Posterior abdominal wall and hernia

Anatomical Description of The Dissection of Posterior Abdominal Wall

1. Posterior Abdominal Wall  Dr. Mushfiqul Hoque Lecturer Dhaka National Medical College 

2. Posterior Abdominal Wall  Osseo- musculo -fascial wall Extends from the last rib to the pelvic brim Consists of 3 parts:  Bony part Muscular part Fascial part 

3. Bony Part In the midline Consists of bodies of the five lumbar vertebrae Inner surface of the lower ribs Iliac fossa and alae of the sacrum

4. Muscular Part Above iliac crest Psoas major Psoas minor (sometimes) Quadratus lumborum Transversus Abdominis (aponeurotic origin) Below iliac crest Iliacus Psoas major 

5. Steps of dissection  Kidney from back A longitudinal incision in the middle line from the eleventh thoracic spine to the third lumbar spine Two transverse incisions, one from each end of the 1st incision laterally for about 3½ inches

6. Layers after skin incision  Above iliac crest Skin Superficial fascia Deep fascia (posterior layer of the thoracolumbar fascia) Sacrospinalis (erector spinae) Middle layer of the thoracolumbar fascia  Quadratus lumborum Anterior layer of the thoracolumbar fascia Subcostal vessels and nerve, iliohypogastric and ilioinguinal nerves Paranephric body (pararenal fat) Renal fascia (false capsule) Perinephric fat or perirenal fat (fatty capsule) True capsule—then kidney.

7. Thoraco-Lumbar Fascia It covers the deep muscles of the back of the trunk and consists of two parts—  Thoracic part: It is a thin aponeurotic layer that covers the sacrospinalis and it separates the muscles of the back from the muscles of the superior extremity. Lumbar part

8. Thoraco-Lumbar Fascia Lumbar Part:  It is thick and membranous. It fills the gap between the 12th rib and the iliac crest and consists of three layers— Anterior Middle  posterior 

9. Thoraco-Lumbar Fascia Posterior Layer:  Very thick and strong and covers the sacrospinalis (erector spinae) muscle  

10. Thoraco-Lumbar Fascia Posterior Layer: (Attachments) Medially—It is attached to the tips of the spinous processes of the lumbar and sacral vertebrae and to the supraspinous ligament. Abdomen Laterally—It fuses with the middle layer at the lateral border of the sacrospinalis (erector spinae) Below—It is attached to the posterior fourth of the outer lip of the iliac crest Above—It is continuous with the thoracic part of the fascia beneath the serratus posterior inferior.

11. Thoraco-Lumbar Fascia Middle Layer:  Less thicker and covers the posterior surface of the quadratus lumborum

12. Thoraco-Lumbar Fascia Middle Layer: (Attachments) Medially—It is attached to the tips of the transverse processes of the lumbar vertebrae and to the intertransverse ligaments Laterally—It blends with the anterior and posterior layers Below—It is attached to the iliac crest Above—It is attached to the lower border of the 12th rib and to the lumbocostal ligament.

13. Thoraco-Lumbar Fascia Anterior Layer: Comparatively very thin and covers the anterior surface of the quadratus lumborum

14. Thoraco-Lumbar Fascia Anterior Layer: (Attachments) Medially—It is attached to a vertical ridge on the anterior surface of the transverse processes of the lumbar vertebra and it separates the quadratus lumborum from the psoas major Laterally—It fuses with the middle layer at the lateral border of the quadratus lumborum and is then continuous with the fascia transversalis Below—It is attached to the iliolumbar ligament and to the adjoining part of the inner lip of the iliac crest Above—It is thickened to form the lateral arcuate ligament which is attached medially to the tip of the transverse process of the 1st lumbar vertebra and laterally to the free end and lower border of the last rib.

15. Abdominal Aorta Continuation of Descending thoracic aorta Passes downwards in front of the vertebral column and on the left of Inferior Vena Cava Ends by dividing into right and left common iliac artery opposite to the body of L4 vertebra  Length: 10-11cm Breadth: 2cm 

16. Inferior Vena Cava Drains blood from the parts of the body below the diaphragm into the right atrium of the heart Formed by the union of right and left common iliac veins in front of the body of L5 vertebra about 2.5 cm to the right of the midline Length: 20-23cm Breadth: 2.5cm

17. Tributaries of the Inferior Vena Cava A pair of Common Iliac Veins Lumbar Veins: third and forth A pair of Renal Veins A pair of Phrenic veins Right Gonadal veins Right supra-renal veins Hepatic veins 

18. Lumbar Plexus Formed within the substance of the psoas major muscle Formed by the union of ventral rami of upper 3 lumbar nerves and the larger upper part of the ventral ramus of fourth lumbar nerve The lower smaller part of the 4th lumbar nerve joins with the 5th lumbar nerve to form the lumbosacral trunk 

19. Hernial Region Inguinal Hernia

20. Hernia Definition: Protrusion of a viscus or a part of a viscus  from its normal position to an abnormal position through an abnormal opening on the wall of its containing cavity due to weakness on the wall. 

21. Inguinal Region Most common place for hernia in male known as inguinal hernia Hernia in inguinal region are of two varieties: Direct inguinal hernia Indirect or oblique inguinal hernia

22. Inguinal Canal  Musculo aponeurotic tunnel Length: 4cm Extends from deep inguinal ring to superficial inguinal ring Canal is directed downwards, forwards and medially Parallel with the medial half of the inguinal ligament   When abdominal content covered by a sac of peritoneum enters the inguinal canal abnormally, it is called inguinal hernia 

23. Inguinal Canal  Contents:   Spermatic cord in male or round ligament of uterus in female Ilio-inguinal nerve 

24. Inguinal Canal  Boundaries:  Anterior wall: skin, superficial fascia and aponeurosis of external oblique muscle Posterior wall: Fascia Transversalis Roof: Arched fibres of the internal oblique and transversus abdominis muscles Floor: grooved upper surface of Inguinal Ligament, on the medial side floor is formed by upper surface of lacunar ligament.  

25. Inguinal Canal  Inlet: Deep Inguinal Ring which is an oval gap in the fascia transversalis located 1.25cm above the mid-inguinal point (midpoint between anterior superior iliac spine and pubic symphysis)  Outlet: Superficial Inguinal Ring which is an oblique triangular gap in the aponeurosis of external oblique above and lateral to the pubic crest or pubic tubercle 

26. Triangle of hesselbach   Inlet: Deep Inguinal Ring which is an oval gap in the fascia transversalis located 1.25cm above the mid-inguinal point (midpoint between anterior superior iliac spine and pubic symphysis)  Outlet: Superficial Inguinal Ring which is an oblique triangular gap in the aponeurosis of external oblique above and lateral to the pubic crest or pubic tubercle 

27. Oblique or indirect inguinal hernia Abdominal contents covered by peritoneum enters the inguinal canal through deep inguinal ring Nech of the hernial sac lies lateral to the inferior epigastric artery 

28. Direct Inguinal hernia Enters through the Triangle of Hesselbach  Enters the canal due to a defect on the posterior wall of the inguinal canal  Neck of the hernial sac lies medial to the inferior epigastric artery 

29. End of class