Acute Appendicitis Pathology

Study Notes

The incidence of appendectomy is declining due to more accurate preoperative diagnosis.

Acute appendicitis begins with obstruction of the lumen, which can be caused by food matter, adhesions, or lymphoid hyperplasia.
Mucosal secretions increase intraluminal pressure, eventually exceeding capillary perfusion pressure and obstructing venous and lymphatic drainage.
Vascular compromise leads to epithelial mucosa breakdown and bacterial invasion by bowel flora.
Increased pressure causes arterial stasis and tissue infarction, resulting in perforation and spillage of infected appendiceal contents into the peritoneum.
Initial luminal distention triggers visceral afferent pain fibers, causing vague and poorly localized pain in the periumbilical or epigastric area.
Continuing inflammation triggers somatic pain fibers, causing pain in the RLQ.

Acute appendicitis should be suspected in anyone with epigastric, periumbilical, right flank, or right-sided abdominal pain who has not had an appendectomy.
Women of child-bearing age require a pelvic exam and pregnancy test.
Additional studies include CBC, UA, and imaging studies.
CBC has limited value, with a sensitivity of 70-90% and low specificity, but a high positive predictive value of 92% and negative predictive value of 50%.
CRP and ESR have been studied with mixed results.
UA findings include pyuria, hematuria, and bacteruria, with >20 wbc per field increasing consideration of urinary tract pathology.
Imaging studies include X-rays, US, and CT, with graded compression US having a reported sensitivity of 94.7% and specificity of 88.9%.
CT is the best choice based on availability and alternative diagnoses.

Primary symptom is abdominal pain, with ½ to 2/3 of patients having a classical presentation.
Pain begins in the epigastrium or periumbilical area, is vague and hard to localize, and later localizes to the RLQ.
Associated symptoms include indigestion, discomfort, flatus, need to defecate, anorexia, nausea, and vomiting.
Migration of pain from the periumbilical area to the RLQ is 64% sensitive and 82% specific for diagnosis.

Findings depend on the duration of illness prior to examination.
Early on, patients may not have localized tenderness, but with progression, tenderness develops over McBurney's point.
Rovsing's sign, rectal exam, and psoas and obturator signs may be helpful in diagnosis.