Descibe the location and dimensions of Vermiform Appendix.
Location
Vermiform appendix is located in the right lower quadrant of abdomen, more specifically in the right iliac fossa. Base of the appendix usually lies at the McBurney’s point which is at the junction of lateral one-third and the medial two-thirds of the line joining the umbilicus to the right anterior superior iliac spine.
Dimensions: Vermiform appendix is a narrow tubular structure that opens into the posteromedial wall of caecum, about 2cm. below the ileo-caecal valve. Its length varies from 2-20 cm (average 9 cm).
What are the various positions of appendix?
The position of appendix is variable. The various positions are:
- Retrocaecal (12 o’clock): Appendix is located behind the caecum. This is the most common position.
- Splenic (2 o’clock): Appendix lies in relation to terminal ileum. It may lie either anterior to ileum (pre-ileal) or posterior to ileum (post-ileal).
- Promonteric (3 o’clock): Appendix is directed towards the sacral promontory.
- Pelvic (4 o’clock): Appendix points towards the pelvic brim.
- Subcaecal/midinguinal (6 0’clock): Appendix lies below the caecum and points towards the mid-inguinal point.
- Paracolic /paracaecal (11 o’clock): Appendix lies in the right paracolic gutter.
Most common position of appendix is retrocaecal (75% of cases)
Describe briefly the blood supply of vermiform appendix.
Arterial supply: is supplied by appendicular artery
Venous drainage: Appendicular vein drains into iliocaecal vein , which drains into superior mesenteric vein ( portal system).
Describe briefly the nerve supply of vermiform appendix.
Appendix is supplied by sympathetic fibers from T10 spinal segment. Pain fibers pass along sympathetic nerves. Therefore, in appendicitis, the visceral pain is referred to the region of umbilicus which is supplied by T10 somatic nerve.
Applied Aspects
Appendicitis
Inflammation of the appendix is known as the appendicitis. Appendicitis usually follows obstruction of the lumen with infection and ulceration od appendix. The causes are: fecolith, calculi, foreign body, tumor, worms, vascular occlusion, inadequate dietary fiber intake, etc.
Appendicitis is more common in older children and young adults. The lumen of the appendix is relatively wide in the infant and is frequently completely obliterated in the elderly. Since obstruction of the lumen is the usual precipitating cause of acute appendicitis, therefore, appendicitis is uncommon at the two extremes of life.
Referred pain in appendicitis
The pain of appendicitis is first felt in the umbilical region as both are supplied by T10 spinal segment (referred pain). With increasing inflammation pain is felt in the right iliac fossa due to involvement of the parietal peritoneum of the region which is sensitive to pain.
McBurney’s point
It is a point at the junction of lateral 1/3rd and medial 2/3rd of a line joining the right anterior superior iliac spine with the umbilicus. It corresponds roughly to the base of the appendix. It is the point of maximum tenderness in case of appendicitis.
Location of the tip of the appendix determines early signs and symptoms of appendicitis.
- In case it is retrocecal: Extension of the hip joint may cause pain because the appendix is affected by stretching of the psoas major muscle.
- In case it is pelvic: Pain may be felt when the thigh is flexed and medially rotated, because the obturator internus is stretched. Pelvic appendix may irritate the bladder or rectum causing suprapubic pain, pain with urination, or feeling the need to defecate.
Acute infection of the appendix may result in thrombosis of the appendicular artery ( as the distal part of appendicular artery runs on the wall of appendix) with rapid development of gangrene and subsequent perforation.
Appendicectomy
It is usually performed through a muscle-splitting incision in the right iliac fossa. The appendix can be located by tracing the taeniae coli along the caecum—they fuse at the base of the appendix.
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