Pathophysiology of hernias + principles of hernia repair Flashcards
What is a hernia?
- Full-thickness defect in an anatomical structure allowing protrusion of viscera
- 2 components =
- Ring (border of defect)
- Sac (mesothelial layer covering hernia contents)
What are different types of hernias?
- Internal vs external
- True hernias vs false hernias / ruptures
- Spontaneous vs acquired
- Reducible vs incarcerated vs strangulated
What is the pathophysiology of hernias?
- Loss of domain
-Adaptation of the abdominal wall to lower volume of contents
-Makes reduction / repair more difficult
-May cause compartment syndrome - Incarceration
-Entrapment of organs leading to luminal obstruction
-May progress to strangulation - Strangulation
-Constriction of blood supply leading to hernia contents = Torsion of vascular pedicle (esp. intestine, uterus, testicle)
-Venous drainage affected first, followed by arterial inflow
-Leads to organ necrosis and potentially rupture
-Can be acute or delayed
-Release of contents may worsen condition
What are umbilical hernias?
- Due to incomplete fusion of ventral abdominal wall
- Inherited
- Often accompany other congenital defects
What are inguinal hernias?
- Direct inguinal hernia = herniation through the inguinal ring adjacent to the vaginal process
- Indirect inguinal hernia = herniation into the cavity of the vaginal process
- Acquired - Relatively common, Usually middle-aged intact female dogs
What is the aetiology of inguinal hernias?
- Short inguinal canal in females
- Several things may weaken / enlarge the inguinal rings =
- Oestrogen
- Malnutrition / catabolic diseases
- Obesity
What are scrotal hernias?
- Indirect inguinal hernias in male dogs
- Aetiology unknown - Possibly congenital defect in inguinal ring
- Usually unilateral
- Present with pain and swelling - Incarceration / strangulation common
What are traumatic hernias?
- False hernias / ruptures
- Lack a sac so more prone to adhesions / incarceration
- Can cause strangulation as ring contracts during healing
What is aetiology of traumatic hernias?
- Usually blunt trauma =
- Traction / avulsion injury to abdominal wall
- Tearing of abdominal muscles close to impact
- Often coexist with severe injuries to other organ systems
What are clinical signs of traumatic hernias?
- Bulging subcutaneous mass / abdominal asymmetry
- May vary in size / shape
- Clinical signs associated with other injuries
What are incisional hernias?
Dehiscence of a surgical abdominal wound due to =
* Excessive force on incision -
- Obesity
- Abdominal effusion / ascites
- Activity / coughing / straining
* Poor holding strength of wound -
- Incorrect suture / knot technique
- Delayed healing due to infection, medication
What are clinical signs of incisional hernias?
- Wound inflammation / oedema
- Swelling over / around wound
- Evisceration - Usually in acute hernias
What is congenital peritoneopericardial diaphragmatic hernias?
- Due to failure of fusion of transverse septum resulting in midline communication between the abdomen and pericardium
- Various viscera can herniate - Causes pulmonary compression and sometimes pericardial effusion and tamponade
- Frequently coexist with other defects
What are clinical signs of peritoneopericardial diaphragmatic hernias?
- May be asymptomatic / incidental finding
- Respiratory signs - Dyspnoea, tachypnoea, cough, wheeze
- GI signs - Anorexia, polyphagia, vomiting, diarrhoea, hepatic encephalopathy
- Right heart failure due to tamponade
What are traumatic diaphragmatic hernias?
- Usually due to blunt trauma with glottis open
- Increased pleuroperitoneal pressure gradient causes tearing of muscle of diaphragm
- Occasionally iatrogenic due to sharp trauma
