A SELECTIVE REVIEW OF POSTMORTEM LESIONS IN HORSESby

Paul C. Stromberg DVM, PhDDiplomate, American College of Veterinary Pathologists

Professor of Veterinary PathologyOhio State UniversityStromberg.1@osu.edu

OBJECTIVES

A. Reinforce or broaden your equine pathology experienceB. See some “neat”, common and not-so-common lesions from horsesC. Practice applying the principles of gross pathology interpretationD. Develop appropriate morphologic diagnoses for the observed lesionsE. Learn how to play the “Gross Pathology Game” correctly or

“When is a response not responsive”

CARDIOVASCULAR SYSTEM

1-2 84927B&F Heart with fibrinonecrotic exudate

Mx= Fibrinonecrotic pericarditis

Cause = foreign body penetration of the pericardial sac

3. 87951-13 Heart with myocardial necrosis

Mx= acute myocardial coagulation necrosis

Cause = phenylbutazone; monensin?

4. 79334 Artery with thrombosis

Mx= granulomatous mesenteric arteritis with arteriosclerosis and thrombosis

Ex= verminous arteritis

Cause= Strongylus vulgaris

5. 90-2751-2 Lt ventricular endocardium with opaque white plaques

1

Mx = endocardial mineralization

Cause = 1) Hypervitaminosis D

A. Inappropriate iatrogenic supplementation

B. Vit D containing plants; Cestrum diurnum, Solanum malacoxylon, Trisetum flavescens

2) Renal failure ~ aminoglycoside therapy (Gentocin)

ENDOCRINE SYSTEM

6. G-884 Adrenal gland

Mx = Diffuse Adrenocortical atrophy

Cause = steroid therapy

7. 805280 Adrenal Gland

Mx = pheochromocytoma

8. Thyroid gland

Mx = Thyroid follicular adenoma (Nodular goiter)

9-10. Brain with large pituitary gland

Mx = pars intermedia adenoma of the pituitary gland

Name 4 associated clinical signs

1. Hyperpyrexia 3. PU/PD2. Hyperhidrosis 4. Hirsutism

HEMATOPOIETIC SYSTEM

2

11-12. 97-1518-1,2 Spleen with “petecchia”

Mx = herniated red pulp - normal finding

13-14. 90-1152-3,4 Spleen with hematomas and icterus

Mx = Splenic infarcts with hemorrhage and icterus

Name the disease = neonatal isoerythrolysis

Cause: maternal sensitization to fetal alloantigens leading to immune-mediated hemolysis

* The key here is that you must know this is a neonate.

15. 90-623-3 Spleen with large white nodules

Mx = LSA

16. E-11939-93 Spleen with black nodules

Mx = metastatic “malignant” melanoma

17. 80475C Spleen, X-sec with “raspberry jam” appearance

Mx = Diffuse lymphoid hyperplasia.

*Note also the splenic LN with hemorrhage

Name the Disease = Equine Infectioius Anemia

Cause = Equine lentivirus

18. Spleen with visible stroma

Mx = diffuse lymphoid atrophy

Name the Disease = CID19. 923916 LN, pharyngeal with lost architecture

Mx = LSA

3

* ID of the tissue here is part of the question

20. 87-683-9 LN, mesenteric with miliary foci

Mx = granulomatous lymphadenitis

Name the associated disease = granulomatous enteritis* Ttissue or organ ID is part of the question

GASTROINTESTINAL SYSTEM

21. Oral cavity with focal ulcer on gingiva

Mx = focal oral ulceration (ulcerative sotmatitis?)

Cause = trauma from “points” on teeth

22. 82002 Tongue with excessive keratin

Mx = glossal hyperkeratosis

Ex = neonatal glossal hyperkeratosis\

23. 85-2295 Esophagus with segmental hyperemia

Mx = segmental coagulation necrosis and hemorrhage(Venous infarction?)

Cause = foreign body

Name the Condition = choke24. Esophagus (close up) with ulceration

Mx = esophageal ulceration

Cause = gastric reflux

Ex = reflux esophagitis

4

25. 99-1846 Esophagus with stricture

Mx = segmental esophageal dilation

Cause = stricture

26. Esophagus, x-sec with thick wall

Mx = esophageal muscular hypertrophy

Cause = functional stenosis of the cardiac valve

27. Stomach with perforation

Mx = gastric rupture

Cause = generally bowel displacement, functional ileus, “colic”

28. 90613A Stomach with yellow SQ portion

Mx = gastric hyperkeratosis

Cause - nursing neonate with insufficient roughage in diet

29-30. G1001F Stomach with bot larvae

Cause = 1. Gasterophilus intestinalis - cardiac region

2. Gasterophilus nasalis - duodenum

Ex = gastric myiasis or gasterophiliasis

31-33. Stomach with large mucosal nodule

Mx = focal granulomatous gastritis

Cause = Draschia megastoma

Ex = gastric nematodiasis or gastric habronemiasis

5

34. 082088A Stomach with visible worms in mucus

Cause = Habronema microstoma, H. muscae

35. Stomach with nodules

Mx = multifocal gastric epithelial hyperplasia

Cause = Trichostrongylus axei

36. 99-799 Stomach with large solitary mass

Mx = gastric SCCA

Name ~ clinicopathologic abnormality = hypercalcemia

37. Small intestine with multiple small dark nodules on serosa

Name the condition = hemomelasma ilei

Histopathology = hemorrhage, hemosiderin and granulation tissue

38. Small intestine with discoloration and white mass

Mx = Lipoma with strangulation of bowel, segmental venous infarction and pre-stenotic dilation.

39. Close up of mucous membrane of colon

Mx = catarrhal colitis

Cause = Salmonella sp.40. 85963D Close of mucous membrane of sm int.

Mx = fibrinous enteritis

Name the Disease = Salmonellosis

41. Close up of GI mucosa with thickened non-ulcerated surface

Mx = GI LSA

6

42-43. 87-683-4,11 GI mucosa close up and X-sec with thickened non-ulcerated surface

Mx = Diffuse granulomatous enteritis

Name the Disease = Granulomatous enteritis

Cause = Unknown

44. 94-1025 Atrophied colon in situ

Mx = Colonic contraction/colonic myenteric aganglionosis

Name the associated condition = “Lethal white foal syndrome”

45. Colon with multiple white foci in bowel wall

Mx = multifocal mural abscesses, suppurative enteritis

Cause = Streptococcus zooepidemicus

46. Colon serosal surface with mural abscesses and large lymph nodes

Cause = Streptococcus zooepidemicus

47. 84736B Colonic serosa with huge abscess

Mx = Focal abscess of the bowel wall

Cause = Rhodococcus equi

48. In situ of GI with marked red discoloration

Mx = Diffuse transmural hemorrhage and necrosis of ventral colon and cecum (venous infarction)

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Name the Disease = Salmonellosis, Colitis X.

49. In situ of GI with diffuse red and ingesta in peritoneal cavity.

Mx = acute peritonitis

Cause = gastric or bowel rupture

50. In situ of Lt colon in a foal

Mx = torsion of pelvic flexure of Lt colon (colonic torsion) with venous infarction.

51. Surface of colon close up with large flat white worm

Cause = Anoplocephala perfoliata

52. 84583B Ileum with small white flatworms (tapeworms)

Cause = Paranoplocephala mammilana

53. 81992B Open sm int with large white round worms

Cause = Parascaris equorum54. 1168 L Colon with medium sized red round worms and small pale round

worms

Cause = Strongylus vulgaris, and small strongyles

55. 86-3685-2 Cecum close up with thickened mucosa

Mx = diffuse granulomatous typhlitis

Cause = small strongyles i.e. cyathostomes

Ex = verminous typhlitis

8

56. 80262B Close up of serosa of bowel with elongated thin nematodes

Cause = Setaria equi

HEPATOBILIARY SYSTEM

57. Millet seed

58-59. 83836A,D Liver with miliary white foci through out

Mx = miliary hepatic necrosis/granulomatous hepatitis

Name the Disease = Septicemic salmonellosis

Ex = embolic hepatitis

60. X-sec of liver with miliary white foci

Mx = multifocal to miliary hepatic necrosis

Name the disease = septicemic collibacilosis

61. 97-1337 Close up of cut liver surface of a foal with diffuse “portal” pattern

Mx = Diffuse portal to periportal hepatic necrosis

Name the disease = Tyzzer’s diseaseCause = Clostridium piliforme

Name an associated clinical sign = icterus

62. 94-2683 5 mo old foal. Cut surface of liver

Mx = 1. Diffuse hepatic fibrosis 2. Multifocal biliary carcinomas 3. Bile retention

Cause = aflatoxin

9

63. 97-1385 Cut surface adult horse liver with white nodule

Mx = metastatic sarcoma. Primary tumor was 60 lb mass in the Lt kidney

Name ~ condition = Stromberg’s Lt inguinal hernia

64. Cut section of liver with “portal pattern”

Name the condition = cholelithiasis and hepatic fibrosis

INTEGUMENTARY SYSTEM

65. Standing whole body horse with scaly skin

Name the disease = multisystemic eosinophilic granulomatous disease

66. Standing horse with swelling and draining tract over withers

Mx = chronic suppurative to granulomatous nuchal bursitis

Name the disease = “Fistulous withers”

Cause = Brucella abortus and Actinomyces bovis

67. Standing horse with swelling behind head

Mx = chronic suppurative to granulomatous supraspinous bursitis

Name the disease = “Poll evil”

Cause = Brucella abortus and Actinomyces bovis

68. Standing horse with multiple skin nodules over withers

Name the condition = nodular necrobiosis or collagenolytic granuloma

69. 80553 Skin nodules

10

Name the condition = cutaneous amyloidosis

70. 2668-2 Depigmented skin

Name the disease - onchocerciasis

Cause = Onchocerca cervicalis

Mx = eosinophilic granulomatous dermatitis with alopecia and depigmentation

71. 19593 White focus at oral commisure

Name the condition = vitiligo

Mx = focal perioral/cutaneous hypomelanosis

72-73. 081653A,B Inguinal mass

Mx = granulomatous dermatitis with granulation tissue

Name the disease = phycomycosis; “kunkers”, “leaches”

Cause = Pythium insidiosum, Basidiobolus haptosporus, Conidiobolus coronatus74-75 84134 ulcerated lesion at oral commissure; X-sec

Name the disease = cutaneous habronemiasis

Cause = Draschia megastoma, Habronema microstoma, H. muscae

Histologic lesion = granulomatous dermatitis with eosinophilic microabscesses

Vector = Stomoxys calcitrans, Musca domestica

DDx = 1) sarcoid 2) phycomycosis

76. 84583D Ext ear canal with ticks

Cause = Otobius megnini

11

77. Penis with proliferative mass

Mx = SCCA

78. 82755A Proliferative ulcerated mass on eyelid of grey horse

Mx = SCCA

79. D327-1 Horse head with ulceration at the alar fold and nares

Mx = SCCA

80. 615959 Grey horse with mass in pinna

Mx = Sarcoid

81. Cross section of skin with black mass

Mx = melanoma82. Close up of muzzle with warts

Name the condition = cutaneous papillomatosis

Cause = equine papillomavirus

83. 675003 Neck with nonulcerated SQ nodules

Mx = LSA or cutaneous lymphoma

84. Close up of hoof with proliferative mass below fetlock

Mx = Sarcoid

12

85. 80-5430-1 Close up of skin with proliferative ulcerated mass of granulation tissue

Mx = Sarcoid

86. U4922-1 Cross section of skin mass with whorling white fibers

Mx = Sarcoid

MUSCULOSKELETAL SYSTEM

87. 20364 Section of hoof

Mx = sole abscess

Pathogenesis =

88. 97-278 Section of hoof

Mx = suppurative osteomyelitis of the distal phalanx (P3) with P3 rotation and hyperkeratosis of the epidermal laminae

Name the Condition = chronic laminitis

89. 95-464 Section of hoof

Mx = necrosis and separation of the digital laminae

Name the condition = acute laminitis

90. 082143B Section of hoof

13

Mx = Navicular bursitis with osteonecrosis of the navicular bone

Name the Disease = navicular disease

Elements of navicular disease

1. Bursitis ~ fibrocartilagenous degeneration

2. Stress fractures (USA)

3. Ischemic necrosis ~ vascular occlusion (Eurpoe)

4*. Septic embolization in foals

91-92. 99-155 Section of hoof

Mx = phalangeal angiomatosis

93. 1-83/95-96 Section of proximal humerus

Mx = segmental subphyseal or metaphyseal necrosis (infarction)Cause = Salmonella sp.

Pathogenesis = septic embolization to the physeal capillary bed

94. 94-1180-5 Section of metatarsal bone

Mx = suppurative metaphyseal osteomyelitis (physitis) with necrosis and sequestrum

Cause = Salmonella sp.

95. 93-2531 Section of tibia

Mx = Physeal osteomyelitis and necrosis (physitis)

96. Section of tibia with well demarcated physeal mass

Mx = myeloma

14

97. Section of P1 to P3 with multifocal white subphyseal masses

Mx = multifocal subphyseal suppurative osteomyelitis with necrosis

Pathogenesis =

98. 79174 Section of tarsal joint with irregular articular cartilage

Mx = Suppurative arthritis/synovitis with ulceration of articular cartilage and osteonecrosis

Cause = iatrogenic bacterial infection

99. 89-2034 Section of shortened thoracic vertebra

Mx = vertebral osteoporosis with compression fracture

Cause = nutritional deficiency/metabolic disease

100. 80201F Articular facet of cervical vertebra; 1 yr old Percheron

Mx = Osteochondrosis dissecans (OCD)

Name the Disease = OCD

Name the associated condition = Cervical vertebral instability

101. 81-836 “Fibrillated” Articular cartilage of elbow

Name the disease = degenerative joint disease

102. 79-6276 Narrow cervical vertebral canal

Mx = cervical vertebral canal stenosis

Name the associated condition = cervical vertebral stenotic myelopathy (“Wobbler”)

15

103. 81981A Long section of cervical vertebrae with prominent lig flavum

Mx = hypertrophy of the ligamentum flavum

Name the associated condition = Cervical vertebral instability or stenotic myelopathy

104. Bilateral distal phalanges with PNB (hyperostosis)

Mx = bilateral phalangeal hyperostosis or PNB

Name the condition = hypertrophic osteopathy (HPO)

Cause = space occupying mas in body cavity; thoracic or abdominal

* this mare had a large ovarian dysgerminoma

105. 90-2095-3 X-sec of nasal cavity with enlarged maxillae

Mx = bilaterally symmetrical hyperostotic fibrous osteodystrophy

Name the disease = nutritional secondary hyperparathyroidism (“Bran Disease”, Big Head”)

Cause = Dietary Ca/P imbalance

106. 83475B Leg muscle with discoloration

Mx = myonecrosis with emphysema

Cause = Clostridium novyi

Etiologic Dx = clostridial myositis

NERVOUS SYSTEM

107-8. 97-1876 Brain with enlarged cerebral hemisphere

Mx= focal suppurative encephalitis (cerebral abscess)

16

Cause = Rhodococcus equi, Streptococcus equi, S. Zooepidemicus

109. 9793-186 Long. Section of brain

Mx = 1) Cholesterol granuloma (Cholesteatoma)2) Cerebral cortical compression atrophy3) Hydrocephalus

110. 86-2579 Coronal section of cerebrum

Mx = leukoencephalomalacia

Cause = fumonesin B1/Fusarium moniliforme;

Name the disease - mouldy corn poisoning

111. 83055C Coronal section of cerebrum

Mx= focal suppurative encephalitis (cerebral abscess)

Cause = Rhodococcus equi, Streptococcus equi, S. Zooepidemicus

112. 80979H X-sec of spinal cord with hemorrhage

Mx = Segmental granulomatous myelitis with myelomalacia and hemorrhage

Cause = Sarcocystis neurona

Etiologic Dx - protozoal myelitis

\113. E-10620-96 X-sec of spinal cord with hemorrhage

Mx = multifocal necrotizing vasculitis with myelomalacia and hemorrhage

Cause = Equine herpesvirus Type 1 (EHV-1)

Etiologic Dx = herpesvirus myelitis

114. 9574-186 Coronal section of midbrain with symmetrical discreet foci

17

Mx = bilateral symmetrical nigropallidal encephalomalacia

2 causes: 1) Centaurea solstitialis (Yellow star thistle)2) Centaurea repens (Russian knapweed)

115. Ventral aspect of whole brain with “something missing”

2 Mx = 1) arrhinencephaly2) holoprosencephaly

116. 99-117 Ventral aspect of whole brain with enlarged optic nerves

Mx = bilateral optic neuritis

Cause = Halicephalobus gingivalis (Micronema deletrix)117. 9760-199 Cauda equina of spinal cord with enlarged peripheral

nerve roots

Mx = granulomatous polyradiculoneuritis of the cauda equina

Cause = unknown

118. In situ eye with worm in conjunctival sac

Cause = Thelasia lacrimalis or T. californiensis

119. 01-1367 Eye with retrobulbar white mass

Most likely Mx = retrobular LSA ~ optic nerve

REPRODUCTIVE SYSTEM

120. 9585-118 Perineum with ulcerated vulva

Mx = vulvar SCCA

121. 9513-209 Perineum with vesicles and ulcers ~ vulva

Mx = multifocal perivulvar vesicular/ ulcerative dermatitis (vulvitis)

18

Cause = EHV-3

Name the disease = coital exanthema

122. 29. Bisected enlarged ovary with numerous cysts

Mx = granulosa cell tumor

Most common associated serum biochemical abnormality = elevated testosterone

Name a related clinical sign = 1) anestrus 2) continuous/intermittent estrus 3) “Stallion-like” behavior

123. 9723-215 Post partum uterus with massive hemorrhage

Mx = hemorrhage/hematoma of the uterine broad ligament

Cause = rupture of the Rt middle uterine artery

Name a common associated lesion = hemoperitoneum

124. 1-15 Male fetus with twisted red umbilical cord

Mx = Umbilical torsion with venous infarction

Name an associated condition = abortion

*Common incidental finding unless infarction accompanies the torsion

125. Fetus with in situ lung containing white nodules

Mx = multifocal granulomatous bronchopneumonia

Most likely cause = Aspergillus spp.

Pathogenesis: open cervix placentitis amniotic fluid spread to fetal airways

126. Twin fetuses, at 7 mo.

19

Name the condition = chronic placental insufficiency (Twin pregnancy)

Features: 1) abortion ~ 7 mo2) one fetus dead, autolyzed3) viable fetus emaciated, pale, smaller than normal

127. 91-3099 Placenta with white stellate area

Name the structure = cervical star

128. 84124 Placenta with linear flat white areas

Name the structure = endometrial cups

When do these occur? 45-150 days

129. 97-601-1 Placenta with rough surface

Mx = fibrinopurulent to necrotizing placentitis

130. 02-1315 Placenta with large white raised masses

Mx = Adenomatous (cystic) dysplasia/hyperplasia of the allantois

131-2 Uterus with pus

Mx = pyometra or suppurative endometritis

RESPIRATORY SYSTEM

133. 79-5391-7 Long. Sec of nasal cavity with white mass at ethmoid

Mx = adenocarcinoma of the ethmoturbinate

20

134. 9752-232 Long sec of nasal cavity with dark red swollen turbinate

Name the condition = progressive nasal hematoma/ethmoidal hematoma

Histopathologic appearance = angiomatosis with hemorrhage, hemosiderosis, granulation tissue, and edema

135. 80301B Coronal section of nasal cavity with white mass in sinus

Mx= maxillary sinus abscess (chronic suppurative sinusitis), periodontitis and FB

136. 86173 Coronal section of nasal cavity with white exudate

Mx = suppurative rhinitis

Cause = Streptococcus equi,

Name the Disease = “Strangles”

Name an associated condition = purpura hemorrhagica

137. 78948 Polyp from the nasal cavity

Mx = mucosal or inflammatory polyp/ granulomatous rhinitis with granulation tissue

Cause = Rhinosporidium seeberi

138. 426 en face view of epiglottis with caudal displacement of epiglottis

Name the condition = entrapment of the epiglottis

Name the underlying condition = epiglottal hypoplasia

139. En face view of the asymmetrical epiglottis

21

Name the condition = laryngeal hemiplegia

140. 86-3472-1 Larynx, asymmetrical pale color

Mx = atrophy of the Lt cricoarytenoideus dorsalis m.

Cause = axonal degeneration of the Lt recurrent laryngeal nerve

141. 78520A Gutteral Pouch with amorphous white “stuff”

Mx = chronic suppurative gutteral diverticulitis (gutteral empyema)“Lufttsackstein”

Cause = Streptococcus equi

142. 84772C Gutteral pouch mucosa, discolored

Mx = granulomatous gutteral diverticulitis

Cause = **Pythium insidiosum, Aspergillus spp.

143. W2188-1 Trachea with yellow cast

Mx = fibrinous tracheitis

Cause -= Equine herpesvirus type 1 (Equine Rhinopneumonitis Virus)

144. Lung, adult with A-V white nodules

Mx = chronic suppurartive bronchopneumonia (pulmonary abscesses)

Cause = Rhodococcus equi

145. 84197D Lung, Arab foal with AV pattern, bulla

Mx = Bronchiolitis/ bronchopneumonia with subpleural emphysema

Cause = equine adenovirus

22

What is the underlying condition = Combined Immunodeficiency Disease

146. Lung, foal with miliary white nodules

Mx = miliary pyogranulomatous pneumonia

Cause = Rhodococcus equi147. 88-306-3 Cut surface of lung, neonate with miliary white foci

Mx = miliary exudative (suppurative) interstitial pneumonia

Cause = E. coli

Etiologic Dx = suppurative (septic) embolic pneumonia

Name the Disease = septicemic collibacillosis

148. 83294B Lung with poorly defined pale foci

Mx = chronic mucoid bronchiolitis

Name the Disease = Chronic Obstructive Pulmonary Disease

Name the associated clinical condition = “Heaves”

149. 82002D Lung with extensive hilar pattern

Mx = Pulmonary edema

150. 99-1583 In situ pleura, foal

Mx = Diffuse fibrinous pleuritis

Cause - E. coli.

151. 81980C Close up of fetal/neonatal lung with yellow foci

Name the condition = mecomium aspiration

23

152. 91-937 Lung with intraluminal bronchial mass

Mx = Granular cell tumor

153. 95-691 Thorax and abdomen, foal, in situ

Mx = diaphragmatic hernia with displacement of the colon into the thorax.

URINARY SYSTEM

154-5. 92-3944 Kidney, whole and section, with white foci

Mx = miliary suppurative nephritis

Etiologic Dx = suppurative embolic nephritis/ septic embolic nephritis

Cause = Actinobacillus equuili

156. RKH10 Section of neonatal kidney colored olive green

Mx = cholemic nephrosis

Name the condition = hepatorenal syndrome

Pathogenesis: Immature or obstructed liver conjugation of bilirubin unconjugated bilirubin hyperbilirubinemia bilirubinuria reabsorption by pct epithelium

157. 7137 Ureter

Mx = hemorrhagic ureteritis

Name the disease: Blister Beetle Poisoning/ cantharidin toxicity

Name an associated lesion in another organ system = 1) myocardial necrosis 2) hemorrhagic gastritis

24

158. Epicauta sp. (Blister Beetles)

159. MAR83-21 Urinary Bladder, open with opaque white material

Mx = chronic mucopurulent to fibrinopurulent cystitis

Cause: 1) Sorghum grass toxicity 2) Sudan Grass toxicity 3) Sarcocystis neurona

Pathogenesis: Damage to lumbar spinal cord or nerve roots bladder atony urine stasis

160. 02-783 Urinary bladder in neonate with rent in dorsal surface

Mx = cystorrhexis (ruptured urinary bladder)

Name a sequella = uroabdomen

Name 3 ~ clinicopathologic abnormalities

1. Hyponatremia2. Hypochloremia3. Hyperkalemia4. High peritoneal fluid/serum Cr ratio

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