Gastrointestinal Function Biochemical Tests Flashcards
What are the key components of the Gi tract?
Mouth - break down of food and mix will amylase containing saliva
Stomach - churning o food with gastric juice (acid and pepsin)intrinsic factor
Duodenum - bike acids and pancreatic juice
Small intestine - absorption water, salts and nutrients.
Large intestine - absorbs water, salts and B12
What are the 2 processes of the GI tract?
Digestion and absorption
What digestion occurs in the stomach?
Physical - mechanical churning of food to make chyme
Chemical - gastric juice containing acid and pepsin stimulated by gastrin.
The intrinsic factor helps with B12 absorption.
What causes peptic ulcers
Heicobactor pylori and gastronoma
How does helicobactor pylori cause peptic ulcers?
The infection weakens the protective layer of the stomach and allows the stomach acid to attack the cell walls. The helicobactor pylori secretes urease to protect itself. (Urea to ammonia and CO2).
How do you diagnose peptic ulcers from helicobactor pylori?
Urea breath test
How is the urea breath test done?
Patient ingests urea and the pylori if present makes it into ammonia and carbon dioxide. The carbon dioxide is then breathed out and measured.
Alternative H.pylori tests?
Serological tests (patients with H.pylori make antibodies to it and these can be tested - is not helpful in saying the H.pylori is gone.
Faecal antigen testing
Treatment of H.pylori?
histamine antagonists (blocks the release of acid in stomach, protein pump inhibitors and antibiotice
Gastinomas - zolinger Ellison syndrome - what does this do?
Gastrin produces tumours in the pancreas or stomach and stimulates gastric acid production. This increase of gastric acid can produce ulcers. Patients can also have diarrhoea as fat malabsorption does not really happen
Are gastronomes normally malignant?
Yes
How do you diagnose a gastrinoma?
Elevated gastrin or giving IV secretin which produces increased gastrin
Pancreas juice?
Is alkaline (contains tryptase, amylase, lypase, elastase)and is essential for digestion of protein, carbohydrate and lipids.
What is acute pancreatitis commonly associated with?
Gall stones and alcoholism, acute abdominal pain
What is the diagnosis for acute pancreatitis?
Elevated serum amylase level and a CT scan, serum lipase, associated with hypcalcaemia, and raised inflammatory markers CRP
Can occur in other abdominal conditions
Chronic pancreatitis occurs because of what?
Impaired secretion of pancreatic enzymes - malabsorption.
How do you test of chronic pancreatitis?
Bicarbonate, and enzyme activity.
You do a faecal elastase - test to assess exocrine pancreatic dysfunction in chronic pancreatitis
What happens when there is low levels of pancreas specific enzyme in chronic pancreatitis?
Pancreatic insufficiency
What organs aren’t functioning correctly to get malabsorption disease?
stomach,pancreas, hepatobiliary system and small intestine
Does the small intestine have a large surface area and what is this increased by?
It does have a large surface area and Vili increases the surface area
What does malabsorption mean?
Failure of the normal digestion and/or absorption of nutrients
This can be generalised or specific
What are the consequences of malabsorption in the mount?
poor food preparation, poor dentition
Causes of malabsorption in in the stomach?
impaired mixing & digestion, ↓ Intrinsic factor
Malabsorption causes - pancreas, bile salts and structural defects
Pancreatic insufficiency - chronic pancreatitis, CF, gallstones,pancreatic Ca
Bile salt insufficiency – fat malabsorption
Structural defects - Infiltration & destruction/removal of small intestine
Malabsorption causes - mucosal disorders, endocrine, fictitious and what?
Mucosal disorders - Coeliac disease, IBD – decreased absorptive area
Endocrine – hyperthyroidism, hormone secreting tumours
Factitious – laxative abuse
Infective agent
What are the consequences of malabsorption?
Weight loss, Failure to thrive
Abdominal distension
Anaemia
Metabolic bone disease
Diarrhoea
How do yo reach a clinical diagnosis?
Clinical history investigations - family, radiotherapy , previous surgery, peptic ulcers, medication, travel, pancreatic disease or alcohol consumption
What are the biochemical tests in the lab for malabsorption?
FBC, film
Ferritin, B12, folate
LFTs
calcium, magnesium
Glucose
CRP
TFT’s
stool microscopy and culture
What are some more specific lab tests needed for malabsorption?
Tissue transglutaminase antibody test - Coeliac disease
- Faecal calprotectin - Inflammatory bowel disease
- Faecal Elastase - Pancreatic insufficiency
- Laxative screens- Gut Hormone assays
- Urinary 5HIAA - Carcinoid syndrome
What are some anatomical investigations?
Radiology - x-ray
Endoscop
Small bowel biopsy
US of liver an pancreas
CT of pancreas
ERCP of pancreatic and bile duct
What are some nutritional assessments in malabsorption?
Anthropometry:
- weight
- height
-BMI
- waist circumference
- skin fold thickens
- mid arm circumference
Treatments of malabsorptions?
Replace missing nutrients, dietary advice, artificial nutrient transport
What is some nutritional support?
Food supplements
Enteral feeds - nasogastric tube - gastrostomy
Total parenteral nutrition (TPN) - nutrients delivered through blood.
What tests do you use to work out Carbohydrate absorption?
Small bowel histology
Xylose absorption tests - can the intestine metabolise monsacarhides?
Intestinal permeability test (lactulose/rhamnose)
Disaccharide deficiency
Lactase deficiency most common and lactase is highest at birth but decreases with age
what are some symptoms of a disaccharide deficiency?
Nausea, bloating, abdominal pain following intake
What are disaccharide deficiency diseases?
Congenital lactase deficiency – AR – very rare
Primary lactase deficiency – 5-15% North Europeans
Secondary lactase deficiency – due to damaged mucosa (coeliac disease, IBD). May be transient
how do you diagnose disaccharide deficiency?
Symptom, monitoring following response to low dairy diet
What are the amino acid absorption disease?
Hartnup disease - impaired transport of neutral amino acids and deficiency in essential amino acids such as tryptophan.
Cistinuria - cysteine, ornathyne, arginine and lysine are affected and no associated nutritional defect.
How do you diagnose amino acid absorption?
Amino acid chromatography
Fat malabsorption - how do you diagnose this?
Faecal fat test - measure stools for unabsorbed fats over 3-4 days
Triglyceride breath test - digest and absorb 14 C labelled trylin. The 14 C is in the fatty tissue and when absorbed tinted to 14 CO2 and can be exhaled and measured
What are bile salts?
Critical for digestion and absorption of lipids and fat soluble vitamins
What are happens during bile salt malabsorption?
Impaired reabsorption of bile salts = excess delivery into colon and production of toxic secondary bile salts
What do bile salts cause?
Excess colonic secretion and watery, secretory diarrhoea
Causes of bile salt malabsorption?
Gastric surgery, pancreatitis, coeliac disease, diabetes
How do you diagnose Bile salt malsorpiton?
75SeHCAT test - retention of 75 De measured by gamma camera after 7 days
A retention of less than 10 percent is abnormal
- serum cholestenone - intermediate in bile salt synthesis - isn’t really used
What is coeliac disease?
Autoimmune disorder which is triggered by sensitivity to gliadin component of gluten
Exposure to gluten increases T-cell mediated immune response against transglutaminase resulting in damages to cells in small intestine and villous atrophy and malabsorption.
What is coeliac disease associated with?
Other autoimmune disorders such as diabetes or thyroid
What is symptoms of celiac disease?
Tiredness, general malaise, classic malabsorption syndrome
How do you diagnose celiac disease?
igA tissue transglutaminase antibodies
How do yoou get a definitive diagnosis of celiac?
Endoscopy and histologocial examination of intestinal biopsy samples
What is the treatment of Celiac disease?
Strict adherence to gluten free diet
Do all people with negative IgG have celiac disease?
No people are just naturally like this
Inflammatory bowel disease covers what diseases?
Crohns and ulcerative colitis.
What are symptoms of IBD?
Frequent bowel movement
Diarrhoea
Bloody stools
Abdominal pain
failure to thrive or weight loss
How do you check for GI symptoms without being invasive?
calprotectin
What is calprotectin>
Protein released into faeces as result of GI inflammation
Why do we use a calprotectin test?
Non invasive
Cheap
Method for determining whether a patient needs invasive procedures such as a colonoscopy or imaging
Good specificity and sensitively for distinguishing non inflammatory bowel disorders (IBS) and inflammatory bowel disease
When is calprotectin high?
IBD
Cancer of stomach and colon
Polyps
Is calprotectin normal in those with IBS?
Yes
Factitious diarrhoea - how do you test for this?
Laxative screens - urine sample to make sure someone isn’t abusing laxatives
Osmotic stimulants can also cause this when used inappropriately and diagnosed using the faecal osmotic gap
How do you calculate the faecal osmotic gap>
290-2 (Faecal potassium + faecal sodium)
What do gut hormones do?
They have regulatory roles in function of the GI tract.
What would over secretion of gut hormones indicate?
Possible cancer or other clinical diseases
How do you test gut hormones?
Patients should be fasted overnight and stopped taking PPI for 14 days and hydrogen receptors antagonist for 72 hours prior to blood sample being taken.
Gut hormones screen: what does gastrin do?
Stimulates gastric hydrogen production
Gut hormones screen: what does glucagon do?
Gluconeogenesis
Gut hormones screen: what does somatostatin do?
Inhibits GI and exocrine pancreatic secretion
Gut hormones screen: what does pancreatic peptide (PP) do?
Inhibits enzyme release from the pancreas and relaxes the gall bladder
Gut hormones screen: what does vasoactive intestinal polypeptide (VIP) do?
Stimulates secretion of water into pancreatic juice and bile inhibits absorption from intestinal lumen, also vasodilation, and relaxation of intestinal smooth muscle
What is a VIPoma - Verner Morrison syndrome?
Pancreatic tumour which secretes excess VIP
What does VIPoma cause?
Watery diarrhoea, hypokalaemia (low potassium)and achlorhydria (low chloride)
Causes weakness and volume depletion
Are VIPoma’s malignant?
Yes most of them are
Where are Carcinoid tumours found?
throughout the GI tract
Carcinoid tumours symptoms?
Vary depending on location but people may develop carcinoid syndrome (flushing and diarrhoea)
People tend to only get symptoms when it’s mestasticides to the liver or the cystemic circulation
What are the carcinoid tumour symptoms related to
Secretion of serotonin or 5-HT
What is the diagnostic test for carcinoid tumour?
Measure 5-HIAA (metabolite of serotonin) inn urine
Metabolism pathway of 5-HT?
Tryptophan
Tryptophan hydroxylase
5HTP
amino acid decarbxylase
5HT
Monoamine oxidase
5HIAA
