GI Labs

Question 1

History: This young stray dog was brought to your clinic as a “hit by car” case and was dead on arrival. Routine necropsy of this dog revealed this lesion.

Describe the lesion.

Answer 1

The enamel surface from the apex to 1/2 or more of the length of several teeth (mandibular canines, incisors) is irregular and pitted, lacks smooth white surface enamel and there is exposure of the underlying dentin which is stained a light brown color.

Question 2

History: This young stray dog was brought to your clinic as a “hit by car” case and was dead on arrival. Routine necropsy of this dog revealed this lesion.

What is your morphologic diagnosis?

Answer 2

Oral cavity: Severe, chronic, multifocal enamel hypoplasia

Question 3

History: This young stray dog was brought to your clinic as a “hit by car” case and was dead on arrival. Routine necropsy of this dog revealed this lesion.

What is the most likely pathogenesis of this lesion in dogs?

Answer 3

Systemic disease such as canine distemper or generalized fever due to septicemia, canine infectious hepatitis, etc. while the tooth is still forming→ degeneration of ameloblasts (which are differentiated and actively forming enamel)→lack of enamel formation. Once inactivated, the ameloblasts remain functionless and the defect cannot be repaired.

Question 4

History: This young stray dog was brought to your clinic as a “hit by car” case and was dead on arrival. Routine necropsy of this dog revealed this lesion.

List an agent that would have the potential to cause this lesion in a dog and broadly outline the critical time period for this problem to occur.

Answer 4

Canine distemper

Critical time period: This problem only occurs during tooth development (ie. in utero and < 6 month of age).

Question 5

History: Rocky, is an 8-year-old, neutered, male boxer that was presented for evaluation of gingival masses.

Describe the lesion.

Answer 5

Diffusely, there is bilateral outgrowth of the gingiva involving both the upper and lower arcades. The gingival multifocally forms masses which vary from 1-3 cm in diameter, are pink to red in color, and focally envelop portions of the teeth, especially the incisors. The lower jaw extends approximately 1.5 cm beyond the upper jaw.

Question 6

History: Rocky, is an 8-year-old, neutered, male boxer that was presented for evaluation of gingival masses.

Provide a morphological diagnosis.

Answer 6

Oral Cavity: Chronic, diffuse gingival hyperplasia Chronic mandibular prognathism

Question 7

History: Rocky, is an 8-year-old, neutered, male boxer that was presented for evaluation of gingival masses.

What are the two potential causes of this lesion?

Answer 7

Since this lesion is diffuse, it is likely either due to Drug administration (ex: Amlodipine, cyclosporine, diphenylhydantoin, nitrendipine, nifedipine) or it may be familial (inherited), where it is most commonly observed in large and giant breed dogs. (Boxer, Great Dane, Collie, Doberman, Dalmatian). This is a Boxer who is not on any meds – so this case is familial.

Question 8

History: Rocky, is an 8-year-old, neutered, male boxer that was presented for evaluation of gingival masses.

If the lesion was focal, what might be the underlying cause?

Answer 8

If focal, it can be due to chronic irritation (periodontal disease or malocclusion).

Question 9

History: Tissue from an 11 year old spayed female Golden Retriever with a 3 month history of progressive anorexia, some weight loss, excessive salivation, and halitosis.

Describe the lesion.

Answer 9

Head: Involving the caudal hard palate and soft palate there is an infiltrative, black mass measuring approximately 2 x 6 x 2 cm. This mass is firm and homogeneous, has infiltrated through the hard palate, which is palpably soft in this region, and extends into the nasal cavity (1.5 cm mass extending into the nasal cavity).

Lungs: Randomly scattered throughout all lung lobes are low to moderate numbers of firm, round black masses which vary in size from 0.5 – 1.0 cm in diameter.

Question 10

History: Tissue from an 11 year old spayed female Golden Retriever with a 3 month history of progressive anorexia, some weight loss, excessive salivation, and halitosis.

Give an appropriate morphologic diagnosis.

Answer 10

Caudal oropharynx: chronic, locally extensive invasive pigmented mass Lung: chronic, multifocal pigmented masses

Question 11

History: Tissue from an 11 year old spayed female Golden Retriever with a 3 month history of progressive anorexia, some weight loss, excessive salivation, and halitosis.

What is your most likely diagnosis for these lesions?

Answer 11

Oral Malignant melanoma with multifocal pulmonary metastases

Question 12

History: Tissue from an 11 year old spayed female Golden Retriever with a 3 month history of progressive anorexia, some weight loss, excessive salivation, and halitosis.

What is the typical behavior of this oral tumor in dogs?

Answer 12

Locally invasive, frequently recur, may invade bone (57% of gingival tumors)

Metastasis is common: 70% to regional lymph nodes 67% to distant sites.

Question 13

History: Esophagus from a 2-year old cow with diarrhea & esophagus from a 2 year old cow with anorexia

Describe the lesion in esophagus A.

Answer 13

Esophagus A– There are multifocal to coalescing, shallow, linear ulcers that are 1-2 mm in width and vary from 2-3 cm in length. The ulcers are multifocally covered by a pale tan friable material. If the tan friable material is removed, the underlying tissue is depressed and reddened.

Question 14

History: Esophagus from a 2-year old cow with diarrhea & esophagus from a 2 year old cow with anorexia

Describe the lesion in esophagus B.

Answer 14

Esophagus B-There are numerous multifocal to coalescing papillary to cauliflower-like grows 0.5 – 1.0cm in diameter extending from the mucosal surface of the esophagus. These growths are tan in color and have numerous papillary fronds.

Question 15

History: Esophagus from a 2-year old cow with diarrhea & esophagus from a 2 year old cow with anorexia

Give a morphologic diagnosis for esophagus A.

Answer 15

Esophagus A: esophagitis, ulcerative & fibrinous (fibrinonecrotic) multifocal to coalescing, acute

Question 16

History: Esophagus from a 2-year old cow with diarrhea & esophagus from a 2 year old cow with anorexia

Give a morphologic diagnosis for esophagus B.

Answer 16

Esophagus B: chronic, multifocal to coalescing papillary masses

Question 17

History: Esophagus from a 2-year old cow with diarrhea & esophagus from a 2 year old cow with anorexia Both these lesions are multifocal and caused by viral infection.

List a potential disease differential for each lesion.

Answer 17

1. BVDV (mucosal disease) →most likely cause for the ulcerative lesions
2. Bovine papilloma virus infection.

Question 18

History: Esophagus from a 6 year old male neutered Bull Terrier. On Monday he ate a toy bone. Now he is regurgitating and cannot keep anything down.

Describe the lesion.

Answer 18

Segmentally, the esophagus was markedly distended. The serosal surface of the distended segment (6.0 x 3.5 x 2.5 cm) was diffusely dark red to black. Within the lumen of the distended segment, was a roughly rectangular to wedge-shaped foreign body measuring 8.0x 5.0 x 3.5 cm, which was white to tan and firm and had a tapered edge at the distal end. The mucosal surface of the distended segment was extensively thinned and depressed (ulcerated), pale, green to black and covered by a thin layer of tan, friable material (fibrin).

Question 19

History: Esophagus from a 6 year old male neutered Bull Terrier. On Monday he ate a toy bone. Now he is regurgitating and cannot keep anything down

Provide a morphologic diagnosis.

Answer 19

Esophagus: Luminal foreign body with obstruction and associated fibrinous and ulcerative esophagitis

Question 20

History: Esophagus from a 6 year old male neutered Bull Terrier. On Monday he ate a toy bone. Now he is regurgitating and cannot keep anything down.

What process may have led to the mucosal ulceration and what might be a potential sequela to this lesion had the animal lived?

Answer 20

Pressure necrosis Esophageal perforation (acute sequela) Esophageal stricture (chronic sequela)

Question 21

History: Esophagus from a 6 year old male neutered Bull Terrier. On Monday he ate a toy bone. Now he is regurgitating and cannot keep anything down.

If this lesion were in a bovine rather than a dog. What might this esophageal obstruction lead to?

Answer 21

Secondary bloat

Question 22

History: Tissue from a feline with a history of halitosis

Describe the lesions.

Answer 22

There are multifocal raised tan plaques on the dorsal surface of the tongue and along both dorsal and ventral lips. The plaques are round to oval, about 0.5-1 cm in diameter, tan, firm, and focally ulcerated. There are also larger (about 1.5 cm) cauliflower-like plaques within the palatopharyngeal fossae.

Question 23

History: Tissue from a feline with a history of halitosis

What are your differential diagnoses?

Answer 23

1. Eosinophilic granulomas
2. Plasma cell/lymphocyte ulcerative proliferative stomatitis

Question 24

History: Tissue from a feline with a history of halitosis The owner had looked in the animal’s mouth and was worried her beloved cat had a tumor.

Explain to her why this is unlikely to be a tumor.

Answer 24

It is rare for a tumor to cause multiple masses involving multiple different regions of the oral cavity, especially involving the tongue and lips, so these masses are unlikely to be tumors.

Question 25

**History**: Tissue from a feline with a history of halitosis You made an impression smear of the lesions and noted numerous eosinophils and macrophages. ## Footnote **What is your diagnosis?**

Answer 25

Eosinophilic granuloma

Question 26

**History**: Tissue from a 750# steer found dead ## Footnote **Describe the lesion.**

Answer 26

Approximately ½ of this section of esophagus is diffusely reddened and slightly thickened by clear glistening fluid (edema). The other 1/2 of the esophagus is pale (blanched) and there is a sharp demarcation between the blanched and congested segments of the esophagus.

Question 27

**History:** Tissue from a 750# steer found dead ## Footnote **Name this lesion.**

Answer 27

Bloat Line

Question 28

**History**: Tissue from a 750# steer found dead ## Footnote **Give an explanation for the appearance of this lesion.**

Answer 28

Gross distension of the rumen puts massive pressure on the diaphragm leading to increased intra-thoracic pressure. The increased intra-thoracic pressure compresses the veins of the intra-thoracic esophagus, leading to blanching of the intrathoracic esophagus. The increased intra-thoracic pressure leads to poor drainage of blood from the head and neck, resulting in congestion of the cervical esophagus, and a line of demarcation at the thoracic inlet.

Question 29

**History**: Tissue from a 750# steer found dead ## Footnote **What other gross changes might be observed in this animal?**

Answer 29

Congestion, edema and hemorrhage in the muscles and lymph nodes of the head and neck. The animal would also be markedly bloated. The lungs may be mildly collapsed (atelectasis) and there may be a stable foam in the rumen.

Question 30

**History**: Tissue from a 4 year old female Boer goat that had developed anorexia and lethargy after she had a stillborn lamb. She was off feed for a few days, but improved following treatment, started to feel much better, developed a ravenous appetite, and gobbled down the high quality alfalfa hay and grain mixture and she had only previously picked at. A few days later, she developed diarrhea and died. ## Footnote **Describe the lesion(s).**

Answer 30

Rumen: There is a large depression in which the mucosa (and ruminal papilla) are absent, measuring approximately 15 cm X 10 cm. The center was covered by grey-green, friable material and the periphery was intensely red in color (hyperemia) and slightly thickened. There were several additional similar ulcers ranging in size from 2-3 cm located in a multifocal pattern around this central ulcer. Variably sized (2-3 cm in diameter) dark red blotches can be observed from the serosal surface which correspond to the mucosal ulcers.

Question 31

**History:** Tissue from a 4 year old female Boer goat that had developed anorexia and lethargy after she had a stillborn lamb. She was off feed for a few days, but improved following treatment, started to feel much better, developed a ravenous appetite, and gobbled down the high quality alfalfa hay and grain mixture and she had only previously picked at. A few days later, she developed diarrhea and died. ## Footnote **Provide an appropriate morphologic diagnosis.**

Answer 31

Rumen: subacute, multifocal, ulcerative and fibrinonecrotic rumenitis with intense peripheral hyperemia.

Question 32

**History:** Tissue from a 4 year old female Boer goat that had developed anorexia and lethargy after she had a stillborn lamb. She was off feed for a few days, but improved following treatment, started to feel much better, developed a ravenous appetite, and gobbled down the high quality alfalfa hay and grain mixture and she had only previously picked at. A few days later, she developed diarrhea and died. ## Footnote **Based on the history, propose a pathogenesis for the development of this lesion.**

Answer 32

Anorexia  felt better  ate abundant grain without time for rumen to re-adapt  rumen acidosis  disruption of mucosa integrity  fungus colonized mucosal defect  mycotic rumenitis.

Question 33

**History:** Tissue from a 4 year old female Boer goat that had developed anorexia and lethargy after she had a stillborn lamb. She was off feed for a few days, but improved following treatment, started to feel much better, developed a ravenous appetite, and gobbled down the high quality alfalfa hay and grain mixture and she had only previously picked at. A few days later, she developed diarrhea and died. ## Footnote **What additional lesions might you have observed in this animal?**

Answer 33

Loss of mucosal integrity of the ruminal mucosa can lead to bacteria (or even fungi) gaining access to the portal blood supply leading to liver abscesses or irregular foci of hepatic necrosis (hepatic necrobacillosis)

Question 34

**History**: Tissue from a race horse that was off feed. ## Footnote **Describe the lesion.**

Answer 34

Involving the squamous (non-glandular) portion of the stomach along the margo plicatus, there is an irregular dark red to black focus of mucosal depression that is approximately 12cm in length and 3-4 cm in width. This region is significantly depressed (ulcer) compared to the adjacent mucosa and the margins of the lesion are not thickened.

Question 35

**History:** Tissue from a race horse that was off feed. ## Footnote **Give a morphologic diagnosis.**

Answer 35

Non-glandular stomach: acute focally extensive gastric ulcer (ulcerative gastritis)

Question 36

**History**: Tissue from a race horse that was off feed. ## Footnote **Do you think this lesion is acute or chronic and provide rationale?**

Answer 36

This is acute. The periphery of chronic ulcers are generally thickened by dense fibrous connective tissue and inflammation and are firm and less pliable.

Question 37

**History**: Tissue from a race horse that was off feed. ## Footnote **Name several predisposing factors that may contribute to the development of this lesion in the horse.**

Answer 37

a. Infrequent, high carbohydrate meals b. Inadequate access to hay or pasture c. Heavy training schedules d. High stress environments e. Excessive use of drugs, especially non-steroidal anti-inflammatories

Question 38

**History**: Tissue from a pig that had respiratory signs a couple of days ago and was recently found dead. A few other pigs are pale and a few have melena. ## Footnote **Describe the lesion(s).**

Answer 38

There is an irregularly shaped, sharply-demarcated, depressed (ulcer), firm area approximately 5 cm in diameter that occupies nearly the entire pars esophagea. The margins of this ulcer are markedly thickened (3X thicker than adjacent normal mucosa), firm and less pliable than the adjacent tissue. When sectioned, the stomach wall at the margins of this defect is markedly thickened by firm dense white tissue (fibrosis). The adjacent gastric lymph nodes are moderately enlarged.

Question 39

**History:** Tissue from a pig that had respiratory signs a couple of days ago and was recently found dead. A few other pigs are pale and a few have melena. ## Footnote **Give an appropriate morphalogic diagnosis.**

Answer 39

Stomach: severe focal chronic ulceration of the pars esophagea (or, severe locally extensive chronic ulcerative gastritis of the pars esophagea) with associated lymphadenomegally

Question 40

**History**: Tissue from a pig that had respiratory signs a couple of days ago and was recently found dead. A few other pigs are pale and a few have melena. ## Footnote **Do you think this lesion is acute or chronic and provide rationale?**

Answer 40

This is chronic. The periphery of the ulcer is markedly thickened by dense fibrous connective tissue and is firm and less pliable.

Question 41

**History**: Tissue from a pig that had respiratory signs a couple of days ago and was recently found dead. A few other pigs are pale and a few have melena. ## Footnote **What are risk factors that contribute to the formation of this lesion?**

Answer 41

Feed: Feed properties that contribute to ulceration include: Small feed particle size, pelleting feeds, diets with high levels of unsaturated fats, low fiber, high energy diets. Irregular feeding patterns (Note: disease may lead to irregular feeding patterns) Stress (transportation, overstocking) Respiratory tract infection: Pneumonia may lead to irregular feeding patterns, lead to stress of intercurrent disease, and in response to infection, the body releases histamine, which stimulates gastric acid secretion. Death was due to hemorrhage associated with the ulcer, resulting in severe anemia (hence the pallor).

Question 42

**History:** Tissue from a 27 year old female giraffe with a history of chronic progressive anemia and hypoproteinemia. ## Footnote **Describe the lesion.**

Answer 42

Uniformly disseminated throughout the majority of the abomasal mucosa are multifocal to coalescing 1-3 mm in diameter, slightly raised, firm, tan nodules. The mucosa has a micronodular appearance; it looks like “Morroccan leather.”

Question 43

**History**: Tissue from a 27 year old female giraffe with a history of chronic progressive anemia and hypoproteinemia. **Provide a morphologic diagnosis.**

Answer 43

Abomasum: Severe, chronic, disseminated, multifocal to coalescing nodular abomasitis

Question 44

**History**: Tissue from a 27 year old female giraffe with a history of chronic progressive anemia and hypoproteinemia. ## Footnote **What is the likely cause?**

Answer 44

Ostertagia ostertagii

Question 45

**History**: Tissue from a 27 year old female giraffe with a history of chronic progressive anemia and hypoproteinemia. ## Footnote **Outline the pathogenesis of this disease, including why it would lead to the development of bottle jaw.**

Answer 45

Destruction of parietal cells by the presence of young adults in the mucosal glands → damaged abomasal glands are lined by immature cells which do not produce adequate HCL or pepsinogen → increase in abomasal pH from 2 to 7 → inability to convert what pepsinogen that was produced to pepsin → Inability to digest protein & massive numbers of bacteria enter small intestine due to decreased abomasal pH → diarrhea, hypoproteinemia, weight loss

Question 46

**History:** Tissue from a 4 week old M German Shepherd. Approximately a week and a half ago the owner noticed that the pup was regurgitating his food frequently and now has raspy sounding breathing ## Footnote **Describe the tissue.**

Answer 46

The diameter of the esophagus was greatly and diffusely dilated ranging from the 3 cm in the cervical region to 3.5 cm in thoracic portions. The tissue was soft and beige pink externally.

Question 47

**History**: Tissue from a 4 week old M German Shepherd. Approximately a week and a half ago the owner noticed that the pup was regurgitating his food frequently and now has raspy sounding breathing ## Footnote **Provide a morphological diagnosis.**

Answer 47

Chronic, diffuse megaesophagus

Question 48

**History:** Tissue from a 4 week old M German Shepherd. Approximately a week and a half ago the owner noticed that the pup was regurgitating his food frequently and now has raspy sounding breathing ## Footnote **Is this likely a congenital or acquired lesion? If congenital, why did clinical signs not appear until it was 2.5 - 3 weeks old.**

Answer 48

Congenital Clinical signs generally do not become apparent until the animal begins to eat solid food

Question 49

**History**: Tissue from a 4 week old M German Shepherd. Approximately a week and a half ago the owner noticed that the pup was regurgitating his food frequently and now has raspy sounding breathing ## Footnote **If this were an older animal, what types of conditions could cause an acquired megaesophagus.**

Answer 49

Neuromuscular disease leading to weakness of the esophageal musculature 1. Primary Idiopathic acquired megaesophagus 2. Secondary acquired megaesophagus: results from another disease causing neuromuscular weakness Ex: Myasthenia gravis (most common), hypoadrenocorticism, polymyositis, polyradiculoneuritis, lead poisoning, systemic lupus erythematosus (SLE), dysautonomia idiopathic.

Question 50

**History**: Tissue from a canine with vomiting (sometimes containing blood), weight loss, and inappetence. ## Footnote **Describe the lesion.**

Answer 50

This section of canine stomach is extensively thickened (up to 4 cm thick) by an irregular firm, uniform, red to tan-colored mass which is affecting approximately 50-60% of the gastric mucosa leading to flattening of the gastric rugae. There is a focal 3 cm in diameter region where the involved mucosa is markedly depressed forming a crater-like lesion (ulcer).

Question 51

**History**: Tissue from a canine with vomiting (sometimes containing blood), weight loss, and inappetence. ## Footnote **Provide a morphological diagnosis.**

Answer 51

. Stomach – locally extensive, ulcerated, mural mass, chronic severe.

Question 52

**History**: Tissue from a canine with vomiting (sometimes containing blood), weight loss, and inappetence. ## Footnote **What is your likely diagnosis?**

Answer 52

Gastric adenocarcinoma.

Question 53

**History**: Tissue from a canine with vomiting (sometimes containing blood), weight loss, and inappetence. ## Footnote **Based on the lesion and your tentative diagnosis, what additional clinical sign might have been observed in this animal?**

Answer 53

Melena

Question 54

**History**: Tissue from a canine with vomiting (sometimes containing blood), weight loss, and inappetence. ## Footnote **Based on your tentative diagnosis, what is the anticipated biologic typical behavior?**

Answer 54

Biologic Behavior: Locally invasive Disease is usually advanced at presentation. Metastasis is expected: Regional lymph nodes (gastric, gastroduodenal, splenic) Intraperitoneal – peritoneal implantation (omentum, mesentery, and peritoneal cacinomatosis) Liver and spleen

Question 55

**History**: Tissue from a 4 yr old mixed breed beef cow with a history of weight loss, hair loss, and submandibular swelling. On PE clinicians were unable to hear the heart on the right side. There were jugular pulses and submandibular edema. ## Footnote **Describe the lesion.**

Answer 55

Heart: The epicardial surface of the heart and internal surface of the pericardial sac are covered by a thick (1-3 cm in thickness) layer of tan fieable material which can be readily removed. The pericardium and adjacent mediastinum are moderately thickened by firm, dense white fibrous connective tissue. There was a 10 cm long and 0.1 cm diameter linear metal foreign body penetrating through the pericardial sac. Reticulum: The serosal surface of the section of reticulum is diffusely adhered to the adjacent diaphragm by dense, white/grey (fibrous) tissue and the reticulum and diaphragm cannot be separated by manual manipulation. The diaphragm is multifocally thickened and less pliable due to the presence of dense, firm white fibrous connective tissue.

Question 56

**History**: Tissue from a 4 yr old mixed breed beef cow with a history of weight loss, hair loss, and submandibular swelling. On PE clinicians were unable to hear the heart on the right side. There were jugular pulses and submandibular edema. ## Footnote **Provide a morphological diagnosis.**

Answer 56

Heart: Severe, chronic diffuse fibrinous and fibrosing pericarditis/epicarditis with a penetrating metallic foreign body Reticulum: Focally extensive, chronic, fibrous adhesions.

Question 57

**History**: Tissue from a 4 yr old mixed breed beef cow with a history of weight loss, hair loss, and submandibular swelling. On PE clinicians were unable to hear the heart on the right side. There were jugular pulses and submandibular edema. ## Footnote **What is the common name for this condition?**

Answer 57

Hardware disease:

Question 58

**History**: Tissue from a 4 yr old mixed breed beef cow with a history of weight loss, hair loss, and submandibular swelling. On PE clinicians were unable to hear the heart on the right side. There were jugular pulses and submandibular edema. ## Footnote **What additional lesions might be observed with this condition?**

Answer 58

Pleural cavity: Severe fibrinous pleuritis Peritoneal cavity: Severe, extensive fibrinous peritonitis with multifocal abscessation The adhesions may lead to free gas bloat.

Question 59

**History**: Tissue from a 2.36 year old female pony with a 3 day history a fever and severe watery foul-smelling diarrhea which was occasionally bloody. ## Footnote **Describe the lesion.**

Answer 59

Small Intestine: There are numerous multifocal to coalescing, often circular regions of the mucosa that are slightly raised, have a central region of tan, friable material (fibrin) surrounded by an encircling rim of firm, pale white tissue. These vary in size from 0.5-1 cm in diameter.

Question 60

**History**: Tissue from a 2.36 year old female pony with a 3 day history a fever and severe watery foul-smelling diarrhea which was occasionally bloody. ## Footnote **Give a morphologic diagnosis.**

Answer 60

Small Intestine: Subacute to chronic, multifocal to coalescing fibrinous (fibrinonecrotic) and ulcerative enteritis

Question 61

**History**: Tissue from a 2.36 year old female pony with a 3 day history a fever and severe watery foul-smelling diarrhea which was occasionally bloody. ## Footnote **List a potential cause.**

Answer 61

Salmonella typhimurium

Question 62

**History**: Tissue from a 2.36 year old female pony with a 3 day history a fever and severe watery foul-smelling diarrhea which was occasionally bloody. ## Footnote **What other lesion might be present in the abdominal cavity?**

Answer 62

Enlarged mesenteric lymph nodes

Question 63

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. ## Footnote **Describe the lesion for specimen A.**

Answer 63

Specimen A (74): The serosal surface appears convoluted (cerebriform) with varying areas of thin and thick tissue. The mucosa was thickened with accentuation and corrugation of intestinal folds. Diffusely, the mucosal surface is covered by a thick layer of tan to greenish friable material which could be readily separated from the mucosa.

Question 64

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. ## Footnote **Describe the lesion for specimen B.**

Answer 64

Specimen B (59): The mucosa of ileum and spiral colon has an irregularly thickened and folded surface which could be observed through the serosa and in cross section. The mucosa was thickened with accentuation and corrugation of intestinal folds.

Question 65

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. ## Footnote **Provide a morphologic diagnosis for specimen A.**

Answer 65

Specimen A: Small intestine. Severe, chronic, diffuse, proliferative and fibrinonecrotic enteritis

Question 66

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. ## Footnote **Provide a morphologic diagnosis for specimen B.**

Answer 66

Specimen B: Small intestine and colon. Severe, chronic, diffuse, proliferative enterocolitis

Question 67

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. These pigs have different forms of the same disease. ## Footnote **What is the likely cause and what is the pathogenesis of the diarrhea?**

Answer 67

Lawsonia: both have a proliferative component and A also has a necrotizing or fibrinonecrotic component. Lawsonia enters cell --\> Infected cells continue to undergo mitosis → Organism inhibits enterocyte differentiation → Decreased expression of apical membrane transporters involved in absorption → Nonabsorbed solutes cause osmotic/malabsorptive diarrhea

Question 68

**History**: Tissue from two different 100 lb pigs. Both have diarrhea and reduced weight gain. ## Footnote **What would be an important differential for Pig A?**

Answer 68

Salmonella

Question 69

**History**: Tissue from a 4 month old puppy with severe diarrhea and dehydration. ## Footnote **Describe this lesion.**

Answer 69

The wall of the small intestine is diffusely dark red in color (hemorrhage) and the serosa has a slightly granular appearance. There are locally extensive regions in which the mucosa is covered by a thin layer of tan friable material (fibrin). The mesenteric lymph nodes are moderately enlarged measuring approximately 2.5 x 2 x 2 cm and are dark red in color.

Question 70

**History**: Tissue from a 4 month old puppy with severe diarrhea and dehydration. ## Footnote **Give a morphologic diagnosis.**

Answer 70

Small intestine: severe acute locally extensive fibrinonecrotic and hemorrhagic enteritis Mesenteric lymph nodes: Moderate lymphadenomegally with congestion.

Question 71

**History**: Tissue from a 4 month old puppy with severe diarrhea and dehydration. ## Footnote **Given the history and gross findings, name the most likely etiologic agent and briefly describe the likely pathogenesis of this animal’s death.**

Answer 71

Virus destroys rapidly dividing crypt epithelial cells → apical enterocytes are continually sloughed normally but cannot be replaced (necrosis of crypt cells) → Villus atrophy → malabsorptive / maldigestive diarrhea →if severe, there will be a completed loss of surface epithelium and an exudative diarrhea The loss of epithelium leads to malabsorption, maldigestion, fluid loss into the lumen, and dehydration. Hypovolemia, electrolyte imbalances, and often secondary sepsis (due to loss of the mucosal barrier) ultimately caused the animal’s demise.

Question 72

**History**: Tissue from a 4 month old puppy with severe diarrhea and dehydration. ## Footnote **You also ran a CBC on this puppy. What would be the expected change?**

Answer 72

Leukopenia (\< 2000). Parvovirus also attacks rapidly dividing cells in the bone marrow leading to leukopenia

Question 73

**History**: Tissue from a 4 month old puppy with severe diarrhea and dehydration. ## Footnote **Cats can become infected by a similar virus as well. What is the disease called and are the clinical signs, lesions, and pathogenesis different than in dogs?**

Answer 73

The feline version of parvo is called panleukopenia. The clinical signs, lesions and pathogenesis are the same as in the dog.

Question 74

**History**: Tissue from a 10 day old pig with diarrhea ## Footnote **Describe the lesion.**

Answer 74

From the serosal surface, the intestinal wall appears thickened and rugated (ropy). The mucosal surface is extensively covered by an adherent, shaggy, tan, friable material.

Question 75

**History**: Tissue from a 10 day old pig with diarrhea ## Footnote **Give a morphologic diagnosis.**

Answer 75

Small intestine: acute, diffuse, fibrinonecrotic enteritis.

Question 76

**History**: Tissue from a 10 day old pig with diarrhea ## Footnote **Differentials are based on both the age of the animal and the type of gross lesion. What are the two top differentials in this case?**

Answer 76

Chronic clostridium perfringens type C, or necrotic coccidiosis (this was necrotic coccidiosis). (Salmonella would be a differential in older pigs, but suckling pigs almost never get salmonella)

Question 77

**History**: Tissue from a 10 day old pig with diarrhea ## Footnote **An apicomplexan parasite caused the diarrhea. By what mechanisms can this parasite cause diarrhea?**

Answer 77

Destruction of villus epithelial cells → Villus atrophy → malabsorption / maldigestion Intracellular organism → decreased enterocyte function → malabsorption / maldigestion Inflammation ± ulceration → increased vascular permeability.

Question 78

**History**: Small intestine from a 3 year-old cow with profuse watery diarrhea and progressive emaciation ## Footnote **Describe the (gross) lesions.**

Answer 78

Small intestine. The intestinal mucosa is diffusely and severely thickened, folded (corrugated), and the surface has a granular appearance.

Question 79

**History**: Small intestine from a 3 year-old cow with profuse watery diarrhea and progressive emaciation ## Footnote **Microscopic examination of small intestine reveals numerous macrophages, epithelioid macrophages, and occasional giant cells within the lamina propria and submucosa. Give an appropriate morphologic diagnosis.**

Answer 79

Small intestine: Severe, diffuse, chronic granulomatous enteritis

Question 80

**History**: Small intestine from a 3 year-old cow with profuse watery diarrhea and progressive emaciation ## Footnote **What is the most likely etiologic diagnosis?**

Answer 80

Mycobacterium avium subspecies paratuberculosis (Map)

Question 81

**History**: Small intestine from a 3 year-old cow with profuse watery diarrhea and progressive emaciation ## Footnote **What are the most appropriate samples to collect for histologic diagnosis of this disease?**

Answer 81

Ileum and draining lymph node

Question 82

**History**: Small intestine from a 3 year-old cow with profuse watery diarrhea and progressive emaciation ## Footnote **Do we need to do a necropsy to diagnose this disease or can it be diagnosed with antemortem tests?**

Answer 82

All three of the following tests tend to be positive in CLINICALLY affected animals (animals with diarrhea and weight loss). When positive, serology (fast) is very useful. Alternatively, the causative organism can be detected with PCR (fast) or by culture methods (takes a long time - 2 to 4 months) on feces

Question 83

**History**: Tissue from a very large, 6 month old dog that was anorexic and not passing feces ## Footnote **Describe the lesions.**

Answer 83

There is approximately 5 cm long section of distal ileum telescoped upon itself that extends into the colon. The internal segment (intussusceptum) appears dark red in color, the wall in cross section is expanded by clear glistening fluid, and the intussusceptum cannot be removed from the outer segment (intussuscipiens).

Question 84

**History**: Tissue from a very large, 6 month old dog that was anorexic and not passing feces ## Footnote **Name the lesion.**

Answer 84

intussusception (acute focally extensive with congestion and edema)

Question 85

**History**: Tissue from a very large, 6 month old dog that was anorexic and not passing feces ## Footnote **In a thin and/or cooperative animal, you can often make a tentative diagnosis via abdominal palpation. How would you imagine this lesion would feel on abdominal palpation?**

Answer 85

The segmentally thickened bowel would feel as if the dog/cat had a whole sausage or hot dog within the intestinal lumen.

Question 86

**History**: Tissue from a very large, 6 month old dog that was anorexic and not passing feces ## Footnote **Are there any factors that could predispose this animal to developing this condition?**

Answer 86

May be due to a) enteritis, b) parasites, c) intestinal surgery, d) linear foreign bodies

Question 87

**History**: Tissue from a 5 year old dog with a 1/2 day history of lethargy, inappetance, painful abdomen, and vomiting. His abdomen was subjectively distended, and a diagnostic abdominocentesis yielded a straw-colored fluid with a lactate of 7. ## Footnote **Describe the lesion.**

Answer 87

Small Intestine: The small intestine is segmentally diffusely dark purple to black in color, the wall is moderately thickened, and the lumen moderate to markedly distended.

Question 88

**History**: Tissue from a 5 year old dog with a 1/2 day history of lethargy, inappetance, painful abdomen, and vomiting. His abdomen was subjectively distended, and a diagnostic abdominocentesis yielded a straw-colored fluid with a lactate of 7. ## Footnote **Give the appropriate morphologic diagnosis.**

Answer 88

Small Intestine: severe, acute, segmental, venous infarction (due to an intestinal volvulus).

Question 89

**History**: Tissue from a 5 year old dog with a 1/2 day history of lethargy, inappetance, painful abdomen, and vomiting. His abdomen was subjectively distended, and a diagnostic abdominocentesis yielded a straw-colored fluid with a lactate of 7. ## Footnote **Propose a pathogenesis for the development of this lesion.**

Answer 89

twisting around the mesenteric root (volvulus) → artery continues to pump blood into the segment but venous return is inhibited → venous congestion → edema (hence mucosal thickening) → hypoxia and subsequent necrosis of the bowel wall (venous infarction).

Question 90

**History**: Tissue from a 5 year old dog with a 1/2 day history of lethargy, inappetance, painful abdomen, and vomiting. His abdomen was subjectively distended, and a diagnostic abdominocentesis yielded a straw-colored fluid with a lactate of 7. ## Footnote **What might the intestine proximal and distal to this lesion look like?**

Answer 90

This lesion could act as an intestinal obstruction. Proximal intestine would be dilated with fluid and ingesta. At necropsy, you will immediately suspect small intestinal obstructive disease as some loops of bowel are distended with fluid (proximal to lesion) and others appear relatedly empty (distal to lesion). The cause will be where these two areas intersect.

Question 91

**History**: Tissue from a 5 year old dog with a 1/2 day history of lethargy, inappetance, painful abdomen, and vomiting. His abdomen was subjectively distended, and a diagnostic abdominocentesis yielded a straw-colored fluid with a lactate of 7. ## Footnote **If this had been a horse, what process may have caused this lesion?**

Answer 91

Strangulating lipoma