Abdominal wall reconstruction and hernias

Question 1

Describe the components of a hernia

Answer 1

Question 2

What is the difference between a true and false hernia?

Answer 2

True hernia is within a normal aperture in the abdominal wall (often congenital), false hernia is in another area (often traumatic)

Question 3

Are traumatic or congenital hernias more likely to be covered in a peritoneal hernial sac?

Answer 3

Congenital, although traumatic hernias may form a peritoneal sac over time (peritonealization). The absence of a sac in traumatic hernias places them at risk of adhesions

Question 4

What is an autopenetrating hernia?

Answer 4

A hernia caused by a fractured rib penetrating the abdominal musculature

Question 5

Describe the anatomy of the abdominal wall, specifically the levels of the fascial attachments to the linea alba as they relate to the rectus abdominis muscle.

Answer 5

Question 6

What is the arcuate line?

Answer 6

The cranial most aspect where the aponeurosis of the internal abdominal oblique and transverse abdominal muscles first transition to a superficial location

Question 7

What are the origins of the external abdominal oblique, internal abdominal oblique and transverse abdominal oblique muscles?

Answer 7

1. external abdominal oblique muscles: originate from the fourth or fifth to the twelfth rib and from the last rib and thoracodorsal fascia and extend in a caudoventral direction
2. internal abdominal oblique muscle: arise from the thoracolumbar fascia caudal to the last rib and from the tuber coxae. These fibers extend cranioventrally.
3. transverse abdominal muscle comes from two parts: the lumbar portion arises from the transverse processes of the lumbar vertebrae and the thoracolumbar fascia, and the costal portion arises from the medial sides of the twelfth and thirteenth ribs and from the eighth to eleventh costal cartilages. Fibers from this muscle extend in a dorsoventral direction.

Question 8

Label the following diagram of the location of common abdominal hernias.

Answer 8

Question 9

What are some potential life threatening sequelae associated with abdominal herniation?

Answer 9

Loss of domain, incarceration and strangulation.

Question 10

What are the sequelae of forcing abdominal hernia contents back into the abdomen in instances of loss of domain?

Answer 10

Acute pulmonary complications, poor organ perfusion (abdominal compartment syndrome).

Progressive pneumoperitoneum, inflatable silastic expanders, and the use of mesh have all been described in humans to combat loss of domain.

Question 11

What is strangulation and what can cause it?

Answer 11

Strangulation is the devitalization of incarcerated hernial contents due to arrested circulation.

Can occur secondary to constriction of blood supply at the hernia ring, or torsion of the vascular pedicle.

Question 12

What are the sequelae of strangulated viscera?

Answer 12

Significant blood, protein and fluid loss. Rupture will cause toxemia and septicemia. Systemic effects may be greater for hernias surrounded by peritoneum as this will allow more rapid uptake of vasoactive substances.

Question 13

What are the main goals of hernia repair?

Answer 13

1. Ensure the viability of the entrapped hernia contents.
2. Release and return viable hernia contents into their normal location.
3. Obliterate redundant hernial sac tissue.
4. Provide a tension free and secure primary closure.

Question 14

When are autologous muscle or fascial flap development preferred over prosthetic implants (such as polypropylene mesh) for hernia closure?

Answer 14

In an infected environment/presence of gross contamination.

Question 15

What are the three indications for surgical repair of an abdominal hernia?

Answer 15

1. Hernia is symptomatic
2. Large protrusion that affects quality of life
3. Risk of strangulation

Question 16

The falciform ligament is the remnant of which embryonic structure?

Answer 16

The umbilical vein (the middle umbilical ligament of the bladder is the remnant of the urachus)

Question 17

Are umbilical hernias considered inherited?

Answer 17

Yes, affected animals should not be bred

Question 18

What other congenital abnormalities have been reported with umbilical herniation?

Answer 18

Failure of caudal sternal fusion, cranioventral abdominal hernias, cryptorchidism, concomitant diaphragmatic hernias.

Any patient presenting with an umbilical hernia should be thoroughly investigated for other congenital abnormalities.

Question 19

Which breeds of dogs are predisposed to umbilical herniation?

Answer 19

Airedale terriers, Basenjis, Pekingese, Pointers and Weimaraners

Question 20

Is there a sex predilection for umbilical herniation?

Answer 20

Not for the general population. Females overrepresented amongst at risk breeds

Question 21

What is an omphalocele?

Answer 21

Large midline umbilical and skin defect that permits abdominal organs to protrude from the body. Usually covered by a transparent membrane of amniotic tissue.

Question 22

Is conservative management reasonable in a puppy with a small asymptomatic (<2-3mm) umbilical hernia?

Answer 22

Yes, may spontaneously regress by 6 months of age

Question 23

What are some techniques that can be used in instances of large abdominal wall defects with umbilical hernia repair?

Answer 23

Fascial release incisions, component separation technique, prosthetic materials.

Question 24

Describe the difference between a direct and indirect inguinal hernia?

Answer 24

Indirect hernias enter the cavity of the vaginal process, whereas direct hernias pass through the inguinal rings adjacent to the vaginal process.

Question 25

Are direct or indirect inguinal hernias more likely to result in strangulation?

Answer 25

Indirect, because the vaginal process is narrow at the inelastic inguinal ring.

Question 26

Are congenital inguinal hernias more likely in male or female dogs?

Answer 26

Male, possibly due to delayed inguinal ring narrowing and late testicular descent.

Question 27

Acquired inguinal hernias are most frequently seen in which patients?

Answer 27

Middle-aged, intact bitches

Question 28

What are the vessels that pass through the caudomedial aspect of the inguinal canal?

Answer 28

External pudendal vessels, genital branch of the genitofemoral nerve, artery and vein

Question 29

What are the anatomic boundaries of the internal and external inguinal rings?

Answer 29

Question 30

Which breeds of dog have a proven inheritable influence for inguinal hernia development?

Answer 30

Golden retrievers, Cocker spaniels and Dachshunds

Question 31

What are the factors potentially involved in inguinal hernia formation?

Answer 31

Anatomic: increased size of vaginal process, short wide inguinal canal in bitches. Hormonal: Estrogen thought to play a role Metabolic: obesity may increase abdominal pressure and fat may dilate the vaginal process

Question 32

What concurrent condition are male dogs with inguinal hernia at increased risk for?

Answer 32

Cryptorchidism, an association between inguinal and perineal hernias has also been described.

Question 33

On which side are inguinal hernias more likely to occur?

Answer 33

Left

Question 34

Is strangulation of hernia contents more common in male or female dogs?

Answer 34

Male

Question 35

What are some clinical signs that might suggest strangulated intestine in an inguinal hernia?

Answer 35

Vomiting, abdominal pain, depression

Question 36

What are some DDx for scrotal hernias?

Answer 36

Testicular torsion, testicular or scrotal abscess, neoplasia, orchitis, hydrocele

Question 37

Why do you need to leave a gap caudally when performing inguinal hernia repair?

Answer 37

To allow unconstrained passage of the external pudendal and genitofemoral vessels, genitofemoral nerve, and spermatic cord (in intact dogs).

Question 38

What muscle flap could potentially be used to augment large inguinal hernia defects?

Answer 38

Sartorius. This can be combined with prosthetic mesh if required.

Question 39

Up to what stage of gestation may an incarcerated gravid uterus in an inguinal hernia potentially be salvaged?

Answer 39

7 weeks

Question 40

What are the most common complications after inguinal hernia repair?

Answer 40

Seroma and hematoma. If castration is not performed swelling of the scrotum may occur in instances of lymphatic and venous drainage occlusion - may require surgical revision.

Question 41

True or false? An increased incidence of testicular tumours in dogs has been associated with scrotal hernias?

Answer 41

True. Castration is recommended with scrotal hernia repair for this reason and to prevent production of offspring.

Question 42

In a strangulated inguinal hernia is the surgical approach abdominal or extraabdominal?

Answer 42

Should be abdominal to ligate and transect structures entering the inguinal ring, this allows for en bloc resection of the hernial sac (+/- scrotal ablation) and removal of macerated tissues.

Question 43

When castration is not performed at the time of scrotal hernia repair, how is recurrent hernia formation prevented?

Answer 43

Partial ligation of the parietal vaginal tunic

Question 44

What is the prognosis for inguinal hernia repair?

Answer 44

Good to excellent if uncomplicated (3% mortality rate).

Question 45

Describe the anatomy of the femoral canal

Answer 45

Femoral herniation typically occurs caudomedial to the femoral vessels and lateral to the inguinal ligament through a potential space known as the femoral canal.

Question 46

What are the most common causes of femoral herniation?

Answer 46

Iatrogenic damage to the pectineus or blunt trauma (can result in a large defect from avulsion of both the pubic and inguinal ligaments)

Question 47

How is closure of an uncomplicated femoral hernia achieved?

Answer 47

Suturing of the pectineus muscle to the inguinal ligament. If contents are incarcerated or strangulated may require a concurrent ventral abdominal approach.

Question 48

What should be placed post-operatively in the case of a tenuous femoral hernia repair?

Answer 48

Hobbles

Question 49

If significant distal limb swelling is observed following femoral hernia repair, what could be the cause?

Answer 49

Obstruction of the lymphatic or venous drainage at the femoral canal. Re-exploration is indicated (or if a femoral nerve deficit is present post-op).

Question 50

What are the most common areas of herniation following blunt trauma?

Answer 50

Ventrolateral abdomen (inguinal, prepubic regions) and paracostal regions. Dorsolateral and paracostal hernias might be more common in cats.

Question 51

A sudden increase in intraabdominal pressure following blunt trauma commonly results in injuries to which area of the abdominal wall?

Answer 51

The paracostal area (between the origins of the tranverse and external abdominal oblique muscles).

Question 52

What are common body wall hernias that result from avulsion forces (contracted abdominal muscles and open glottis limiting increases in intrabdominal pressure)?

Answer 52

Prepubic, inguinal and dorsolateral (muscle avulsion from the transverse processes of the lumbar vertebrae)

Question 53

What injury is commonly found in conjunction with paracostal herniation?

Answer 53

Diaphragmatic herniation

Question 54

What percentage of patients with abdominal hernias have other significant injuries?

Answer 54

75%

Question 55

What are the most definitive radiographic signs of abdominal herniation?

Answer 55

Loss of abdominal strip, absence of an organ from its normal location, organ displacement into the subcutaneous tissues. Ultrasound, CT, MRI may be beneficial in difficult to diagnose cases.

Question 56

What is the ideal time of repair of acute traumatic herniation?

Answer 56

Controversial - delay of a few days if non-urgent may improve the quality of tissue for closure (reduced edema, improved blood supply), excessive delay may result in contraction and strangulation or increased adhesions.

Question 57

Are acute or chronic abdominal body wall hernias best approached directly over the hernia or via a ventral midline approach?

Answer 57

Acute: often best approached through ventral midline. Allows assessment of abdominal organs and often more easily repaired intra-abdominally. Chronic: can be repaired via direct incision over the defect (so long as no strangulation of content)

Question 58

Why are vascularized tissue flaps preferred over the use of prosthetic mesh in hernia repair where possible?

Answer 58

Can survive in an infected or highly contaminated environment

Question 59

Describe a decision making tree for abdominal hernia repair.

Answer 59

Question 60

How are prepubic tendon ruptures repaired?

Answer 60

Suture placed through holes in the cranial pubic ligament and then through holes in the pelvis (modified dorsal recumbency position useful to reduce tension on the closure). A rectus abdominus muscle flap has also been described.

Question 61

What can be used to augment repair of a prepubic ligament rupture when shredded or avulsed?

Answer 61

Mesh cuff or double layer mesh technique.

Question 62

How are paracostal hernias repaired when there is limited soft tissue attachments remaining to bone?

Answer 62

By passing sutures through bone tunnels, or bone anchors or around ribs. If there is adequate soft tissue the transverse abdominal, internal and external abdominal oblique muscles are repaired primarily via an intraabdominal approach.

Question 63

What are some potential causes of incisional herniation?

Answer 63

Technical causes are the most common! Otherwise excessive forces on the incision (increased intra-abdominal pressure), or poor holding strength of the wound (incorporating fat in sutures, inappropriate material/size, infection, inappropriate suture interval [should be 4:1 suture to length of the wound, i.e. 5-7 mm fascial bites, and 3-4 mm of travel])

Question 64

What is an early sign of impending incisional dehiscence?

Answer 64

Swelling and serosanginous discharge

Question 65

What are some difficulties associated with chronic incisional hernia repair?

Answer 65

May have loss of domain, significant fibrous tissue may make identification of the holding layers difficult. May require repair with prosthetic mesh materials.

Question 66

What are some factors associated with an increased duration of hospitalization in patients with evisceration?

Answer 66

Evisceration secondary to trauma, high lactate on admission, small body size.

Question 67

What are the advantages of autologous vs. mesh hernia repair?

Answer 67

Autologous: dynamic and vascular support particularly in a contaminated environment. Mesh: simpler to perform and no donor site morbidity.

Question 68

What are some autologous repair options for large body wall hernias?

Answer 68

Vacuum-assisted closure, separation of abdominal body wall components (fascial releasing incisions and adjacent tissue transfer [see image]), abdominal wall partitioning (a series of parasagittal staggered incisions in the fascia), muscular flaps (cranial sartorius, external abdominal oblique, rectus abdominis).

Question 69

What are the limits of the cranial sartorius muscle flap?

Answer 69

Can cover 30% of caudal abdomen when positioned transversely along pubis, can reach 80% of length of abdomen if positioned parallel to midline. Good for prepubic, inguinal and femoral hernias.

Question 70

What vascular pedicle supplies the cranial sartorius muscle flap?

Answer 70

A branch of the femoral artery

Question 71

What defects are external abdominal oblique myofascial flaps useful for?

Answer 71

Ventral, cranial to mid-abdominal wall defects (10 x 10cm in size has been reported). Is an island flap reliant on the cranial branch of the cranial abdominal artery.

Question 72

What vessels supply the rectus abdominis muscle flap?

Answer 72

The cranial and caudal superficial epigastric vessels. It is thicker than the sartorius muscle flap. Good for prepubic tendon rupture

Question 73

What vessels supply the cranial sartorius muscle flap?

Answer 73

A branch of the femoral artery and vein in the proximal third of the muscle

Question 74

What vessels supply the rectus abdominus flap?

Answer 74

The cranial and caudal superficial epigastric vessels. Provides additional thickness and strength compared to the cranial sartorius.

Question 75

What are the typical causes of prosthetic material failure in hernia repair?

Answer 75

Infection or tension. Also require adequate skin and subcutaneous coverage.

Question 76

Why is it ideal to interpose omentum on the peritoneal surface of a prosthetic material?

Answer 76

Helps to seal the defect, brings blood supply and healing cells to the area, avoids the risk for visceral adhesions

Question 77

What are the main disadvantages of prosthetic implant materials in hernia repair?

Answer 77

Sinus formation and chronic infection

Question 78

What is the most widely used synthetic mesh material?

Answer 78

Polypropylene (porous non-absorbable material that allows abundant growth of fibrous tissue). Composite meshes may have benefits but are yet to be studied in animals.

Question 79

What are some potential advantages and disadvantages of tissue grafts over synthetic mesh materials?

Answer 79

Tissue grafts (SIS, dermis or pericardium) are completely resorbed and replaced by native collagenous tissues. This may increase wound strength and reduce the risk of chronic FB inflammatory responses. However, remodelling and replacement may be inconsistent and it remains to be determined whether use of tissue grafts results in strong wounds long term. Their response in infected wounds is also unknown.

Question 80

What are the different mesh implantation techniques?

Answer 80

Overlay, underlay and interpositional

Question 81

Which mesh implantation technique is preferred?

Answer 81

Underlay, as has the lowest rate of reherniation and wound related complications (infection, seroma, hematoma). Downside is direct contact with abdominal viscera which may result in enterocutaneous fistula formation and adhesions. This can be minimized with the use of omentum.

Question 82

Why are interpositional mesh implantation techniques infrequently used?

Answer 82

Minimal attachment between the mesh and the adjacent fascia (strength holding layer) resulting in frequent re-herniation.

Question 83

What is the disadvantage of overlay mesh techniques?

Answer 83

High rate of wound related complications (seroma, hematoma, extrusion, infection). Advantage is that there is minimal contact with the abdominal viscera reducing the risk of adhesion and enterocutaneous fistula formation.

Question 84

What are the common complications associated with abdominal wall herniorrhaphy?

Answer 84