Appendix Positions and Questions

Most Common Positions of the Appendix

There is excessive debate regarding the exact incidence of various positions of appendix. Although the position of the base is constant, there are wide variation in the position of the tip of appendix. Most common position of appendix is retrocaecal (65) % followed by Pelvic (20%). Other common positions are preileal and post ileal. Retroileal position of appendix is the least common. It is seen in only 0.2%.

The positions of the appendix are described as

1. Posterior to the cecum and lower part of the ascending colon (retrocecal and retrocolic)

2. Descending over the pelvic brim (pelvic/descending)

3. Below the cecum (subcecal)

4. Anterior to the terminal ileum and in relation to the anterior abdominal wall (preileal)

5. Posterior to the terminal ileum (postileal)

Points to remember in finding the base of appendix

Mcburney's point - Used as surface marking for the base of the appendix.

The three teniae coli converge at the tip of the cecum to form the continuous longitudinal muscle layer of the appendix

Ileocaecal fold of mesentary can be used to trace the base of appendix

Q1. Which of the following is the least common position of appendix?

a) Retroileal

b) Retroceacal

c) Postileal

d) Pelvic

Q2. Most Common malignancy of appendix is?

a) Carcinoid Tumor

b) Adenocarcinoma

c) Squmaous Cell carcinoma

d) MIxed Cellularity

Q3. All are features of Acute Appendicitis on Ultrasound examination except?

a) A compressible blind ending tube

b) Diameter of more than 7 mm

c) Loss of submucosal echogenicity

Q4. What is not true as differential diagnosis for appendicits in the elderly

a) Adenocarcinoma appendix

b) Diverticulitis

c) Pyelonephritis

d) Colitis

Q5. Not true about appendicitis in pregnancy?

a) Risk of appendicitis in pregnancy remains the same as in non pregnant woman of same age group.

b) Appendicitis ocurs more commonly in the 1st two trimesters.

c) The effect of negative laparotomy for appendicitis in pregnant patient is significant

d) Early appendectomy is the appropriate therapy in suspected appendicitis during all stages of pregnancy.

Answers

1.a

2. b

It was previously believed that carcinoid tumors are the most common tumors of the appendix ( Sabiston 17th) but now data from SEER ( Surveillane, epidimology and End results) show that mucinous adenocarcinomas are more common

Sabiston 18th page 1344.

All these are true

4.a)

Altough adenocarcinoma of appendix can present as appendicitis, it is never kept as a differential diagnosis when appendicits is contemplated

5. c

The risk of negative laparotomy in suspected appendicitis in pregnancy is minor. However a ruptured appendicitis could be catastrophic. Early diagnosis and surgery for appendicitis should be performed in pregnancy.

There may be diagnostic confusion as during the third trimester of pregnancy, the cecum and appendix are displaced laterally and are rotated by the enlarged uterus. Pain occurs more laterally in the flank, leading to delay in diagnosis and an increased incidence of perforation.

Study Notes

McBurney's point, the junction of the lateral and middle thirds of the line that joins the right anterior superior iliac spine to the umbilicus, is used as a surface marking for the base of the appendix. The three teniae coli converge at the tip of the cecum to form the continuous longitudinal muscle layer of the appendix. The base of the appendix can be located by tracing the anterior taenia coli to the tip of the cecum. The ileocecal fold of peritoneum, which connects the terminal 2.5 cm of ileum to the cecum, can also be used to locate the base of the appendix. A short, triangular mesoappendix extends along the length of the appendix and connects it to the lower portion of the mesentery of the ileum.

Pathophysiology of Acute Appendicitis

The most commonly accepted theory of the pathogenesis of appendicitis is that it results from obstruction followed by infection. The lumen of the appendix becomes obstructed by hyperplasia of submucosal lymphoid follicles, a fecalith, tumor, or other pathologic condition. Once the lumen of the appendix is obstructed, the sequence of events leading to acute appendicitis is probably as follows:

Mucus acumulates in the lumen of appendix, The pressure inside increases, Mucus gets converted into pus, Obstruction to lymphatics, edema, mucus ulcers and finally perforation.