Functional and infective pathology of the lower GI tract: diarrhoea and constipation Flashcards
According to the NICE guidelines, what is the definition of diarrhoea?
- abnormal passage of loose or liquid stools
According to the NICE guidelines, what is the definition of acute diarrhoea?
- >3 times/day daily and/or a volume of stool greater than 200g/day
- <14 days in duration
According to the NICE guidelines, what is the definition of chronic diarrhoea?
- >3 times/day daily and/or a volume of stool greater than 200g/day
- >4 weeks in duration
How common is chronic diarrhoea in the UK, and is it more common on young or elderly?
- 7% prevalence in UK
- 14% prevelence in elderly
If a patient has chronic diarrhoea (>4 weeks) what does this generally suggest?
- pathology is present
- investigations my be required
What is the most common cause of acute diarrhoea?
- viral infections
- norovirus, rotavirus
Following viral infections as the most common cause of diarrhoea, what is the second most common cause of diarrhoea?
- bacterial infections
- Salmonella, Campylobacter, Clostridium difficile, cholera
In addition to viral and bacterial infections, what else that is nasty can cause acute diarrhoea?
- parasites
In addition to viral, bacterial and parasitic infections, what is the next major cuase of acute diarrhoea?
- medications
- antibiotics, metformin and meprazole are common
What must all chronic pathology causing diarrhoea start out as?
- acute pathology
At a very basic level what causes infections and medications to cause diarrhoea?
- increased secretion or decreased absorption of fluids and electrolytes
The cystic fibrosis transmembrane conductance regulator (CFTR) can be affected in infections such as cholera. How does cholera/Salmonella cause diarrhoea?
- increase cAMP and protein kinase A
- efflux of ATP mediated Cl- into lumen
- Na+ moves down electro charged gradient paracellularly
- K+ and H2O will follow
The sodium–glucose cotransporters (SGLTs) in the GIT are responsible for glucose absorption. If pathology is present what can this cause to SGLTs?
- SGLTs do not function causing Na+ and glucose not to be absorbed and remain in the lumen
- H2O moves into the lumen due to osmosis
Diarrhoea can have a direct effect on the bowel. What does a direct effect relate to?
- cell death leading to loss of absorptive area
- inflammation causing fluid to be extruded into the bowel
Diarrhoea can have an indirect effect on the bowel. An indirect effect relates to the toxins that are secreted by pathogens. What are they able to mimic and what can this cause?
- endogenous cell signalling
- able to act on ion channels
Diarrhoea can have an indirect effect on the bowel. An indirect effect relates to the toxins that are secreted by pathogens. What can these toxins do the epithelial cells of the GIT that can cause leakage into the GIT?
- form pores in the cell membrane
- increase the permeability of tight junctions
Diarrhoea can have an indirect effect on the bowel. An indirect effect relates to the toxins that are secreted by pathogens. What can some toxins become that can trigger diarrhoea?
- can be cytotoxic or pro-inflammatory
- both can cause fluid increase into GIT
In addition to pathogens causing diarrhoea, medications are able to induce diarrhoea. What % of adverse effects of drugs are diarrhoeal and roughly how many different drugs can cause diarrhoea?
- 7%
- >700 drugs
In addition to pathogens causing diarrhoea, medications are able to induce diarrhoea. What % of drugs are antimicrobials (kills bacteria?
- 25%
There are a number of mechanisms in which drugs are able to cause diarrhoea. What are osmotically active drugs?
- drug is poorley digested and absorbed
- H2O is pumped into lumen to reduce drug concentration through osmosis
There are a number of mechanisms in which drugs are able to cause diarrhoea. How can drugs cause secretory changes which affect on ion absorption and cause diarrhoea?
- alter ion secretion
- ions are pumped into GIT like Cl- and Na+
- H2O follows due to osmosis
There are a number of mechanisms in which drugs are able to cause diarrhoea. How can drugs cause changes in bowel times?
- laxatives speed up bowel movements
- H2O and electrolytes cannot therefore be absorbed
There are a number of mechanisms in which drugs are able to cause diarrhoea. How can drugs cause malabsorption of macronutrients such as carbohydrates and fat, that ultimately lead to diarrhoea?
- fat and carbohydrates are not digested
- H2O is pumped into lumen due to osmosis
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days), do you generally need to doing any investigations?
- no
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days), investigations are not generally required as the symptoms will clear themselves. However, in what scenarios would you perform investigations?
- when patient is unwell
- presence of blood or pus in stools (IBD)
- recent antibiotics, hospital admission or on PPI
- foreign travel (3rd world countries)
- immunocompromised patients
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days), investigations are not generally required as the symptoms will clear themselves. However, what infection must be rules out, especially if a patient has been admitted to hospital?
- C.difficile
Generally what ions are present in high concentrations in diarrhoea content?
- Na+
- K+
- H2O
- HCO3-
Generally Na+, K+, HCO3- and H2O are present in high concentrations in diarrhoea content. What can this lead to in the patient?
- dehydration
- hypokalaemia (low K+)
- acidosis (unusual – and often secondary to acute kidney injury if it happens rather than bicarbonate loss)
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days) treatment is generally not required. However, one simple treatment patients are instrcuted to do is what?
- rehydrate
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days) treatment is generally not required. However, patients are encouraged to rehydrate. Patients are encouraged to consume a hypertonic solution containing what and why hypertonic solutions?
- hypertonic means high solute concentration
- dioralyte contains hypertonic saline/glucose concentration
- encourages Na+/glucose absorption down concentration gradients from lumen into enterocytes
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days) treatment is generally not required. However, if patients are unwell what can be done?
- may require hospital assessment or admission
- subsequent diagnostics once acute episode settles
In a patient who presents with acute diarrhoea (>3 loose bowel movements/day for <14 days) treatment is generally not required. However, even if an infection suchas C.difficile is present, are antibiotics often used?
- no
- unless severe
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what is the most common, but very rare cause that patients are worried about?
- colonic cancer
- generally patients with new onset diarrhoea and >60 years old
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), following cancer what is the second most serious pathology of the colon that clinicians see?
- inflammatory bowel disease
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what are the 2 most common disease in the small intestines that we need to rule out?
- inflammatory bowel disease (crohns)
- coeliac disease
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what is the most common causes iof chronic diarrhoea in the GIT that we need to be aware of?
- functional bowel syndrome
- specific cause unknown
Hyperthyroidism can cause what symptoms in the GIT?
- diarrhoea
- need to check if patient has chronic diarrhoea
How can osmotic problems in the GIT cause chronic diarrhoea?
- malabsorption meaning nutritents are not absorbed
- can cause steatorrhoea
- fluid is drawn into the lumen to dilute the nutrients due to osmosis
What can cause secretory problems in the GIT that can then go onto cause chronic diarrhoea?
- excessive gut hormones such as gastrin
- infections
- radiation therapy
What is the most common cause of failure to absorb nutrients in the GIT, and how can this go onto cause chronic diarrhoea?
- coeliac disease (gluten, specifcally gliadin)
- causes inflammation and fluid leaks into lumen
In the GIT an onstruction of stricute can cause a narrowing of the GIT. How can this cause chronic diarrhoea?
- solids are unable to pass
- liquids are able to pass
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what are the 4 tests that can be performed on a patients stool sample?
1 - infections and parasites microbiology
2 - faecal calprotectin (IBD) (inflammation)
3 - quantitative faecal immunohistochemical test (qFIT - bowel cancer)
4 - faecal elastase (pancreatic exocrine function)
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what are some of the most common blood tests that can be performed?
- thyroid function (hyperthyroidism)
- full blood count including Hb, WBC and platelets
- inflammatory markers (CRP)
- coeliac screen (tissue transglutaminase (tTG) blood test)
- vitamin B12, folic acid, ferritin
- gut hormones
- vitamin and mineral levels if concern about malnutrition
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), in addition to faecal calprotectin as a measure of inflammation from IBD in the stool, what other inflammatory measure can be performed in the blood?
- C reactive protein (CRP)
What is the quantitative faecal immunohistochemical test (qFIT) that is now being used to screen patients for bowel cancer?
- a test performed on stool
- measures microscopic blood in bowel
- increased haemoglobin in blood = increase risk of cancer
When deciding whether a quantitative faecal immunohistochemical test (qFIT) should be performed in a patient when screening for bowel cancer, what is the most common contradiction?
- rectal bleeding
- if already bleeding, we dont need the qFIT
If a patient with chronic diarrhoea and a negative quantitative faecal immunohistochemical test (qFIT), does this mean the patient definitely does not have bowel cancer?
- no
- need further tests to confirm the qFIT
If a patient with chronic diarrhoea has been investigated with blood and stool measures, but the clinician requires more invasive measures, what is the gold standard test to be performed on the large intestines?
- colonoscopy
If a patient with chronic diarrhoea has been investigated with blood and stool measures, but the clinician requires more invasive measures, the gold standard test to be performed on the large intestines is the colonoscopy. What are the risks of colonoscopy?
- damage to inside of GIT
- increased risk of bleeding
If a patient with chronic diarrhoea has been investigated with blood and stool measures, but the clinician requires more invasive measures, the gold standard test to be performed on the large intestines is the colonoscopy, but this can damage inside of the GIT and increase the risk of bleeding. What is now the most common alternative that is less invasive?
- virtual colonoscopy (CT scan with contract)
- no biopsies can be taken though
In patients who require further investigation of the large intestines, colonoscopy and virtual colonoscopy can be performed. What is one other technique that can be used?
- capsule colonoscopy
- takes pictures through GIT
If a patient needs surgical investigations of the small intestines, are we able to get a camera in the whole small intestines like in the large intestines?
- no extreme ends only
- colonoscopy can see terminal ileum
- oesophago-gastro-duodenoscopy can see jejunem
What is the least invasive method for looking at patients small intestines which are difficult to look at using colonoscopy and endoscopy?
- MRI scan
What is the most common condition to affect the bowels in the UK, and probably worldwide?
- irritable bowel syndrome (IBS)
The most common condition to affect the bowels in the UK, and probably worldwide is irritable bowel syndrome (IBS). According to the NICE definition, what factors are included to confirm a diagnosis?
- abdominal pain (defaecation and/or stool frequency)
- bloating or distension made worse with food
- mucous present in stool
The most common condition to affect the bowels in the UK, and probably worldwide is irritable bowel syndrome (IBS). According to the NICE definition, what must be ruled out to confirm a diagnosis of IBS?
- lternative conditions excluded
- bowel cancer, IBD, coeliacs
How common is irritable bowel syndrome?
- 20-30% worldwide
Is irritable bowel syndrome more common in men or women?
- women
What ages is irritable bowel syndrome more common in?
- 20-30 year olds
In irritable bowel syndrome we do not know the exact cause, but what are the 4 most commonly described causes?
1 - genetic factors
2 - gut infections
3 - dietary factors (up to 90% report certain food triggers)
4 - psychosocial factors
In patients with irritable bowel syndrome what is the most important thing to do with a patient?
- reassure them they dont have cancer
In patients with irritable bowel syndrome (IBS) dietary manipulation can sometimes help. How can insoluble dietary fibre be useful in treating IBS?
- acts as an osmotic agent that cannot be digested
- H2O is pumped into lumen to dilute due to osmosis
- increased fibre and H2O increases bowel movements
In patients with irritable bowel syndrome (IBS) dietary manipulation can sometimes help. How can soluble dietary fibre be useful in treating IBS?
- increase soluble fibre supplements in constipation
- maintain adequate fluid intake (contentious)
In patients with irritable bowel syndrome (IBS) dietary manipulation can sometimes help. How can fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP), which are short-chain carbohydrates (sugars) that are poorly absorbed be useful in treating IBS?
- identify foods that trigger symptoms and remove
In a patient with chronic diarrhoea (>3 loose stools/day for >4 weeks), what is generally the first medical treatment that is given to patients?
- Loperamide
Loperamide, commonly known as imodium is generally the first medication given to patients with chronic diarrhoea (>3 loose stools/day for >4 weeks). What is the mechanism of action of Loperamide?
- agonist of opiod receptors
- inhibits gut motility by binding with opiod receptors
- acetylcholine and prostaglandins are reduced
- anal sphincter tone is increased, reducing incontinence and urgency
Loperamide, commonly known as imodium is generally the first medication given to patients with chronic diarrhoea (>3 loose stools/day for >4 weeks). What is the most common side effect of Loperamide?
- constipation
If patients are presenting with abdomaonl cramps, they may be prescribed an antispasmodic drugs such as hyoscine butylbromide, more commonly known as buscopan. What is the mechanism of action of hyoscine butylbromide?
- blocks muscarinic receptors in the GIT tract
- induces smooth-muscle relaxation
In a patient with constipation, they may be prescribed with laxatives such as ispaghula husk. How do these help with constipation?
- act as bulk forming agents increasing bolus
- increased bolus increases peristaltic contractions
What is the definition of constipation?
- <3 bowel movements/wk
- excessive straining
- abdominal pain or bloating
How common is constipation?
- 1-2% of the population
Is constipation more common in men or women, and does the prevelence change with age?
- 2-3 times more common in women
- increases with age
What are the 2 most common functional causes of acute constipation?
- dehydration
- behavioural (nervous at school etc)
What medications are more commonly associated with acute constipation?
- opioids (morphine, codeine)
- loperamide (imodium)
Acute presentations of constipation can begin as an acute pathophysiology, but can also be the begining of a chronic pathology. What is the most common thing that constipation is compared against?
- constipation v bowel obstruction
What do opiod medication bind to in the brain and GIT, and what type of cell membrane receptors are these?
- opiod receptors
- opiod receptors are G couple protein receptors
Endorphones are endogenous opioid neuropeptides and peptide hormones. When they are released they bind to the inhibitory neurons, namely mu, kappa, and delta which allow dopamine, serotonin, and norepinephrine to be released into the CNS. What does the release of dopamine, serotonin, and norepinephrine cause a reduction in?
- pain
The GIT walls contain mu opiod receptors. What are the 2 major effects activation of the mu opiod receptors in the GIT can have?
- reduced GIT motility
- increased sphinter tone
- both are bad for constipation
The GIT walls contain mu opiod receptors. Opiod is able to bind with all opiod receptors inducing reduced GIT motility and increased sphinter tone. What medication, as part of our core drug list is used to treat diarrhoea, but as a consequence can cause constipation?
- loperamide (imodium)
- specifically in the large intestines
What is the most common cause of chronic constipation?
- irritable bowel syndrome
Pregnancy is a common cause of constipation. What % of women experience constipation?
- 40%
If a patient is referred with chronic constipation to a clinician what is generally the patients main worry of the cause, and often high up on the clinicians concerns?
- cancer
Over and under secretion of thyroid secretions can affect GIT motility. Does hypo and hyperthyroidism cause diarrhoea or constipation respectively?
- hyperthyroidism = increased metabolic rate and muscle contractions including GIT smooth muscle, causing diarrhoea
- hypothyroidism = reduced metabolic rate and muscle contractions including GIT smooth muscle, causing constipation
Chronic constipation can cause anorectal problems, what are the 4 most common?
1 - haemorrhoids
2 - anal fissures (tears of rectum)
3 - painful defaecation
4 - rectal prolapse (bottom end of rectum falls out)
Hirschsprung’s disease can cause constipation, what is this disease?
- congenital absence of ganglia in bowel
- no ganglia = no peristalsis
- 90% diagnosed in infancy
- 1% diagnosed in adults
Hirschsprung’s disease can cause constipation due to a congenital absence of ganglia in bowel causing poor or no peristalsis. Why is this detected very early in infancy?
- often infants dont pass their first bowel movement
In addition to anal problems in chronic constipation, what are 2 of the most common symptoms patients compain of?
- abdominal pain
- bloating
Patients with chronic constipation can have problems holding urine, what is this called?
- urinary retention
Patients with chronic constipation can have faecal impactio, what is this faecal impaction?
- hard stool that cannot be passed
Patients with chronic constipation can overflow diarrhoea. What is overflow diarrhoea?
- constipation can cause a blockage
- solid cannot pass but fluid can
When assessing a patient with chronic constipation, what are the 4 most important questions in the history taking?
1 - length of time of symptoms
2 - recent changes in medications
3 - history of lower GI issues before
4 - associated symptoms
When assessing a patient with chronic constipation, what are the 4 most important things to consider in the examinartion?
1 - rectal examination (empty rectum v impacted stool)
2 - abdominal tenderness or masses
3 - palpable stool in colon per abdomen
4 - sinister masses
In patients with chronic constipation what are the blood tests that should be performed?
- full blood count
- thyroid function (hypothyroidism can cause constipation)
- inflammatory markers CRP
In patients with chronic constipation what are the stool tests that should be performed?
- inflammatory marker faecal calprotectin
- qFIT for blood caused by cancer
In an acute setting with someone with constipation, what imaging techniques can be used to rule out a bowel obstruction?
- CT scan is best option
- X-ray can be used
In someone with constipation, what invasive techniques could be used to identify the cause?
- colonoscopy
- virtual colonoscopy
What are 2 special investigations that can sometimes be performed in patients with constipation?
1 - bowel transit time tests
2 - pelvic floor tests
What are diverticula?
- small, bulging pouches
- form in the lining of the GIT
- common in lower end of large intestine
- increase after age 40 but seldom cause problems.
What is diverticulor disease?
- protrusion of diverticula through the bowel wall musculature
- can cause constipation and become inflamed
What is one of the main risk factors for diverticulor disease?
- poor dietary fibre implicated
Where in the world has the highest incidence of diverticulor disease?
- western countries
Who is most likley to suffer with diverticulor disease?
- >60% are >70 years old
- BUT 90% have no symptoms
Where is the highest abundance of diverticula in the large intestines?
- sigmoid colon
- potentially due to highest intra-luminal pressure
In acute constipation we need to rule out a bowel obstruction. What is absoloute constipation?
- no passage of stool or flatus out of rectum
- often indicates distal mechanical obstruction of colon
What % of patients with constipation tend to settle on their own?
- >90%
- history and examination is key here
Bowel obstruction can be caused by intrinsic factors. What are these?
- compression of the GIT from outside bowels
Bowel obstruction can be caused by intrinsic factors, compression of the bowel from outside the GIT. What are the 3 most common in order, with 1 being the most common?
1 - adhesions/scar tissue (small bowel)
2 - hernias (small bowel)
3 - abdominal masses (cancer)
Bowel obstruction can be caused bowel wall obstructions in the GIT. What are the 2 most common?
- neoplasia/cancer
- inflammation or fibrotic stricture/narrowing
Bowel obstruction can be caused by things within the lumen. What is the most common cause?
- foreign bodies
- bezoar (debris and hair mixed together)
What is a close loop bowel obstruction?
- bowel is closed at top and bottom
- very dangerous
If a patient presents with a bowel obstruction, in addition to history and examnination, what imaging technique is used to rule out or confirm a bowel obstruction, and is super specific for detecting bowel obstructions?
- CT scan
If a patient presents with a bowel obstruction, and it is not settling on its own or through treatment, what would be the final invasive treatment?
- if closed loop large bowel obstruction - EMERGENCY
- competent ileocaecal valve (50%) prevents reflux into ileum
If a patient presents with a bowel obstruction, and it is not settling on its own or through treatment, why is an obstructed colon with right lower abdominal pain something that needs to monitored the most?
- sign that the caecum is getting bigger and bigger
- could perforate and is very dangerous
When treating patients with chronic constipation, what are the 3 lifestyle factors that need to be addressed?
1 -adequate dietary fibre
2 - addequate hydration
3 - avoid inactivity
When treating patients with chronic constipation, with a faecal impaction, which is essentially hard stool that cannot be passed, hwo can they be treated?
- enemas (rectal injections to soften the stool)
- suppositories (medication that dissolves into the rectum)
- manual evacuation is rarely needed
When treating patients with chronic constipation, how can patients with behavioural problems such as anxiety of passing stool in public or at a friends be treated?
- do noit ignore call to pass stool
- remove stimulation of anxiety
When treating patients with chronic constipation, what is the main medication that is used?
- laxatives
What are the main 4 groups of laxatives?
1 - bulk forming agents
2 - osmotic laxatives
3 - stimulant laxatives
4 - stool softener
Bulk forming laxatives are often the first laxative that is used when treating constipation. How do these laxatives work?
- retaining fluid in stool increasing and softening stool mass
- increased mass triggers enteric reflex stimulating peristalsis
Bulk forming laxatives are often the first laxative that is used when treating constipation. Which bulk forming medication is used?
- ispaghula husk
- fibrous
Osmotic laxatives can also be used to help treat constipation. How do osmotic laxatives help treat constipation?
- retain fluid in gut and draws fluid into the bowel lumen
- increases faecal mass and soften stool
- enteric nervous stimulated causing peristalsis
Osmotic laxatives can also be used to help treat constipation. What is our core drug that we need to know?
- lactulose
Stimulant laxatives can also be used to help treat constipation. How do these laxatives treat constipation?
- cause acute inflammation causing fluid to flow into the lumen
- stimulates bowel nerves, increasing peristalsis
- can also have secretory/osmotic activity
Stimulant laxatives can also be used to help treat constipation. What is the core stimulant laxatives drug we need to be aware of?
- senna, commonly known as senokot
Stool softener laxatives can also be used to help treat constipation. What is the core stimulant laxatives drug we need to be aware of?
- docusate sodium
- often 2nd line of treatment
Docusate sodium is the stool softener laxative that we need to be aware of. How can these laxatives be used to treat constipation?
- allows water and fats to penetrate stools
- stools become softer andpass along the GI tract easier
- can also reduces straining on defaecation
Are laxatives commonly used in isolation?
- no
- normally in combination
c
- eectrolyte imbalances (unusual)
Laxatives can be an effective treatment for constipation. But there can be some side effects. In additon to electrolyte imbalance, what are the most common side effects of laxatives?
- diarrhoea or excessive flatus
- bloating (Bulk-forming and osmotic laxatives)
- cramps (osmotic and stimulant laxatives)
Laxatives can be an effective treatment for constipation. But there can be some side effects. If a patient has a suspected obstruction, should laxatives be used?
- no
- can cause complete bowel obstruction
- generally prescribed following investigation
