Disorders of Gastric Secreation Flashcards
What the stomach secreates
- Acid
- Intrinsic Factor
- Pepsinogens
- Lipase
- Bicarbonate/Mucous
Causes of Elevated Acid Secretion
• Elevated gastrin • Elevated vagal tone • Elevated histamine (mastocytosis, basophilic granulocytic leukemia) • Elevated parietal cell mass/idiopathic • Paraneoplastic (non-gastrin: rare)
• Expected response to reduced delivery
of acid to antrum
– Antral pH elevated
increased gastrin
What does it mean when we see elevated gastrin levels when pH is <2?
Elevation independent of antral
acidification; naughty, naughty!!
• Syndrome resulting from clinical consequences of hypersecretion of gastric acid due gastrin secreting neuroendocrine tumor
Zollinger-Ellison Syndrome
Zollinger-Ellison Syndrome causes
– Isolated gastrinoma (75%)
– As component of Multiple Endocrine Neoplasia I (MEN I [25%])
Diagnostic features of Zollinger-Ellison Syndrome in regards to:
Basal acid secreation
Gastrin levels
• Elevated basal acid secretion (15
mEq/hr)
• Gastrin > 150 pg/ml (Nl < 100)
– > 1000 pg/ml diagnostic with low pH
What’s weird about secretin in Zollinger-Ellison syndrome>
• Secretin stimulation: Gastrin
increases > 120 pg/ml (usually secretin inhibits gastrin!)
Pts on this type of medication can get a false negative test for ZE syndrome
PPI
ZE syndrome in this presents as a single gastrinoma, – Localize and remove for cure
– Typically in duodenum/pancreas
Sporadic type
ZE syndrome; multifocal, not curable
– Associated hyperparathyroidism,
other islet cell tumors, pituitary
tumors
MEN1 type
In more severe ZE syndrome, ulcers are in what area?
What can we do for treatement?
– Extends to distal duodenum/jejunum
– Relapsing ulcer, high PPI dose to cure
What is diarrhea like in severe ZE syndrome?
Large acidic fluid volume
– Inactivation of pancreatic enzymes
– Hypokalemia, steatorrhea, weight loss
Random causes of elevated Gastrin secreation
- H. pylori (via reduced somatostatin)
- Antral G-cell hyperplasia
- Gastric outlet obstruction
- Retained antrum (gastric surgery)
- Cysteamine treatment
- Short bowel syndrome
- Renal failure (rare)
Conditions Causing Low
Acid Secretion
• Medications – PPI, H2RA, anti-cholinergic • Inflammatory destruction of parietal cells (gastritis) • Acute H. pylori infection • Vagal injury/transection • VIP producing tumors
Consequences of low acid secraetion
• Overall well tolerated with modern diet; impaired protein digestion • Impaired absorption of Fe, Ca, B12 • Gastric bacterial overgrowth • Enteric infections/tuberculosis • Small bowel bacterial overgrowth • Impaired delivery of certain drugs
Carrier glycoprotein that binds to
Vitamin B12 to permit active
transport in ileum
• Produced by parietal cell
IF
Conditions affecting____ secretion
affect IF secretion
acid
What test do we use to test for Vit B 12 deficieny
Schilling test
Give pt radiolabelled Vitamin B12 orally and measure it; if its low, give it along with IF, if it corrects, what does this tell us?
issue with IF
Give pt radiolabelled Vitamin B12 orally and measure it; if its low, give it along with IF; it if doesn’t correct, what is the next step?
repeat after empiric antibiotic treatment for SBBO; if corrects we know its bacterial issue
if pt does schilling test and was tx for SBBO but still has low vit B12, what is our diagnosis?
pancreatic insufficiency
or terminal ileal disease
Cause of reduced pepsin or lipase secreation
the same things that lower acid secreation
Affect of low pepsin and lipase on inidivual
• Perhaps less important for
digestion with modern diet
• Play a role in killing ingested
infectious agents
Cause of decreased bicarb/mucous secreations
same as those that cause low acid secreation AND from NSAID/aspirin use
consequence of low bicarb, mucous?
mucosal injury
