Approaches to the abdomen Flashcards
Layers of the abdominal wall in the flank
Skin
SQ
Ext abdominal oblique
Internal abdominal oblique
Transversus
Peritoneum
Vessels that can be lacerated during standard STANDING laparoscopic approach
Circumflex iliac artery/vein Located close the dorsal border of the internal abdominal oblique muscle
Layers of the abdominal wall at the ventral midline
Skin
SQ
External rectus sheath
Rectus adominis
Internal rectus sheath
Linea alba
(retropetitoneal fat)
Peritoneum
External abdominal oblique origin and insertion
- 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
Origin & insertion of int abdominal oblique
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
Transversus muscle
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
Rectus abdominis origin and insertion
Origin: 4-9th costal cartilages
Insertion: principally via the accessory ligament—on the head of the femur, but also on the prepubic tendon
Components of the rectus sheaths
External: combined aponeuroses of the external and internal abdominal abliques
Internal: aponeurosis of the transversus abdominis musce
Components of the deep inguinal ring
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
Vessels that may be lacerated during laparoscopic entry to the abdomen with ventral approaches UGA
Superficial and deep caudal epigastric arteries/veins
Located at the abaxial portions of the rectus abdominis muscle
Possible abdominal approaches
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)
Grid vs modified grid technique for flank laparotomies
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
Direction of muscle fibres for EAO, IAO, transversus
EAO - caudoventral
IAO - cranioventral
Transversus - vertical
Advantages & Disadvantages of flank approach
+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
Advantages & disadvantages of grid and modified grid
Grid + minimal bleeding
- difficult access
Modified grid + better access
- bleeding/decreased visualisation from EAO incision
Consequences of vessel laceration during laparoscopic trochar insertion (4)
1) Impaired visualisation
2) SQ haematoma formation
3) Haemoperitoneum
4) Increased surgical time
Label the vessels of the ventral abdominal wall
A = Pudendoepigastric trunk
B = External pudendal artery
C = Superficial caudal epigastric artery
D = Deep caudal epigastric artery
Rough course of the deep caudal epigastric arteries according to Davis et al Vet Surg 2019
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
According to Davis et al 2019 Vet Surg, what equations can be used to predict the location of the deep caudal epigastric arteries
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
Roughly where are superficial caudal epigastric arteries located with respect to midline and the deep arteries (Davis 2019 Vet Surg)
16-53% of the way from midline to the deep caudal epigastric arteries
Adv and disadv of different abdominal approaches
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.
