Fingers fail to accurately assess anal sphincter tone

Researchers hope the findings will lead to a reduction in forced anal examinations.

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Trying to figure out someone’s proclivities regarding anal sex? Save everyone some trouble and flip a coin (or better yet, just ask them!) instead of reaching for your rubber gloves.

Anal examinations (involving a visual inspection and a medical practitioner’s finger being inserted into the anus to check for anything out of the ordinary) are a perfectly legitimate, and often helpful, medical procedure.

Such examinations provide useful information in the diagnosis of medical conditions such as prostate cancer, haemorrhoids, anal fissures and gastrointestinal bleeding.

However, they can also be used in less friendly and non-clinical scenarios, like forced anal examinations. A 2018 study reported at least nine countries had recently used forced anal examinations in order to prosecute people alleged to be a sexual and/or gender minority.

In this scenario, prosecutors believe reduced sphincter tone is evidence that the individual in question has engaged in receiving anal sex.

The justification for the use of forced anal examination can be traced back to the work of Ambroise Tardieu, a 19^th century French forensic pathologist, who – among other things – claimed that men who engaged in anal sex had “loose anuses” as a result of their sexual practices.

Unsurprisingly, there is no evidence to suggest that Tardieu’s claims are true – particularly the bit about sticking a finger up someone’s clacker being a good way to figure out if they have been the receiver of some amorous anal activity.  

That is, until a group of US researchers actually set out to test whether anal sphincter tonality, measured through a digital anal rectal examination (or DARE, because everyone loves a good, discrete acronym), is truly an accurate way to “detect persons engaging in receptive anal intercourse”.

Their findings were published in BMJ Public Health.

The researchers recruited over 800 participants (who were almost all cisgendered men) who had had sex with another man in the last five years or identified as either a minority sexual orientation or as a transgender person who had sex with men, from two longitudinal studies assessing anal cancer screening protocols.

Participants completed a survey about their sexual behaviour, including whether they primarily engaged in insertive or receptive anal sex (or engaged in both equally), before undergoing a DARE.

Importantly, the healthcare practitioner undertaking the DARE was not aware of participant’s preferences when engaging in anal sex.

Two types of sphincter tone were assessed during the DARE and scored according to the 6-point Digital Rectal Examination Scoring System (DRESS) scale: resting tone (controlled by the internal sphincter muscle, an involuntary smooth muscle) and squeeze tone (controlled by the external sphincter muscle, a voluntary striated muscle).

Scores for resting tone ranged from “no discernible tone at rest” to “very high tone, a tight anal canal, difficult to insert finger”, while the squeeze tone scores ranged from “no discernible increase in tone with squeezing effort” to “very strong squeeze, to the point of being painful to the examiner”.

Eleven percent of participants were found to have decreased sphincter resting tone, with lower resting tone scores in participants who predominantly received anal sex compared to the other two groups.

Six percent of participants had decreased sphincter squeeze tone, but there were no differences in average DRESS scale scores between individuals based on their preferred position for anal intercourse.

However, neither resting nor squeeze tone scores were particularly accurate at determining whether someone preferred receiving anal sex – performing at 53% and 51% respectively – meaning the finger test is only slightly more accurate than tossing a coin.

“[Therefore], the accuracy of sphincter tonality to detect receptive anal intercourse is virtually nil,” the researchers wrote.

“Given virtually no accuracy, a finger inserted into the anus has no utility to detect individuals practising receptive anal intercourse and should not be used as such.”

While The Back Page is encouraged by the findings and hopes they will lead to a reduction of forced anal examinations in countries where homosexuality is illegal, we’re have a sinking suspicion that these countries are fans of doing their own research and may stick to an outdated way of thinking rather than adjusting their views and approaches based on data and evidence.

Send your favourite medical acronyms to penny@medicalrepublic.com.au.