Session 7: Distal GI Tract Pathology Flashcards
Definition of diarrhoea.
Loose or watery stools. More than 3 times a day
General pathophysiology of diarrhoea.
Unwanted substance in the gut are present and the body wants to get rid of it. Usually comes down secretions of ions to let water follow, instead of increased gut motility. The colon becomes overwhelmed due to the increased water content in the colon and diarrhoea occurs.
What are the two broad categories of diarrhoea?
Osmotic diarrhoea and secretory diarrhoea
Give broad causes of secretory diarrhoea. (General)
Either too much ion secretion into the bowel or not enough absorption of sodium.
Explain secretory diarrhoea due to too much ion secretion and common causes.
A net secretion of Cl- and HCO3- due to toxins, virus, medication or e.g. serotonin acting on CFTR to make it hyperactive. This leads to a colon lumen with too much Cl- and water will follow.
Causes secretory diarrhoea due to not enough sodium absorption.
Too little absorption of sodium due to e.g. reduced surface area of the intestines for absorption, damage to mucosa and intestinal wall like in Crohn’s. Intestinal rush leading to reduced time for absorption of sodium.
Explain osmotic diarrhoea
Due to malabsorption of nutrients in the small intestines leading to a build up of the osmotic gradient in the intestines.
Give causes of osmotic diarrhoea.
Celiac disease, lactose intolerance, antacids like magnesium sulphate. E.g. lactose intolerance leads to lactose in the large intestines. This leads to osmotic force keeping water from being absorbed.
Stool volume of osmotic diarrhoea vs secretory diarrhoea
In osmotic there is only a moderate increase whereas in secretory diarrhoea there is a very large volume excreted.
Response to fasting in osmotic diarrhoea vs secretory diarrhoea.
Osmotic diarrhoea ceases on fasting where as secretory diarrhoea does not.
Osmolality of stool in osmotic diarrhoea vs secretory diarrhoea.
Normal or increased in osmotic. Normal in secretory
Definition of constipation
Straining during defecations, Lumpy or hard stools, Feeling of incomplete evacuation, feeling of obstruction or blocking. Having fewer than 3 unassisted bowel movements in a week
Risk factors of constipation.
3:1 female:male, medication, low level of physical activity, age (very young <4 and old)
Give causes of slow colonic transport.
Large colon, fewer peristaltic movements and shorter ones, fewer intestinal pacemaker cells present, hypothyroidism, diabetes, parkinson’s, MS
Treatment of constipation
Psychological support, increased fluid intake, increased physical activity, laxatives, increased dietary fibres, fibre medication.
Give examples of laxatives.
Osmotic, stimulatory, stool softeners.
What is the appendix?
A diverticulum off the caecum with a complete longitudinal muscle layer.
Give examples of locations of the appendix.
Retro-caecal, pelvic, sub-caecal, Para-ileal
Why is the position of the appendix important?
Because it will change the clinical presentation of appendicitis.
Give the broad categories of appendicitis.
Acute with mucosal oedema. Gangrenous with transmural inflammation and necrosis. Perforation.
Explain the ‘classic’ cause of appendicitis.
A blockage of the appendiceal lumen leading to increased pressure in the appendix. This can be due to lymphoid hyperplasia following a viral infection, faecolith or a foreign body. This leads venous pressure to rise and oedema in the appendix. Ischaemia in the wall of the appendix follows and can cause bacteria to follow.
Classic presentation of appendicitis.
Poorly localised peri-umbilical pain, anorexia, nausea and vomiting, a low grade fever and as the appendicitis gets worse following 12-24 hours right iliac fossa pain
How is it possible to have appendicitis but no pain in right iliac fossa?
If the appendix is positioned retro-caecal or pelvic then it will not reach the right iliac fossa and reach the parietal peritoneum.
Pain in retro-caecal or pelvic appendicitis.
Supra-pubic pain, right sided rectal pain or vaginal pain.
In which people might appendicitis be difficult to diagnose?
In children and pregnant women.
Explain why appendicitis might be hard to diagnose in children.
History is difficult and symptoms may be much more non-specific.
Explain why appendicitis might be hard to diagnose in pregnant women?
Their anatomy is altered.
Signs of appendicitis.
Patients appear slightly ill. There is a slight fever as well as tachycardia. Localised right quadrant tenderness once the appendix has started to push on the parietal peritoneum. Rebound tenderness
Explain rebound tenderness.
In right iliac fossa. Upon pushing by the right iliac fossa there is generally no increased pain on the pressure but on release instead.
Where do you test for rebound tenderness?
McBurney’s point
What is McBurney’s point?
A point 2/3 of the way from umbilicus to ASIS.
Investigations of appendicitis.
Blood tests with raised WBC which may be very non-specific. History and physical examination. Rebound tenderness. ALWAYS tests for pregnancy and urine dip to rule out ectopic or UTI. CT scan (not common)
Treatment for appendicitis.
Open appendicectomy or laparoscopic appendicectomy (increasingly common)
What is diverticulosis?
An asymptomatic condition where outpourings are found in the mucosa and submucosa which herniate through the muscular layers.
Where does diverticulosis most commonly occur?
In the sigmoid colon along where nutrient vessels known as vasa recta penetrate the bowel wall.
Causes of diverticulosis.
Thought to be caused by increased intra-luminal pressure.
Why does diverticulosis most commonly occur in the sigmoid colon?
Due to higher pressure in the sigmoid colon due to storage of faeces.
What is symptomatic diverticulosis called?
Diverticular disease.
What is acute diverticulitis?
When the diverticula become inflamed and/or perforate with bleeding and abscess formation.
