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Biochemistry And Endocrinology > Gastrointestinal Function Biochemical Tests > Flashcards

Gastrointestinal Function Biochemical Tests Flashcards

1
Q

What are the key components of the Gi tract?

A

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

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2
Q

What are the 2 processes of the GI tract?

A

Digestion and absorption

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3
Q

What digestion occurs in the stomach?

A

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.

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4
Q

What causes peptic ulcers

A

Heicobactor pylori and gastronoma

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5
Q

How does helicobactor pylori cause peptic ulcers?

A

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).

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6
Q

How do you diagnose peptic ulcers from helicobactor pylori?

A

Urea breath test

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7
Q

How is the urea breath test done?

A

Patient ingests urea and the pylori if present makes it into ammonia and carbon dioxide. The carbon dioxide is then breathed out and measured.

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8
Q

Alternative H.pylori tests?

A

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

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9
Q

Treatment of H.pylori?

A

histamine antagonists (blocks the release of acid in stomach, protein pump inhibitors and antibiotice

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10
Q

Gastinomas - zolinger Ellison syndrome - what does this do?

A

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

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11
Q

Are gastronomes normally malignant?

A

Yes

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12
Q

How do you diagnose a gastrinoma?

A

Elevated gastrin or giving IV secretin which produces increased gastrin

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13
Q

Pancreas juice?

A

Is alkaline (contains tryptase, amylase, lypase, elastase)and is essential for digestion of protein, carbohydrate and lipids.

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14
Q

What is acute pancreatitis commonly associated with?

A

Gall stones and alcoholism, acute abdominal pain

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15
Q

What is the diagnosis for acute pancreatitis?

A

Elevated serum amylase level and a CT scan, serum lipase, associated with hypcalcaemia, and raised inflammatory markers CRP

Can occur in other abdominal conditions

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16
Q

Chronic pancreatitis occurs because of what?

A

Impaired secretion of pancreatic enzymes - malabsorption.

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17
Q

How do you test of chronic pancreatitis?

A

Bicarbonate, and enzyme activity.

You do a faecal elastase - test to assess exocrine pancreatic dysfunction in chronic pancreatitis

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18
Q

What happens when there is low levels of pancreas specific enzyme in chronic pancreatitis?

A

Pancreatic insufficiency

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19
Q

What organs aren’t functioning correctly to get malabsorption disease?

A

stomach,pancreas, hepatobiliary system and small intestine

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20
Q

Does the small intestine have a large surface area and what is this increased by?

A

It does have a large surface area and Vili increases the surface area

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21
Q

What does malabsorption mean?

A

Failure of the normal digestion and/or absorption of nutrients

This can be generalised or specific

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22
Q

What are the consequences of malabsorption in the mount?

A

poor food preparation, poor dentition

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23
Q

Causes of malabsorption in in the stomach?

A

impaired mixing & digestion, ↓ Intrinsic factor

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24
Q

Malabsorption causes - pancreas, bile salts and structural defects

A

Pancreatic insufficiency - chronic pancreatitis, CF, gallstones,pancreatic Ca

Bile salt insufficiency – fat malabsorption

Structural defects - Infiltration & destruction/removal of small intestine

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25
Q

Malabsorption causes - mucosal disorders, endocrine, fictitious and what?

A

Mucosal disorders - Coeliac disease, IBD – decreased absorptive area

Endocrine – hyperthyroidism, hormone secreting tumours

Factitious – laxative abuse

Infective agent

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26
Q

What are the consequences of malabsorption?

A

Weight loss, Failure to thrive

Abdominal distension

Anaemia

Metabolic bone disease

Diarrhoea

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27
Q

How do yo reach a clinical diagnosis?

A

Clinical history investigations - family, radiotherapy , previous surgery, peptic ulcers, medication, travel, pancreatic disease or alcohol consumption

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28
Q

What are the biochemical tests in the lab for malabsorption?

A

FBC, film

Ferritin, B12, folate

LFTs

calcium, magnesium

Glucose

CRP

TFT’s

stool microscopy and culture

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29
Q

What are some more specific lab tests needed for malabsorption?

A

Tissue transglutaminase antibody test - Coeliac disease

  • Faecal calprotectin - Inflammatory bowel disease
  • Faecal Elastase - Pancreatic insufficiency
  • Laxative screens- Gut Hormone assays
  • Urinary 5HIAA - Carcinoid syndrome
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30
Q

What are some anatomical investigations?

A

Radiology - x-ray
Endoscop
Small bowel biopsy
US of liver an pancreas
CT of pancreas
ERCP of pancreatic and bile duct

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31
Q

What are some nutritional assessments in malabsorption?

A

Anthropometry:
- weight
- height
-BMI
- waist circumference
- skin fold thickens
- mid arm circumference

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32
Q

Treatments of malabsorptions?

A

Replace missing nutrients, dietary advice, artificial nutrient transport

33
Q

What is some nutritional support?

A

Food supplements

Enteral feeds - nasogastric tube - gastrostomy

Total parenteral nutrition (TPN) - nutrients delivered through blood.

34
Q

What tests do you use to work out Carbohydrate absorption?

A

Small bowel histology

Xylose absorption tests - can the intestine metabolise monsacarhides?

Intestinal permeability test (lactulose/rhamnose)

35
Q

Disaccharide deficiency

A

Lactase deficiency most common and lactase is highest at birth but decreases with age

36
Q

what are some symptoms of a disaccharide deficiency?

A

Nausea, bloating, abdominal pain following intake

37
Q

What are disaccharide deficiency diseases?

A

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

38
Q

how do you diagnose disaccharide deficiency?

A

Symptom, monitoring following response to low dairy diet

39
Q

What are the amino acid absorption disease?

A

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.

40
Q

How do you diagnose amino acid absorption?

A

Amino acid chromatography

41
Q

Fat malabsorption - how do you diagnose this?

A

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

42
Q

What are bile salts?

A

Critical for digestion and absorption of lipids and fat soluble vitamins

43
Q

What are happens during bile salt malabsorption?

A

Impaired reabsorption of bile salts = excess delivery into colon and production of toxic secondary bile salts

44
Q

What do bile salts cause?

A

Excess colonic secretion and watery, secretory diarrhoea

45
Q

Causes of bile salt malabsorption?

A

Gastric surgery, pancreatitis, coeliac disease, diabetes

46
Q

How do you diagnose Bile salt malsorpiton?

A

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
47
Q

What is coeliac disease?

A

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.

48
Q

What is coeliac disease associated with?

A

Other autoimmune disorders such as diabetes or thyroid

49
Q

What is symptoms of celiac disease?

A

Tiredness, general malaise, classic malabsorption syndrome

50
Q

How do you diagnose celiac disease?

A

igA tissue transglutaminase antibodies

51
Q

How do yoou get a definitive diagnosis of celiac?

A

Endoscopy and histologocial examination of intestinal biopsy samples

52
Q

What is the treatment of Celiac disease?

A

Strict adherence to gluten free diet

53
Q

Do all people with negative IgG have celiac disease?

A

No people are just naturally like this

54
Q

Inflammatory bowel disease covers what diseases?

A

Crohns and ulcerative colitis.

55
Q

What are symptoms of IBD?

A

Frequent bowel movement
Diarrhoea
Bloody stools
Abdominal pain
failure to thrive or weight loss

56
Q

How do you check for GI symptoms without being invasive?

A

calprotectin

57
Q

What is calprotectin>

A

Protein released into faeces as result of GI inflammation

58
Q

Why do we use a calprotectin test?

A

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

59
Q

When is calprotectin high?

A

IBD
Cancer of stomach and colon
Polyps

60
Q

Is calprotectin normal in those with IBS?

A

Yes

61
Q

Factitious diarrhoea - how do you test for this?

A

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

62
Q

How do you calculate the faecal osmotic gap>

A

290-2 (Faecal potassium + faecal sodium)

63
Q

What do gut hormones do?

A

They have regulatory roles in function of the GI tract.

64
Q

What would over secretion of gut hormones indicate?

A

Possible cancer or other clinical diseases

65
Q

How do you test gut hormones?

A

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.

66
Q

Gut hormones screen: what does gastrin do?

A

Stimulates gastric hydrogen production

67
Q

Gut hormones screen: what does glucagon do?

A

Gluconeogenesis

68
Q

Gut hormones screen: what does somatostatin do?

A

Inhibits GI and exocrine pancreatic secretion

69
Q

Gut hormones screen: what does pancreatic peptide (PP) do?

A

Inhibits enzyme release from the pancreas and relaxes the gall bladder

70
Q

Gut hormones screen: what does vasoactive intestinal polypeptide (VIP) do?

A

Stimulates secretion of water into pancreatic juice and bile inhibits absorption from intestinal lumen, also vasodilation, and relaxation of intestinal smooth muscle

71
Q

What is a VIPoma - Verner Morrison syndrome?

A

Pancreatic tumour which secretes excess VIP

72
Q

What does VIPoma cause?

A

Watery diarrhoea, hypokalaemia (low potassium)and achlorhydria (low chloride)

Causes weakness and volume depletion

73
Q

Are VIPoma’s malignant?

A

Yes most of them are

74
Q

Where are Carcinoid tumours found?

A

throughout the GI tract

75
Q

Carcinoid tumours symptoms?

A

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

76
Q

What are the carcinoid tumour symptoms related to

A

Secretion of serotonin or 5-HT

77
Q

What is the diagnostic test for carcinoid tumour?

A

Measure 5-HIAA (metabolite of serotonin) inn urine

78
Q

Metabolism pathway of 5-HT?

A

Tryptophan
Tryptophan hydroxylase
5HTP
amino acid decarbxylase
5HT
Monoamine oxidase
5HIAA

Biochemistry And Endocrinology (16 decks)

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