Appendicitis and Peritonitis

The appendix a normal true diverticulum of the cecum that is prone to acute and chronic inflammation Acute appendicitis is most common in adolescents and young adults, but may occur in any age group The lifetime risk for appendicitis is 7%; males are affected slightly more often than females Despite the prevalence of acute appendicitis, the diagnosis can be difficult to confirm preoperatively and may be confused with mesenteric lymphadenitis, acute salpingitis, ectopic pregnancy, mittelschmerz and Meckel diverticulitis

Appendicitis: Pathogenesis luminal obstruction, usually caused by a small stone-like mass of stool, or fecalith, or, less commonly, enlarged lymph node during infection, a gallstone, tumour, or mass of worms  Luminal obstruction  Progressive increases in intraluminal pressure compromise venous outflow  ischemic injury Ischemic injury + stasis of luminal contents  bacterial proliferation  inflammatory responses including tissue oedema and neutrophilic infiltration of the lumen, muscular wall, and periappendiceal soft tissues

Appendicitis: Morphology In early acute appendicitis subserosal vessels are congested and there is a modest perivascular neutrophilic infiltrate within all layers of the wall The inflammatory reaction transforms the normal glistening serosa into a dull, granular, erythematous surface Diagnosis of acute appendicitis requires neutrophilic infiltration of the muscularis propria. Although mucosal neutrophils and focal superficial ulceration are often present, these are not specific markers of acute appendicitis. In severe cases a prominent neutrophilic exudate  serosal fibrinopurulent reaction  focal abscesses may form within the wall (acute suppurative appendicitis)  further appendiceal compromise areas of hemorrhagic ulceration and gangrenous necrosis that extends to the serosa (acute gangrenous appendicitis), which is often followed by rupture and suppurative peritonitis.

Appendicitis: Clinical Features CLASSIC Clinical Features Vague, often colicky, periumbilical pain (or epigastric) that ultimately localizes to the right lower quadrant (occurs in only 66% of patients. However, in a male patient these symptoms are sufficient to advise surgical exploration.) \  Within 12 hours, pain shifts to right lower quadrant, with steady ache worsened by walking or coughing nausea, vomiting, low-grade fever, and a mildly elevated peripheral white cell count A classic physical finding is McBurney's sign, deep tenderness located two thirds of the distance from the umbilicus to the right anterior superior iliac spine (McBurney's point)  Localized tenderness with guarding in the right lower quadrant  Rebound tenderness COMPLICATIONS appendiceal perforation  If the process evolves slowly, adjacent organs such as the terminal ileum, cecum, and omentum may wall off the appendiceal area so that a localized abscess will develop rupture of primary appendiceal abscesses may produce fistulas between the appendix and bladder, small intestine, sigmoid, or cecum peritonitis Pyelophlebitis (Septic thrombophlebitis (pylephlebitis) of the portal venous system portal venous thrombosis liver abscess bacteremia NOTE: recurrent acute appendicitis does occur, often with complete resolution of inflammation and symptoms between attacks Recurrent acute appendicitis may also occur if a long appendiceal stump is left after initial appendectomy.

Tumors of the Appendix The most common tumour of the appendix is the carcinoid. It is usually discovered incidentally. Although intramural and transmural extension may be evident, nodal metastases are very infrequent, and distant spread is exceptionally rare Conventional adenomas or non-mucin-producing adenocarcinomas also occur in the appendix and may cause obstruction and enlargement that mimics acute appendicitis Mucocele, a dilated appendix filled with mucin, may simply represent an obstructed appendix containing inspissated mucin or be a consequence of mucinous cystadenoma or mucinous cystadenocarcinoma With cystadenocarcinoma, invasion through the appendiceal wall can lead to intraperitoneal seeding and spread. In the most advanced cases the abdomen fills with mucus and fibrosis , a condition called pseudomyxoma peritoneii 

Peritonitis Bacterial peritonitis Inflammation of the serosal membrane that lines the abdominal cavity and the organs contained therein Bacterial peritonitis  occurs when bacteria from the gastrointestinal lumen are released into the abdominal cavity, typically following perforation. occurs most commonly as a complication of acute appendicitis, peptic ulcer, cholecystitis, diverticulitis, and intestinal ischemia. Acute salpingitis, abdominal trauma, and peritoneal dialysis are other potential sources of contaminating bacteria. E. coli, streptococci, S. aureus, enterococci, and C. perfringens are implicated most often but virtually any bacteria can be associated with bacterial peritonitis.

Clinical Presentation: Peritonitis Acute peritonitis is most often infectious and is usually related to a perforated viscus (and called secondary peritonitis). When no intraabdominal source is identified, infectious peritonitis is called primary or spontaneous. The cardinal manifestations of peritonitis are acute abdominal pain and tenderness, usually with fever The location of the pain depends on the underlying cause and whether the inflammation is localized or generalized. Rigidity of the abdominal wall is common in both localized and generalized peritonitis. Bowel sounds are usually absent. Tachycardia, hypotension, and signs of dehydration are common. Leukocytosis and marked acidosis are common laboratory findings. Plain abdominal films may show dilation of large and small bowel with oedema of the bowel wall. Free air under the diaphragm is associated with a perforated viscus. CT and/or ultrasonography can identify the presence of free fluid or an abscess. When ascites is present, diagnostic paracentesis with cell count (>250 neutrophils/ L is usual in peritonitis), protein and lactate dehydrogenase levels, and culture is essential. In elderly and immunosuppressed patients, signs of peritoneal irritation may be more difficult to detect.

Peritoneum: Tumours Most tumors of the peritoneum are malignant and can be divided into primary and secondary forms. Primary tumors arising from peritoneal lining are mesotheliomas that are similar to tumors of the pleura and pericardium. Peritoneal mesotheliomas are almost always associated with significant asbestos exposure. It has been hypothesized that swallowed asbestos fibers somehow penetrate through the intestinal wall to reach the peritoneum. Secondary tumors of the peritoneum are quite common. In any form of advanced cancer, direct spread to the serosal surface or metastatic seeding (peritoneal carcinomatosis) may occur. The most common tumors producing diffuse serosal implants are ovarian and pancreatic adenocarcinoma. Appendiceal mucinous carcinomas may produce pseudomyxoma peritoneii. However, any intra-abdominal malignancy, as well as a wide variety of tumors of extra-abdominal origin, may spread to the peritoneum.

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