The differential diagnosis of an acute abdomen is most appropriately considered by its anatomic location (Table
5-1
).
Common gynecologic causes of lower quadrant pain include mittelschmerz, ovarian cyst, endometriosis, fibroids, ovarian torsion, pelvic inflammatory disease, ovarian tumor, ectopic pregnancy, infection of the uterus, threatened abortion, and round ligament pain secondary to pregnancy.
Medical conditions that may present as acute abdomen are many. Common examples include lower lobe pneumonias, acute myocardial infarction (MI), DKA, acute hepatitis, porphyria, adrenal hemorrhage, and musculoskeletal problems. Appendicitis is a clinical diagnosis. The triad of right lower quadrant pain, anorexia, and leukocytosis is the most sensitive diagnostic tool. Nausea and vomiting usually follow the onset of pain. The patient may have a low-grade fever and mild leukocytosis. Fevers with higher temperatures or increased WBC counts suggest perforation.
Thirty percent of patients with appendicitis have an elevated WBC count, whereas 95% have a left shift.
The intensity of pain is somewhat in proportion to the degree of irritation to the parietal peritoneum. Therefore, a retrocecal appendix (which is the most common location) may cause only a dull ache, given the lack of contact with the parietal peritoneum.
TABLE 5–1. Differential Diagnosis of the Acute Abdomen
Laboratory Findings
Laboratory studies are undertaken to support a clinical hypothesis. The evaluation generally includes a CBC, liver chemistries, amylase and lipase, coagulation profile, urinalysis, and urine pregnancy test.
Lactic acid level should be obtained for patients with suspected ischemic bowel. An elevated level is associated with tissue hypoperfusion.
Beta-hCG levels must be obtained for all women of childbearing age to exclude the possibility of ectopic pregnancy.
Radiographic studies:
Chest radiograph should be obtained on all patients with acute abdomen to rule out free air. Pneumonia may present as an acute abdomen.
