Read N W, Sun W M
Gastrointestinal Mobility Unit, Centre for Human Nutrition, Northern General Hospital, Sheffield.
Gut. 1991 Jun;32(6):670-3. doi: 10.1136/gut.32.6.670.
Anal dilatation in response to gentle parting of the buttocks has been advocated as a sign of sexual abuse in children, but nothing is known of the physiology of this response or its existence in normal subjects, in patients with spinal disease, and in patients with a weak sphincter and whether it can be elicited after training. To answer these questions we investigated the effect of parting the buttocks on anal function. Combined anal manometry and electromyography was conducted in six normal subjects (five men, one woman, aged 19-53 years), in 18 patients with faecal incontinence (three men, 15 women, aged 30-80 years), and in seven paraplegic patients (six men, one woman, aged 25-36 years), in four of whom the posterior sacral roots had been cut. Parting the buttocks in normal subjects reduced the pressure in the anal canal from 102 (20) to 14 (3) cm H2O (mean (SEM), p less than 0.00001), but did not cause the anus to gape. This drop in pressure was associated with increased electrical activity in the external anal sphincter. Normal subjects could consciously relax the external anal sphincter and reduce the anal pressure but not so as to result in anal gaping during traction on the buttocks, even after anal dilatation. Stimulation of the anal lining by moving a probe in and out of the anal canal increased the activity of the external anal sphincter, raising anal pressures. Paraplegic patients who had lost conscious control of their external sphincters showed anal gaping when the buttocks were parted. A similar phenomenon was seen in patients with faecal incontinence who had weakness of the external anal sphincter, while incontinent patients with weakness of both sphincters showed anal gaping even at rest. Inasmuch as the results of our study can be applied to children, the data suggest that reflex anal dilatation should only be used to support a diagnosis of sexual abuse if sphincter function is otherwise normal and there is no evidence of cerebrospinal disease. Although our results do not support the notion that children could become so conditioned to repeated digital or penile penetration of the anus that they can cause the anus to gape when the buttocks are parted, neither do they exclude it.
轻柔分开臀部时出现的肛门扩张，被认为是儿童遭受性虐待的迹象，但对于这种反应的生理学机制、在正常受试者、脊髓疾病患者、括约肌功能薄弱患者中的存在情况，以及训练后是否能引发这种反应，人们一无所知。为了回答这些问题，我们研究了分开臀部对肛门功能的影响。对6名正常受试者（5名男性，1名女性，年龄19 - 53岁）、18名大便失禁患者（3名男性，15名女性，年龄30 - 80岁）和7名截瘫患者（6名男性，1名女性，年龄25 - 36岁，其中4人骶后根已切断）进行了肛门测压和肌电图联合检查。在正常受试者中，分开臀部会使肛管压力从102（20）厘米水柱降至14（3）厘米水柱（均值（标准误），p < 0.00001），但不会导致肛门张开。这种压力下降与肛门外括约肌电活动增加有关。正常受试者能够有意识地放松肛门外括约肌并降低肛门压力，但即使在肛门扩张后，在分开臀部时也不会导致肛门张开。通过将探头插入和拔出肛管刺激肛管内壁，会增加肛门外括约肌的活动，提高肛门压力。失去对外括约肌有意识控制的截瘫患者，在分开臀部时会出现肛门张开。在肛门外括约肌薄弱的大便失禁患者中也观察到类似现象，而两个括约肌都薄弱的失禁患者即使在静息时也会出现肛门张开。鉴于我们的研究结果可应用于儿童，数据表明，只有在括约肌功能正常且无脑脊液疾病证据的情况下，反射性肛门扩张才应仅用于支持性虐待的诊断。虽然我们的结果不支持儿童会因反复的手指或阴茎插入肛门而形成条件反射，以至于在分开臀部时会导致肛门张开这一观点，但也不排除这种可能性。
