Acute appendicitis is caused by obstruction of the appendix lumen, usually by a fecalith, leading to bacterial overgrowth and inflammation. It most commonly affects adolescents and young adults. Early symptoms include periumbilical pain that moves to the lower right abdomen, nausea, vomiting, and fever. On physical exam, tenderness is found at McBurney's point. Without treatment, complications can arise like perforation or abscess. The most common tumor of the appendix is carcinoid tumor, while other rare tumors can cause appendicitis-like symptoms.

1. Acute Appendicitis
• Appendix normal true
diverticulum of cecum
• Acute appendicitis  most
common in adolescents and
young adults
• Lifetime risk  7%
• Males >females

2. Pathogenesis
• Initiated by progressive increase in
intraluminal pressure  compromise
venous outflow
• 50% to 80% of cases associated
with luminal obstruction by small
stone-like mass of stool (fecalith) or
less commonly gallstone, tumor, or
mass of worms (oxyuriasis
vermicularis)

3. • Stasis of luminal contents 
bacterial proliferation, triggers
ischemia and inflammatory
responses, resulting in tissue edema
and neutrophilic infiltration of lumen,
muscular wall, and periappendiceal
soft tissues

4. Morphology
• Early cases  subserosal vessels are
congested, perivascular neutrophilic
infiltrate within all layers of the wall
• Serosa dull, granular with
erythematous surface

5. • Diagnosis requires neutrophilic
infiltration of the muscularis
propria
• Severe cases  prominent
neutrophilic exudate with serosal
fibrinopurulent reaction

6. • Focal abscesses may form within the
wall (acute suppurative
appendicitis)
• Compromise of appendiceal vessels
leads to large areas of hemorrhagic
ulceration and gangrenous necrosis
extending to serosa creating acute
gangrenous appendicitis followed
by rupture and suppurative
peritonitis

7. Clinical Features
• Early acute appendicitis
produces periumbilical pain
that ultimately localizes to
right lower quadrant, followed
by:
– nausea
–Vomiting
–low-grade fever
–mildly elevated peripheral
white cell count

8. • Physical finding McBurney sign
• Deep tenderness located two thirds
of distance from umbilicus to right
anterior superior iliac spine
(McBurney point)

9. • Retrocecal appendix may generate
right flank or pelvic pain
• Malrotated colon may give rise to
appendicitis in left upper quadrant
• Neutrophilic leukocytosis

10. Complications
• Appendiceal perforation
• Pyelophlebitis
• Portal venous thrombosis
• Liver abscess
• Bacteremia

11. Clinical differential diagnosis
• Mesenteric lymphadenitis
• Acute salpingitis
• Ectopic pregnancy
• Mittelschmerz (German: "middle
pain")-pain caused by minor pelvic
bleeding at time of ovulation
• Meckel diverticulitis

12. Tumors of the Appendix
• Most common tumor of appendix 
welldifferentiated neuroendocrine
(carcinoid) tumor
• Usually discovered incidentally at the
time of surgery or
• examination of resected appendix
• carcinoid  benign tumor, form solid
bulbous swelling at the tip of
appendix

13. Carcinoid tumor
Gross
Microscopic

14. • Adenomas or non–mucin-producing
adenocarcinomas also occur in
appendix and may cause obstruction
and enlargement that mimics acute
appendicitis

15. • Mucocele  dilated appendix filled
with mucin
• Represent obstructed appendix
containing inspissated mucin or
consequence of mucinous
cystadenoma or mucinous
cystadenocarcinoma

16. • Invasion through appendiceal wall
can lead to intraperitoneal seeding
and spread
• In women resulting peritoneal
implants may be mistaken for
mucinous ovarian tumors

17. • Most advanced cases  abdomen
fills with tenacious, semisolid mucin,
a condition called pseudomyxoma
peritonei