McBurney's Sign
McBurney's sign is direct tenderness to palpation at McBurney's point—located approximately one-third the distance from the anterior superior iliac spine to the umbilicus—and when positive in a patient with right lower quadrant pain, fever, and leukocytosis, it strongly suggests acute appendicitis and warrants immediate imaging with CT abdomen/pelvis with IV contrast rather than proceeding directly to surgery. 1
Anatomical Location and Clinical Technique
McBurney's point represents the typical anatomical location of the appendix base, positioned at the junction of the lateral and middle thirds of a line connecting the umbilicus to the right anterior superior iliac spine (ASIS). 1, 2 The sign is elicited by applying direct pressure at this specific point during abdominal examination. 3
Important Anatomical Caveat
Only 35% of appendix bases actually lie within 5 cm of McBurney's point, with 15% located more than 10 cm away from this traditional landmark. 2 This anatomical variability explains why less than half of patients with confirmed appendicitis demonstrate maximal tenderness precisely at McBurney's point. 2 Despite this limitation, tenderness at McBurney's point remains a key finding in the assessment of patients with suspected appendicitis. 3
Clinical Significance in the Diagnostic Algorithm
When McBurney's Sign is Positive
A positive McBurney's sign in the context of right lower quadrant pain, fever, and leukocytosis creates a clinical picture highly suggestive of appendicitis, but clinical assessment alone misdiagnoses acute appendicitis in 34-68% of cases. 4 The negative appendectomy rate without preoperative imaging ranges from 14.7-25%, which drops dramatically to 1.7-7.7% when CT is performed first. 4
Therefore, even with a positive McBurney's sign and classic presentation, proceed directly to CT abdomen and pelvis with IV contrast (sensitivity 85.7-100%, specificity 94.8-100%) rather than immediate appendectomy. 1, 4 This approach is critical because:
- CT identifies alternative diagnoses in 23.2-45.3% of patients presenting with right lower quadrant pain and classic symptoms 4
- Alternative conditions include right colonic diverticulitis (8%), ureteral stones, intestinal obstruction (3%), gynecologic pathology (21.6%), and other gastrointestinal conditions (46%) 4
Related Physical Examination Findings
When evaluating a patient with suspected appendicitis, assess for additional peritoneal signs that support the diagnosis:
- Rovsing's sign: Palpation of the left lower quadrant elicits pain in the right lower quadrant (LR+ = 3.52 in suspected appendicitis), occurring when pressure displaces gas and fluid causing peritoneal irritation at the inflamed appendix 1, 5
- Cough/hop pain: Patient experiences pain with coughing or hopping (LR+ = 7.64 in undifferentiated abdominal pain) 5
- Rebound tenderness: Indicates peritoneal irritation 1
- Guarding and rigidity: Suggest more advanced peritoneal inflammation 1
Alternative Examination Technique
The "pinch-an-inch" test offers a less uncomfortable alternative to traditional rebound testing: grasp and elevate a fold of abdominal skin over McBurney's point, then allow it to recoil briskly against the peritoneum—pain upon recoil indicates peritonitis. 6 This can be particularly useful when classic peritoneal signs are subtle. 6
Critical Clinical Pitfalls
Do Not Rely on Clinical Findings Alone
No single history, physical examination finding, laboratory test, or clinical scoring system can eliminate the need for imaging studies in suspected appendicitis. 5 The classic triad of migrating right lower quadrant pain, fever, and leukocytosis is present in only a minority of patients. 1
Fever is Frequently Absent
Do not exclude appendicitis based on absence of fever—it is absent in approximately 50% of appendicitis cases. 4 Low-grade fever, when present, is reported in only 30-80% of different populations. 1
Age-Related Variations
In elderly patients, the typical triad is infrequently observed, and signs of peritonitis (abdominal distension, generalized tenderness, rebound) are more common. 1 Comorbidities and concurrent medications may mask the clinical presentation. 1
Atypical Presentations
Approximately 50% of appendicitis cases present atypically, requiring a lower threshold for imaging. 4 Female patients of childbearing age have more atypical presentations and lower diagnostic accuracy on ultrasound. 1
Recommended Imaging Protocol
Order CT abdomen and pelvis with IV contrast without enteral contrast for rapid acquisition and excellent diagnostic performance. 4 Key CT findings include:
- Appendiceal diameter ≥7-8.2 mm 4
- Periappendiceal fat stranding 4
- Absence of intraluminal gas 4
- Presence of appendicoliths (predicts perforation with OR 2.47-2.67) 1