BY3BC1- Medical biochemistry Lecture 5 - Gastrointestinal tract tests LO- - Gastric function - Exocrine (producing digestive enzymes) pancreatic function - Conditions associated with malabsorption of nutrients - Inflammatory bowel diseases Overarching theme - GI tract- stomach, pancreas, small intestine, colon, etc anatomically all different - Biochemical function tests often need to be used together with other investigate procedures: - Biopsy/histology, endoscopy (allows a doctor to see the inside of a person), CAT scans etc - Particularly true most of the G.I tract where access is relatively easy - During an endoscopy an endoscope goes into a persons body it has a light and tiny camera attached to it. The size and flexibility of the endoscope depends on where the test is being done flexible endoscopes for colons. They can even take small samples for further investment in the histology labs. stomach - Peptic ulcer disease caused by Helicobacter pylori (bacteria that enters your body and can remain for long periods of time can cause ulcers and damages the lining of your stomach) - The acid in the stomach then can get through the lining casing ulcers, bleeding in advance cases and infections. - Invasive procedures - Biopsy followed by - Histology (98% sensitivity) - Urease (CLO) test on biopsy (9tt-95% sensitivity) (an enzyme only in Helicobacter pylori) - Colour change due to alkaline amnomia - Non-invasive prodders - Serology (IgG against H.pylori)- good sensitivity but poor specificity (false positives) - ELISA for stool antigens (look for h.pylori) - Breath test using [14C] or 13[C] urea - eradication check
- Antibodies persist Urea breath test 13/14CO2 13/14C-Urea Urease 13/14CO2 NH3 13/14CO2 13/14CO2 Fasting plasma gastrin enteric neuron - Gastrin is released from the G cells in the gastric antrum in response to food intake and stimulants acid secretion (is a peptide hormone) causes the parietal cells to produce HCL and protects against certain bacteria acetylcholine parietal cell HCI - Measured by immunoassay particular sandwich ELISA - The most common reason for measuring fasting plasma gastrin is a gastrin secreting tumour (gastroinoma) - Patients with gastrinoma will have a high basal fasting acid secretion and as a consequence peptic ulcer disease Acute pancreatitis - Severe abdominal pain with acute inflammation of pancreas O histamine 4 ECL cell gastrin G cell - Caused by excessive alcohol, gall stoned but many cases idiopathic (no cause identifiable) - Serum amylase >1tt times upper limit of normal is very strong evidence of acute pancreatitis and rises quickly in the first 12 hours of the onset of symptoms and goes back to normal is 3-5 days. Low in normal conditions somatostatin somatostatin releasing cell - Amylase is a pancreatic enzyme which has leaked into the blood stream - Lower elevations may be due to other causes - Perforated duodenal ulcer, intestinal obstruction, renal failure (amylase is quite small and is excreted in urine).
Chronic pancreatitis - Loss of pancreatic function, often due to chronic alcoholic intake. Also autoimmune (immune system attacks the pancreas) forms and in