Approaches to the abdomen

Question 1

Layers of the abdominal wall in the flank

Answer 1

Skin

SQ

Ext abdominal oblique

Internal abdominal oblique

Transversus

Peritoneum

Question 2

Vessels that can be lacerated during standard STANDING laparoscopic approach

Answer 2

Circumflex iliac artery/vein Located close the dorsal border of the internal abdominal oblique muscle

Question 3

Layers of the abdominal wall at the ventral midline

Answer 3

Skin

SQ

External rectus sheath

Rectus adominis

Internal rectus sheath

Linea alba

(retropetitoneal fat)

Peritoneum

Question 4

External abdominal oblique origin and insertion

Answer 4

• Origin*: Lateral surface of ribs 4-18 & thracolumbar fascia
• Insertion*: linea alba (broad apnoeurosis with IAO), pre-pubic tendon, tuber coxa and body of the ileum
• Innervation*: ventral branches of thoracic and lumbar spinal nerves
• Fibre* direction: caudoventrally

Slit-like gap adjacent to the pre-pubic tendon form the external inguinal ring

Combined aponeuroses of ext and int abdominal obliques insert together on the linea and form the external rectus sheath

Question 5

Origin & insertion of int abdominal oblique

Answer 5

Origin: tuber coxa and adjacent inguinal ligament

Insertion: costal arch and linea alba (its combined aponeurosis with EAO forms the external rectus sheath)

Innervation: ventral branches of thoracic and lumbar spinal nerves

Fibre direction: cranioventrally

Caudal free border forms the cranial border of the deep inguinal ring

Question 6

Transversus muscle

Answer 6

Least extensive of the andominal wall muscles

Fibres run vertically

Origin: transverse processes of lumbar vertebrae

Also inserts on the linea alba - its aponeurosis forms the internal rectus sheath

* in ruminants and camelids; has dorsal and ventral aponeuroses

Question 7

Rectus abdominis origin and insertion

Answer 7

Origin: 4-9th costal cartilages

Insertion: principally via the accessory ligament—on the head of the femur, but also on the prepubic tendon

Question 8

Components of the rectus sheaths

Answer 8

External: combined aponeuroses of the external and internal abdominal abliques

Internal: aponeurosis of the transversus abdominis musce

Question 9

Components of the deep inguinal ring

Answer 9

Caudal margin of the internal abdominal ablique cranially

Inguinal ligament caudally (arises from the coxal tuber and ends within the prepubic tendon)

Medial and lateral borders are ill defined

Question 10

Vessels that may be lacerated during laparoscopic entry to the abdomen with ventral approaches UGA

Answer 10

Superficial and deep caudal epigastric arteries/veins

Located at the abaxial portions of the rectus abdominis muscle

Question 11

Possible abdominal approaches

Answer 11

Ventral midline lap

Ventral paramedian

Diagonal paramedian

Inguinal or parainguinal

Vaginal - colpotomy (confined to the caudal abdo, small risk of evisceration and haemorrhage is lacerate vaginal branch of uterine aa

Pararectal - limited to caudal abdo - described mainly for access to the retroperitoneal portions of the bladder for removal of cystic calculi (CR of access to small colon obstruction Durket 2019 EVE)

Laparoscopic (flank or ventral approaches)

Flank (grid or modified grid)

Question 12

Grid vs modified grid technique for flank laparotomies

Answer 12

Grid = incision/separation of each mm layer along their fibres

Modified grid - EAO is incised vertically, then IAO & transversus bluntly separated along the direction of fibres

Question 13

Direction of muscle fibres for EAO, IAO, transversus

Answer 13

EAO - caudoventral

IAO - cranioventral

Transversus - vertical

Question 14

Advantages & Disadvantages of flank approach

Answer 14

+Severe wound complications are rare - therefore may be beneficial for late gestation mares where possible (eg CR Howes 2018 EVE)

+ Done standing in many cases, avoids GA complications esp in late term mares

• Negates ability for full abdo exploration
• Some lesions may be inaccessible thus requiring need for subsequent ventral midline laparotomy
• High incisional complication rate (although usually minor consequence)
• Not suitable for acute colic cases
• High risk of contamination

Question 15

Advantages & disadvantages of grid and modified grid

Answer 15

Grid + minimal bleeding

• difficult access

Modified grid + better access

• bleeding/decreased visualisation from EAO incision

Question 16

Consequences of vessel laceration during laparoscopic trochar insertion (4)

Answer 16

1) Impaired visualisation
2) SQ haematoma formation
3) Haemoperitoneum
4) Increased surgical time

Question 17

Label the vessels of the ventral abdominal wall

Answer 17

A = Pudendoepigastric trunk

B = External pudendal artery

C = Superficial caudal epigastric artery

D = Deep caudal epigastric artery

Question 18

Rough course of the deep caudal epigastric arteries according to Davis et al Vet Surg 2019

Answer 18

Origonates from the pudendoepigastric trunk and courses lateral to the prepubic tendon, following the caudal border of the external rectus sheath for a few cm before penetrating the sheath. Then courses craniolaterally to an apex at the midpoint between umbilicus and prepubic tendon, before running craniomedially towards the umbilicus

Question 19

According to Davis et al 2019 Vet Surg, what equations can be used to predict the location of the deep caudal epigastric arteries

Answer 19

At the umbilicus -> body circumference x0.04

At the midpoint between umbilicus and pre pubic tendon attachment -> body circumference x 0.07

At the prepubic tendon attachment -> body circumference x 0.03

Question 20

Roughly where are superficial caudal epigastric arteries located with respect to midline and the deep arteries (Davis 2019 Vet Surg)

Answer 20

16-53% of the way from midline to the deep caudal epigastric arteries

Question 21

Adv and disadv of different abdominal approaches

Answer 21

Ventral midline or paramedian + usually good cosmesis/inconspicuous

• long layoff

Flank + can avoid GA +↓ incidence of catastrophic incisional complications

• limited access, some lesions not operable, ↑ incisional complication rate (allbeit mild) - cosmesis can be compromised, - can lacerate circumflex iliac aa (!)

Colpotomy +can perform standing, +excellent cosmesis + quick layoff +no 1° closure = cheap

• can only explore caudal most abdo, - inadvertant penetration of a viscus (fatal) or cervical damage are reported, - fatal haemorrhage may occur if vaginal br of uterine aa is penetrated during colpotomy, - evisceration (low risk), - adhesion formation (but seldom problematic)

-

Pararectal +can do standing, + no 1° closure = cheap, + quick layoff, + good cosmesis

• caudal most abdo only (desc for bladder calculi, small colon lipoma) and even then not visible, - care to avoid internal pudendal artery and vein & branches (ventral perineal and caudal rectal vessels) & pudendal nn (innervates perineum and rectal sphincter), - risk of evisceration (small) - technically challanging as one hand in the rectum throughout.