The midclavicular line: a wandering landmark.

Although the midclavicular line (MCL) is the usual reference point for clinical assessment of liver size and localization of the cardiac apex beat, we found substantial interobserver variation in locating the MCL. The distance from the midline to the MCL as estimated by 20 clinicians in three subjects varied by up to 10 cm. More variation was found for estimates in the obese subject than for those in the two subjects of normal build (p = 0.004). No difference in variation was found between consultants and house staff. The limitations of the MCL as a reference point are discussed in light of these findings.