Appendicitis Differential Diagnoses
Author: Sandy Craig, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP more...
The overall accuracy for diagnosing acute appendicitis is approximately 80%, which corresponds to a mean negative appendectomy rate of 20%. Diagnostic accuracy varies by sex, with a range of 78-92% in male patients and 58-85% in female patients.
The classic history of anorexia and periumbilical pain followed by nausea, right lower quadrant (RLQ) pain, and vomiting occurs in only 50% of cases. Vomiting that precedes pain is suggestive of intestinal obstruction, and the diagnosis of appendicitis should be reconsidered.
The differential diagnosis of appendicitis is often a clinical challenge because appendicitis can mimic several abdominal conditions (see the Differentials section). [ 12 ] Patients with many other disorders present with symptoms similar to those of appendicitis, such as the following:
Other problems that should be considered in a patient with suspected appendicitis include appendiceal stump appendicitis, typhlitis, epiploic appendagitis, psoas abscess, and yersiniosis.
Misdiagnosis in women of childbearing age
Appendicitis is misdiagnosed in 33% of nonpregnant women of childbearing age. The most frequent misdiagnoses are PID, followed by gastroenteritis and urinary tract infection. In distinguishing appendiceal pain from that of PID, anorexia and onset of pain more than 14 days after menses suggests appendicitis. Previous PID, vaginal discharge, or urinary symptoms indicates PID. On physical examination, tenderness outside the RLQ, cervical motion tenderness, vaginal discharge, and positive urinalysis support the diagnosis of PID.
Although negative appendectomy does not appear to adversely affect maternal or fetal health, diagnostic delay with perforation does increase fetal and maternal morbidity. Therefore, aggressive evaluation of the appendix is warranted in pregnant women.
The level of urinary betahuman chorionic gonadotropin (beta-hCG) is useful in differentiating appendicitis from early ectopic pregnancy. However, with regard to the WBC count, physiologic leukocytosis during pregnancy makes this study less useful in the diagnosis than at other times, and no reliable distinguishing WBC parameters are cited in the literature.
Misdiagnosis in children
Appendicitis is misdiagnosed in 25-30% of children, and the rate of initial misdiagnosis is inversely related to the age of the patient. The most common misdiagnosis is gastroenteritis, followed by upper respiratory infection and lower respiratory infection.
Children with misdiagnosed appendicitis are more likely than their counterparts to have vomiting before pain onset, diarrhea, constipation, dysuria, signs and symptoms of upper respiratory infection, and lethargy or irritability. Physical findings less likely to be documented in children with a misdiagnosis than in others include bowel sounds; peritoneal signs; rectal findings; and ear, nose, and throat findings.
Considerations in elderly patients
Appendicitis in patients older than 60 years accounts for 10% of all appendectomies. The incidence of misdiagnosis is increased in elderly patients.
Older patients tend to seek medical attention later in the course of illness; therefore, a duration of symptoms in excess of 24-48 hours should not dissuade the clinician from the diagnosis. In patients with comorbid conditions, diagnostic delay is correlated with increased morbidity and mortality.
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CT scan reveals an enlarged appendix with thickened walls, which do not fill with colonic contrast agent, lying adjacent to the right psoas muscle.
Sagittal graded compression transabdominal sonogram shows an acutely inflamed appendix. The tubular structure is noncompressible, lacks peristalsis, and measures greater than 6 mm in diameter. A thin rim of periappendiceal fluid is present.
Transverse graded compression transabdominal sonogram of an acutely inflamed appendix. Note the targetlike appearance due to thickened wall and surrounding loculated fluid collection.
Technetium-99m radionuclide scan of the abdomen shows focal uptake of labeled WBCs in the right lower quadrant consistent with acute appendicitis.
Normal appendix; barium enema radiographic examination. A complete contrast-filled appendix is observed (arrows), which effectively excludes the diagnosis of appendicitis.