Exam 1 - Colonic Disease Flashcards
what is the function of the colon?
secretion & absorption of water & electrolytes - helps firm up feces
production of mucus
motility - segmentation, peristalsis, & mass transmit
immune surveillance & immune tolerance
why is the ileocolic valve important?
stops back up from colon into ileum - could cause dysbiosis problem
what is the longest part of the colon?
descending colon
why does it take longer to see diarrhea from small bowel causes when compared to large bowel disease?
the large bowel compensates for the small bowel, but in large bowel disease, fairly mild disease can cause diarrhea very quickly
what is the role of the colonic microbiome?
development of mucosal immune system
energy metabolism of epithelial cells - butyrate, need fermentation of butyrate for energy!!
vitamin synthesis (folate, vitamin K, & biotin)
absorption of complex macromolecules
what are some common helminths that cause large bowel disease?
trichuris vulpis & heterobilharzia americanum
what are some common protozoal causes of large bowel diarrhea in cats?
tritrichomonas fetus
giardia intestinalis (small bowel in dogs & large bowel in cats)
what cats are commonly affected by t. fetus?
common in pure bred cats & shelter cats - typically young cats
T/F: some cats infected with t. fetus can be apparently healthy with no clinical signs
true
how is t. fetus diagnosed?
fecal direct smear - lacks sensitivity
in-house culture - sensitivity around ~55%
fecal PCR - most sensitive, gold standard!!
what is the gold standard test for diagnosing t. fetus infection in cats?
fecal PCR
T/F: t. fetus is resistant to metronidazole
true
what is the treatment used for t. fetus infections causing large bowel diarrhea in cats?
ronidazole - 30mg/kg every 24 hours for 2 weeks
what are the adverse effects associated with ronidazole?
neurotoxicity!!
an owner brings in their bengal cat they recently adopted with large bowel diarrhea, this is seen on the fecal - what is it? how do you treat it?
tritrichomonas fetus
ronidazole
what are some fungal/mold causes of large bowel diarrhea?
histoplasma capsulatum, phythium insidiosum, & prototheca zopffi
what bacterial causes commonly cause large bowel diarrhea?
campylobacter, clostridium perfringens, & clostridium difficile
what are the 3 main treatments used for chronic enteropathies of the colon listed in order?
diet trial - if they respond, fiber-responsive colitis
tylosin trial - antibiotic responsive colitis
biopsy then immunosuppressant trial (IBD)
what are your main options for diet trials?
intestinal diets - moderately restricted fat content, omega-3 fatty acid supplementation, & high digestibility
exclusion diets - novel protein sources & hydrolyzed antigen
fiber supplementation - psyllium husk, fructooligosacchararides, & canned pumpkin
what is a more practical term to use instead of dysbiosis?
antibiotic responsive diarrhea
what is dysbiosis?
imbalance in the intestinal microbiota that may be a primary problem or can be secondary to another disease
T/F: not every dog with antibiotic responsive diarrhea has dysbiosis & not every dog with dysbiosis has antibiotic responsive diarrhea but there is overlap
true
what are the proposed mechanisms in which dysbiosis/antibiotic responsive diarrhea can lead to diarrhea & malabsorption?
competition for nutrients is increased
production of secretory stimulants (think e. coli)
decreased brush border enzyme activity
what is the treatment recommended for dysbiosis?
abx - tylosin at 20mg/kg every 12 hours for 4-6 weeks, metro, but know that signs often relapse as soon as meds are stopped
prebiotics - fiber!!!
may try probiotics or potentially a fecal microbiota transplant
T/F: IBD can affect any part of the intestinal tract
true
T/F: it is unusual for IBD to just affect the colon in dogs
true
what is the most common age of onset of IBD? what is the most common clinical sign?
6 years in dogs & cats
diarrhea
what clinical signs are seen in boxers with e. coli associated granulomatous colitis?
large bowel diarrhea +/- weight loss
T/F: in e. coli associated granulomatous colitis, most dogs develop clinical signs prior to 2 years of age
true
what is the treatment for large bowel signs in IBD?
intestinal or elimination diet +/- prebiotics
anti-inflammatory/immunosuppressive drugs with prednisone/prednisolone being your top choice
chlorambucil - add on agent in cats
cyclosporine - add on agent in dogs
sulfasalazine - for large bowel disease in dogs only!!!
what breed of dog is commonly affected by e. coli associated granulomatous colitis?
boxer dogs
what is granulomatous colitis?
granulomatous inflammation with PAS positive macrophages & intralesional bacteria that is caused by e. coli
how is e. coli associated granulomatous colitis diagnosed?
fluorescence in situ hybridization (FISH) & culture
how is e. coli associated granulomatous colitis treated?
enrofloxacin at 10mg/kg every 24 hours for at least 6 weeks
why does enrofloxacin need to be prescribed for at least 6 weeks in dogs with e. coli associated granulomatous colitis?
if the medication is stopped, signs of e. coli associated granulomatous colitis will come back
this biopsy shows a lesion that is caused by e. coli in the colon - what is it?
granulomatous colitis of boxers
neoplasia in the colon is associated with what clinical signs? what finding is commonly detected during a physical exam?
tenesmus & dyschezia, large bowel diarrhea, hematochezia, obstruction, weight loss, & vomiting if the disease is diffus
mass detected on rectal exam or abdominal palpation
what are the most common tumor types seen in the colon of dogs?
adenocarcinoma, lymphoma, gi stromal tumors, & benign adenomas/polyps/leiomyomas (less common)
T/F: large intestinal tumors are more common than gastric & small intestinal tumors
true
what are the most common tumor types seen in the colon of cats? what is the general risk of metastasis?
adenocarcinoma, lymphoma, & mast cell tumors
high rates of metastasis
____________ intussusception accounts for 2/3 of intussusceptions in dogs & cats, & of these, _________ is the most common
enterocolic
ileocolic
what clinical signs are associated with intussusception?
vomiting, inappetence, diarrhea, +/- abdominal pain - can occur as a complication of acute gi disease
what is seen on physical examination of a patient with an intussusception?
may feel a cylindrical mass in the abdomen, may protrude through the rectum
how do you differentiate an intussusception from a rectal prolapse?
use a thermometer - if prolapsed rectum, you can’t pass it between the prolapse and the anus
in patients with intussusception you can pass it
how is an intussusception diagnosed?
physical exam, target lesion on ultrasound, & surgical exploration
what is the treatment for an intussusception?
surgery - reduce it or R&A
what lesion is seen on this ultrasound image?
ileocolic intussusception
how are some ways in which signalment helps you when creating your differential list for a patient with colonic disease?
patient age - neoplasia is less likely in young animals
young animals are more likely to have infections & dietary intolerance/allergy
breed predispositions - think boxers & the granulomatous colitis
what are the main clinical signs associated with large bowel disease?
diarrhea & constipation
how do you differentiate small & large bowel diarrhea?
small bowel - large volumes of watery diarrhea, normal to mildly increased frequency, no tenesmus or urgency, no mucus, may have melena, & weight loss
large bowel - normal to mildly increased volumes, markedly increased frequency, tenesmus & urgency usually present, mucus frequently present, fresh blood can be present, & weight loss is uncommon
T/F: a sick patient should have a stress leukogram, so the absence of one suggests addison’s disease
true
what diagnostic tests should be done for a patient with large bowel disease?
cbc - look for stress leukogram
chemistry - evaluate patient for systemic disease that can cause diarrhea & also evaluate for consequences of gi disease
ua
what is a zinc sulfate fecal centrifugation useful for? how can you increase its sensitivity?
detecting helminths & other parasites
pool 3 days worth of feces
when is a direct fecal smear useful?
detecting protozoal trophozoites
why is it difficult to interpret a positive bacterial culture for salmonella or campylobacter?
healthy dogs & cats can be colonized by these organisms!!! are they just there or are they actually causing an issue
what is the best testing used for detecting giardia?
IFA antigen testing
why is it hard to establish a causal relationship of clostridium & large bowel diarrhea?
enterotoxin producing strains of clostridium have been found in healthy dogs
what clostridium species have been associated with large bowel diarrhea in dogs?
clostridium perfringens & clostridium difficile - both produce enterotoxins
what aspect of clostridium actually causes the diarrhea?
the enterotoxins cause the diarrhea
what diagnostic test is used for diagnosing phythium?
elisa tests
what diagnostic tests are used for diagnosing heterobilharzia?
fecal sedimentation & fecal PCR
what diagnostic tests are used for diagnosing histoplasmosis as a cause of large bowel diarrhea?
cytology & EIA for antigen in serum or urine
when are survey abdominal rads most useful for patients with gi problems?
better used when the patient has vomiting as well as diarrhea
when is rectal scraping especially useful as a diagnostic tool for animals with large bowel disease?
may be used to detect infectious agents such as histoplasmosis/prothecosis
performed on conscious/mildly sedated dogs
what is the stage 1 in approaching chronic large bowel diarrhea?
rule out parasitism using a fecal float/sedimentation & deworm with fenbendazole (50mg/kg by mouth every 24 hours for 3 days)
do a diet trial with a highly digestible diet
what is the stage 2a in approaching chronic large bowel diarrhea?
rule out systemic disease - not often seen with large bowel diarrhea - CBC, chem, UA, FeLV/FIV snap test in cats
what is the stage 2b in approaching chronic large bowel diarrhea?
further fecal testing - look for t. fetus in cats, giardia antigen testing in cats, & may test for heterobilharzia
may do diagnostic imaging - rads/ultrasound
what is the stage 3 in approaching chronic large bowel diarrhea?
therapeutic trials - novel protein or hydrolyzed antigen diet, add soluble fiber to the diet, antibiotic trial with tylosin
+/- probiotics & fecal transplant
what is the stage 4 in approaching chronic large bowel diarrhea?
abdominal ultrasound +/- rads if they haven’t been done yet
intestinal biopsy for upper & lower gi tract or surgical biopsy (not commonly done on the colon)
what is the stage 4 in approaching chronic large bowel diarrhea?
abdominal ultrasound +/- rads if they haven’t been done yet
intestinal biopsy for upper & lower gi tract or surgical biopsy (not commonly done on the colon)
what is constipation?
infrequent or difficult evacuation of feces
what is obstipation?
intractable constipation that is refractory to treatment
what is megacolon?
abnormal dilation of the colon resulting from constipation or obstipation
what is dilated megacolon?
end stage disease due to the loss of motility
what is hypertrophic megacolon?
megacolon due to obstruction that is potentially reversible
what are some obstructional causes of constipation?
luminal mass, mural mass, extra-mural issue
T/F: painful defecation can be a cause of constipation
true - anal fistulas
what are the 2 categories of neuromuscular causes of constipation?
primary & secondary
what is the most common cause of constipation in cats?
idiopathic megacolon
what is the general approach that should be taken for an animal that presents with constipation?
rule out drugs that reduce gi motility
rule out metabolic disease - CBC, chem, urinalysis, & TT4
rule out obstruction - abdominal rads, +/- u/s, biopsies
what medications are used for treatment for constipated patients?
hyperosmotic laxatives - lactulose or miralax
colonic prokinetics - cisapride (need to have it compounded!!)
what therapies are used for patients that are constipated?
removal of impacted feces - rectal suppositories, enemas, & manual extraction
surgery
what patients are colectomies reserved for?
cats that are refractory to medical management - try to preserve the ileocolic valve
