Abdominal wall and retroperitoneum

Question 1

Diaphragm

Answer 1

Description of the muscle and central tendon

• Domed fibromuscular sheet that separates the thorax and abdomen
• Muscle of respiration
• Viewed from the front, the fibres of the diaphragm arch upwards to form two domes, the right being higher than the left, connected by a central tendon at the level of the xiphisternum
• Viewed from the side, the shape of the domes is an inverted J, with the long arm extending up from the upper lumbar vertebrae and the short arm arising from the xiphisternum
• It arises from
  
  • The posterior surface of the xiphoid process anteriorly
  • The inner aspect of the lowest 6 ribs
  • The lateral and medial arcuate ligaments [fascial condensations, quadratus lumborum and psoas muscles]
  • The left and right crura attached to the upper lumbar vertebrae
• Inserts into the central tendon of the diaphragm
  
  • which is trefoil/3 leafed in shape, middle anterior merges with the lateral leaves that extend posteriorly
  • Blends with the fibrous pericardium

Description of foramen

• 3 large openings & 6 smaller ones
• Aortic hiatus lies between the two crura at T12 connected by the median arcuate ligament
  
  • Aorta (left aspect)
  • Thoracic duct (right aspect)
  • Sometimes azygous vein
• Oesophageal hiatus, to the left of midline but between the fibres of the right crus at T10
  
  • Phrenooesophageal ligament (from transversalis fascia blending with endothoracic fascia)
  • Vagal trunks
  • Oesophageal branches of the left gastric artery, veins and lymphatics
  • Oesophagus
• Vena-cava foramen, the adventita of the IVC fuses with the central tendon fibres
  
  • IVC
  • R phrenic nerve
• Through both crura
  
  • Splanchnic nerves
• Through the left crus
  
  • Hemiazygos vein
• Under the medial arcuate ligament
  
  • Sympathetic trunk
• Under the lateral arcuate ligament
  
  • Subcostal nerves and vessels
• Lumbocostal triangle – formed by the gap between the fibres arising from the ribs and the lateral arcuate ligament
  
  • Site of potential Bochdalek hernia
• Through the left dome of diaphragm
  
  • L phrenic nerve
• Embryology:
  
  • 4 sources (septum transversum, cervical myotomes, pleuroperitoneal membranes, oesophageal mesentery)
    
    • Septum transversum
      
      • Mass of mesoderm lying towards the cranial end of the coelomic cavity
      • Cranial portion forms pericardium, central portion forms part of diaphragm, caudal portion invaded by developing liver
    • Cervical myotomes
      
      • C3-4-5, invades the septum transversum, brings nerve supply to central diaphragm
    • Pleuroperitoneal membranes
      
      • Mesodermal folds that close the peripheral communication between the thoracic and abdominal portions of the coelom
    • Oesophageal mesentery
• Surface anatomy:
  
  • Xiphisternum = T8 = level of central tendon = VENA CAVA (8) – note this is behind the R 6^th costal cartilage
  • T10 = Oesophagus (10)
  • T12 = AorticHiatus (12)
• Surrounding structures and relations:
  
  • The liver, spleen, transverse colon, stomach, pancreas, adrenal glands, and kidneys contact the under surface of the diaphragm
  • Traversing through
    
    • Aorta
    • Thoracic duct
    • Azygos & hemiazygos veins
    • Sympathetic trunk
    • Splanchnic nerves
    • Vena cava
    • Phrenic nerves
    • Oesophagus
    • Vagal trunks
• Arterial supply:
  
  • Mostly from posteriorly
    
    • R & L Inferior phrenic arteries in the abdomen, usually from the aorta but can be from coeliac axis or renal arteries (RIPA is the most common extrahepatic source of HCC arterial supply in the bare area of liver)
    • R & L superior phrenic arteries (smaller) arising from aorta in the chest
  • Anterior supply
    
    • Musculophrenic terminal branches of the internal thoracic arteries
  • Periphery
    
    • Partly from lower 6 intercostal arteries
• Venous drainage:
  
  • Follows arterial?
• Innervation:
  
  • Motor
    
    • Phrenic only
    • Phrenic nerves (C3-4-5) which enter centrally and radiate outwards
    • Left and right nerves to respective domes, the L phrenic supplies the R crus fibres around the oesophagus
  • Sensory
    
    • Both phrenic and intercostals
    • Phrenic centrally and intercostals peripherally
• Lymphatics:
  
  • ?
• Structure within the organ and cell types:
  
  • Mostly slow twitch muscle fibres
• Relevance to operations:
  
  • Incisions in the diaphragm usually made parallel and 1.5cm from the costal margin, to avoid injury to larger branches of the phrenic nerve, if incision made more centrally can then should be in radial fashion
  • Relaxing incisions for paraoesophageal surgery can be made along the muscle fibres, beware on R of IVC and L hepatic vein

Question 2

Incisions for femoral hernia

Answer 2

Modified McEvedy

• High approach, best for incarcerated
• Oblique skin
• Vertical anterior rectus sheath just medial to semi lunar line
• Reflect rectus muscle medial

Lotheissen

• Standard trans-inguinal approach opening the external oblique
• Incise transversalis fascia to expose femoral hernia (*not sure about this)
• Reduce the hernia out of the femoral canal

Lockwood

• Low incision
• Elective incision, not good for bowel resection or pulling up a stuck sac

Classically three approaches are described to open femoral hernia repair: Lockwood’s infra-inguinal approach, Lotheissen’s trans-inguinal approach and McEvedy’s high approach.

The infra-inguinal approach is the preferred method for elective repair, approaching the femoral canal from below through an oblique incision 1 cm below and parallel to the inguinal ligament. This approach however offers little scope for resecting any compromised bowel.

The trans-inguinal approach involves a skin incision 2 cm above the inguinal ligament, dissecting through the inguinal canal and thus weakening this important structure. The danger with this, particularly in the presence of wound infection, is that a hernia may form later which would be difficult to repair. In addition, if necrotic bowel is encountered the risk of infection may preclude the use of synthetic mesh to repair the inguinal canal and predispose to inguinal hernia occurrence.

The high approach involves an oblique skin incision 3 cm above the pubic tubercle running laterally to cross the lateral border of the rectus muscle, that is divided allowing preperitoneal dissection of the sac. This approach is preferred in the emergency setting when strangulation is suspected allowing better access to and visualisation of bowel for possible resection.

Question 3

Nerve supply to the anterolateral abdominal wall

Answer 3

T7-T12 all muscles

• Internal oblique and transversus lowest fibres (that go on to form the conjoint tendon) also supplied by the hypogastric and ilioinguinal nerves

Question 4

External oblique muscle describe

Answer 4

• Origin
  
  • Ribs and costal cartilage 5-12 (lower eight ribs)
  • The slips interdigitate
    
    • Upper 4 with serratus anterior
    • Lower 4 with latissimus dorsi
• Insertion
  
  • Anteriorly & inferiorly & medially
  • The posterior muscle fibres attach to the into the outer lip of the anterior half of the iliac crest
    
    • The muscle has a free edge posteriorly – this forms the anterior boundary of the inferior lumbar triangle of petit
  • The middle and anterior fibres insert into the external oblique aponeurosis that passes anterior to the rectus abdominis to the linea alba
  • Inferiorly the edge rolls inwards to form the inguinal ligament that extends from the ASIS to the pubic tubercle
• Function
  
  • Flexion of the anterior abdominal wall (erector spinae relaxed)
  • Lateral rotation of the trunk
  • Protection of abdominal viscera
  • Compression of the abdominal space for coughing (erector spinae contracted)
• Innervation
  
  • Lower 6 intercostal nerves (& subcostal), entering the muscles laterally (T7-12)
  • The intercostal nerves travel medially in a plane between the transversus abdominis muscle and the internal oblique muscle
• Blood supply
  
  • Cranial portion by the lower 6 intercostal arteries
  • Caudal portion by a branches of either the deep circumflex iliac artery or lumbar arteries or the iliolumbar artery
• Surrounding structures
• Relevance to surgery
  
  • The muscular fibres become aponeurotic medial to a boundary created by two intersecting lines
    
    • 1^st line is a vertical line from the medial tip of the 9^th costal cartilage
    • 2^nd line is from the ASIS to the umbilicus

Question 5

Internal oblique muscle origin and insertion

Answer 5

• Origin
  
  • The iliac crest (iliopsoas fascia) and lateral half of the inguinal ligament
• Insertion
  
  • Fibres run medially and upwards becoming an aponeurosis that splits to enclose the rectus abdominis and then reuniting at the linea alba
  • Below the arcuate line the fibres pass anteriorly
  • The lower fibres of internal oblique are muscular until they reach the conjoint tendon with its insertion into the pubic crest and ramus
  • The lowermost fibres contribute the cresmaster fibres to the scrotum as it passes through the anterior abdominal wall

Question 6

Features of the ideal mesh

Answer 6

Biocompatible

• Physically and chemically inert
• Harmless
  
  • Non allergenic
  • Non migratory
  • Non erosive or fistulating
  • Non adherent
  • Predictable biological response, no seroma or capsule formation
  • Non carcinogenic
• Reinforce and resist mechanical stress (strong biomechanically)
• Minimal shrinkage

Risk of infection low

• Nota source of infection
• Resistant to infection

Handling/utility

• Easy to handle
• Easy to place
• Good memory
• Not limited to certainlocations or hernia types

Economic

• Easy to manufacture
• Easy to sterilise
• Cost effective

Longevity

• Not restrictive to future imaging or surgical intervention
• Retains characteristicsin long term

Question 7

Management options in varicocele

Answer 7

Conservative; supportive underwear, NSAIDs

• Indications for intervention
  
  • R sided and/or non decompressible varicocele needs further evaluation
  • Young age/infertility/hypoplastic testicle
  • Pain

Interventional (embolisation/coiling), risk of coil migration

Surgical:

• Subinguinal (probably best because you don’t miss collaterals from cremaster vein
• Inguinal
• High (retroperitoneal, open or lap)
• Low microsurgical approaches have lower recurrence and complication rates than high non-microsurgical approaches. Although data are limited and of low quality, some studies have shown improvement in semen parameters (over three to six months) and fertility after repair of varicocele

Question 8

There are two of them

Describe the boundaries of lumbar triangles

Answer 8

Superior triangle (of Grynfeltt)

• Superior: 12th ribs
• Medial/posterior: quadratus lumborum
• Lateral/anterior: free edge of internal oblique
• Roof: latissimus dorsi
• Floor: transversalis fascia

Inferior (of Petit)

• Anterior/lateral: free edge external oblique
• Posterior/medial: latissimus dorsi
• Inferior: iliac crest
• Floor: internal oblique muscle

Question 9

Where do spigellian herniae occur?

Answer 9

Through a defect in the spigellian aponeurosis/fascia (aponeurosis of the transverse abdominal muscle) bounded laterally by the semi lunaris and rectus muscle medially

Typically in the spigellian belt, 6cm zone cephalad to the interspinous line (between the two ASIS)