GI/Pancreas Flashcards
What is the difference between dog’s and cat’s esophagus?
Dog: 100% striated muscle
Cat: only upper 2/3 are striated muscle, the rest 1/3 is smooth muscle
What can cause the resting membrane potential less negative (more easily excitable) in GI tract? What can cause it to be more negative (harder to depolarize)?
Less negative
- stretch of the smooth muscle
- stimulation by acetylcholine released from the endings of parasympathetic nerves
- stimulation by several specific gastrointestinal hormones
More negative
- catecholamines
- stimulation of sympathetic nerves
What are the enteric nerve system composed of? And what are their functions?
Myenteric plexus - control the GI movement
Submucosal plexus - control the local blood flow and GI secretion
List 5 different enteric neurotransmitter/hormone substances
Substance P
Vasoactive intestinal peptide
Acetylcholine
Dopamine
Cholecystokinin
Somatostatin
Adenosine triphosphate
Norepinephrine
Serotonin
Nitric oxide
Which parts of the GI system dose vagus nerve innervated?
esophagus, stomach, small intestines, pancreas, first half of the large intestines
- The second half of large intestines and anus are innervated by pelvic nerves
Where is cholecystokinin secreted and what are its functions?
I cells of the duodenum, jejunum and ileum
It stimulates pancreatic enzymes and bicarb secretion, GB contractions, and inhibits gastric emptying
Where is gastrin secreted and what are its functions?
G cells in the gastric antrum
It stimulates gastric acid secretion and growth of the gastric mucosa
Where is motilin secreted and what is its functions?
M cells of stomach and upper duodenum during fasting
It increases GI motility
Why are the GI villi vulnerable to ischemia?
Because of the countercurrent blood flow of the arterioles and venules in the villi.
Most of the oxygenated blood (~80%) diffused from the arterioles to the venules without reaching the tip of the villi.
Fill out the blank about the gastric secretion.
True or False: Pepsinogen in the stomach can only become active in acidic environment.
True
Under acidic environment, pepsinogen is activated to form active pepsin and has proteolytic effect.
How does the body control gastric acid secretion?
Food goes down to antral end of the stomach → stimulates G cells secrete gastrin → gastrin reach the ECL cells in the oxyntic glands (gastric glands) → stimulates histamine release →histamine stimulate parietal cells secrete HCl
What are the pancreatic enzymes for proteins, carbohydrates and fat digestion?
Proteins: trypsin, chymotrypsin, carboxypolypeptidase
Carbohydrates: pancreatic amylase
Fat: pancreatic lipase, cholesterol esterases, phospholipase
What is the enzyme that activates the trypsinogen?
Enterokinase (secretes by the intestinal mucosa)
How does pancreas prevent self-digestive under normal condition?
The pancreatic cells that secrete proteolytic enzymes also secrete trypsin inhibitor at the same time to prevent activation of trypsin inside the pancreas
What are the three basic stimuli for pancreatic secretion?
Acetlycholine
Cholecystokinin
Secretin (make pancreas secretes lots of water and bicarbs by pancreatic duct epithelium)
True or False: only 50% of bile salts undergo enterohepatic circulation.
False
94% of bile salts go through enterohepatic circulation.
List the compositions of the bile
Water
Bile salt
Bilirubin
Cholesterol
Bicarb
Electrolytes
Fatty acids
Lecithin
What is the precursor of bile salt?
Cholesterol
What is the life span of an intestinal epithelial cell?
2-5 days
Where does the vomiting center locate?
Medulla oblongata of the brainstem
Muscarinic receptors
Where does the chemoreceptor trigger zone locate?
Area postrema of the floor of 4th ventricles (no BBB)
D2 receptors
5-HT3 receptors
What is the difference in the pathway of vestibular-induced vomiting between dogs and cats?
In dogs, the signal transmits from the vestibular system to the CRTZ zone and then to the vomiting center; in cats, the signal directly transmits from the vestibular system to the vomiting center
How can you determine intestinal dilation via x-rays in dogs and cats?
Dogs: diameter of the small intestine should be less than 1.6x of the height of L5 vertebral body at its narrowest point.
Cats: no bigger than 12mm or less than 2x of the height of L4 vertebral body
Where do enterochromaffin cells locate and what do they do?
They locate in small intestines and secrete serotonin (5-HT) in response to mechanical or chemical stimuli → regulates intestinal secretion and motility
What is the MOA of maropitant?
Neurokinin-1 (NK-1) receptor antagonist
It blocks the substance P to the NK-1 receptors in the CNS and GI tract.
What is MOA of ondansetron?
Selective 5HT-3 receptor antagonist
It blocks CRTZ and vagal nerve endings in the GI tract.
- The serotonin receptor in the vomiting center is 5HT-1
What is the MOA of metoclopramide?
D2 antagonist (CRTZ zone), 5HT-3 antagonist (mild), 5HT-4 agonist (for the prokinetic effect)
What is the proposed pathophysiology of extrapyramidal effect from metoclopramide?
A striatal D2 receptor blockade
Clinical signs: involuntary or uncontrollable movements. tremors. muscle contractions
Treatment: d/c metoclopramide, give antihistamine/anticholinergic drugs
What is the MOA of cisapride?
5HT-4 agonist →Increases acetylcholine at the myenteric plexus
What is the MOA of erythromycin for its prokinetic effect?
Motilin receptor agonists
Works for canine colon motility but not feline
What is the MOA of omeprazole and pantoprazole?
Proton-pump inhibitor (PPI) → irreversibly inhibits the H+/K+ ATP pumps in the gastric gland
What is MOA of sucralfate
1) antipeptic effect - absorb pepsin
2) form a barrier at the mucosal surface
3) increases mucus viscosity
For dogs with GDV, which arteries are most commonly lacerated and lead to hemoabdomen?
Short gastric arteries
Name the vessels.
- Splenic artery
- Short gastric arteries
- Lt. gastroepiploic artery
- Lt. gastric artery
- Rt. gastric artery
- Celiac artery
What are the 5 types of techniques for gastropexy?
- Incisional
- Belt-loop
- Circumcostal
- G-tube placement
- Gastrocolopexy
- Endoscopy assisted
What is the key component of successful gastropexy?
Make sure the incisions on the gastric serosa and peritoneal wall both reach the muscular surface.
Describe how to perform an incisional gastropexy.
- Make a midline incision on the ventral abdomen and enter the abdomen.
- Identify the gastric antrum and where it is expected to joint on the peritoneum, which should be right lateral or right ventral lateral peritoneum which is 2-3 cm caudal to the last rib.
- Make a 4 cm seromuscular incision at the gastric antrum either parallel or perpendicular to the gastric long axis
- Make a second 4cm incision on the peritoneum and transversus abdominis muscle.
- Appose both incisions with 2-0 monofilament absorbable sutures in a simple continuous suture pattern, beginning with the craniodorsal edge of the incision
- Close the abdomen
Describe esophagostomy tube placement.
- Patient is anesthetized and endotracheally intubated, and positioned in right lateral recumbency.
- The left cervical area is clipped and surgically prepped.
- The operator measures the esophagostomy tube from the left mid cervical area to the 7-9th intercostal space and make a mark on the tube.
- The assistant inserts a Carmalt forceps from oral cavity into the esophagus until the tip reaches the mid cervical esophagus, and the assistant tents skin with the tip of forceps
- The operator (with sterile gloves) use a #10 or #11 scalpel blade to make a incision through the skin, connective tissue and esophageal wall so that the tip of the forceps can push through
- Place the esophagostomy tube in between the forceps tip and allow the forceps to hold the end of the tube.
- Pull the tube back to the oral cavity with the forceps and then re-insert the tube into the esophagus. At the same time gently manipulate the other end of the tube to facilitate the placement.
- Once the entire to is in the esophagus, the direction of the part of the tube that exit the left mid cervical esophagus will flip from caudal to cranial. Make sure the tube is inserted to the pre-measured depth
- Place a purse-string suture around the tube entrance on the left cervical area.
- Place a finger trap suture at the base of the tube at where it enters the skin to secure it.
- Take x-rays to confirm tube placement.
Describe the NG tube placement.
- Apply proparacaine into the nostril 15 min prior to tube placement.
- Measure the NG tube from the tip of the nose till the last rib.
- flush the NG tube with saline and apply lubricant on the tube
- Keep patient’s head in natural position. Insert the NG tube into the nostril at medial-ventral direction. Assist the tube insertion direction by pushing the nose dorsally (piggy-nose).
- Once the tube reach the pre-measured mark. Remove the stylet. Secure the tube with suture or tape and staples.
- Take x-rays from the nose to the stomach to confirm tube placement.
After a gastrotomy tube is placed, how long should you wait until you can feed the animal and why?
12-24 hours; have to wait for fibrin formation to seal the stoma
- A permanent stoma will form in 7-14 days
What is Cullen’s sign?
Periumbilical ecchymosis → usually associated with peritoneal or retroperitoneal hemorrhage
During abdominocentesis, which patient position is the most ideal position to avoid puncture of the spleen?
Left lateral recumbency
Describe diagnostic peritoneal lavage
- Position the patient in left lateral recumbency.
- Surgically clip and clean the midline. Insert a catheter and remove the stylet. Attach a syringe to the catheter
- Insert 22ml/kg warm sterile normal saline in a drip set into the abdomen.
- Gentle massage and rotate the patient.
- Aspirate the fluid back from the syringe
In the study published by Zacher et al in 2010 about lactate measurement in patients with GDV, what kind of changes in lactate were associated with better survival and fewer complications?
Initial lactate < 4 mmol/L and/or > 40% reduction after fluid resuscitation
Reference: Zacher LA, Berg J, Shaw SP, Kudej RK. Association between outcome and changes in plasma lactate concentration during presurgical treatment in dogs with gastric dilatation-volvulus: 64 cases (2002-2008).J Am Vet Med Assoc. 2010;236(8):892-897.
What are the examples of protein-losing enteropathy?
Eosinophilic bowel disease
Lymphocytic-plasmacytic bowel disease
Lymphangiectasia
Diffuse intestinal fungal disease
Intestinal neoplasia
How do NSAIDs cause GI ulcer & GI bleed?
NSAIDs inhibit COX pathway, and therefore inhibit biosynthesis of prostaglandins from AA. Prostaglandins protect upper GI from mucosal damage (by inhibit gastric acid secretion, stimulate mucus and bicarb secretion)
True or False: The canine esophagus is comprised almost exclusively of striated muscle, so metoclopramide and cisapride have no beneficial effect.
True
Metoclopramide and cisapride are smooth muscle prokinetic agents
What type of virus is parvovirus (DNA vs RNA; enveloped vs non-enveloped)?
non-enveloped DNA virus
True or False: Patients with septic peritonitis and has persistent ionized hypocalcemia during hospitalization was associated with poor prognosis
True (CCM textbook)
What are the predictive values for glucose and lactate in the diagnosis of bacterial peritonitis
Blood glucose is at least 20 mg/dL higher than abdominal effusion glucose
Blood lactate is at least 2.0 mmol/L lower than abdominal effusion glucose
More recently a cut off of 4.2mmol/L lactate in abdominal fluid and a difference in glucose of >2.06mmol/L have been found to be more sensitive and specific
What are the poor prognosis indicators for septic peritonitis?
Refractory hypotension, DIC, respiratory diseases, cardiovascular collapse
Cats: hypothermia and bradycardia
Mortality rates fro bacterial peritonitis in dogs and cats
Dogs: 12.5-56%
Cats: 30-60%
When a blind needle paracentesis is performed, what is the minimal amount of fluid required for the result to be positive?
5.2 - 6.6 ml/kg
When a peritoneal dialysis catheter is used for abdominocentesis, what is the minimal amount of fluid required for the result to be positive?
1.0 - 4.4 ml/kg
Why is BUN less reliable in the diagnosis of uroabdomen?
BUN can easily move across between the peritoneum and blood vessels
What are the diagnostic criteria for uroabdomen in dogs and cats?
Dogs:
- Abdominal effusion creatinine is 2 times higher than plasma creatinine
- Abdominal effusion K is 1.4 times higher than plasma creatinine
Cats:
- Abdominal effusion creatinine is 2 times higher than plasma creatinine
- Abdominal effusion K is 1.9 times higher than plasma creatinine
Where do H2 blockers work on?
Gastric parietal cells
Why H2 antagonist can cause tolerance?
Possible compensatory hypertrophy of ECL cells with hyperproduction of histamine and rebound acidity when H2 abruptly discontinued
Why H2 antagonists should not be combined with PPIs?
PPIs are weak bases, so they need to be in an acidic environment to dissociate and interact with the cysteine residue of the H/K pump
Why PPIs should not be suddenly discontinued?
There is a compensatory hypersynthesis of H/K pumps (as PPIs irreversibly bind)
Drop 50% dose per week, then once a day, then discontinue
Is one PPI better than any other?
Esomeprazole in one study showed better pH control than traditional PPIs but not enough evidence to universally recommend.
Which drugs can be impaired in their absorbtion by concurrent use of PPIs?
- azole antifungals
- iron
- mycophenolate
- clopidogrel (P450 in humans only)
Rank the potency of the following H2 blockers from the most the least:
cimentidine, ranitidine, nizatidine, famotidine
Famotidine > Nizatidine > Ranitidine = Cimentidine
Which of the following H2 blocker does not go through first-pass hepatic metabolism?
cimentidine, ranitidine, nizatidine, famotidine
Nizatidine
Which of the following H2 blocker absorption is delayed by food?
cimentidine, ranitidine, nizatidine, famotidine
Cimentidine
True or False: Ranitidine is excreted in the urine and famotidine is metabolized by liver.
False
Ranitidine is metabolized by liver and famotidine is excreted in the urine