Waking up on the wrong side of the operating table Frequency of laterality errors and how to prevent them
Laterality errors, also known as side discrepancies, refer to
instances when the incorrect side is noted in one or more
sections of diagnostic reports or documentation. For example, a
radiology report that notes that a lesion is on the left side of
the body, when in reality it is on the right, would be considered
a laterality error. Uncorrected laterality errors are most
frequently associated with wrong-side surgeries, which can result
in wrong limb amputation, wrong-side arthroscopy, or resection of
A recent study published by several members of the Department of
Radiology at Massachusetts General Hospital aimed to determine
the frequency of laterality errors in radiology reports using a
radiology reports search engine. They found that in the year
2007, 88 side discrepancies were reported in addenda, meaning
that the error was put in the report, but was later corrected.
However, far more reports are not corrected. In January alone of
that year, 36 reports with laterality errors were never corrected
(only 7 were corrected that month). Fortunately, only 3 patients
were affected and no patient harm occurred.(1)
These errors are not exclusive to radiology. A study published in
EYE (journal of the Royal College of Ophthalmologists) found that
of the 100 randomly chosen ophthalmology notes, 32 had at least
one laterality error (confusing right and left eyes), which
equates to incorrect laterality documentation in one-third of the
random charts reviewed.(2)
Recommendations on prevention of laterality errors
Avoid using the abbreviations for left and right (L and R).
When in a hurry, they are often mixed up and illegible.
Involvement of the patient and/or relatives is very
important. When consenting patients for surgery or prescribing
treatments, explaining to the patient what is to be done and
listening to any queries remains an important mechanism in
reducing laterality errors.(3)
Always rely on written information when composing reports or
implementing patient care – listening to a staff member orally
explain without anything written to back it up can result in
Follow your organization’s procedure for site identification
and marking prior to any procedure.
Complete the appropriate “Time Out” steps before a procedure
is to be performed.
Do not use the following abbreviations, which have been
categorized as “error prone” by the Institute for Safe Medication
Practices. Write the words to identify the anatomy involved.
Laterality Error Inducing Abbreviations as noted by the Institute
for Safe Medication Practices (ISMP)
“a” can be mistaken as an “o” which could read “o.d.”,
meaning right eye
“a” can be mistaken as an “o” which could read “o.s.” or
“o.l”, meaning left eye
“a” can be mistaken as an “o” which could read “o.u.”,
meaning both eyes
“o” can be mistaken as an “a” which could read “a.d.”,
meaning right ear, confusion with omne in die
“o” can be mistaken as an “a” which could read “a.s.”,
meaning left ear
“o” can be mistaken as an “a” which could read “a.u.”,
meaning both ears
Sangwaiya MJ, et al. Errare humanum est: frequency of
laterality errors in radiology reports. AJR Am J Roentgenol.
2009;192(5):W239–W244. doi: 10.2214/AJR.08.1778.
ElGhrably I, Fraser S. An observational study of
laterality errors in a sample of clinical records. Eye.
DiGiovanni CW, Kang L, Manuel J. Patient compliance in
avoiding wrong-site surgery. J Bone Joint Surg Am 2003;