L8 - Impact of Surgery Flashcards
What are the two types of Bariatric surgery performed?
- Gastric restrictive
- food intake restricted - Malabsorptive operation
- nutrients diverted from absorption through a gastrointestinal short cut
What hormones contribute to appetite reduction?
Increased GLP-1
Decreased Ghrelin production
Restrictive procedures: Laparoscopic adjustable gastric band
- placement of an inflatable prosthetic ring just below gastro-oesophageal junction to create small proximal gastric pouch.
- reduce food intake, induce an early feeling of satiety
- band can be adjusted post-operatively by injecting or removing fluid via sub cutaneous injection port
Laparoscopic sleeve gastrectomy
- super obese patient
- resection of greater curvature of stomach
- permanent removal
Combined restrictive / malabsorptive procedures : Laparoscopic gastric bypass
Restriction of food intake by creating a small gastric pouch and mild malabsorption by bypassing they duodenum and proximal jejunum.
- food will travel from pouch
- connections called roux limb
- reduced absorption of vitamins may be experienced
Biliopancreatic diversion with duodenal switch
- Vertical subtotal gastrectomy associated with consistent reduction of the absorbing inestine
- bile and pancreatic juice mix with food in the distal small bowel segment , common limb
Partial gastrectomy
Lower half stomach removed.
Surgeon will close of patients duodenum, receives partially digested food from stomach.
Complete gastrectomy
Stomach gene, oesophagus connect directly to small intestine
Sleeve gastrectomy
Tube shaped stomach
Right hemicolectomy
Removing RHS colon and attaching small intestine to LHS colon (remaining portion)
Describe neutrophil mediated injury as a result of taking NSAIDS
- neutrophils adhere to endothelium
- liberates oxygen free radicals
- releases proteases
- obstructs capillary blood flow
- NSAIDs thought to up-regulate adhesion molecules
Describe distribution of cyclo-oxygenase inhibitors
COX-2
- high concentrations in platelets, vascular, endothelial cells, stomach, kidney collecting tubules.
- significantly increases in inflammatory and mitogenic stimuli
COX-1
- majority of cells
Describe use of aspirin
Anti-inflammatory drugs.
Used in prevention of thrombotic cerebrovascular and CVD disease.
Effects prostaglandin synthesis - causing symptoms of dyspepsia
Why are bisphosphonates given?
Treatment of patients with osteoporosis.
Prophylaxis of osteoporosis
However
- severe gastric and duodenal ulceration
Inhibition of COX-1 in GI tract leads to..
Reduction of prostaglandin secretion.
Increases susceptibility to mucosal injury.
COX-2 present in fewer cells and induced by inflammation
Two types of microscopic colitis
Collagenous colitis
Lymphocyte colitis
Describe what occurs in collagenous colitis
Infilitration of lymphocytes into colonic epithelium AND Distinctive thickening of sub-epithelial collagen layer.
Thickened collagen layer
- serves as a diffusion barrier
- reduced Cl- & Na+ absorption
Thickened sub epithelial collagen layer in lamina propia
Compare lymphocyte colitis to collagenous colitis?
LC
- infiltration of lymphocytes into colonic epithelium
- preservation of crypt architecture
CC
- infiltration lymphocytes into colonic epithelium and distinctive thickening of sub-epithelial collagen.
Why might patients with collagenous colitis get secretory diarrhoea?
Increase in immunoreactive prostaglandin E2 & NO in colonic epithelium, may contribute to a secretory diarrhoea.
Thickened collagen layer serving as diffusion barrier, hence reduced net Na+. Cl- absorption.
- epithelium loses ability to absorb ion
Drugs which may cause diarrhoea
NSAIDs Ranitidine Omeprazole Lansoprazole Tidopinin
Describe action of Histamine 2- receptors
Inhibit H+ secretion.
Raise pH.
May increase permeability and function of intestinal barrier.
Intestinal microbiota composition altered.
Describe the role of intrinsic factor in absorption of b12
Parietal cells - intrinsic factor
- Dietary B12 binds to R-factor (secreted from salivary glands)
- Pancreatic enzymes cleave B12 from R-factor
- B12 allowed to bind to IF
- B12 & IF complex bind to receptors on ileum
- receptors allow for absorption of b12
Summarise functions of different parts of small bowel
- Duodenum: receives acidic content from stomach which are neutralised by pancreatic secretions and bile added to facilitate fat absorption
- Jejunum: secretion of water, nutrient absorption
- Ileum: longest segment and responsible for processing carbs and proteins
- Terminal ileum: B12 absorption and bile acid absorption
Very briefly describe the entero-hepatic circulation of bile
- RBC broken down as aa removed from globin to leave ‘heme’
- Haem oxidised -> bilivirdin
- reduced to –> bilirubin
- bilirubin conjugated (addition of aa) to make it water soluble
- Conjugated bilirubin converted to urobilogen by bacterial proteases
- then to stercobilinogen (excreted in faeces)
- Conjugated bilirubin excreted from liver with primary and secondary bile acids: BILE!
Function of the colon
- absorption of water and electrolytes
- breakdown of fibre by colonic bacteria to short chain fatty acids
- formation and elimination of faeces
Gastroparesis
Stomach cannot empty itself of food in a normal fashion.
Billroth II
Greater curvature of stomach, connected to first part of jejunum in end to side anastomoss.
Follows resection of antrum.
Billroth I
Pylorus removed.
Distal stomach anastomosed directly to the duodenum.
Describe dumping
- post prandial flushing, hypotension, diarrhoea and hypoglycaemia
- caused by dysregulated gastric emptying, osmotic load and peptide hormone release
Management of dumping
- diet
- antidiarroreals
- SSI - octreotide
Octreotide
Octapeptide mimicing somatostatin.
Potent inhibitor of GH, glucagon and insulin.
Effect on gut function of Right hemicolectomy
Ileocaecal resection
- uncompensated limited absorption of sodium against electrochemical gradient.
Terminal ileal resection
- permanent reduction in vitamin B12 absorption - parenteral replacement
- reduced bile acid absorption resulting in bile mediated fluid and electrolyte secretion by colon
Describe briefly some mechanisms of peptic ulcer disease
Gastric mucosal integrity depends on careful balance of secretion of aggressive (acid, pepsin) and defensive (HCO3, mucin and substances)
Pepsin (proteolytic enzyme)
State some causes of peptic ulcer disease
- H.Pylori infection
- medications: NSAIDs, aspirin
- Hypersecretory conditions (ZE)
- Curling ulcer (stress induced)`
Curlings ulcer
Acute gastric erosion resulting as a complication from severe burns when reduced plasma volume leads to ischaemia and cell necrosis.
- sloughing of the gastric mucosa
How do prostoglandins stimulate gastric protection and how do NSAIDs effect this
Production of
- mucus
- bicarbonate
- phospholipid
- mucosal blood flow
NSAIDs
- inhibit COX1 and 2 , enzymes essential to prostoglandin synthesis
Effect of inhibition of COX 1
Expressed in stomach.
Inhibition results in reduced mucosal blood flow and reduced mucosal defence.
Osmotic diarrhoea
Increased solute in lumen drives osmotic diarrhoea.
Fasting usually resolves osmotic diarrhoea
Secretory diarrhoea
Body secretes electrolytes into intestine.
Causes water to build up.
Not resolved by fasting.
Inflammatory diarrhoea
Breach of GI barrier and disruption of epithelium
- reduced absorption
- inflammatory response stimulates secretion
e. g. Microscopic colitis , chemotherapy
Antibiotic associated diarrhoea
Disturbance of colonic microflora.
Osmotic diarrhoea due to loss of bacteria that metabolise non-absorbed carbohydrates and bile acids.
- increased motility
Microscopic colitis associated diarrhoea
Syndrome of watery diarrhoea with normal colonic appearances and histologic changes of inflammation with or without thickening of the sub epithelial collagen table.
