Pathology of the GI tract

1
Pathology of the GI tract

• Tim Morgan DVM, PhD

2
Alimentary Canal

• Continuous tube
• Tube within a tube
• Mouth (oral end)
• Anus (aboral end)
• Function
• Acquire nutrients
• Digest nutrients
• Absorb nutrients
• Expel non-digestible portion

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Prehension

• Fairly complex series of events
• Hunger centers in the brain
• Higher senses to locate food
• Lips especially in herbivores
• Tongue
• Teeth
• Esophagus

4
Digestion

• Mouth
• Grinding
• Salivary enzymes starches
• Stomach
• Mixing vat
• Acidification (monogastrics)
• Fermentation (ruminates)

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Digestion

• Small intestine
• Pancreas
• Enzymes
• Buffer
• Bile
• Emulsifies lipids

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Digestion

• Carbohydrates
• Polysaccharides
• Enzymatically broken down to monosaccharides
• Hydrolysis

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Digestion

• Proteins
• Polypeptides
• Enzymatically broken down to amino acids
• Hydrolysis

8
Digestion

• Fats
• Triglycerides 3 fatty acids on a glyceride
  backbone
• Enzymatically broken down to monoglycerides and
  fatty acids
• Hydrolysis

9
Absorption

• Ingested fluid
• 1.5 liters
• Secreted fluid
• 7 liters
• Total fluid
• 8-9 liters
• Not having to pass 9 liters of fecal fluid a day
• Priceless

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Absorption

• Mostly takes place in the small intestine
• Dependant upon surface area
• Mucosal folds ? 3x increase
• Villi ? 10x increase
• Microvilli (brush border) ? 20x increase
• Total 600x increase in surface area
• area of a tennis court

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Absorption

• Carbs (monosaccharides)
• Active transport
• Proteins (amino acids)
• Active transport
• Fats (monoglycerides and fatty acids)
• Micelles diffuse into cell membrane
• Reconstituted to tryglycerides in SER
• Dumped into lacteals as chylomicrons
• Travel thru lymphatics and are dumped into the
  caudal vena cava

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Dilemma

• Nutrients are composed of same materials as the
  GI tract
• Enzymes/mechanisms that breakdown nutrients can
  also affect GI tract
• Selective absorption
• Nutrients kept in
• Toxic compounds kept out
• Most contaminated environment
• Up to 10 12 organisms per gram

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Defense mechanisms

• Washing
• Saliva, mucous, fluid secretion
• Flushes bacteria etc. away before they get a
  chance to adhere
• Keeps cells moist and happy
• Prevents buildup of harmful materials
• Buffers

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Defense mechanisms

• Enzyme control
• Secreted in an inactive form
• Protein cleavage
• pH
• Cofactors
• Fuse or pin

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Defense mechanisms

• Cell turnover
• Stratified squamous epithelial cells in upper GI
• Mucosal epithelial cells in lower GI
• Cells shed from villous tips
• Crypts form proliferative pool
• Cells become more mature as they move up the
  villi
• Average turnover time 3 days
• Damage rapidly repaired by sliding of mucosal
  epithelial cells

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Defense mechanisms

• Nutrient sequestration
• Fe sequestration
• Fe required for bacterial growth
• Fe binding proteins
• Bacterial response hemolytic toxins
• Competition
• Large numbers of normal intestinal flora/fauna
• Limits niches available for invading organisms
• Initial colonization very difficult to unseat

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Defense mechanisms

• Innate immunity
• Paneth cells
• Antimicrobial peptides
• Defensins
• Cathelicidins
• Toll-like receptors
• Neutrophils
• Macrophages

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Defense mechanisms

• Acquired immunity
• Separate (sort of) immune system
• GALT
• Secretory IgA
• Resistant to degradation
• Blocks uptake of toxic compounds
• Very tight control
• Always bacteria present
• Pathogenicity may depend on number or organisms
  or other specific circumstances/conditions
• Always protein antigens present
• Under-responsive ? infection
• Over-responsive ? chronic inflammation
• IBD, Crohns, ulcerative colitis, PLE, amyloidosis

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Summary

• Contradictory function
• Absorb nutrients/exclude toxins
• Digest nutrients, dont digest self
• React to pathogens, dont react too much
• Effective defense mechanims
• Constant washing
• Rapid turnover
• Competition
• Environmental monitoring
• Environmental control

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Clinical Signs

• Ptyalism (drooling)
• Regurgitation undigested food
• Vomiting partially digested food
• Diarrhea
• Tenesmus
• Dehydration not specific for GI disease
• Abdominal pain (colic)
• Electrolyte abnormalities
• Melena digested blood
• Hematochezia bloody feces
• Cholemesis/hematemesis

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Oral Cavity

• Developmental
• Traumatic
• Toxic
• Inflammatory
• Infectious
• Viral, bacterial, fungal
• Autoimmune
• Neoplastic

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Developmental

• Cleft palate (palatoschesis)
• Failure of maxillary bones to fuse
• Variably sized defect in hard palate
• May interfere with nursing, feeding, chronic
  nasal infections

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Developmental

• Cleft lip/hare lip
• Brachygnathia
• Superior shortened maxillae
• Inferior shortened mandibles
• Prognathism

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Developmental

• Dentition
• Heterotopic polydontia
• Common in horses
• Anomalous dentition
• Missing or retained deciduous teeth
• Odontodystrophy
• Enamal hypoplasia
• Secondary to distemper virus infection in dogs
• Fluorine toxicity, malnutrition, vitamin A
  deficiency

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Traumatic

• Fractures
• Dislocations
• Foreign bodies
• Bones dogs
• Linear cats

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Inflammatory

• Stomatitis general term
• Glossitis, gingivitis, pulpitis
• Infectious diseases of the oral cavity
• Viral
• Bacterial
• Fungal

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Viral Stomatitis vesicular stomatitides

• Vesicle small circumscribed elevation of the
  epidermis/MM containing a serous liquid
• Vesicular stomatitides cannot be differentiated
  grossly call state or federal vet immediately
• Foot and mouth disease (Picornavirus)
  ruminants, pigs not in US
• Vesicular stomatitis (Rhabdovirus) ruminants,
  pigs, horses in US
• Vesicular exanthema (Calicivirus) pigs not in
  US
• Swine vesicular disease (Enterovirus) pigs
  not in US

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Oral Cavity Vesicular Stomatitides
Ruptured vesicle, sheep, FMD
Ruptured vesicles, snout, pig, FMD
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Foot Mouth, bovine
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Vesicular Stomatitides - VS
Ruptured vesicles, coronary band,
horse, VS
Vesicle on teat of cow, VS
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Viral Stomatitis Erosive Ulcerative
Stomatitides

• Erosion loss of superficial layers of epidermis
  or mucosal membrane
• Ulceration loss of all layers of epidermis or
  mucosal membrane
• Penetrates the basement membrane
• Viral erosive ulcerative stomatitides
• BVD-MD
• Malignant Catarrhal Fever
• Rinderpest
• Bluetongue
• Equine Viral Rhinotracheitis
• Felince Calicivirus

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BVD Mucosal Disease

• Bovine viral diarrhea virus (BVDV)
• Highly contageous
• Rarely fatal
• Fever, diarrhea, mucosal ulcerations, leukopenia
• Multiple serotypes
• Cytopathic
• Non-cytopathic

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BVD Mucosal Disease

• Normal disease course
• Immunocompetent animal
• Subclinical or mild disease
• Mucosal disease course
• Infection during 4th month of gestation
• Abortion, fetal mummification, develpmental
  anomalies (cerebellar hypoplasia)
• Surviving animals
• Persistent infection
• Immunotolerant to virus

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BVD Mucosal Disease

• Persistently infected, immunotolerant animal
• Super-infected with a cytopathic strain
• Unable to mount effective immune response
• Severe ongoing infection
• Near 100 fatality rate
• Anorexia, bloody diarrhea, fever, mucoid nasal
  discharge, ulcerative lesions throughout GI tract

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BVD Mucosal Disease
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Malignant Catarrhal Fever (MCF)

• Caused by several different gamma herpes viruses
• Cattle, deer, most other ungulates
• Ovine herpes virus 2
• North America
• Alcelaphine herpes virus 1
• Endemic in African wildebeest
• Causes disease in zoo ruminants and cattle in
  Africa

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Malignant Catarrhal Fever (MCF)

• Gross lesion is ulceration of mucosal surfaces,
  edema, mucopurulent nasal discharge,
  lymphadenopathy
• Microscopic lesions
• Lymphoid proliferation
• Fibrinoid vascular necrosis

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Malignant Catarrhal Fever (MCF)
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Feline Calicivirus

• RNA virus
• High rates of mutation
• Variable virulence
• Persistent infections
• Minimal clinical signs
• Virus shed in saliva, nasal secretions, feces
• Clinical signs
• Ulcers on tongue and foot pads
• Conjunctival edema, edema of face limbs
• Pneumonia in kittens

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Viral Stomatitis Papular Stomatitides

• Papule small, circumscribed, superficial, solid
  elevation of skin or mucous membrane
• Pustule visible collection of pus within or
  beneath the epidermis or mucous membrane
• Macule discolored circular area on skin or
  mucous membrane that is not elevated above the
  surface. Smoking remains of a papule or pustule

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Bovine Papular Stomatitis

• Young cattle 1 month to 2 years old
• Parapox virus
• Epidermal proliferation
• Papules, nodules, macules
• Tongue, gingiva, palate, esophagus, rumen, omasum
• Eosinophilic intracytoplasmic inclusions

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Bovine Papular Stomatitis
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Contagious Ecthyma (Orf)

• Sheep and lambs, goats, rarely man
• Parapox virus
• Epidermal proliferation
• Lips, mouth, teats
• Weight loss/poor growth due to pain
• Self limiting

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Contagious Ecthyma (Orf)
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Papillomatosis

• Papovavirus
• Bovine papilloma virus
• Canine papilloma virus
• Papillomas (warts) on mucosa of mouth, esophagus,
  rumen (cattle)
• Usually self-limiting lesions

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Papillomatosis
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Papillomatosis
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Papillomatosis
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Bacterial Stomatitides

• Associated with trauma
• Feeding, iatragenic, foreign body
• Opportunistic normal bacterial inhabitant
• Actinobacillus, actinomyces, fusobacterium

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Necrotizing stomatitides

• Oral necrobacillosis
• Calf diphtheria
• Necrotic membrane
• Foul breath, anorexia, fever

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Wooden tongue

• Actinobacillus lignieresii
• Often associated w/lingual groove
• Chronic infection
• Severe fibrosis
• Wooden tongue

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Wooden tongue

• Pyogranulomas
• Club-shaped bacterial colonies
• Splendora-Hepli
• sulfur granules

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Periodontal Disease

• Periodontal tissues
• Gingiva, cementum, periodontal ligament, alveolar
  supporting bone
• gt85 of dogs and cats 4 years and older are
  affected
• Pathogenesis
• Placque formation
• Mucin, slouphed epithelial cells, aerobic gram
  bacteria
• Mineral salts deposite on plaque
• Tartar/calculus
• Tartar ? gingival irritation
• pH change
• Pathogenic gram aerobic anaerobic bacteria
  proliferate beneath gingiva

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Periodontal Disease

• Destructive inflammation forms gingival crevice
• Sub-gingival bacteria continue to proliferate
• Deeper pockets of destruction
• Gingival stroma
• Periodontal ligament
• Alveolar bone
• Tooth loss, bacteremia, osteomyelitis, bacterial
  endocarditis

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Stages of Periodontal Disease
Stage I gingivitis, gingival edema
Stage III stroma loss, deep pockets
Stage II gingivitis, pockets
Stage IV bone loss, loose teeth
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Inflammatory, non-infectious

• Inappropriate immune/inflammatory response
• Self antigen autoimmune
• Unknown antigen immune mediated
• Generally a problem of small animals (Dogs and
  Cats)

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Auto-immune

• Considered dermatologic diseases
• Frequently affect muco-cutaneous junctions
• Pemphigus vulgaris
• Severe, acute or chronic vesicular/bullous
  disease of humans, dogs, cats
• Flaccid bullae erosions of muco-cutaneous
  junctions, oral mucosa, skin to lesser extent
• Clinical signs
• Salivation, halitosis, mucosal erosion/ulceration
• Severity varies greatly
• Histology
• Basal cells remain attached to basement membrane
• tomb stone appearance
• Destruction of acanthocytes (acantholysis)
• Lichenoid infiltration of lymphocytes and plasma
  cells
• Scattered neutrophils and eosinophils

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Auto-immune

• Bullous pemphigoid
• Grossly impossible to tell from pemphigus
  vulgaris
• Histology
• Subepidermal blister formation
• No acantholysis
• Reported in humans, dogs, horses, possible cases
  in cats

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Immune Mediated

• Feline plasma cell gingivitis
• Raised, erythematous, proliferative lesion
• Glossopalatine arch
• Periodontal gingiva

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Immune Mediated

• Feline plasma cell gingivitis
• Histologic appearance
• Gingival hyperplasia
• Gingival ulceration
• Large numbers of plasma cells
• Russell bodies
• Secondary suppurative inflammation over areas of
  ulceration
• Increased serum gamma globulin

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Immune Mediated

• Eosinophilic ulcer (Rodent ulcer, Eosinophilic
  granuloma complex)
• Chronic superficial ulcerative disease of mucosa
  and mucocutaneous junction
• Frequently affects upper lip of cats
• Siberian huskies
• Affected area is thickened, red, ulcerated

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Immune Mediated

• Eosinophilic ulcer
• Histologic appearance
• Ulcerated surface
• Moderate to large numbers of eosinophils with
  macrophages, lymphocytes, and plasma cells
• Collagenolysis

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(No Transcript)
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Uremic glossitis

• Relatively common lesion associated with renal
  failure in dogs and less commonly in cats
• Clinical signs
• Cyanotic buccal mucosa
• Fetid ulceration of tongue
• Margins of ulcer swollen

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Uremic glossitis

• Histologic appearance
• Necrosis of mucosal epithelium with ulceration
• Vascular necrosis of small arterioles of tongue
• Ischemic vascular lesion
• Pathogenesis poorly understood
• Poor correlation between blood ammonia levels and
  lesion development

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Proliferative and neoplastic oral lesions

• Gingival hyperplasia
• Non-neoplastic proliferation of gingival tissue
• Caused by chronic inflammation
• May be associated with periodontal disease
• Generalized or localized
• Brachycephalic breeds

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Gingival hyperplasia

• Histologic appearance
• Mature fibrous connective tissue
• Hypocellular
• May have focal areas of ulceration and
  inflammation

68
Epuloides

• Fibromatous epulis
• Fibrous mass arising from the periodontal
  ligament
• Firm, hard, gray to pink
• Similar in appearance to focal gingival
  hyperplasia
• Between teeth or on hard palate near teeth
• Carnasal teeth in brachycephalic breeds
• May mechanically displace the teeth
• Attached to the periosteum
• Do not invade bone

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Epuloides

• Fibromatous epulis
• Histologic appearance
• Interwoven bundles of fibroblastic tissue
• More cellular than gingival hyperplasia
• May have areas of bone production
• Ossifying epulis

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Epuloides

• Acanthomatous epulis (acanthomatous
  ameloblastoma)
• Odontogenic epithelial origin
• Rough, cauliflower-like lesion
• Dental arcade of dogs
• Locally invasive
• Invades and destroys bone
• Do NOT metastasize

71
Epuloides

• Acanthomatous epulis
• Histologic appearance
• Highly cellular
• Interconnecting odontogenic epithelial sheets
  bordered by columnary to cuboidal cells
• Contain numerous, usually empty, blood vessels

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Other tumors of dental origin

• Less common than epuli
• Ameloblastoma
• Dental lamina
• Outer enamel epithelium
• Odontogenic epithelium
• May produce dentin or enamel matrix
• Rare in all species, but less rare in cattle
• Young cattle

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Other tumors of dental origin

• Complex odontoma
• Fully differentiated dental components
• Disorganized, no tooth like structures
• Young horses
• Compound odontoma
• Mass containing numerous tooth-like structures
• denticles
• Young dogs, cattle, and horses
• Mandibular or maxillary arch

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Oral tumors of non-dental origin

• Squamous cell carcinoma
• Most common oral neoplasm is cats
• Ventral surface of the tongue, along the frenulum
• Nodular, red-grey mass
• Friable
• Often ulcerated
• Locally invasive
• Metastasize to regional lymph nodes
• Rarely metastasize to lung

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Squamous cell carcimona

• 2nd most common oral neoplasm in dogs
• Usually involves tonsil
• Small granular plaque ? 2-3x size of the tonsil
• Nodular, firm, white, frequently ulcerated
• Locally invasive
• Metastasize to regional lymph nodes
• Frequently met to distant sites, especially lung
• SCC arising from the gingiva is less likely to
  met than tonsillar SCC in dogs
• Horses cattle
• Rare, slow growing, very destructive, met to
  regional lymph nodes

76
Melanoma

• Most common oral tumor in dogs
• Rare in cats and large animals
• Almost always malignant
• Most have metastasized by the time of dx
• More common in males than females
• More common in pigmented animals
• No correlation between degree of pigmentation and
  biologic behaviour
• Met to lymph nodes, distant organs, especially
  lungs
• Median survival time 65 days in untreated
  animals

77
Melanoma

• Gross appearance
• Nodular, variably pigmented masses
• Anywhere in the oral mucosa
• Invasive and destructive
• May or may not be ulcerated

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Melanoma
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Melanoma

• Microscopic appearance
• Variable
• Heavily pigmented to amelanotic
• Cytologically appear as round cells

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Melanoma
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Fibrosarcoma

• Can occur in all animals, but usually seen in
  dogs
• 3rd most common oral tumor of dogs
• 25 occur in dogs lt 5 yrs of age
• Occur in gums around upper molars and in the
  cranial ½ of the mandible

82
Fibrosarcoma

• Gross appearance
• Nodular to multi-nodulare
• /- ulceration
• Firm
• Local invasion
• 35 metastasize to lymph nodes
• Early pulmonary metastasis

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Fibrosarcoma

• Histologic appearance
• Moderately cellular
• Streams of fibroblastic cells
• High mitotic rate
• Collagenous extra-cellular matrix

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Osteosarcoma

• Bones of the skull or jaw
• Similar in appearance to fibrosarcoma
• Bone lysis and proliferation on radiographs

85
Round cell tumors

• Mast cell tumors
• Discreet mass
• Lymphosarcoma
• Tonsillar
• Epitheliotrophic
• Plasma cell tumors
• Discreet mass
• Pleomorphic plasma cells

86
Salivary Glands

• Sialoadenitis inflammation of salivary gland
  uncommon in vet medicine
• Sialodacryoadenitis (SDA) coronavirus of lab rats
• Rabies and canine distemper
• Ranula cystic distention of duct of sublingual
  or mandibular glands
• Occurs on floor of mouth alongside the tongue
• Cause is unknown
• Salivary mucocoele (sialocoele) pseudocyst
  filled with saliva that causes inflammation with
  formation of granulation tissue
• Possible causes include trauma, foreign body or
  sialolith
• Sialolith stone in gland or duct
• Formed from sloughed gland epithelium that
  becomes surrounded by mineral
• Tumors usually derived from glandular/duct
  epithelium (adenoma, adenocarcinoma)
• May also see mesenchymal or mixed tumors
  including osteosarcoma

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Salivary Ranula
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Diagnosis of Sialocoele

• Aspirate mass with large bore needle
• Thick fluid that resembles mucus
• Macrophages filled with vacuoles (ingested mucin)
• May also see hematoidin crystals (from RBC
  degradation)
• Rx surgical drainage and removal of affected
  salivary gland

89
Salivary gland
Chronic inflammation of mandibular salivary gland
secondary to sialocoele in dog
Sialocoele wall composed of granulation tissue
90
Esophagus

• Tube
• Smooth and striated muscle
• Glands
• Mucosal epithelium

91
Esophagus developmental anomalies

• Developmental anomalies of the esophagus are rare
• Segmental aplasia
• Esophago-respiratory fistula
• Esophageal diverticulae
• Hyperkeratosis/squamous metaplasia

92
Esophagus traumatic lesions

• Obstruction
• choke
• Occurs at areas of esophageal narrowing
• Larynx
• Thoracic inlet
• Base of heart
• Diaphragmatic hiatus
• Clinical signs
• Salivation, wretching, regurgitation, dehydration

93
Esophagus

• Complications of choke
• Esophageal rupture ? cellulitis, death
• Esophageal dilation mega-esophagus
• Ulceration with subsequent stricture
• Common in cattle
• Hedge apples
• Aspiration pneumonia

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Esophagus
95
Esophagitis

• Esophageal biopsy from horse with 2 month history
  of regurgitation
• Mucosal ulceration
• Marked submucosal inflammation
• Disruption of submucosal glands
• Outcome could be stricture or aspiration
  pneumonia

96
Megaesophagus

• Dilation of esophagus due to insufficient or
  uncoordinated peristalsis in the mid and cervical
  esophagus
• Observed in humans, cattle, horses, cats, dogs
  and llamas
• Primary clinical sign is regurgitation after
  ingestion of solid food
• May be congenital with onset clinical signs at
  weaning
• Persistent right aortic arch (dilation cranial to
  heart)
• Idiopathic denervation in several dog breeds and
  Siamese cats
• May be acquired later in life secondary to
  (dilation cranial to stomach)
• Myasthenia gravis (autoimmune disease against ach
  receptors at nm jxn)
• Autoimmune myositis (inflammation of esophageal
  wall muscles)
• Polyneuritis
• Hypoadrenocorticism
• Hypothyroidism
• Polyradiculoneuropathy
• Toxins such as botulism, lead, OPs
• Parasites such as Toxoplasma gondii and
  Trypanosoma cruzi
• Idiopathic

97
Megaesophagus

• Persistent right aortic arch
• Upper right normal development of aortic arch
  (inset shows normal embryonic development of
  great vessels)
• Lower right when embryonic right fourth aortic
  arch becomes adult aorta, esophageal constriction
  occurs (inset shows vascular malformation
• Constricting ring formed by right aortic arch,
  pulmonary artery, and ductus arteriosus
• Dilation of esophagus occurs cranial to heart

98
Megaesophagus
99
Megaesophagus

• Diagnosis
• Survey and contrast radiography
• Esophagoscopy
• T3 and T4 before and after TSH stimulation (R/O
  hypothyroidism)
• Cortisol concentrations with dexamethazone
  suppression (R/O hypoadrenalcorticism)
• Plasma cholinesterase levels (R/O OP tox)
• Antiacetylcholine receptor antibody assay (R/O
  MG)
• Toxoplasma titer

100
Megaesophagus
Dilated esophagus anterior to stomach
101
Megaesophagus
102
Esophageal Parasitic Disease

• Spirocerca Lupi of canids
• Nematodes reach esophageal submucosa after they
  migrate through the wall of aorta
• Form granulomas in wall of intrathoracic
  esophagus, and granuloma opens to esophageal
  lumen allowing eggs to pass out through feces
• Associated clinical problems include dysphagia,
  aortic aneurysms, spondylitis, HPO, and
  esophageal fibrosarcoma/osteosarcoma
• Intermediate host is dung beetle
• Dx thoracic radiography, fecal exam
• Rx ivermectin

103
Spirocerca lupi
104
Aortic Nodules and Aneurysms
During the time that parasites are normally in
the aorta, or if parasites are arrested in the
aorta during migration, they may cause the
formation of small nodules or larger, more
diffuse granulomas and aneurysms which can
rupture leading to fatal extravasation into the
abdominal cavity.
105
Epidemiology
The slide illustrates the general distribution of
reported Spirocerca sarcoma in the Southeast.
Incidence of simple Spirocerca infection would
follow a similar distribution. Bailey at Auburn
recorded an 8 infection rate in Alabama in a
survey between 1951 and 1963, but only 2 from
1963-1970. Georgia surveys show less than 1 of
the dogs infected. Bailey considered the feeding
of uncooked intestinal tracts of chickens to be a
primary source of infection for dogs . Incidence
of Spirocerca has decreased in recent years due
to better care of dogs, the shift to confinement
poultry operations, and reduction of dung beetle
numbers by large scale use of agricultural
insecticides.
106
Egg of Spirocerca lupi
Note the small size, thick wall and larvae. A
whipworm egg is also present. Recovery of eggs is
dependent on a patent opening to the lumen of the
digestive tract and therefore ova are not
consistently found. Spirocerca worms do not live
more than a few years and lesions do not always
contain worms at necropsy.
107
Esophagus Miscellaneous Conditions

• Idiopathic muscular hypertrophy of distal
  esophagus
• Seen in horses, no clinical significance
• Esophagitis
• Often result of trauma
• Secondary bacterial infection
• Esophageal erosions/ulcers
• Reflux, trauma, viral disease
• BVD MD in cattle
• Papillomas

108
Ruminant Forestomach
Normal Anatomy
Rumen papillae
Reticulum epithelial folds
Omasum epithelial folds
109
Ruminant Forestomach

• Bloat (ruminal tympany)- Overdistention of rumen
  and reticulum by gases produced during
  fermentation
• Primary tympany (legume bloat, frothy bloat)
• Following diet change, rumen pH decreases to 5-6,
  foam forms which blocks cardia and causes rumen
  to distend (seen clinically as distended left
  paralumbar fossa)
• Secondary tympany
• Physical or functional obstruction/stenosis of
  esophagus leads to eructation failure and gases
  accumulate in rumen
• Esophageal foreign body, vagal nerve dysfunction,
  lymphosarcoma, etc.
• Foreign bodies
• Hair balls, plant balls
• Hardware disease
• Lead poisoning
• Rumenitis
• Lactic acidosis (Grain overload)
• Bacterial secondary to acidosis or mechanical
  injury
• Mycotic secondary to acidosis or antibiotic
  administration
• Lesions due to infarcts caused by fungal
  vasculitis
• Primary fungi are Aspergillus, Mucor, Absidia,
  etc
• Miscellaneous
• Parakeratosis
• Vagus indigestion

110
Ruminant Forestomach - Bloat

• Post mortem diagnosis often based on observing
  bloat line which is a line of demarcation between
  the bloodless distal esophagus and the congested
  proximal esophagus at thoracic inlet

111
Ruminant Forestomach Foreign Bodies

• Trichobezoars hairballs
• Hair forms nidus
• Phytobezoars plant balls

112
Ruminant Forestomach Foreign Bodies

• Hardware disease
• Ingestion of baling wire, nails perforates
  through wall of reticulum (reticulitis) and
  enters peritoneal cavity (peritonitis) or
  pericardial sac (pericarditis)

Hardware disease fibrinous pericarditis
113
Rumenitis (Lactic Acidosis)

• Common disease of cattle that consume excessive
  readily digestible carbohydrates, especially
  grain (grain overload)
• Within 2-6 hours, microbial population of rumen
  changes to gram positive bacteria (Strep bovis)
  which results in production of lactic acid
• Rumen pH falls below 5 which destroys protozoa,
  lactate-using organisms and rumen motility ceases
• Lactic acid causes chemical rumenitis.
• Absorption of lactic acid into bloodstream causes
  lactic acidosis resulting in cardiovascular
  collapse (shock), renal failure and death
• If survive, may develop bacterial or mycotic
  rumenitis in several days, or liver abscesses
  (necrobacillosis) or laminitis in several weeks
• Dx check pH of rumen fluid obtained by stomach
  tube, examine rumen fluid with microscope ( no
  protozoa, few gram negative, mostly gram positive
  bacteria on gram stain)

114
Grain Overload
115
Reticulitis/Rumenitis
116
Rumenitis
117
Mycotic Rumenitis
118
Miscellaneous Rumen Conditions

• Ruminal parakeratosis seen in cattle and sheep
  fed diets with less than 10 roughage
• Papillae are enlarged, adhered together and firm
• Affected papillae contain excessive layers of
  keratinized epithelial cells, bacteria and food
  material
• May alter nutrient absorption, decrease feed
  efficiency

119
Miscellaneous Rumen Conditions

• Vagus Indigestion (chronic indigestion)
• Seen in cattle and sheep
• Gradual development of rumenoreticular and
  abdominal distention
• Four types recognized based on site of functional
  obstruction
• Type I failure of eructation resulting in
  free-gas bloat, usually due to inflammatory
  lesions that involve vagus nerve (hardware
  disease, pneumonia, etc)
• Type II failure of transport from omasum to
  abomasum via omasal canal, usually due to abscess
  in wall of reticulum near vagus (hardware
  disease), or lymphoma or papilloma blockage
• Type III abomasal impaction due to feeding of
  dry coarse roughage with restricted access to
  water, especially in winter
• Type IV poorly characterized partial
  forestomach obstruction that usually occurs
  during gestation, may be due to enlarging uterus
  shifting abomasum to more cranial position
• Dx definitive may require exploratory left
  paralumbar fossa laparotomy and rumenotomy

120
Stomach and Abomasum

• Similar function and response to injury among
  ruminant abomasum and simple-stomached animals

Normal horse stomach
Histologic appearance
121
Abomasal Disorders

• Abomasal displacement (LDA, RDA)
• Abomasal volvulus
• Abomasal ulcers
• Abomasal Impaction
• Abomasal inflammation (abomasitis)
• Bovine viral diarrhea and mucosal disease
• Abomasal parasites
• Lymphosarcoma

122
Abomasal Displacements

• Usually to left side in high producing dairy
  cattle within one month of parturition
• Result of abomasal atony with gas distention and
  displacement upward along left abdominal wall
• Fundus and greater curvature displaced creating
  partial obstruction
• No interference with blood supply but passage of
  ingesta slowed leading to chronic partial
  anorexia
• Also see metabolic alkalosis related to
  sequestration of chloride in abomasum (HCL
  production continues)
• RDA occurs infrequently but atony, gas
  production and displacement occur as in LDA
• Then have rotation (volvulus) of abomasum on its
  mesentery resulting in ischemia
• Rotation is usually in counterclockwise when
  viewed from rear
• Leads to complete anorexia, necrosis of abomasal
  wall, shock

123
Right Displaced Abomasum with Rotation
124
Abomasal Ulcers

• Seen in adult cattle and calves
• Many etiologic possibilities such as viral
  disease (BVD, rinderpest, MCF)
• Nonviral in dairy cows 6 weeks after
  parturition (stress, heavy grain feeding?)
• Nonviral feedlot cattle on high grain rations
• Nonviral hand fed dairy calves on milk replacer
  that start to eat roughage
• Nonviral suckling beef calves on good summer
  pasture
• Fungal secondary to rumen acidosis. Caused by
  infarcts due to fungal invasion and destruction
  of small arterioles
• Ulcers most common along greater curvature
• Type 1 erosion/ulcer, no hem
• Type II hemorrhagic
• Type III perforation/local peritonitis
• Type IV perforation with acute diffuse
  peritonitis

125
Perforating Abomasal Ulcer
126
Dietary Abomasal Impaction

• Seen in cattle and sheep fed poor quality,
  indigestible roughage during cold weather, can
  also be sand if on poor quality pasture with
  sandy soil
• See abomasal atony and chronic dilation
• Dehydration, anorexia, alkalosis, and progressive
  starvation
• Abomasal emptying defect is an idiopathic
  condition in Suffolk sheep

127
Abomasal Inflammation

• Braxy in sheep and cattle
• Caused by Clostridium septicum
• Hemorrhagic abomasitis with submucosal emphysema
• Bacteria produces exotoxin that leads to toxemia
  and shock

128
BVD-MD

• Pestivirus that has cattle as primary host but
  most even-toed ungulates are susceptible
• Two biotypes noncytopathic and cytopathic
  (effect in cultured cells)
• All age cattle are susceptible
• Persistently infected cattle are natural
  reservoir noncytopathic virus transmitted in
  utero, therefore infected at birth and infection
  lasts for life
• Clinical disease and reproductive failure in
  cattle in contact with persistently infected
  cattle
• Acute and chronic MD are highly fatal forms of
  BVD seen in persistently infected cattle that
  become infected with cytopathic biotype (from
  non-CPE mutation, other cattle or MLV vaccine)
• Acutely, see erosions/ulcers throughout GI tract
  especially over Peyers patches, necrosis of
  lymphoid tissue, interdigital skin lesions
• Chronically, see intermittent diarrhea and
  gradual wasting with lesions similar to acute but
  less severe
• Dx require diagnostic lab support paired
  serum samples with 4 fold rise in titer, PCR,
  virus isolation (submit lymph node, spleen, gut
  lesions)

129
Abomasal Parasites

• Haemonchus contortus common parasite of sheep
  and other ruminants
• Third stage larvae eaten on grass enter gastric
  glands onto surface as adults
• Feed on blood serious anemia and
  hypoproteinemia (seen as submandibular and
  mesenteric edema)

130
Haemonchus

• Residual damage in abomasal mucosa caused by
  third stage larvae
• There is focal destruction of deep glands and
  lymphocytic inflammation

131
Abomasal Parasites

• Ostertagiosis
• Sheep and goats O. circumcincta
• Cattle O. ostertagia
• Live as larval stages in gastric glands giving
  mucosa a rough and thick appearance
• Chronic inflammation, mucous cell hyperplasia and
  lymphoid nodules
• Poor weight gain, diarrhea, and hypoproteinemia

132
Abomasal Lymphosarcoma

• Lymphosarcoma can be primary, metastatic or
  multicentric in origin
• In cattle, often caused by bovine leukemia virus

133
Horse Stomach

• Stomach capacity is only about 2.5 gallons
• Located on left side of abdomen beneath rib cage
• Junction of distal esophagus and cardia is
  one-way valve (in but not out)
• therefore, horses cannot vomit gastric contents
• Celiac artery supplies blood to stomach

134
Stomach Colic Conditions

• Gastric dilatation
• Gastric rupture
• Gastric impaction
• Gastric Ulcer Syndrome (adults/foals)
• Gastric parasites
• Gastric neoplasia

135
Gastric Dilatation

• Caused by overeating fermentable foodstuff
  producing excessive gas or intestinal obstruction
• Overeating leads to increase in volatile fatty
  acids which inhibit gastric emptying
• Obstruction usually in small intestine and fluid
  accumulates in stomach
• Right dorsal displacement of colon around cecum
  obstructs duodenal outflow
• Proximal enteritis-jejunitis leads to gastric
  fluid buildup

136
Gastric Rupture

• Stomach rupture is fatal outcome of uncorrected
  gastric dilatation
• Tear usually occurs along greater curvature
• Most (approximately 2/3) occur secondary to
  mechanical obstruction, ileus or trauma
• Remaining due to overload or idiopathic causes

137
Gastric Impaction

• Uncommon cause of colic
• May be associated with pelleted feeds, persimmon
  seeds, straw, barley, etc
• Also associated may be poor dentition, lack or
  water, rapid eating

138
Equine Gastric Ulcer Syndrome

• Currently recognized EGUS in adults gt1 year of
  age, in order of decreasing frequency
• Primary erosion/ulceration of nonglandular
  (squamous) mucosa
• Primary glandular ulcer disease
• Secondary squamous ulceration
• Currently recognized syndromes in foals lt1 year
  of age, in order of decreasing frequency
• Gastroduodenal ulcer disease (GDUD)
• Primary erosion/ulceration of squamous mucosa
• NSAID-induced ulcer disease (primary glandular
  ulcer disease as for adults)

139
Normal Equine Stomach Fill

• Gastric fill and contents composition in horse
  allowed free access to forage
• Fill line is not much above lower esophageal
  sphincter
• Coarser contents layer at top and fine
  particulates filter to bottom
• Upper, coarser mat is furthest away from acid
  secreting mucosa and more accessible to swallowed
  saliva has higher pH than more liquid contents
  at bottom
• Bottom contents adjacent to HCL-producing
  parietal cells

140
Normal Gastric Acid Secretion
141
Equine Gastric Ulcer Syndrome

• Erosion and/or ulceration of nonglandular
  (squamous) mucosa
• Seen as a primary or secondary condition
• Seen in adult horses under intensive training,
  any breed
• Pathogenesis is poorly understood

142
EGUS (proposed pathogenesis)

• Exercise in horses causes pH change in proximal
  part of stomach
• The more liquid, highly acidic contents in the
  lower glandular stomach are squeezed up around
  the more solid contents by increased
  intra-abdominal pressure (red arrows) due to
  tensing of abdominal muscles as part of the
  movement at faster gaits

Merritt, AAEP, 2003
143
Primary Glandular Ulcer Disease

• Ulceration of glandular mucosa, especially in
  pyloric region
• Causes include NSAID toxicity (leads to down
  regulation of PGE2 production within glandular
  mucosa)
• Changes in mucosal blood flow and Helicobacter
  infection have not been demonstrated

144
Primary Glandular Ulcer Disease

• Multiple sites of glandular mucosal ulceration
  (yellow arrows) induced by NSAID toxicity
• Squamous mucosa (upper right) is free of lesions

145
Secondary Squamous Ulceration

• Primary lesion commonly occurs in duodenum (GDUD)
  of foals never seen in horses gt1 year old
• In adults may see gastric outflow obstruction
  caused by duodenal stricture reflux?
• In adults may also see secondary to any condition
  causing glandular ulcerative gastritis (NSAID)

146
Secondary Squamous Ulceration

• Endoscopic view of normal pyloric sphincter
  region (yellow arrow, upper right) in its
  commonly open state- this allows for reflux of
  duodenal contents
• Endoscopic view of severe inflammation around
  pyloric canal yellow arrow indicates mucosal
  erosion such lesions can scar and result in
  stricture that reduces gastric emptying

147
Gastric Ulcer

• Stomach from adult thoroughbred mare that was
  unthrifty and partially anorectic
• There are erosions/ulcers in both the glandular
  and nonglandular portions of the mucosa

148
Current Syndromes in Foals (lt 1 yr of age)

• Gastroduodenal ulcer disease (GDUD) - sucklings
  and early weanlings
• Cause is unknown
• In early stage of GDUD see roughened duodenal
  mucosa covered with fibrinous plaque causes
  some disruption of gastric emptying with some
  secondary squamous erosion and ulceration
• May recover after supportive Rx or develop
  advanced disease

149
Advanced GDUD in foals

• Clinical signs include drooling, teeth grinding,
  periodic bouts of colic especially after
  suckling, and weight loss
• If signs persist for a week, may indicate
  stricture of duodenum by inflammation and
  mechanical obstruction to gastric emptying
• Barium meal will be retained longer than 1 hour
• Endoscopy will show erosion/ulceration of
  squamous mucosa of stomach and lower esophagus

150
Advanced GDUD in Foals
Endoscopic views of reflux esophagitis and
squamous gastritis that are commonly seen in
foals with chronic GDUD. Lighter islands of
tissue in esophagus are remnants of normal
mucosa. Broken yellow line in stomach is site of
margo plicatus. Severe ulceration has occurred
Post-mortem finding of 2 distinct strictures of
duodenum (arrows) which is a serious consequence
of GDUD
151
Primary Erosion/Ulceration of Squamous Mucosa in
Foals

• May cause unthriftiness and/or mild colic
• Etiology and pathogenesis are unknown
• Must always rule out partial obstruction of
  gastric outflow as after a previously
  unrecognized GDUD

152
Stress-Related Gastric Ulcers in Foals

• Primarily seen in foals suffering from a severe
  illness or trauma
• May involve down-regulation of PGE2 due to
  reduced mucosal blood flow
• Lesions usually confined to glandular mucosa just
  adjacent to margo plicatus may be severe enough
  to perforate

153
Gastric parasites

• Gastrophilus spp (horse bots)
• Larvae of bot flies, adult flies are not
  parasitic and cannot feed, lay eggs and die
• Three species (G. intestinalis lays yellow eggs
  on hairs of forelimbs G. haemorrhoidalis black
  eggs on hairs of lips G. nasalis white eggs on
  hairs of submaxillary area)
• Larvae of all three embed in mucosa of mouth
  before passing to stomach, attach to stomach
  lining by oral hooks, cause mild gastritis, pass
  out in feces in 8-10 months

154
Horse Bots
Large numbers of larvae attached to gastric mucosa
Adult bot fly
155
Gastric Parasites

• Habronema (H. muscae, H. microstoma, Draschia
  megastoma
• H. microstoma and D. megastoma deposit larvae,
  but H. muscae lays eggs containing larvae.
• Larvae ingested by housefly or stablefly maggots
  which develop in manure
• Larval forms develop inside the maggot, becoming
  infective third stage larvae at about time adult
  fly emerges from pupa
• Larvae deposited on lips, nostrils and wounds of
  horses as flies feed if licked and swallowed,
  larvae mature in stomach
• If larvae in wounds not licked and swallowed,
  they stay in or around wound causing cutaneous
  habronemiasis
• Infected flies can also be eaten by horse
• In stomach, H. muscae and H. microstoma are on
  mucosal surface under layer of mucus cause mild
  catarrhal gastritis
• In stomach, D. megastoma causes granulomas up to
  10 cm in diameter
• Filled with necrotic debris and worms
• Covered by epithelium except for small opening
  for egg passage

156
Habronema
Posterior end of adult Habronema spp worm showing
spicule
Cutaneous habronemiasis
Nodule in stomach caused by D. megastoma
157
Stomach Conditions of Pigs

• Gastric ulcers
• Edema disease
• Parasites

158
Pig Gastric Ulcers

• Seen in pigs of all ages but most common in
  confined growing pigs (45-90 kg)
• Cause unknown but finely ground feed and stress
  are risk factors
• Lesions occur at pars esophagea and begin as
  areas of hyperkeratosis, this erodes and later
  have ulcer.
• Pigs can bleed out and produce tarry stool, or be
  chronically unthrifty

159
Edema Disease

• Acute to peracute toxemia caused by several
  serotypes of E. coli that are able to produce a
  verotoxin (related to Shigella) now called
  SLT-IIv (Shiga-like toxin type II variant)
• Toxin affects capillaries and small arteries
  leading to edema and ischemia in many organs
• Usually occurs in young pigs 1-2 weeks after
  weaning and affects healthiest animals in a group
• We will talk more about this disease later

160
Edema disease
Periocular edema
Submucosal edema in glandular region
Edema in stomach wall
161
Stomach Parasites of Pigs

• Hyostrongylus rubidus (red stomach worm)
• Direct life cycle
• Seen in grazing pigs
• Adults are on mucosal surface in film of mucus
• Larvae are in mucosa and may cause severe
  hypertrophic gastritis with proliferation of
  gastric glands

162
Stomach Neoplasia

• Cattle lymphosarcoma anywhere in forestomach
• Usually associated with BLV
• Squamous cell carcinoma of rumen also seen rarely
• Horse squamous cell carcinoma of nonglandular
  region of stomach
• Pig tumors of stomach very rare