What is McBurney's point?

McBurney's Point: Anatomical Landmark for Appendicitis

McBurney's point is the anatomical landmark located at the junction of the lateral and middle thirds of a line drawn from the umbilicus to the right anterior superior iliac spine (ASIS), representing the classic location of maximal tenderness in acute appendicitis. 1

Anatomical Significance and Historical Context

McBurney's point was first described by Charles McBurney in 1891 as the location where tenderness is typically maximal in cases of acute appendicitis. Despite advances in diagnostic technology, tenderness at McBurney's point remains a key physical examination finding in the assessment of patients with suspected appendicitis. 1

The anatomical significance of this point relates to the typical location of the appendix base, which traditionally was thought to correspond to this surface landmark. However, modern research has challenged the precision of this correlation.

Anatomical Accuracy of McBurney's Point

Research has demonstrated significant variability in the actual location of the appendix relative to McBurney's point:

• Only 4-35% of appendices are located exactly at or within 5 cm of McBurney's point 2, 3
• In 36% of cases, the appendix is more than 5 cm away from McBurney's point 3
• 70-75% of appendix bases are located below and medial to the line joining the umbilicus with the right ASIS 2, 4

A study using MDCT imaging found the mean distances between the appendix and McBurney's point were:

• Superoinferior: 33.0 ± 24.1 mm
• Mediolateral: 20.8 ± 19.3 mm
• Radial: 42.1 ± 26.7 mm 3

Clinical Implications

Despite the anatomical variability, McBurney's point remains clinically relevant for several reasons:

1. Diagnostic value: Tenderness at McBurney's point is still a valuable clinical sign in the evaluation of suspected appendicitis, even though the World Organisation of Gastroenterology has shown that less than half of patients with appendicitis have maximal tenderness at this exact location. 2

2. Surgical planning: Knowledge of the potential variability in appendix location is important for surgeons. Studies show that surgeons would alter their incision site in approximately 35% of cases if they had precise information about the appendix location from imaging. 3

3. Diagnostic algorithms: The Alvarado score, which incorporates right lower quadrant tenderness (often assessed at McBurney's point), is a widely used clinical scoring system for appendicitis. 5

Practical Applications

When examining a patient with suspected appendicitis:

• Palpate McBurney's point for tenderness, but also examine the entire right lower quadrant
• Remember that the appendix location varies widely among individuals
• Consider that tenderness may be maximal at locations other than McBurney's point, particularly in a more medial and inferior position
• Advanced imaging (ultrasound or CT) may be necessary to precisely locate the appendix before surgical intervention

Common Pitfalls

1. Over-reliance on McBurney's point: Assuming that absence of tenderness at McBurney's point excludes appendicitis
2. Anatomical variation: Failing to consider that the appendix may be in an atypical location (retrocecal, pelvic, etc.)
3. Surgical planning: Using only McBurney's point to guide incision placement without considering imaging findings

McBurney's point remains an important clinical landmark in the evaluation of appendicitis, but clinicians should be aware of its limitations as an exact anatomical marker for the appendix.