Saturday, 20 April 2013

Tidbits about appendicitis

These are the pimp questions regarding appendicitis and related topics that our sweet attendings loved to ask: (no sarcasm there; our surgery attendings were sweet!)

Q: How do you find the appendix when it's not immediately visualized upon opening the abdomen?
A: We trace the taenia coli of the cecum. The three taenia coli will converge at the terminal end of the cecum, which is also the base of the appendix.

Q: What is the mechanism of perforated appendicitis?
A: As the inflamed appendix gets progressively distended and edematous, blood vessels are compressed. Blood flow is compromised, causing ischemia of the appendiceal walls. Prolonged ischemia with bacterial invasion results in a gangrene. This gangrenous area serves as a weak spot on the wall where a perforation can easily occur.

Q: What is the mass that is sometimes found in the location of appendicitis?
A: A palpable mass found in the classic RLQ site is the result of walled-off appendiceal inflammation. Walling off is performed by the omentum, the small bowel, and/or the cecum, as a defense mechanism. The mass is called periappendicular mass, which may consist of a local abscess. Some people call this stage "infiltrative appendicitis".

Q: What is the typical WBC count in appendicitis?
A: In acute uncomplicated appendicitis, there is mild leukocytosis at around 10,000-18,000/ul. A WBC count higher than this suggests perforated appendicitis (it can reach 30,000/ul or more). Vague signs and symptoms with normal WBC count could be due to chronic appendicitis.

Q: What are the meanings of Rovsing's sign, Blumberg's sign, psoas sign, and obturator sign?
A: Rovsing's and Blumberg's signs indicate irritation of the peritoneal wall. Psoas and obturator signs help determine the position of the appendix. If the psoas sign is positive, the appendix is likely retrocecal. If the obturator sign is positive, it is likely located behind the internal obturator muscle.

Q: Why does the pain in appendicitis begin initially at the umbilical or epigastric region, before shifting to the right lower quadrant?
A: The initial referred pain is caused by the common visceral innervation shared by the appendix and some other structures. Sympathetic innervation is by T10, whereas parasympathetic innervation is by vagus nerve (CN X). As the inflammation progresses and starts to irritate the parietal peritoneum, which has somatic innervation, the pain will then shift to the characteristic location at the RLQ.
Points to remember:: 1) the internal organs do not have somatic innervation, and 2) the representation of our internal organs in the brain is very imprecise, unlike the highly accurate somatic sensory homunculus.

Q: Describe the radiographic findings in chronic appendicitis.
A: In radiography with barium enema contrast, chronic appendicitis may appear to have irregular walls, or as a partial-filling defect, or a non-filling defect. Irregular walls are caused by edema in the appendiceal mucosa. A partially-filled appendix suggests the presence of a mass, which may be a periappendiceal abscess compressing the lumen, or other pathology. A non-filling appendix strongly suggests chronic appendicitis; this finding is due to the re-inflammation of the fibrotic appendix.

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