10. Diseases of the appendix and the peritoneum

The appendix

The appendix is considered a true diverticulum of the cecum, and like any diverticulum, its prone for acute and chronic inflammations. Tumors can also occur there, but the most common pathology in the appendix is acute appendicitis.

Acute appendicitis

Acute appendicitis is most common in adolescents and young adults but can also occur in younger or elder persons.

Acute appendicitis is thought to be initiated by increased intraluminal pressure that obstruct the venous outflow, and this increased pressure is often caused by luminal obstruction, and the things that can obstruct are usually:

  • Fecalith, small stone-like masses of stool
  • Foreign bodies
  • Gallstones
  • Worms
  • Tumors
  • Lymphoid hyperplasia

The obstruction of the venous outflow leads to ischemic injury and stasis of luminal contents. This gives the bacteria a perfect place to proliferate in, which in turn will trigger the inflammatory responses. Tissue edema and neutrophilic infiltration of the lumen, muscular wall and periappendiceal tissue will take place. The criteria to diagnose an acute appendicitis is the neutrophilic infiltration of the muscularis propria. In more severe cases, focal abscesses may form within the wall, and this is then called an acute suppurative appendicitis. The latter ones can also even progress to large areas of hemorrhagic ulceration and gangrenous necrosis, into an acute gangrenous appendicitis, which is often followed by rupture and pus-forming peritonitis.

The patient will experience a periumbilical pain in the right lower quadrant. The pain is followed by nausea, vomiting and a mild fever. You might recall the McBurney’s sign and point from anatomy, which is deep tenderness found 2/3 of the distance from the umbilicus to the right anterior superior iliac spine which can be present in patients with acute appendicitis. However, not everyone shows this symptom, and the diagnosis can be confused with acute salpingitis, ectopic pregnancy, pain associated with ovulation (Mittelschmerz) and Meckel diverticulitis.

Treatment is removal of the appendix.

Chronic appendicitis

Chronic appendicitis shows the same symptoms as the acute one, but much milder. The symptoms also come and go, and this can last for weeks, months or years. Many times, it’s also not diagnosed until it becomes an acute appendicitis.

Tumors of the appendix

Tumors in the appendix are rare, but we will discuss them anyway.

The most common found in the appendix is the carcinoid, also known as a neuroendocrine tumor, and its usually discovered during resection surgery of an appendix. This type of neoplasm is usually seen on the distal tip of the appendix, like a yellow, solid swelling. Metastasis to lymph nodes and more distantly is very rare, even when intramural and transmural invasion is often seen. Since it’s a neuroendocrine cancer, it produces the hormones histamine, kallikrein, prostaglandins and serotonin when well differentiated.

Carcinoid of the appendix. Notice how yellow and solid it is, and that it is located in the distal tip.

Conventional adenocarcinomas and non-mucin-producing adenocarcinomas can also occur in the appendix and mimic the way acute appendicitis presents which obstruction and enlargement of the appendix.

Mucocele is a dilated appendix filled with mucus and can be caused by an obstruction and contain thickened mucus. Or it may be a consequence of mucinous cystadenocarcinoma. The latter one can invade through the wall of the appendix and lead to intraperitoneal seeding. In the most severe cases, this spread can lead to pseudomyxoma peritonei which you can read more about below.


Peritonitis is the inflammation of the peritoneum. The symptoms are usually severe pain, swelling of the abdomen, fever and weight loss. If you press the patient’s abdomen, the patient experiences rebound tenderness. This means that when the patient feels pain when you release the pressure from your finger, because the peritoneum snaps back into its place.

The cause for peritonitis is usually bacterial, like E. coli, coccus, clostridium and chlamydia. Primary peritonitis occurs due to bacterial infection of ascitic fluid (called spontaneous bacterial peritonitis), while secondary peritonitis is more frequent and usually occurs due to perforation or inflammation of abdominal organs.

Peritonitis is a severe condition because it can lead to paralytic ileus, adhesions of organs or even sepsis.

Retroperitoneal fibrosis

Ormond’s disease, also known as retroperitoneal fibrosis is a condition characterized by the development of extensive fibrosis throughout the retroperitoneum. The exact pathogenesis is unknown but may be related to an immune response against atherosclerotic plaques. Fibrosis usually begins around a severely atherosclerotic aorta. It’s also associated to certain autoimmune disorders like Sjögren and Crohn’s. It can also occur as a result of trauma, radiation or certain drugs.

The condition presents with nonspecific symptoms like dull pain in the back. The fibrosis may envelop retroperitoneal structures like the inferior vena cava or ureter, potentially causing renal failure.

Pseudomyxoma peritonei

This condition, often called PMP, is a rare (1-2 cases per million people) condition of the peritoneum. It begins with an adenocarcinoma or mucinous cystadenocarcinoma in the appendix which perforates the wall of the appendix and spreads to the peritoneum. The tumor cells multiply and continue to produce mucin which fills the peritoneal cavity. The increased abdominal pressure can obstruct the intestines.

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11. Hepatic lesions caused by circulatory disorders. Nonviral inflammatory diseases of the liver. Drug hepatopathies

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