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