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Communicating risk: words or numbers?

We are becoming increasingly familiar with the identification of risks that need to be disclosed when seeking consent for treatment. Previously, we relied upon an arbitrary numerical cut-off expressed as a threshold percentage to determine what we would or would not disclose. But we now are accustomed instead to ask ourselves what the reasonable person in our patient’s circumstances would want to know. In addition, there may be specific topics that must be disclosed to the particular patient in front of you, as in the case of the patient who wanted especially to know whether surgery on one eye could lead to loss of sight in the other (see ‘Disclosing the miniscule risk for consent’).

For the moment, pinpointing risk is thus more or less straightforward. But how should we communicate these risks to patients?

Mr Ollosson suffered chronic disabling testicular pain after vasectomy in 2012. He claimed that he was not given adequate information about the risk of this complication. Properly informed, he would have avoided undergoing the surgery. During a subsequent trial in the High Court, general practitioners accustomed to performing vasectomy acted as expert witnesses. Both gave evidence as to what they would normally disclose prior to seeking consent for vasectomy. They agreed that risks such as infected haematoma, chronic scrotal pain and testicular atrophy should be disclosed, together with a 2% incidence of ‘…post-vasectomy pain severe enough to interfere with quality of life and daily activities and work’. 

In relation to practice in 2012, the experts agreed that as a substitute for setting out population risk as percentages, the use of words such as ‘a small possibility of post-vasectomy pain which can be chronic’ was commonplace, and an appropriate way of describing long term pain.

Two urologists also provided expert evidence. Their approach differed from the general practitioners, since they both preferred to communicate risk using percentages. One viewed the use of a word such as ‘small’ as liable to a variety of interpretations, failing to distinguish risks that were low in frequency from those that were low in severity. By contrast, expressing risk in percentages gives at minimum an idea of frequency. The other urologist acknowledged that reasonable patients would accept 1-2% as a ‘small’ percentage, but reiterated the point that a small possibility should not hint at a small impact.

Recognising that Mr Ollosson had been extremely unlucky, the judge found nevertheless that, taking all the facts of the case into consideration, the patient had been adequately informed of the risk.

Focussing on the adequacy of describing a risk as ‘small’, the court found this to be a satisfactory method of communicating risk. The judge accepted that the word means different things to different people, but ‘small’ remains a word that encompasses and satisfactorily conveys the level of risk involved. The judge was less comfortable with the use of the alternative adjective of ‘rare’, although did not give his reasons for this distinction. Perhaps because the word emphasises exceptionality and infrequency, tempting us towards a point where the entity described as ‘rare’ disappears altogether. In contrast, the word ‘small’ indicates a modest but finite, undeniable measure of risk.

None of these semantics should obscure the obvious point: that percentages can be used freely if the clinician so chooses and this may well become necessary should a patient seek clarification of the small risk. The case provides rare judicial guidance that it is perfectly acceptable to describe the incidence of risks and complications in everyday words rather than using statistics, whilst awaiting the patient’s reaction prior to introducing numeric descriptions of the population risk, if needs be.


Robert Wheeler
Department of clinical law, September 2019