Diseases of the peritoneum and intestines Flashcards
Where is the normal route of lymphatic drainage?
Right ventral diaphragm - through small holes channels that eventually anastamose with thoracic duct
What do mesothelial cells produce?
A polysaccharide that acts as low-viscosity lubricant
What are four potential responses of mesothelial cells to irritation?
- Hypertrophy, hyperplasia, metaplasia > cuboidal columnar shape
- Produce plasminogen activator
- Phagocytosis
- Slough, releasing inflammatory mediators and increasing local vascular permeability and neutrophil chemotaxis
What does the plasminogen activator mesothelial cells produce do?
Converts plasminogen> plasmin, which lyses any leaked fibrin to protect against adhesion formation
If the source of irritation is not cleared and mesothelial cells slough into the peritoneal cavity, what events occur past 3-4 days?
- Granulation tissue forms across opposed surfaces
- More mesothelial cells differentiate from sub-serosal mesenchyme to repair the peritoneal surface
1 + 2 = adhesion formation
What are two factors that favor adhesion formation?
- Sepsis
- Presence of foreign material
- Hypoxia
Define internal hernia
Displacement of viscera through a normal of abnormal hole within the peritoneal cavity without the formation of a hernial sac (rare_
Define external hernia
Herniation of viscera within a sac past the boundary of the abdominal wall
What does an external hernia consist of?
Hernial sac + herniated viscera + hernial ring
Give two examples of internal hernias
- Herniation through epiploic foramen
2. Herniation through hole in omentum or mesentery
What compound can be responsible for blue-black discolouration of tissue post mortem?
Sulphmethaemoglobin
What sort of hernia could pregnancy predispose to?
Ventral abdominal hernia
What sort of hernia might patent umbilical ring predispose to? What is the usual consequence?
Umbilical hernia
Usually fine as hernial ring is wide enough
Why do inguinal hernias occur?
Because the deep inguinal ring remains patent in adult males following the descent of the testes
What is an indirect inguinal hernia?
Herniation of viscera through the deep inguinal ring into the inguinal canal
May evolve into scrotal hernia if continues past vaginal ring
What is a direct inguinal hernia?
Viscera pass subcutaneously outside the inguinal canal and sit in the submucosa. More prone to strangulation
What is the most common type of diaphragmatic hernia? Which part of the diaphragm usually tears in small animals compared to horses?
Acquired pleuroperitoneal diaphragmatic hernia usually due to trauma
Muscular part is more usual in small animals
Tendinous part more usual in horses
What are five potential consequences of abdominal trauma?
- Septic peritonitis due to perforation of GIT
- Bruising or laceration of viscera
- Rupture of hollow organs
- Herniation of viscera
- Leakage of blood, urine, bile, inflammatory exudate into abdominal cavity
What is a common parasite that encysts in the peritoneal cavity of sheep?
Cysticercus - taenid tapeworm
Define ascites
Accumulation of excess non-inflammatory fluid in peritoneal cavity (transudate or modified transudate)
What are the two major mechanisms for ascites to develop?
- Obstruction of peritoneal fluid drainage e.g neoplasm at RV diaphragm or sternal lymph nodes
- 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
Name four pathologies that can result in peritonitis.
- Uroperitoneum
- Bile in thorax > septic peritonitis due to detergent action
- Intraperitoneal injection of medication including antibiotics
- Pancreatic necrosis
What is a chylothorax?
Chylous ascites due to leakage of chyle from ruptured lymphatic channel > mild granulomatous peritonitis
Describe how FIP infection causes peritoneal effusion.
- Viral ag-ab complexes are phagocytosed by macrophages and deposited into walls of blood vessels
- Complement is activation, neutrophils emigrate and local inflammation increases blood vessel permeability
- Peritoneal and pleural effusion with high protein
What are the four types of fat necrosis ?
- Enzymatic fat necrosis - pancreatitis
- Focal or multifocal fat necrosis - obesity
- Yellow fat disease - lots of polyunsaturated fats and low vitamin E in diet > ROS damage and ceroid lipofuschin accumulation
- Massive fat necrosis in cattle
What are the consequences of peritonitis?
Paralytic ileus > adhesion formation
Absorption of bacterial toxins into circulation causing toxaemia and death
Actual organism may also spread via lymphatics to cause septicaemia
What is the most common tumour of the peritoneal connective tissues?
Lipoma
What is it called when you sample the peritoneal fluid?
Abdominocentesis
What is peritoneal carcinomatosis?
Implantation of a secondary neoplasm over the peritoneal cavity e.g ovarian cancer, stomach cancer, haemangtiosarcoma
What is the retroperitoneal space?
Loose fibrofatty CT immediately external to the retroperitoneal cavity
What are two sources of gas in the proximal intestine?
Swallowed (aerophagia)
Produced by intestinal bacteria
What are three consequences of intestinal stasis?
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
What are three risks associated with vomiting?
Oesophageal ulceration
Aspiration pneumonia
Fluid and electrolyte loss (especially Cl-)
What might be seen in the caecum of a horse with large intestinal obstruction?
Tympany due to distension with the gases of bacterial fermentation
What is one congenital condition in a foal causing a functional obstruction?
Congental colonic agangliosis - born with no ganglia of myenteric plexus
What is one abnormality that might be seen in event of an extrinsic obstruction?
Hyperplasia and hypertrophy of the muscularis mucosal layer
What are three conditions that might predispose to rectal prolapse?
Colitis
Prostatic enlargement
Constipation
Consumption of oestrogenic pastures (sheep)
What does obturation mean?
Occlusion of intestine by intraluminal mass
What are two factors that might predispose to constipation?
Prostatic enlargement
Pelvic or spinal cord trauma where the autonomic nerves were damaged
What is an enterolith? Which species most commonly get them?
Usually struvite distributed in concentric lamellae around a foreign object e.g food
What is one potential consequence of a linear foreign body?
Plication of intestines - mesenteric aspect can saw intestine in half
What is one potential consequence of a blunt foreign body?
Local pressure necrosis +/- rupture and peritonitis
What is the likely effect after 10 minutes of hypoxia in the small intestine?
Enterocytes sloughing from tips of villi
What is the likely effect after 60 minutes of hypoxia in the small intestine?
Necrosis of serosal mesothelium and fibrin exudation into the peritoneal cavity
What is the likely effect after 3 hours of hypoxia in the small intestine?
Enterocytes from tip - base of villi have all sloughed - regeneration will be much slower
What is the likely effect after 6 hours of hypoxia in the small intestine?
Smooth muscle of muscularis externa begins to devitalise
What does hypoxia do to motility of the SI?
Initial hypermotility followed by ileus
How does the LI hold up compared to the SI in the face of hypoxia?
More resistant - may be 3 hours before enterocytes in pits have sloughed
Define strangulation
External compression of venous return of an intestinal segment
Define torsion
Rotation of an intestinal segment about its long axis
Most common in caecum of cattle and horses
What can predispose to caecal torsion in a cow?
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
Define intestinal volvulus
Rotation of intestine segment about its mesenteric axis
With what behaviour is mesenteric torsion commonly associated in pigs? What about lambs? Dogs?
Gluttony in pigs
Seen in suckling or artificially feeding lambs
In dogs may be due to bulky intestinal contents due to EPI
In which direction is rotation of the large colon most common in horses?
Dorsomedial
What are three things that might predispose to intussusception?
Linear FB
Enteritis
Abscess on small intestine
Intramural tumour
Which pathogen is associated with arterial infarction of the intestines in horses? What other symptom might their presence cause?
Strongylus vulgaris larvae
Might cause intermittent colic due to transient slow blood flow
What are two mechanisms for intestinal stenosis?
Reparative fibrosis
Intestinal smooth muscle hypertrophy
What is the term for frank blood per anus?
Haematochezia
What is an intestinal polyp?
An intestinal adenoma
What sort of lymphoma do horses usually get?
B cell lymphoma
What is ileus?
lack of normal smooth muscle tone and peristaltic movements of the intestines and/or stomach
What are three things that might cause to ileus?
Irritation following abdominal surgery
Shock
Toxaemia
Electrolyte imbalances (hypocalcemia, hypokalaemia)
What are four clinical signs associated with ileus?
Absence of borborygmi
Vomiting or reflux
Abdominal distension
Anorexia
Which pathogen has been implicated in Grass sickness?
Clostridium C
