Acute Appendicitis• Appendix normal true

diverticulum of cecum• Acute appendicitis most

common in adolescents and young adults

• Lifetime risk 7%• Males >females

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)

• 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

Morphology• Early cases subserosal vessels are

congested, perivascular neutrophilic infiltrate within all layers of the wall

• Serosa dull, granular with erythematous surface

• Diagnosis requires neutrophilic infiltration of the muscularis propria

• Severe cases prominent neutrophilic exudate with serosal fibrinopurulent reaction

• 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

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

• Physical finding McBurney sign• Deep tenderness located two thirds

of distance from umbilicus to right anterior superior iliac spine (McBurney point)

• Retrocecal appendix may generate right flank or pelvic pain

• Malrotated colon may give rise to appendicitis in left upper quadrant

• Neutrophilic leukocytosis

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

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

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

Carcinoid tumor

Gross

Microscopic

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

• Mucocele dilated appendix filled with mucin

• Represent obstructed appendix containing inspissated mucin or consequence of mucinous cystadenoma or mucinous cystadenocarcinoma

• Invasion through appendiceal wall can lead to intraperitoneal seeding and spread

• In women resulting peritoneal implants may be mistaken for mucinous ovarian tumors

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