There are many things that we do routinely in our day-to-day practice without much thought, but how often do we stop and ask, “Why?” In this column, we present one such question and an evidence-based response. We hope that this will spark intrigue in other urologists to similarly ask more questions. We welcome your submission to AUANews for our new series, “Why Do We Do That?”

Everyone is familiar with this picture prior to any abdominal or penoscrotal case: someone grabs a razor/clipper and another with 3-inch tape to gather the hair. It has become something of a ritual, but why do we do this? Is it really necessary to shave all that hair? How thorough do we need to be? If we cause small nicks in the skin, are we actually making it worse?

Naturally, there is a concern for infection given that hair is known to host a complex microbiome sheltering various bacteria, fungi, and viruses.¹ With this idea in mind, time and time again patients are shaven prior to procedures or arrive preshaven. While the concern for infection is not unfounded, these areas are sterilely prepped prior to the case, so the question becomes: Are these new makeovers necessary?

The 3 shaving methods most commonly mentioned in scientific studies and meta-analyses on the relationship between surgical site infections (SSIs) and preoperative hair removal are shaving via razor, electric clipping, and depilatory creams. They overall perform similarly with no change in SSIs compared to no shaving at all, as will be discussed below. However, shaving with a razor has been noted in a few studies to lead to an increase in SSIs through microscopic trauma allowing bacterial invasion.^2-5 At the same time, a small number of studies, including one published in The Journal of Sexual Medicine on male genitalia cases, fail to confirm this result of increased rate of SSIs following shaving.⁶

There has been a growing body of evidence from recent individual studies and meta-analyses that show no difference in SSIs between those that had preoperative hair removal via razor, clipping, and depilatory creams vs those that had no hair removal. Tanner et al published a systematic review in 2007 stating “there is insufficient evidence to state whether removing hair impacts on SSI or when is the best time to remove hair. However, if it is necessary to remove hair then both clipping and depilatory creams result in fewer SSIs than shaving using a razor.”³ The Tanner systematic review had a subsequent update published in 2021 with a total of 19 randomized controlled trials and 6 quasi-randomized controlled trials, including a total of 8,919 participants. The authors conclude that while these studies suggest little, if any, difference in SSI when comparing preoperative hair removal via clippers or depilatory creams compared to no preoperative hair removal, the evidence is of low quality given high risk of bias in the studies they analyzed along with imprecise data.⁴

Beyond the method of hair removal technique, there has also been interest in the timing, venue, and person conducting hair removal. Meta-analysis by Tanner et al found that shaving the day of surgery had a small reduction in SSIs when compared with day before surgery, though it is again considered low-certainty evidence due to heterogeneity of shaving methods included along with “serious imprecision.”⁴

The WHO published Global Guidelines for the Prevention of Surgical Site Infection in 2018, which included an analysis of the data on effectiveness and optimal method of hair removal.⁷ The overall conclusion was that the evidence is of low quality, is “mostly underpowered and limited by flawed methodology,” and “timing of hair removal and the location have not been sufficiently studied.” The WHO recommended that future well-designed and adequately powered studies are needed to draw firmer conclusions. A 2023 JAMA review on SSI prevention listed avoiding shaving with a razor as one of its main recommendations in avoiding SSI.⁵

More recently, a single-center prospective 12-month study by Dhamnaskar et al of all elective clean or clean-contaminated abdominal surgeries with primarily closed wounds assigned patients nonrandomly to preoperative shaving or no shaving.⁸ The results showed no difference in SSI rates at postoperative dates 7, 14, and 30. This finding, combined with the abovementioned studies, further suggests that preoperative hair removal does not affect SSI rates.

Even with this actively growing evidence suggesting preoperative hair removal may not truly affect SSI rates, it has been noted in multiple studies that it is surgeon dependent, and the evidence, though large in sample size, continues to be of insufficient quality to lead to universal recommendations.^6,8 Even in the 2023 review on SSI prevention in JAMA mentioned earlier, the authors discuss different strategies without explicitly discussing preoperative hair removal.⁵ JAMA and the WHO do mention avoiding razors for hair removal given many studies that describe slightly increased SSI risk with use of razors and if shaving is done 1 day preoperatively.^4,5,7 Though there seems to be evidence pointing toward not shaving prior to cases, there needs to be higher-quality research in support of this change before routinely adopting this measure. While there is definitely something to be said about potential patient and procedural selection for these cases, it is still important to reckon with the results as laid before us as they continue to be published.

After a decade of small studies, meta-analyses, guidelines, and reviews, we are back to where we started: preoperative hair removal does not appear to alter the incidence of SSI. Surgeons, like anybody else, may be resistant to change, but we must ask if we are continuing to perform an antiquated ritual with no clinical benefit.