PATHOLOGY - Diarrhoea Flashcards
How do you approach the investigation of diarrhoea?
- Assess history, signalement and clinical signs
- Clinical examination
- Diagnostic testing
- Management/treatment
Which history questions are useful to ask when investigating diarrhoea?
- Is the diarrhoea acute or chronic?
- Is the diarrhoea constant or intermittent?
- Describe the appearance of the diarrhoea?
- Has there been any recent dietary or environmental changes?
- Is the patient a scavenger?
- Are any of the animals the patient is in contact with also experiencing diarrhoea?
- Anthelmintic and vaccination history?
- Is the patient systemically unwell? (such as PUPD, jaundice, signs of endocrine disease, lethargic, etc.)
- Has the patient been vomiting?
- How is the patient’s appetite?
When is diarrhoea classified as chronic?
When diarrhoea has been going on for over two weeks, it is classified as chronic
Why is it important for the client to describe the appearance of the diarrhoea?
The appearance of the diarrhoea can help to distinguish if the diarrhoea is originating from the small or large intestine
What are the characteristic features of small intestinal diarrhoea?
Normal to large volumes of diarrhoea
Normal to mildly increased frequency of defaecation
Meleana
Concurrent weight loss
Concurrent vomiting
Ascites
Why do you get concurrent weight loss with small intestinal diarrhoea?
The small intestine is the site of nutrient absorption so you can see concurrent weight loss with small intestinal diarrhoea as the small intestine will be unable to absorb nutrients properly
When would you see ascites with small intestinal diarrhoea?
You can see ascites with small intestinal diarrhoea if there is a protein-losing enteropathy
What are the characteristic features of large intestinal diarrhoea?
Small volumes of diarrhoea
Increased frequency of diarrhoea (usually associated with urgency)
Mucus
Haematochezia
Concurrent faecal tenesmus
Concurrent dyschezia
What are the two main aims of the clinical examination when investigating diarrhoea?
Determine if there are any clinical signs that can help discriminate the cause of the diarrhoea and determine the clinical status of the patient
What should you assess in detail during the clinical examination when investigating diarrhoea?
Signs of systemic disease
Pyrexia
Signs of hepatic disease (jaundice)
Signs of kidney disease
Signs of malnutrition (low BCS)
Assess if the abdomen is painful
Palpate for any abdominal masses
Ascites
Assess for dehydration
Assess for hypovolaemia
What can be indicated by pyrexia when investigating diarrhoea?
Pyrexia can be indicative of an infectious or inflammatory cause of diarrhoea
What can be indicated by weight loss when investigating diarrhoea?
Malnutrition can be indicative of a chronic malabsorptive or maldigestive disorder resulting in diarrhoea
What can be indicated by ascites when investigating diarrhoea?
Ascites can be indicative of diarrhoea secondary to a protein-losing enteropathy
What are the differential diagnoses for acute diarrhoea?
Abrubt dietary change
Dietary indiscretion
Infectious disease (parasites, viral, bacterial)
Acute colitis
Acute haemorrhagic diarrhoea syndrome
Abdominal catastrophe
Acute pancreatitis
Acute hepatic disease
Peritonitis
Addison’s disease
Toxins
What are some of the parasitic causes of acute diarrhoea?
Giardia
Coccidia
What are some of the viral causes of acute diarrhoea?
Parvovirus
Distemper
Coronavirus
Rotavirus
What are some of the bacterial causes of acute diarrhoea?
Salmonella
Campylobacter
Clostridia
E. coli
Which two strains of clostridia cause acute diarrhoea?
Clostridia pefringens
Clostridia difficile
What are the differential diagnoses for acute haemorrhagic diarrhoea?
Parvovirus
Coronavirus
Salmonella
Clostridium perfringens
E. coli
Acute haemorrhagic diarrhoea
Abdominal catastrophe
How do you narrow down the differental diagnoses for acute diarrhoea?
Exclude infectious causes of diarrhoea
Exclude systemic causes of diarrhoea
Which diagnostic tests can be done when investigating acute diarrhoea?
Haematology
Biochemistry
Diagnostic imaging
Faecal analysis (faecal parasitology and faecal culture and sensitivity)
What are the aims of haematology and biochemistry when investigating acute diarrhoea?
Haematology and biochemistry can be used to identify systemic disease as well as gather more information on the patient’s clinical status
What information can you gain from haematology when investigating diarrhoea?
Inflammatory leukogram (can indicated inflammatory conditions)
Lack of stress leukogram (can indicate Addison’s)
Look at the protein levels (can indicate protein losing enteropathy and be a therapeutic target)
What should you be aware of when assessing liver enzymes when investigating acute diarrhoea?
You should be aware that acute diarrhoea can cause mild to moderate increases in liver enzymes as a consequence of there being increased toxic substances in the intestines which will be drained by the hepatic portal vein to be detatoxified by the liver which can put stress on the liver, resulting in increased liver enzymes
What is a distinctive feature of hypoadrenocorticism (Addison’s disease) on biochemistry?
Hyperkalaemia
Hyponatraemia
Which additional test can be done to diagnose acute vomiting secondary to hypoadrenocorticism (Addison’s disease)?
ACTH stimulation test
Why is it so important to do diagnostic imaging when investigating acute diarrhoea?
It is important to do diagnostic imaging when investigating acute diarrhoea to rule out abdominal catastrophe
Describe the structure of parvovirus
Parvovirus is an enveloped DNA virus
Describe the pathogenesis of parvovirus
Parvovirus has a tissue tropism for rapidly diving cells such as intestinal epithelial cells and haematopoietic cells. Parvovirus damages the intestinal epithelial cells, resulting in severe acute haemorrhagic diarrhoea and impairment of the intestinal mucosal defences, allowing for the translocation of bacteria, causing sepsis. Parvovirus also targets haematopoietic cells which can result in neutropenia, which also increases the risk of sepsis. Sepsis can result in SIRS and disseminated intravascular coagulation (DIC) which can be fatal
Which signalement is prone to parvovirus infection?
Unvaccinated dogs
(T/F) Parvovirus is unable to infect vaccinated dogs
FALSE. Some dogs can be incompletely vaccinated and present with parvovirus. Sometimes vaccinations can be blocked by prolonged maternal derived antibodies
Which dog breeds are prone to parvovirus infection?
Rottweilers
What are the clinical signs of parvovirus?
Acute haemorrhagic diarrhoea
Anorexia
Vomiting
Pyrexia
Hypothermia (sign of sepsis)
Clinical signs of DIC
Which faecal analysis tests can you do to diagnose parvovirus?
Faecal antigen test
Serology for anti-CPV antibodies
Faecal PCR
What are the potential limitations of faecal antigen tests for diagnosing parvovirus?
Clinical signs of parvovirus can begin before viral shedding, which can result in a false negative on the faecal antigen test so it is important to repeat the test if you have strong suspicion of parvovirus. Furthermore, a faecal antigen test for parvovirus can present with a false positive following vaccination
Which faecal analysis test would give a diagnosis of parvovirus before a faecal antigen test?
A haemagglutination inhibition test can provide a diagnosis before a faecal antigen test, however, not many labs provide this test
What are the benefits and limitations of a serology for anti-CPV antibodies to diagnose parvovirus?
A serology for anti-CPV antibodies evaluates the body’s immune response to parvovirus and can be used to confirm diagnosis. However, it is not good for initial diagnosis as the body needs time to establish an immune response and produce antibodies against parvovirus before this test is useful
Which additional diagnostic tests should you do if you suspect parvovirus and why?
- Haematology to assess for neutropenia
- Biochemistry to assess electrolytes to determine approprate fluid therapy
- Venous blood gas analysis to asses acid base balance to determine approprate fluid therapy
- Coagulation profile to assess for disseminated intravascular coagulation (DIC)
These tests will help in clinical decision making
How do you manage a parvovirus infection?
Intravenous fluid therapy
Antibiotics if neutropenic
Antiemetics
Nutritional support
Interferon
Plasma or colloids if indicated
Remember have definitive diagnosis before using interferon as expensive
What are interferons?
Interferons are signalling proteins which are released in response to viruses causing nearby cells to heighten their anti-viral defences
Which signalement is more prone to salmonella associated diarrhoea?
Young and immunocompromised patients, or patients with a concurrent gastrointestinal infection are more prone to salmonella-associated diarrhoea
Why are there concerns for an increased prevalance of salmonella associated diarrhoea?
There is a risk of increased prevalance of salmonella associated diarrhoea due to raw fed diets
Which signalement is more prone to campylobacter associated diarrhoea?
Young and immunocompromised patients, patients with a concurrent gastrointestinal infection, and patients with poor hygiene are more prone to campylobacter-associated diarrhoea
(T/F) All E.coli in the gastrointestinal tract are pathogenic
FALSE. Most of the E.coli in the gastrointestinal tract are commensals, only specific strains are pathogenic
What are the pathogenic strains of E.coli?
Enterotoxic E.coli (ETEC)
Enteropathogenic E.coli (EPEC)
Enterohaemorrhagic E.coli (EHEC)
Enteroinvasive E.coli (EIEC)
How do you diagnose bacterial causes of diarrhoea?
Faecal culture and sensitivity
ELISA for specific enterotoxins
PCR
What is acute haemorrhagic diarrhoea syndrome?
Acute haemorrhagic diarrhoea syndrome is a disease characterised by acute onset vomiting (sometimes haematemesis) and acute onset haemorrhagic diarrhoea which can rapidly progress to severe dehydration
Which strain of clostridia is associated with acute haemorrhagic diarrhoea syndrome?
Clostridium perfringens
Dysbiosis results in colonisation of C.perfringens in the small intestine (is a commensal of the colon), and the enterotoxin produced causes haemorrhagic necrosis of the small intestinal mucosa
How do you manage acute haemorrhagic diarrhoea syndrome?
Intravenous fluid therapy
Antibiotics if neutropenic
Antiemetics
Nutritional support
Plasma or colloids if indicated
How do you symptomatically manage acute diarrhoea?
Dietary modification (low fat diet with smaller, frequent meals)
Probiotics
Intravenous fluid therapy if indicated
Antiemetics if there is concurrent vomiting
What are the differential diagnoses for chronic diarrhoea?
Parasitism
Alimentary lymphoma
Intestinal neoplasia
Chronic intussusception
Lymphangiectasia
Chronic idiopathic enteropathies
Chronic colitis
Exocrine pancreatic insufficiency (EPI)
Chronic liver disease
Chronic renal disease
Addison’s disease
Give three examples of parasitic causes of chronic diarrhoea
Giardia (small intestinal)
Trichuris (large intestinal)
Tritrichomonas foetus (large intestinal)
What is lymphangiectasia?
Lymphangiectasia is the chronic dilatation of the lymphatic vessels within the intestine resulting in leakage of lymphatic fluid into the intestinal lumen resulting in diarrhoea and malabsorption resulting in weight loss
What are the key signs of intestinal lymphangiectasia on haematology and biochemistry?
Lymphopenia
Hypocholesterolaemia
Hypoalbuminaemia
Which diagnostic tests can be done when investigating chronic diarrhoea?
Faecal analysis
Haematology
Biochemistry
ACTH stimulation test for Addisons
Trypsin like immunoreactivity test for EPI
Diagnostic imaging
Endoscopy and biopsy
Exploratory laparotomy and biopsy
Which faecal analysis tests can be done to diagnose giardiosis?
Zinc sulphate faecal flotation test
ELISA for giardia antigens
PCR
Which faecal analysis test for giardia has the most specificity?
ELISA for giardia antigens
How do you treat giardiosis?
Fenbendazole
What are the aims of haematology and biochemistry when investigating chronic diarrhoea?
Haematology and biochemistry can be used to identify systemic disease as well as gather more information on the patient’s clinical status
When investigating chronic diarrhoea, why is it so important to assess blood cobalamin (vitamin B12) levels?
When investigating chronic diarrhoea it is important to monitor cobalamin levels as cobalamin is an essential co-factor for rapidly dividing cells and a deficiency in cobalamin is a marker of severe intestinal disease, malabsorption of cobalamin at the ileum, decreased intrinsic factor production, and indirectly results in decreased epithelial turnover. Low cobalamin is a negative prognostic indicator and a therapeutic target
Which diagnostic test can be done to diagnose exocrine pancreatic insufficiency?
Trypsin like immunoreactivity test (trypsin will decrease)
What are the purposes of ultrasound when investigating chronic diarrhoea?
The main benefits of ultrasound when investigating chronic diarrhoea is the ability to assess the gastrointestinal lumen and wall for signs of neoplasia, obstruction, and to assess whether endoscopy or exploratory laparotomy should be performed to determine the diagnosis (i.e. endoscopy would not be appropriate if you needed to biospy the large intestine etc)
What can be done to differentiate between neoplastic and non-neoplastic causes of chronic diarrhoea?
Histoplathology of a intestinal mucosal biopsy
Why is it so important to determine a definitive diagnosis for chronic diarrhoea?
A definitive diagnosis is very important as it allows for more targeted management/treatment of the chronic diarrhoea
What are the classifications of chronic idiopathic enteropathies?
Food responsive chronic enteropathy
Antibiotic responsive enteropathy
Glucocorticoid responsive enteropathy
How do you diagnose chronic idiopathic enteropathies and idiopathic inflammatory bowel disorder?
Chronic enteropathies and idiopathic inflammatory bowel disease are diagnosed by exclusion of other causes of gastrointestinal disease and based on their response to therapeutics
How do you manage chronic idiopathic enteropathies?
Dietary modification trials
Antibiotic trials
Manipulation of intestinal flora (prebiotics and probiotics)
Immunosupporessive therapy
Often requires a lot of trial and error and important to manage owner expectations as there is high risk of recurrence
Which dietary modifcations can be attempted to manage chronic idiopathic enteropathies?
Hypoallergenic diets
Hydrolysed protein diets
Low fat diets
Prebiotics and probiotics
Fibre supplementation
Which immunosuppressive therapy combination can be useful for managing chronic idiopathic enteropathies?
Prednisolone and chlorambucil
What adjunct therapy should be included in the management of chronic idiopathic enteropathies?
Parenteral or high dose oral cobalamin (vitamin B12)
What is protein-losing enteropathy?
Protein-losing enteropathy (PLE) is a condition in which there is excess loss of serum proteins into the gastrointestinal tract due to different aetiologies
What are some of the key complications of protein-losing enteropathy?
Pulmonary thromboembolism
Pulmonary effusion
Important to investigate any tachpnoea and dyspnoea
How can protein losing enteropathies result in pulmonary thromboembolisms?
When serum proteins are lost into the gastrointestinal tract, the coagulation factors are also lost
Sometimes anticoagulants will be given prophylactically for cases of severe PLE
What are the key signs of protein-losing enteropathy on biochemistry?
Hypoproteinaemia with hypoalbuminaemia and hypoglobulinaemia
What is the risk associated with biopsies in patients with hypoproteinaemia?
Patients with hypoproteinaemia are at increased risk of dehiscence with full thickness biopsies
