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
- 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