Ch 84 - Abdominal Wall Reconstruction and Hernias

Question 1

What is an auto-penetrating hernia?

Answer 1

A traumatic abdominal wall hernia caused by a fractured rib penetrating through abdominal musculature

Question 2

In the cranial, middle and caudal thirds of the abdomen, which aponeuroses are sitting superficial and deep to the rectus abdominis?

Answer 2

Cranial:
- External Abdominal Oblique - Superficial
- Internal abdominal oblique - Both
- Transverse Abdominis - Deep

Middle
- External Abdominal Oblique - Superficial
- Internal Abdominal Oblique - Superficial
- Transverse Abdominus - Deep

Caudal
- All superficial

Question 3

Where do the internal and external abdominal obliques and the transverse abdominis originate from?

Answer 3

External abdominal oblique
- Originates from 4/5th to 12th rib and from last rib and thoracodorsal fascia
- Runs in caudoventral direction

Internal Obdominal oblique
- Originates from thoracolumbar fascia caudal to last rib and from tuber coxae
- Runc cranioventrally

Transverse Abdominis
- Lumbar portion arising from the transverse processes of the lumbar vertebrae and thoracolumbar fascia
- Costal portion - Arising from medial sides of 12th and 13th rib as well as 8th-11th costal cartilages
- Runs in dorsoventral direction

Question 4

What are substernal midline defects often associated with?

Answer 4

• Congenital peritoneal pericardial diaphragmatic hernia
• PPDH often assoc with incompletely fused caudal sternebrae

Question 5

List methods of explansion used in human surgery for loss of domain

Answer 5

• Progressive pneumoperitoneum
• Silastic expanders
• Staged reduction
• Prosthetic material

Question 6

How can intestinal strangulation lead to rapid systemic illness?

Answer 6

• Bacterial transmigration
• Vasoactive substances release (arachidonic acid metabolites, cytokines, leucotrienes, kinins) from tissue and blood cell autolysis
• Redistribution of fluids and severe cardiopulmonary effects

Question 7

What is the embryological cause of ventral abdominal wall hernias?

Answer 7

Failure of fusion or delayed fusion of the lateral folds (primarily the rectus abdominis)

Question 8

What disorders have been associated with congenital ventral abdominal hernias?

Answer 8

• Fucosidosis
• Ectodermal dysplasia
• Cryptorchidism

Question 9

What initially protects an omphalocoele?

Answer 9

A thin transparent membrane of amniotic tissue

Question 10

What is gastroschisis?

Answer 10

A congenital ventral abdominal hernia, very similar in appearance to an omphalocoele but it is paramedian

Question 11

What breeds are predisposed to umbilical hernias?

Answer 11

• Airedale terriers
• Basenjis
• Pekingese
• Pointers
• Weimeraners

Question 12

What are the 2 broad classifications of inguinal hernias?

Answer 12

• Indirect - hernia contents enters the cavity of the vaginal process
• Direct - Hernia contents pass through the inguinal ring adjacent to the vaginal process (less common)

Question 13

Are inguinal hernias common?

Answer 13

• Congenital is rare
• Acquired is common

Question 14

Describe the anatomical boundaries of the inguinal rings?

Answer 14

• Internal inguinal ring: Bound by rectus abdominis, inguinal ligament and internal abdominal oblique
• External inguinal ring: Longitudinal slit in the aponeurosis of the external abdominal oblique

Question 15

What structures pass throught the inguinal canal?

Answer 15

• Genital branch of genitofemoral nerve, artery and vein
• Cremaster muscle passes through external ring
• Pass through the caudomedial aspect

Question 16

Which breeds have been shown to have heritable inguinal hernias?

Answer 16

• Golder Retrievers
• Cocker Spaniels
• Dachshunds

Question 17

List factors which may predispose an animal to an inguinal hernia

Answer 17

• Bitches have a shorter and wider inguinal canal
• Most commonly occur during aestrus in intact bitches, suggesting oestrogen has a close association (changing strength and character of connective tissue)
• Associated between inguinal and perineal hernias in male dogs
• Obesity (accumulation of fat around the round ligament)

Question 18

List some differentials for an inguinal hernia

Answer 18

• Soft tissue maass
• Mammary tumour or cyst
• Lipoma
• Enlarged LN
• Abscess
• Haematoma
• Testicular torsion/abscess/neoplasia
• Orchitis

Question 19

List closure options for an inguinal hernial which cannot be primarily closed

Answer 19

• Polypropylene mesh onlay
• Sartorius muscle flap

Question 20

Why is castration recommended after a scrotal hernia?

Answer 20

• Reduce recurrence
• Prevent offspring (may be heritable)
• Increased risk of testicular neoplasia
• Testicular necrosis

Question 21

Where is the femoral canal located in relation to the inguinal canal?

Answer 21

Lateral to the inguinal ligament (caudolateral to inguinal canal)

Question 22

What are the two lacunae of the femoral canal?

Answer 22

• Muscular lacunae - Femoral nerve within iliopsoas muscle
• Vascular lacunae - Craniolateral to muscular lacunae and contains femoral artery and vein and saphenous nerve
• Iliopectineal arch (iliac and transverse fascia) seperated the lacunae.

Question 23

Where does herniation tend to occur in femoral hernias?

Answer 23

• In the femoral canal; a potential space caudomedial to the femoral vessels

Question 24

Broadly speaking, how do you correct femoral hernias?

Answer 24

• Intra-abdominal closure of the hernia sac
• Extra-abdominal reconstruction of the hernia ring

Question 25

List options for repair of a cranial pubic ligament avusion if primary repair is not possible

Answer 25

• Underlay mesh
• Rectus abdominis flap
• Sartorius flap

Question 26

What are the 2 borad causes of incisional hernia?

Answer 26

• Excessive force on incision
• Poor holding strength of the wound

Question 27

What is the suture-to-wound length ratio to abdominal wall closure?
What are the recommended suture bites?

Answer 27

• 4:1 ratio
• Equates to 5-7mm fascial bites with 3-4mm of interval

Question 28

What is the most consistent sign of impending abdominal wall dehiscense?

Answer 28

Swelling and serosanguinous drainage from the incision

Question 29

Is debridement recommended for treatment of acute incisional hernia?

Answer 29

Not unless fascial edges are devitalised, infected or unidentifiable
Contraindicated as it caused excessive and unnecessary tissue trauma and set the wound back to its substrate phase, delaying the onset of rapid fascial strength gain and increases tension due to reduction of tissues for closure

Question 30

List some autologous repair methods for large abdominal wall defects

Answer 30

• Vacuum assisted closure
• Separation of anatomic components (fascial releasing incision and adjacent tissue transfer)
• Abdominal wall partitioning (multiple parasagittal releasing incisions in staggered pattern)
• Cranial sartorius muscle flap (branch of femoral artery and vein at proximal third)
• External abdominal Oblique muscle flap (cranial branch of cranal abdominal artery supplies middle zone of lateral abdominal wall)
• Rectus abdominis muscle flap (cranial and caudal epigastric vessels)

Question 31

List some nonautogenous repair methods for large abdominal wall defects

Answer 31

• Synthetic mesh (polypropylene - inert, woven, monofilament, porous)
• Tissue grafts or bioprosthetic mesh (porcine SIS)

Question 32

What are the three methods of mesh placement?
Which is most commonly used?

Answer 32

• Overlay
• Interposition
• Underlay

Underlay most often used, lowest rate of reherniation and wound complications
- Better distribution of tension
- Superior formation of post-op connective tissue
- Sliding myofascial flaps or adjacent adipodermal flaps placed over and underlay mash provide another layer of mechanical buttress and barrier from infection
- Underlying omental patch to minimise adhesions