Diseases of the peritoneum and intestines

Question 1

Where is the normal route of lymphatic drainage?

Answer 1

Right ventral diaphragm - through small holes channels that eventually anastamose with thoracic duct

Question 2

What do mesothelial cells produce?

Answer 2

A polysaccharide that acts as low-viscosity lubricant

Question 3

What are four potential responses of mesothelial cells to irritation?

Answer 3

1. Hypertrophy, hyperplasia, metaplasia > cuboidal columnar shape
2. Produce plasminogen activator
3. Phagocytosis
4. Slough, releasing inflammatory mediators and increasing local vascular permeability and neutrophil chemotaxis

Question 4

What does the plasminogen activator mesothelial cells produce do?

Answer 4

Converts plasminogen> plasmin, which lyses any leaked fibrin to protect against adhesion formation

Question 5

If the source of irritation is not cleared and mesothelial cells slough into the peritoneal cavity, what events occur past 3-4 days?

Answer 5

1. Granulation tissue forms across opposed surfaces
2. More mesothelial cells differentiate from sub-serosal mesenchyme to repair the peritoneal surface
   1 + 2 = adhesion formation

Question 6

What are two factors that favor adhesion formation?

Answer 6

1. Sepsis
2. Presence of foreign material
3. Hypoxia

Question 7

Define internal hernia

Answer 7

Displacement of viscera through a normal of abnormal hole within the peritoneal cavity without the formation of a hernial sac (rare_

Question 8

Define external hernia

Answer 8

Herniation of viscera within a sac past the boundary of the abdominal wall

Question 9

What does an external hernia consist of?

Answer 9

Hernial sac + herniated viscera + hernial ring

Question 10

Give two examples of internal hernias

Answer 10

1. Herniation through epiploic foramen

2. Herniation through hole in omentum or mesentery

Question 11

What compound can be responsible for blue-black discolouration of tissue post mortem?

Answer 11

Sulphmethaemoglobin

Question 12

What sort of hernia could pregnancy predispose to?

Answer 12

Ventral abdominal hernia

Question 13

What sort of hernia might patent umbilical ring predispose to? What is the usual consequence?

Answer 13

Umbilical hernia

Usually fine as hernial ring is wide enough

Question 14

Why do inguinal hernias occur?

Answer 14

Because the deep inguinal ring remains patent in adult males following the descent of the testes

Question 15

What is an indirect inguinal hernia?

Answer 15

Herniation of viscera through the deep inguinal ring into the inguinal canal
May evolve into scrotal hernia if continues past vaginal ring

Question 16

What is a direct inguinal hernia?

Answer 16

Viscera pass subcutaneously outside the inguinal canal and sit in the submucosa. More prone to strangulation

Question 17

What is the most common type of diaphragmatic hernia? Which part of the diaphragm usually tears in small animals compared to horses?

Answer 17

Acquired pleuroperitoneal diaphragmatic hernia usually due to trauma
Muscular part is more usual in small animals
Tendinous part more usual in horses

Question 18

What are five potential consequences of abdominal trauma?

Answer 18

1. Septic peritonitis due to perforation of GIT
2. Bruising or laceration of viscera
3. Rupture of hollow organs
4. Herniation of viscera
5. Leakage of blood, urine, bile, inflammatory exudate into abdominal cavity

Question 19

What is a common parasite that encysts in the peritoneal cavity of sheep?

Answer 19

Cysticercus - taenid tapeworm

Question 20

Define ascites

Answer 20

Accumulation of excess non-inflammatory fluid in peritoneal cavity (transudate or modified transudate)

Question 21

What are the two major mechanisms for ascites to develop?

Answer 21

1. Obstruction of peritoneal fluid drainage e.g neoplasm at RV diaphragm or sternal lymph nodes
2. Overproduction of peritoneal fluid e.g increased permeability of blood vessels due to endotoxaemia or renal failure, hypoalbuminaemia, increased hydrostatic pressure as in R sided CHF or cirrhosis

Question 22

Name four pathologies that can result in peritonitis.

Answer 22

1. Uroperitoneum
2. Bile in thorax > septic peritonitis due to detergent action
3. Intraperitoneal injection of medication including antibiotics
4. Pancreatic necrosis

Question 23

What is a chylothorax?

Answer 23

Chylous ascites due to leakage of chyle from ruptured lymphatic channel > mild granulomatous peritonitis

Question 24

Describe how FIP infection causes peritoneal effusion.

Answer 24

1. Viral ag-ab complexes are phagocytosed by macrophages and deposited into walls of blood vessels
2. Complement is activation, neutrophils emigrate and local inflammation increases blood vessel permeability
3. Peritoneal and pleural effusion with high protein

Question 25

What are the four types of fat necrosis ?

Answer 25

1. Enzymatic fat necrosis - pancreatitis 2. Focal or multifocal fat necrosis - obesity 3. Yellow fat disease - lots of polyunsaturated fats and low vitamin E in diet > ROS damage and ceroid lipofuschin accumulation 4. Massive fat necrosis in cattle

Question 26

What are the consequences of peritonitis?

Answer 26

Paralytic ileus > adhesion formation Absorption of bacterial toxins into circulation causing toxaemia and death Actual organism may also spread via lymphatics to cause septicaemia

Question 27

What is the most common tumour of the peritoneal connective tissues?

Answer 27

Lipoma

Question 28

What is it called when you sample the peritoneal fluid?

Answer 28

Abdominocentesis

Question 29

What is peritoneal carcinomatosis?

Answer 29

Implantation of a secondary neoplasm over the peritoneal cavity e.g ovarian cancer, stomach cancer, haemangtiosarcoma

Question 30

What is the retroperitoneal space?

Answer 30

Loose fibrofatty CT immediately external to the retroperitoneal cavity

Question 31

What are two sources of gas in the proximal intestine?

Answer 31

Swallowed (aerophagia) | Produced by intestinal bacteria

Question 32

What are three consequences of intestinal stasis?

Answer 32

Contents act osmotically - pull fluid out Undigested food in lumen provides substrate for bacteria, get overgrowth Distension may collapse mural blood vessels causing vascular injury, venous infarction, necrosis and potentially perforation

Question 33

What are three risks associated with vomiting?

Answer 33

Oesophageal ulceration Aspiration pneumonia Fluid and electrolyte loss (especially Cl-)

Question 34

What might be seen in the caecum of a horse with large intestinal obstruction?

Answer 34

Tympany due to distension with the gases of bacterial fermentation

Question 35

What is one congenital condition in a foal causing a functional obstruction?

Answer 35

Congental colonic agangliosis - born with no ganglia of myenteric plexus

Question 36

What is one abnormality that might be seen in event of an extrinsic obstruction?

Answer 36

Hyperplasia and hypertrophy of the muscularis mucosal layer

Question 37

What are three conditions that might predispose to rectal prolapse?

Answer 37

Colitis Prostatic enlargement Constipation Consumption of oestrogenic pastures (sheep)

Question 38

What does obturation mean?

Answer 38

Occlusion of intestine by intraluminal mass

Question 39

What are two factors that might predispose to constipation?

Answer 39

Prostatic enlargement | Pelvic or spinal cord trauma where the autonomic nerves were damaged

Question 40

What is an enterolith? Which species most commonly get them?

Answer 40

Usually struvite distributed in concentric lamellae around a foreign object e.g food

Question 41

What is one potential consequence of a linear foreign body?

Answer 41

Plication of intestines - mesenteric aspect can saw intestine in half

Question 42

What is one potential consequence of a blunt foreign body?

Answer 42

Local pressure necrosis +/- rupture and peritonitis

Question 43

What is the likely effect after 10 minutes of hypoxia in the small intestine?

Answer 43

Enterocytes sloughing from tips of villi

Question 44

What is the likely effect after 60 minutes of hypoxia in the small intestine?

Answer 44

Necrosis of serosal mesothelium and fibrin exudation into the peritoneal cavity

Question 45

What is the likely effect after 3 hours of hypoxia in the small intestine?

Answer 45

Enterocytes from tip - base of villi have all sloughed - regeneration will be much slower

Question 46

What is the likely effect after 6 hours of hypoxia in the small intestine?

Answer 46

Smooth muscle of muscularis externa begins to devitalise

Question 47

What does hypoxia do to motility of the SI?

Answer 47

Initial hypermotility followed by ileus

Question 48

How does the LI hold up compared to the SI in the face of hypoxia?

Answer 48

More resistant - may be 3 hours before enterocytes in pits have sloughed

Question 49

Define strangulation

Answer 49

External compression of venous return of an intestinal segment

Question 50

Define torsion

Answer 50

Rotation of an intestinal segment about its long axis | Most common in caecum of cattle and horses

Question 51

What can predispose to caecal torsion in a cow?

Answer 51

Sudden change to high concentrate ration Osmotic effect of increased VFA production leading to caecal atony and distension with watery ingesta The same thing can happen with a horse caecum and colon also

Question 52

Define intestinal volvulus

Answer 52

Rotation of intestine segment about its mesenteric axis

Question 53

With what behaviour is mesenteric torsion commonly associated in pigs? What about lambs? Dogs?

Answer 53

Gluttony in pigs Seen in suckling or artificially feeding lambs In dogs may be due to bulky intestinal contents due to EPI

Question 54

In which direction is rotation of the large colon most common in horses?

Answer 54

Dorsomedial

Question 55

What are three things that might predispose to intussusception?

Answer 55

Linear FB Enteritis Abscess on small intestine Intramural tumour

Question 56

Which pathogen is associated with arterial infarction of the intestines in horses? What other symptom might their presence cause?

Answer 56

Strongylus vulgaris larvae | Might cause intermittent colic due to transient slow blood flow

Question 57

What are two mechanisms for intestinal stenosis?

Answer 57

Reparative fibrosis | Intestinal smooth muscle hypertrophy

Question 58

What is the term for frank blood per anus?

Answer 58

Haematochezia

Question 59

What is an intestinal polyp?

Answer 59

An intestinal adenoma

Question 60

What sort of lymphoma do horses usually get?

Answer 60

B cell lymphoma

Question 61

What is ileus?

Answer 61

lack of normal smooth muscle tone and peristaltic movements of the intestines and/or stomach

Question 62

What are three things that might cause to ileus?

Answer 62

Irritation following abdominal surgery Shock Toxaemia Electrolyte imbalances (hypocalcemia, hypokalaemia)

Question 63

What are four clinical signs associated with ileus?

Answer 63

Absence of borborygmi Vomiting or reflux Abdominal distension Anorexia

Question 64

Which pathogen has been implicated in Grass sickness?

Answer 64

Clostridium C