Diseases of the Small Intestine

Question 1

Describe the anatomy and purpose of the functional unit of the small intestine: the villus

Answer 1

• The villi are finger like projections of the small intestinal mucosa that greatly enhance the functinoal surface area of the GIT
• They are covered by epithelial cells (enterocytes) and goblet cells
• Crypt cells are located at the base of the villi and are responsible for intestinal secretions and continually produce undifferentiated epithelial cells
• The epithelial cells differentiate as they migrate up the villus and are shed in ~3 days
• Differentiated enterocytes are responsible for both digestive and absorptive processes

Question 2

Describe the normal process of digestion within the small intestinal lumen

Answer 2

• The SI lumen essentially provides an optimal environment for hydrolysis and emulsification of major dietary constiuents
• The lumen provides an optimal pH and temperature and movements aid in mixing of the contents
• Bile salts are mixed to emulsify fats
• Pancreatic enzymes are released into the lumen to hydrolyse proteins and carbohydrates
• Only terminal hydrolysis of proteins and carbohydrates are performed by enzymes on the microvillar membrane.

Question 3

By which process are the following absorbed from the small intestine?

1. Simple sugars
2. Amino acids
3. Oligopeptides
4. Products of fat digestion
5. Fat soluble vitamins (A, D, E, K)
6. Folate
7. Cobalamin

Answer 3

1. sugars: active or facilitated carrier-mediated transport
2. amino acids: active or facilitated carrier-mediated transport
3. Oligopeptides: active or facilitated carrier-mediated transport
4. Passive diffusion
5. Passive diffusion
6. Via carrier mediated diffusion in the proximal small intestine
7. Bound to intrinsic factor, via receptor mediated endocytosis in the ileum

Question 4

The default response of the SI immune system is one of tolerance.

Describe the role of the various cells in maintaining mucosal immune system tolerance

Lymphocytes

Answer 4

• Lymphocytes are present within the Peyer’s patches and mesenteric lymph nodes
• Plasma cells are abundant in the lamina propria
  
  • Most plasma cells produce locally acting IgA
• T cells are either located within the LP or intra-epithelial spaces
  
  • T cells are differentiated by expression of CD4⁺ and CD8⁺ molecules
• CD4 (T helper cells) recognise antigen presented with MHC II molecules on antigen presenting cells
• CD8 (cytotoxic T cells) recognise MHC I presented antigen
  
  • CD4 cells predominate in the canine LP, whereas CD8 cells predominate in the feline LP
• Continuous recognition and interaction with antigen leads to the LP lymphocytes being highly differentiated and specific.

Question 5

The default response of the SI immune system is one of tolerance.

Describe the role of the various cells in maintaining mucosal immune system tolerance

Dendritic Cells

Answer 5

• Dendritic cells capture, store and present antigen to the lymphocytes
• The can extend processed between the enterocytes to sample the luminal contents
• They essentially provide surveillance of the local microbiome
• The DCs are responsible for either upregulation of an immune response or tolerogenesis by activation of regulator T cells (Treg)

Question 6

The default response of the SI immune system is one of tolerance

Describe the role of the various cells in maintaining mucosal immune system tolerance:

Macrophages, neutrophils, mast cells and eosinophils

Answer 6

• Macrophages in the Peyer’s patches and LP phagocytose and present antigen in conjunction with MCH II
  
  • antigen thus presented can stimulate T cells (regulator or effector cells) and B cells
• Macrophages also secrete cytokines, chemokines and inflammatory mediators
• Neutrophils are only present in small numbers unless there is significant inflammation
• Eosinophils and mast cells have primarily pro-inflammatory roles (less involved in self-tolerance)

Question 7

The default response of the SI immune system is one of tolerance

Describe the role of the various cells and note their role in maintaining mucosal immune system tolerance:

Enterocytes

Answer 7

• The enterocytes provide a functional barrier to entry or both the microbiome and potential pathogens
• Enterocyte express TLRs and interact with the microbiome
• MHC II is constituitively produced by dog enterocytes,and upregulated during inflammation in cats
• Enterocytes can produce cytokines, chemokines and pro-inflammatory mediators in disease states

Question 8

The default response of the SI immune system is one of tolerance

Describe the roll of the various cells noting their involvement in maintainance of mucosal immune system tolerance:

Enteric neurons

Answer 8

• Bidirectional communication exists between the neurons and the gut and vice versa
  
  • Immune cell release of mediators can generate axon reflexes
  • Enteric neurons release immunoactive neuropeptides including substance P
• The enteric neurons can alter and effect intestinal motility, secretion and absorption.

Question 9

List the innate immune defenses of the small intestine

Answer 9

1. Peristaltic movement - antigen clearance
2. Mucus layer
3. Enterocyte barrier
4. Presence of the microbiome
5. Presence and function of the innate immune cells
6. Possibly the production of defensins by enterocytes
   
   • This is poorly defined in the dog and cat

Question 10

List the major mechanisms by which normal SI homeostasis can be disrupted

Answer 10

1. Genetic factors
2. Barrier dysfunction
3. Dysbiosis

All lead to inappropriate exposure to luminal antigen. This can lead to inflammation and alteration of the balance between effector and regulatory mucosal T cells.

Question 11

Describe the two main outcomes following an inappropriate antigenic challenge in the small intestine.

Answer 11

1. Challenge contained:
   
   • mucosa repairs and the normal tolerogenic environment returns
2. Challenge continues unabated / mucosa cannot repair / abnormal immune response:
   
   • Chronic inflammation ensues
   • Increased antigen - increased MHC II expression
   • Increased expression of vascular addressins leads to enhanced recruitment of lymphocytes (via MAdCAM-1) and other inflammatory cells
   • Increased expression of matrix metalloproteinases leads to architectural changes

Question 12

List the various mechanisms that can contribute to signs of small intestinal disease.

Provide an example of a disease causing each mechanism

Answer 12

1. Luminal disturbance
   
   • exocrine pancreatic insufficiency
2. Brush border membrane disease
   
   • Poorly defined diseases in dogs
   • Various breed specific abnormalities that lead to cobalamin deficiency
3. Microvillar membrane damage
   
   • Enteropathic E coli.
4. Enterocyte dysfunction
   
   • Bacterial exotoxins
   • Malnutrition and ischaemia also inpair enterocyte function
5. Epithelial barrier dysfunction
   
   • NSAID use
6. Villus atrophy
   
   • Viral infections
   • Chemotherapy drugs incl. vincristine
7. Disordered motility
   
   • secondary to intestinal obstruction
8. Mucosal inflammation
   
   • numerous triggers
9. Hypersensitivity
   
   • dietary responsive bowel disease
10. Neoplasia
    
    • focal (adenocarcinoma) or diffuse (lymphoma)
11. Nutrient delivery failure
    
    • Lymphangiectasia
12. Congenital abnormalities
    
    • atresia, stenosis, duplications, diverticulae

Question 13

List the broad mechanisms that can trigger ileus

Provide 2 examples of each mechanism.

Answer 13

1. Functional
   
   • Post-surgery
   • Irritable bowel syndrome
2. Inflammatory
   
   • Parvovirus / other infectious disease
   • Peritonitis
3. Metabolic
   
   • Diabetes mellitus
   • hypokalaemia
   • Endotoxaemia
4. Neuromuscular
   
   • Dysautonomia
   • Visceral myopathy
5. Physical
   
   • Foreign body
   • Mass / Tumour
   • Intussusception

Question 14

List the major clinical features of small intestinal disease

Answer 14

• Diarrhoea
• Malabsorption
• Melena
• Protein losing enteropathy
• Borborygmi / flatulence
• Weight loss / failure to thrive

Question 15

List and describe the pathophysiological mechanisms the contribute to the formation of diarrhoea

Answer 15

Note: While the various mechanisms can be describe separately, it is most often a combination of mechanisms that ultimately cause diarrhoea

1. Osmotic
   
   • Most SI diseases have a component of osmotic
   • Water is passively drawn into the lumen due to changes in the luminal environment
2. Malabsorption
   
   • reduced absorption leads to osmotic diarrhoea
   • increased bacterial fermentation of unabsorbed solutes can lead to the production of volatile fatty acids and products that cause an increase in colonic secretions
3. Permeability
   
   • Inflammatory or neoplastic disease that causes exudation
4. Secretory
   
   • Chemical or bacterial toxins trigger increased secretions

Question 16

Describe the mechanisms of malabsoprtive diarrhoea giving examples

Answer 16

1. Maldigestion leads to malabsorption as nutrients are not made available for absorption at the mucosal surface
   
   • Maldigestion can occur secondary to diseases such as EPI where a lack of pancreatic enzymes leads to reduced proteolysis and carbohydrate hydrolysis
2. Luminal mechanisms:
   
   • alterations in pH (especially decreases due to excessive gastrica acid production) can lead to destuction of endogenous pancreatic enzymes
   • Cholestatic liver disease / ileal loss of bile salts - both can lead to fat malabsortption and dysbiosis
   • Dysbiosis can lead to bacterial utilisation of nutrients and reduced availability
3. Mucosal mechanisms:
   
   • Acute or chronic inflammation can lead to reduced villus surface area
   • Ileal disease can lead to reduced presence of cobalamin cotransporter
4. Transport phase abnormalities:
   
   • Primary lymphangiectasia - reduced passive fat transport and increased fat/protein/lymph loss
   • Secondary transport abnormalities occur with lymphatic obstruction due to neoplasia, inflammation or infection
   • Right sided CHF and hepatopathy causing portal hypertension can also lead to reduced passive diffusion from the lumen into the portal blood stream

Question 17

List the tests with specific indications in the investigation of small intestinal disease

Provide a brief description of the indications and usefulness of each

Answer 17

1. Faecal tests:
   
   • Floatation: Identification of most intestinal parasites
   • ELISA: Sensitive for the rapid diagnosis ofGiardia or parvovirus in clinic
   • PCR: Tritrichomonas, and identification of clostridial enterotoxin genes. Also useful for detection of viral particles including parvovirus and coronavirus
   • Occult blood: Very sensitive test for haemoglobin (endogenous or exogenous). Primarily used to assess for causes of anaemia, not as a primary investigative test of SI disease
   • Alpha₁-Protease Inhibitor: Mainly used to assess for early PLE in the case of hypoalbuminaemia without diarrhoea or screen Soft-coated Wheaten Terriers before breeding
2. Serum folate:
   
   • Can be increased or decreased with intestinal disease
   • Decreases indicate proximal intestinal damage
   • Increases can occur with dysbiosis, but this test is not diagnostic of SIBO or dysbiosis
3. Serum cobalamin:
   
   • Primarily decreased with distal ileal disease or with exocrine pancreatic insufficiency
   • Not a diagnostic test per se, but more a marker of intestinal disease
   • Low cobalamin indicates a need for supplementation

Question 18

What indirect tests are available to assess intestinal function?

Answer 18

1. Permeability tests:
   
   • lactulose:rhamnose absorption - tested by assessment of urinary excretion following orogastric administration
2. Faecal alpha₁-proteinase inhibitor:
   
   • tests for faecal protein loss
3. Breath tests
   
   • Breath hydrogen and breath urea tests for bacteria and Helicobacter respectively
   • Not widely available or utilised
4. Serum unconjugated bile acids
   
   • Some bacteria may deconjugate bile acids allowing them to be passively absorbed, avoiding enterohepatic cycling.
5. Indirect assessment of motility or transit time
   
   • Barium studies, PWD US, scintigraphy
   • SMART capsule can measure peristaltic pressures

Question 19

When and why might indirect tests of small intestinal function be indicated?

Answer 19

1. Must exclude extra-GIT causes of malabsorption first.
   
   • Obtain serum for TLI
2. Approximately 50% of dogs with small intestinal disease and malabsorption may have normal small intestinal biopsies
   
   • Therefore may attempt to prove functional disease indirectly prior to biopsy

Question 20

What are the general limitations of indirect small intestinal functional tests in dogs?

Answer 20

• Most of the tests assessing for functional small intestinal disease are non-specific or provide variable and imprecise results. There is a distinct lack of data correlating results to clinical disease or histopathological diagnoses.
• Motility studies can be influenced by diet composition and stress and standardisation is poor. Significant variablility exists in normal dogs/cats
• SUBA results do not correlate with diagnoses and can vary in normal dogs - best used for assessment of hepatic disease
• Gamma emitting (⁵¹Chromium-EDTA) radiation limits the use of the originally designed permeability tests
• Lack of reference range data in normal and abnormal animals together with clinical reference to underlying disease limits the use of permeability testing

Question 21

List the diagnostic imaging options for investigating small intestinal disease.

Note the indications for each, together with the limitations of each

Answer 21

1. Radiography
   
   • Acute vomiting or vomiting associated with diarrhoea
   • Palpable abdominal abnormalities including pain or a mass
   • To help exclude/investigate for a foreign body/obstruction
   • May be useful to identify ileus or mesenteric torsion
2. Contrast radiography / BIPS
   
   • May help assess for partial obstruction or identify radiolucent foreign bodies
   • Studies assessing transit time are not physiologically significant
   • ​Largely replaced by ultrasonography due to improved sensitivity and specificity
3. Ultrasonography
   
   • Indicated for assessment of both acute and chronic disease
   • Sensitive for the identification of masses or obstruction
   • Can identify abnormalities in chronic disease.
     
     • eg. layering changes in neoplasia, mucosal striations in lymphangiectasia, mucosal heterogeneity with inflammatory disease
   • Useful to guide the decision for biopsy acquisition - endoscopy versus surgical
   • Useful to exclude or confirm concurrent non-intestinal disease including lymphadenopathy

Question 22

List the causes of chronic diarrhoea for which intestinal biopsy results can be normal

Answer 22

1. Antibiotic responsive diarrhoea
2. Brush border membrane disease
3. Dietary responsive diarrhoea
4. Food intolerance
5. Type 1 hypersensitivity to food (pending on extent of fasting)
6. Irritable bowel syndrome
7. Intestinal sclerosis (if biopsies are not deep enough)
8. Patchy disease of any type (including IBD)
9. Colonic disease
10. Extra-gastrointestinal causes of diarrhoea (eg. EPI)

Question 23

Discuss the clinical evidence for the use of probiotics in dogs with acute or chronic diarrhoea

Answer 23

1. By definition, probiotics are orally administered living organisms that provide benefits beyond those of basic nutrition
   
   • A major caveat is the fact that what defines optimal enteric health is poorly defined
2. Possible mild reduction in the number of days of diarrhoea in actue diarrhoea (but that study included a probiotic/prebiotic mixture)
3. General lack of evidence across studies to indicate any effect of probiotics on clinical signs with chronic diarrhoea.

Limitations:

1. Large numbers of studies used changes in faecal score to assess response - is this an appropriate measure of effectiveness
2. Bias is a major limitation as is underpowering of many studies
3. Majority of studies looking at use in acute diarrhoea have small numbers of dogs and significant risk of bias.
4. 50% improvement as a goal for probiotic use may be too optimistic, with human studies reporting 25% reduction in diarrhoea most often.
5. Variability in the strain of probiotic used in the different studies makes comparison between studies difficult
6. Dose recommendations are limited as only a narrow dose range has been evaluated
7. Quality control of individual probiotics may be of concern also

Question 24

Apart from variable improvement in faecal scoring, what other potentially beneficial changes have been reported with the use of probiotics?

Answer 24

1. Faecal IgA reported to be elevated with probiotic use
2. Circulating vaccine associated CDV IgG and IgA elevated in dogs receiving probiotic E. faecium
3. Lymphocyte proliferation and rabies titre were higher in sled dogs given probiotic E faecium
4. Increase in T cell markers Fox P3+ and TGF-b (both important cytokines in the development and role of regulatory T cells) in dogs treated with VSL#3

Question 25

Highlight the evidence surrounding the use of probiotics in cats for the management or prevention of diarrhoea

Answer 25

* *E faecium SF-68* reduced periods of diarrhoea \> 2 days in shelter cats when compared to placebo * *E faecium* SF-68 also reduced some clinical signs associated with antibiotic (amoxicillin/clavulanate) induced diarrhoea * Probiotics may help to maintain the faecal microbiome diversity during periods of stress * Probiotics may help to maintain faecal microbiome diversity and reduce clinical signs associated with chronic herpes virus (pilot study from 2009 that has not been followed up)

Question 26

List the various bacteria considered to be clinically relevant causes of diarrhoea in dogs

Answer 26

1. *Campylobacter* spp. 2. *Salmonella* spp. 3. *Clostridium* Spp 4. *Escherichia coli* 5. *Yersinia pseudoturberculosis*

Question 27

Discuss the clinical implications, diagnosis (including challenges) and treatment of campylobacter diarrhoea in dogs

Answer 27

* Campylobacter can be found in up to 100% of faecal samples in healthy and diarrhoeic dogs - proving symptomatic infection is therefore impossible. * This varies from humans where all campylobacter spp are considered pathogenic * Raw chicken is a major risk factor for infection * Co-infection with viral causes of diarrhoea causes the most overt clinical signs * The organism can adhere to the intestinal enterocytes, invade and cause an ulcerative enterocolitis * The organism can induce the activation of NF-kB and production of the neutrophil chemokine IL-8 * PCR is the preferred diagnostic test to confirm infection, though a positive culture may be more specific (with PCR used for speciation) _Treatment:_ * Generally supportive care only * Erythromycin, tylosin or clindamycin may be effective * Usually sensitive to fluoroquinolones, but hard to justify * Care with zoonoses for immunocompromised people

Question 28

Discuss the diagnosis (including challenges), clinical implications, and treatment of Salmonella diarrhoea in dogs

Answer 28

_Diagnosis:_ * Faecal culture or PCR (or blood culture with septicaemia) * Subclinical carriage is common and has been reported in up to 30% of healthy dogs _Clinical implications:_ * Most often a cause of diarrhoea in the young, parasitized, kenneled or immunocompromised * Coprophagia and eating a BARF/raw meat diet increases the exposure risk significantly * Infection can cause the following: * Transient, subclinical carriage * Actue gastroenteritis * Acute bacteraemia and septicaemia * Infection and establishment of a carrier state * Clinical gastroenteritis can be severe with abdominal pain, haemorrhagic diarrhoea, fever, anorexia, dehydration with hyperkalaemia/hyponatraemia, marked depression and shock _Treatment:_ * Guided by clinical condition, with parenteral antibiotics reserved for severely affected or septicaemic patients. * Fluoroquinolones are effective against most species and unlikely to induce a carrier state Note that FISH has identified invading organisms in SI biopsies even when stool cultures have been negative

Question 29

Discuss the clinical findings, diagnosis and treatment of E coli associated diarrhoea in dogs

Answer 29

* Clinical findings are largely dependent on the E coli strain and the presence of concurrent infection, especially viral infections (eg. parvovirus) * Enterotoxigenic (ETEC) * Produce heat-stable and heat-labile toxins * Cause excessive secretion by the SI and secretory diarrhoea * Enterpathic (EPEC) * Cause of granulomatous colitis in boxer dogs * Enterohaemorrhagic (EHEC) * Haemolytic uremic syndrome * Trophism for the large intestine * Can be a cause of acute or contribute to chronic diarrhoea _Diagnosis:_ * Challenging to prove causation of E. coli * PCR probes for pathogenicity markers or toxins required _Treatment:_ * largely supportive with appropriate antibiotic selection. * Eg. Enrofloxacin treatment for granulomatous colitis in boxer dogs

Question 30

Salmon Poisoning What is the cause of this disease in dogs? How can it be diagnosed and treated?

Answer 30

* Salmon poisoning is caused by *Neorickettsia helmintoeca* and *Neorickettsia elokominica* * The rickettsial organism lives within a fluke that is present within salmon from Northern California to Washington and in Brazil * Highly fatal disease without appropriate treatment * high fever, HGE, vomiting, lethargy, oculonasal discharge and a peripheral lymphadenopathy _Diagnosis:_ (suspicion with history of eating raw fish from endemic area) * Identify the fluke eggs within faeces * Identify intracytoplasmic inclusions within the macrophages from lymph node aspirates _Treatment:_ * Oxytetracycline IV q 8 hours for at least 5 days * Praziquantel for the trematode vector

Question 31

What is Prototheca? What are the clinical signs of protothecosis and how can the disease be treated?

Answer 31

* *Prototheca* spp. are achlorophyllous algae * They naturally live within animal waste and sewage-contaminated food/water * Typically causes a cutaneous infection in cats * Large intestinal disease is most common in dogs * Rarely, can become disseminated and infect the GIT, lymph nodes and CNS * Host cellular immunity likely plays a role in the disseminated form _Treatment:_ The disseminated form is invariably fatal. Treatment has been attempted with amphotericin B and itraconazole, but the course of disease is only slowed

Question 32

List the common protozoal infections of the gastrointestinal tract of dogs and cats

Answer 32

1. Isospora 2. Cryptosporidium 3. Giardia 4. Toxoplasma ? 5. Trichomonads (including tritrichomonas inhabit the large intestine)

Question 33

What is cryptosporidium, how does it infect dogs or cats and what are the clinical consequences?

Answer 33

* Cryptosporidium is an obligate intracellular protozoal organism with many different species now identified. * Transmission is via the faecal oral route * Infection can vary from assymptomatic (most common) to self limiting diarrhoea in cats and rarely dogs * Severe haemorrhagic diarrhoea can be seen in immunocompromised animals, especially with coinfections _Diagnosis:_ * Faecal float assessed under oil immersion * Direct immunofluorescence * PCR _Treatment:_ * Generally supportive treatment only * tylosin and azithromycin - most likely to help due to treatment of con-infections * Nitazoxanide is effective in humans

Question 34

What is giardia, how does it infect dogs or cats and what are the clinical consequences? What are the treatment options?

Answer 34

* Giardia spp are a motile protozoan parasite found in soil or contaminated water sources * Transmission to dogs and cats is via the faecal oral route * Ingested oocysts excyst in the upper GIT and the trophozoites attach to the small intestinal mucosa * Oocysts are passed in the faeces 1-2 weeks after infection * Most infections are mild to assymptomatic, however acute to chronic and severe diarrhoea and weight loss can be seen. * ELISA is likely to be the preferred method of diagnosis with a sensitivity of ~ 90% and specificity of 95%. * Faecal floatation requires the collection and assessment of 3 samples over 5 days due to intermittent oocyst shedding * Faecal IFA and PCR are also available and provide reliable and sensitive results. * Treatment with fenbendazole at 50 mg/kg PO q 12 hours for 3-5 days is generally curative * Treatment with metronidazole at 25 mg/kg PO q 12 hours can eliminate infection in 2/3 dogs, but adverse effects are common at this dose * Febantel (in Drontal) is of questionable efficacy, but reduces shedding of oocysts * Environmental decontamination is necessary - bathe the pet and clean the environment with steam or a quaternary ammonium product

Question 35

List the various forms of idiopathic IBD. Make note of any specific clinical, treatment or prognostic differences for each

Answer 35

1. Lymphocytic-plasmacytic enteritis * Most common form of IBD * Must exclude pathogens including viral, bacterial and protozoal infection * Typically affects older animals 2. Eosinophilic enteritis * Must exclude parasites and dietary responsive disease. Treatment trials are always indicated * Often involes the stomach and colon * Most common in younger animals * Erosion and ulceration are common * Can occur as a paraneoplastic process with mast cell tumour and occasionally lymphoma * Prognosis is more guarded than other forms of IBD 3. Feline eosinophilic sclerosing fibroplasia * Rare and affects middle aged cats and Ragdolls * Histological variant of EE? 4. Neutrophilic enteritis * Most often associated with bacterial infection 5. Granulomatous enteritis * Most commonly seen in the ileum of cats associated with FIPV 6. Proliferative enteritis * Rare, segmental and probably seen with infection

Question 36

Describe the cause of lymphangiectasia and pathophysiological consequences

Answer 36

1. Primary lymphangiectasia is generally thought to be congenital and typically only affects the small intestine 2. Secondary lympangiectasia can be due to any cause of lymphatic obstruction including IBD and right sided CHF _Pathophysiology:_ * Marked lymphatic dilatation leads to rupture and leakage of protein rich lymph into the intestinal lumen * Protein losing enteropathy * Immune dysfunction secondary to lymphcyte loss * Mucosal inflammation and lipogranulomatous inflammation can be seen in conjunction with lacteal dilatation in both primary and secondary lymphangiectasia * The development of inflammation and lymphangitis leading to further obstruction could be one of the reasons for late presentation of a congenital problem.

Question 37

Descirbe the treatment options for primary lymphangiectasia and rationale for each

Answer 37

* As primary lymphangiectasia is typically associated with significant mucosal inflammation at the time of diagnosis, anti-inflammatory doses of prednisolone are generally recommended * Glucocorticoids are treating the secondary lymphangitis, liopgranulomas and/or LP infiltrate, not the dilated lacteals per se. * An ultra low-fat diet that is calorie dense and highly digestible can be "curative"if instigated prior to the onset of lipogranulomas. * If congenital, then "curative" is more referring to cure of the associated clinical and clinicopathological signs/findings. * Supplementation with fat-soluble vitamins is likely to be necessary