Session 2: Abdominal Wall and Hernias Flashcards
When might you get visceral pain? (Very general)
During visceral stretching
Visceral inflammation
Visceral ischaemia
Not much of a response from e.g. pinching the viscera.
Describe visceral pain.
Diffuse and poorly define. It is often midline due to bilateral innervation.
What often accompanies visceral pain?
Nausea, vomiting and sweating.
Explain the sympathetic outflow to the gut.
T5-L2 preganglionic
Pass through the sympathetic trunk without synapsing there meaning it is still preganglionic.
It forms three presynaptic splanchnic nerves still preganglionic.
These splanchnic nerves synapse with prevertebral ganglia extend from prevertebral ganlgia to viscera meaning it is now postganglionic.
What are the three presynaptic splanchnic nerves that are formed?
Give their nerve roots as well.
The greater splanchnic nerve (T5-9)
The lesser splanchnic nerve (T10-11)
The least splanchnic nerve (T12)
Give examples of what these nerves will form as they become postganglionic.
Coeliac
Renal
Superior mesenteric
Inferior mesenteric
nerves.
etc…
Explain why visceral pain is diffuse and poorly defined.
Because the sensory afferent of the gut follows the path of the sympathetic outflow, but it does so in reverse.
An example would be a caecal volvulus which is a distended bowel. This causes visceral afferents to be activated in the small bowel. The impulse goes back to the superior mesenteric ganglia and continues back along the least splanchnic nerve. It passes back through the sympathetic chain into the dorsal horn of the spine and converge with somatic afferents at the spinal level of T9-T10. The brain the interprets the visceral afferent to be coming from T9-T10 dermatomes and you get peri-umbilical pain.
Definition of a hernia.
A protrusion of part of the abdominal contents beyond the normal confines of the abdominal wall.
Aka beyond the confines of its containing cavity.
Signs of hernias that are not stuck.
Fullness or swelling
Gets larger when intra-abdominal pressure increases
Aches
Signs and symptoms of hernias that are incarcerated (stuck).
Pain
Cannot be moveed
Nausea and vomiting and usually other signs of bowel obstruction
System problems if bowel has become ischaemic.
Common causes of hernias.
Weakness in its containing cavity like:
- Congenitally related
- Post-surgery where wound have no healed adequately also called incisional hernias.
- Normal points of weakness
Anything that increases abdominal pressure:
- Obesity
- Weightlifting
- Chronic constipation
- Coughing
A hernia consists of 3 parts.
Which?
The sac
Contents of the sac
Coverings of the sac
What is the sac of a hernia?
A pouch of peritoneum. Parietal peritoneum.
What is the contents of the sac?
Usually a loop of bowel or omentum.
What is the coverings of the sac?
Layer of the abdominal wall with its muscles and such.
Weaknesses in the abdominal wall.
Inguinal canal
Femoral canal
Umbilicus
Previous incisions
What is the inguinal canal?
An oblique passage through the lower part of the abdominal wall from where structure pass through from abdomen-testis (spermatic cord).
From where the round ligament goes from uterus-labium majus.
Give a common reason for indirect hernias in males due to developmental abnormalities.
If processus vaginalis only obliterates partially or not at all.
Structures of the inguinal canal.
Floor of the inguinal canal.
Inguinal ligament and lacunar ligament medially
Roof of the inguinal canal.
Internal oblique and transverse abdominis. The muscular arches and its aponeurosis.
Posterior boundary of the inguinal canal.
Transversalis fascia and conjoint tendon medially.
Anterior boundary of the inguinal canal.
Aponeurosis of external oblique.
Where can the deep inguinal ring be found?
In the posterior wall located laterally.
Where can the superficial ring be found?
Anteriorly located medially.
What are the most common abdominal hernias?
Inguinal hernias. They comrpise of approximately 75% of all abdominal hernias.
10% umbilical
10% incisional
3-5% femoral
What subdivisions of inguinal hernias are there?
Which are more common?
Indirect hernias (50%)
Direct hernias (25%)
Important landmarks in order to discern whether a hernia is direct or indirect (or femoral).
Inferior epigastric vessels are vessels branching of external iliac artery and vein just before they cross the inguinal ligament to become femoral artery and vein.
Indirect inguinal hernias will be found laterally to these vessels.
Direct inguinal hernias will usually be found medial to these vessels.
Femoral hernias will be found inferior to the inguinal ligament.
Where will direct hernias most commonly be found?
In Hesselbachs triangle herniating through the superficial inguinal ring.
What is Hesselbachs triangle?
An important landmark where direct hernias will usually be found. It is a point of weakness in the abdominal wall. The superficial inguinal ring can be found here as well.
Borders of Hesselbachs triangle.
Medial: rectus abdominis muscles
Lateral border: inferior epigastric vessels
Inferior border: Inguinal ligament
Where will indirect hernias herniate?
They pass through the deep inguinal ring and through the inguinal canal out of the superficial inguinal ring.
Depending on where the processus vaginalis was obliterated they can potentiall descend into the scrotum.
Wher will femoral hernias herniate?
Through the femoral triangle or more specifically through the femoral canal
Remember the contents of the femoral triangle: NAVEL
Nerve, Artery, Vein, Empty space, Lymphatics.
The hernia will go through the empty space i.e. the femoral canal where the opening is the femoral ring and out through the saphenous opening.
Are femoral hernias more common in males or females?
Why?
In females due to pelvic anatomy.
Females have a wider pelvis.
Why are femoral hernias a serious condition?
Because they can easily become stuck i.e. incarcerated and they can be strangulation hernias as well as they might push on the femoral artery or vein.
What is an omphalocele?
A failure of the midgut to return to the abdomen during development.
This means that viscera will persist outside the abdominal cavity withing the umbilical ring. The viscera will be covered in peritoneum.
Consequences of omphalocele.
Mortality rate is high but if it is managed to be pushed in by surgical intervention there is a chance for the gut to develop relatively normally.
Why does an omphalocele occur?
Because as the gut develops it will develop faster than the abdominal cavity can handle. This means that some of the gut will squeeze through into the umbilical cord via the umbilical ring. This is completely normal because as the abdominal cavity expands the gut contents will return to its original position.
However sometimes this does not happen and an omphalocele occurs.
What is gastroschisis?
A defect in the ventral abdominal wall.
This means that this abdominal viscera will not be covered in peritoneum and exposed to amniotic fluid.
Consequences of gastroschisis.
They tend to get problems with gut development and might develop intestinal atresia and short/inflamed gut.
There will be problems arising around feeding.
How does survival compare between gastroschisis and omphalocele?
Why?
Survival rate is higher in gastroschisis cases than omphalocele because less of genetic complications. Gastroschisis are not associated with genetic problems whereas omphaloceles commonly are such as Trisomy 13, 17 and 21.
Which age group is commonly associated with umbilical hernias?
Commonly found in infants as the hernia can be found at the site of the umbilicus. They are not usually painful and 80-90% close by age of 3.
What are para umbilical hernias?
Acquired as adult. They go through the linea alba in region of the umbilicus.
Risk factors of para umbilical hernias.
Females more likely to get one
Obesity
