B54 pathology of the appendix and peritoneum Flashcards
Appendicitis causes
- obstruction, most commonly by a fecolith, hard ball of feces, or by a gallstone, tumor, or worm.
- idiopathic
Describe pathogenesis of appendicitis
Obstruction causes increase in luminal pressure due to fluid buildup. Increased pressure collapses the veins. This can also occur due to idiopathic appendicitis, when swelling causes veinous collapse.
Ischemia then occurs, and bacteria proliferate, causing a purulent necrosis, and eventual rupture.
Clinical presentation of appendicitis
Dull abdominal pain, fever, and leukocytosis, potentially vomiting, constipation, or diarrhea.
Progressing to a constant, more severe lower right quadrant pain.
Can also be clinically silent until rupture and peritonitis/sepsis.
What are the tumors of the appendix
Carcinoids are the most frequent appendix tumor, and the appendix is the most frequent site for carcinoids to form.
They are slow growing neuroendocrine tumor that almost never metastasize.
Mucoceles
- Not a proliferative disorder or neoplasm, but a luminal dilation of the appendix, filled with mucinous secretions, associated with obstruction by a fecolith.
Mucinous neoplasm
- Benign mucinous cystadenoma
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Malignant mucinous cystadenocarcinoma
- Is invasive, through the appendix into the peritoneum, spreading to organs along the peritoneum.
- Often mistaken for mucinous ovarian tumor metastases to the peritoneum.
- In extreme cases can fill the peritoneal cavity with semi-solid mucin, that is repeatedly drained but ultimately fatal.
Adenocarcinomas
- Like those seen in the colon/intestine. These are rare in the appendix.
- Cause obstruction and can lead to appendicitis.
What are the pathologies of the peritoneum? 4
Penumoperitoneum, Ascites, Peritonitis, and Tumors
Define exudate vs transudate
Transudate:
- due to altered hydrostatic or oncotic pressure in the vessels
- less than 3 g/dL of protein, less than half the protein concentration of the serum
- low specific gravity, less than 1.012
Exudate:
- due to inflammation,
- more than 3 g/dL of protein, more than half the protein concetrtion in the serum
- high specific gravity, higher than 1.02
What are the causes of pneumoperitoneum
Pneumoperitoneum from air within the cavity, from any source that can cause a rupture of the GI within the abdomen
- perforated ulcers
- obstruction
- diverticulum
- necrotizing enterocolitis
- GI cancer
- trauma
- ischemic bowel
What are the characteristics and causes of ascites?
Ascites
- Fluid in the peritoneum
- Detectable at 500mL
- usually a serous transudate, from:
- Neutrophils indicate infection
- RBCs indicate disseminated abdominal cancer
Most often caused by
- cirrhosis
- other liver disease and portal hypertension
- Right sided heart failure
- Neophrosis syndrome, hypoalbuminemia
What are the characteristics and causes of peritonitis?
Bacterial peritonitis:
- Yellow, FibrinoPurulent exudate covering the entire peritoneum.
- Can cause paralytic ileus
Causes:
- Occurs most often after rupture or perforation of the GI - causing a mixed infection with GI bacteria
- secondary infection occuring after ascites - aka spontaneous peritonitis, usually infection is with a single species.
- after acute pancreatitis
What are the consequences of peritonitis?
Adhesions, -> GI stenosis, infertility
Intra-abdominal organ abscesses
Septic shock
What are the tumors of the peritoneum?
Primary tumors:
- are very rare, but when they occur are very aggressive with mean survival of 6 months.
- mesothelioma - asbestos exposure, similar tumor to pleural mesothelioma
- carcinoma - resembles ovarian epithelial tumors, serous or mucinous cystadenocarcinomas. ~75% are serous.
Metastatic tumors:
- Most peritoneal tumors are metastatic
- Ovarian are most commoon
- Pancreas
- Stomach
- Local invasion from any intra-abdominal carcinoma.
