IFA because it has high sensitivity and specificity
What are my test options if I am worried about my patients cat having tritrichomonas foetus?
visualization of trophozoite on direct -wet mount
-pouch TF culture
Fecal PCR
Where is serum folate absorbed?
(vitamin B9) is absorbed in the PROXIMAL small intestine by folate carriers
What leads to hypofolatemia?
chronic proximal intestinal disease (duodenal disease)
What is elevated serum folate concentrate a marker of?
dysbiosis
THIS DOES NOT MEAN TX WITH antibiotics
When does hypocobalaminemia occur?
-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
Do normal serum folate and cobalamin concentrations allow us to exclude chronic GI disease?
NO.
(remember you need patients fasted to obtain a serum sample for testing)
