aspects of gastric secretions Flashcards by mohamed nascer

what are the main constitutes of gastric secretions?

HCL —> parietal cells –> triggered by gastrin

Pepsinogen —-> chief cells

Intrinsic factor ——> required from B12 absorption from parietal cells too ( glycoprotein )

Alkaline mucous —-> from mucous cells

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what are properties of gastric secretion ?

20-50 ml

colorless - pale yellow

1.6-4.8 acidic

0-40 mmol/l

10-50 mmol/l

has pepsin

has mucin

has intrinsic factor

bile might be present in the gastric secretion as a normal component

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hyposecretion of gastric juices can occur with which diseases ?

Pernicious anemia

extensive carcinoma of the stomach

chronic gastritis

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what happens to gastrin level in hyposecretion of gastric juices?

Gastrin level are expected to rise because of the reduced acid secretion causes the loss of the negative feedback inhibition

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what are the conditions that are investigated by clinical biochemistry ?

GERD

peptic ulcer

vitamin B12 deficiency

gastrinomas —> zollinger elison syndrome

effectiveness of vagotomy

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describe GERD?

backflow of acid and stomach content into esophagus

occur when stomach acid frequently flow back into the tube connecting mouth and stomach ( Esophagus )

this backwash can irritate the lining of esophagus

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what are the common signs and symptoms of GERD?

burning sensation in chest ( HEARTBURN ) usually after eating which might be worse at night

chest pain

difficulty swallowing

vomiting of food or sour liquid

sensation of a lump in throat

if theres a night time acid reflux this also cause chronic cough

new or worsening asthma

disrupted sleep

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describe PH monitoring ( it is confirmatory for gerd )?

Inserting a naso-esophageal catheter with acid sensitive tip

performed during fasting

the catheter stay in the nose for a period of 24 hours while the patient performs normal daily routine

preparations :

fasting 4-6 hours prior the appointment

Stop proton pump inhibitors , H2 blockers and antacids

Advanced method : for PH measuring is the wireless PH testing —> Radiotelemetry PH sensing capsule to the mucosa of the distal esophagus

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what are the benefits of endoscopy?

endoscopy can help confirm the diagnosis of reflux by demonstrating complications of reflux —> esophagitis , barrets esophagus

can help evaluate the anatomy –> hernia, masses, etc

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what is manometry?

diagnostic procedure used to measure pressure at GIT and esophagus

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what are the uses of manometry?

evaluate muscle and sphincter function helping diagnosing motility disorders

assessing lower esophageal sphincter ( LES ) pressure for surgical planning

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describe ulcer?

peptic ulcer is a sore on the lining of the stomach , small intestine or esophagus

peptic ulcer in stomach ——> gastric ulcer

duodenal ulcer is a peptic ulcer that develops in the first part of the small intestine ( duodenum )

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describe peptic ulcer caused by helicobacter pylori ?

one of the peptic ulcer causes is helicobacter pylori infection

the infection worsens the stomach mucosal lining by causing inflammation which results in disruption of mucous layer —-> allow HCL and pepsin to cause damage producing ulcerations

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what enzyme does H pylori secrete?

Urease

which will convert urea to ammonia and CO

ammonia will neutralize the acid allowing the bacteria to survive

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where does the urea come from ?

urea normally produced from catabolism of amino acids and then it is secreted in the urine ( urea cycle in the liver )

small amount of the urea in the stomach will come from blood capillaries to the lumen of the intestine /stomach —> h.pylori will hydrolyze this urea to form ammonia

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what are the non invasive tests for h. pylori ?

Urea breath test ( UBT )

serological helicobacter pylori igG antibody

fecal helicobacter pylori antigen

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describe the urea breath test ?

patients are given C13 ( CARBON ISOTOPE ) labelled urea with a fruit drink or a capsule

the breath sample is taken after 30 minutes

high concentration of labelled C13 in CO2 indicates presence of H . pylori in gastric mucosa

what is gastrin?

gastrin is a peptide hormone from G cells in the pyloric antrum of the stomach , duodenum and the pancreas .

what is the function of gastrin?

stimulate the secretion of gastric acid (HCL )–> parietal cells

aid in gastric motility

how can we measure peptide hormones?

ELISA technique : blood sample antigen antibody interactions

what is the most common reason for measuring gastrin in the plasma?

gastrinoma ————->zollinger ellison snydrome

what is zollinger ellison syndrome?

gastrin secreting neoplasm located in pancreatic islets

very high secretion of gastrin 60% + compared to basal secretion

usually part of MEN1

what could result from high gastrin level?

high gastrin, stimulates HCL causing ulcers

describe measuring gastric acid?

level of gastric acid secretion differ in various disease states and their measurements may help in the diagnosis and treatment of these disease

high levels of acidity are seen in ———–> duodenal ulcer and patients with zollinger- ellison syndrome

low acid output —> predispose to enteric infection like E.coli and V. cholerae cuz acid protects from infecitons

Low or absent acid secretion —> found in pernicious anemia , atrophic gastritis and gastric carcinoma

what are the 2 tests we use to measure basal and stimulated acid secretion?

Two types of gastric acid output : Basal gastric acid output (BAO ) Post stimulation ( maximum acid output- MAO ) measures volume, acidity , pH. etc

describe measuring gastric acid basal output ( BAO )?

basal acid output BAO represents the output of a fasting , unstimulated stomach the level of BAO can fluctuate diurnally , even hourly and its obtained by aspiration of gastric acid for an hour from a fasted stomach ( every 15 minutes )

describe the process of measuring gastric basal acid output ( BAO )?

overnight fast intubation collect secretion every 15 minutes for 1 hour as base line ( base acid output )

describe post stimulation ( maximum acid output- MAO )?

collect secretion every 15 minutes for 1 hours following a pentagastrin administration ( 6mg/kg subcutaneously ) Measure the volume . PH. acidity by titration and calculate the total acidity in the total volume for the basal and the stimulated samples

what is pentagastrin ?

organic molecular entity Synthetic pentapeptide that mimics the actions of endogenous gastrin work by stimulating the secretion of gastric acid , pepsin and intrinsic factor ( similar to the action of gastrin ) has been used as a diagnostic aid it is similar to gastrin

describe the normal results of basal acid output?

normal : Up to 5 mEq/hour Ulcer will have -----> 5-15 mEq/hour Zollinger- ellison syndrome ----> more than 20 mEq/hour

what is the Basal acid out seen in gastric ulcer and duodenal ulceR?

normal basal acid output is found in gastric ulcer and some patient with duodenal ulcer

describe the results of maximum acid output?

in normal patients ---> 1-20 mEq/hour in ulcer patients ----> 20-60 mEq/hour Zollinger - ellison syndrome ------> more than 60 mEq/hour

What is the acid ouput in Achlorhdria?

0 mEq/hour

how is achlorhydria diagnosed?

only when there is no free HCL even after maximum stimulation

what happens to acid output in pernicious anemia?

there is no acid output due to gastric mucosal atrophy

describe b12 deficiency?

intrinsic factor is a glycoprotein that is needed for B12 absorption from the terminal ileum it is secreted by the parietal cells of the stomach damage to stomach ---> pernicious anemia ---> no intrinsic factor ---> no b12 absorption

what are the causes of intrinsic factors?

impaired IF production can occur in adults due to autoimmune destruction of parietal cells, which secrete IF : pernicious anemia gastrectomy can significantly reduce the productions of IF Rare congenital autosomal recessive disorders can result in deficiency of IF without gastric atrophy Atrophic gastritis

what are the two types of intrinsic factors antibodies in pernicious anemia?

Type 1- Intrinsic factor blocking antibodies ---> block the binding site on intrinsic factor for vitamin B12 Type 2- intrinsic factor binding antibodies ----> target different site on intrinsic factor and prevent the intrinsic factor and vitamin B12 complex from attaching to the binding sites in small intestine ( SO THE COMPLEX CANT BIND TO SMALL INTESTINE )

what is vagotomy ?

surgical operation in which one or more branches of vagus nerve are cut typically to reduce the rate of gastric secretions ( treating peptic ulcer ) cuz the process of releasing acids and HCL is under control of gastrin and vagus nerve

how do you know if vagotomy was successful ?

post vagotomy insulin test

describe post vagotomy insulin test?

when insulin is administered , it induces hypoglycemia ----> which normally trigger vagally mediated gastric acid secretion gastric secretion and total acid will be collected and measured after insulin administration in a successful vagatomy, the acid secretion will be reduced of absent if gastric acid secretion persists , it suggests an incomplete vagotomy the tests requires careful monitoring of the blood glucose level and should be performed under controlled conditions to manage the risks associated with induced hypoglycemia after a successful vagotomy there is no response and acid level is very low