Child sexual abuse Differential Diagnosis
Beside the normal findings, normal variants and unspecific findings, there are a number of important differential diagnoses to consider when evaluating children with abnormal anogenital findings for possible sexual abuse.

One of the areas of concern is accidental genital injuries. The pattern of injury and accompanying history however frequently provide sufficient information for differentiating them from abusive trauma. Most accidents result from straddling, referring to children falling on hard objects like a bicycle bar or a furniture arm with their genital area. Usually this causes an injury of the external genital structures which are crushed between the object and the underlying bones. The injuries involve the labia majora and minora and the clitoral hood and rarely involve the deep and protected structures like the hymen and the posterior fourchette. Published reports regarding accidental genital injuries describe them to be mostly minor and superficial, located anterior, external and unilateral. In most cases of accidental injuries the hymen is not involved [Dowd et al., 1994; Bond et al., 1995; Pokorny et al., 1992; Pokorny, 1997; West et al., 1989].

Exceptions are rare cases of accidental penetrating injuries [Boos, 1999]. Other types of injury reported in the literature include a case of posterior vaginal laceration near the hymen by a water slide accident [Kunkel, 1998], seatbelt injuries in motor vehicle accidents [Baker, 1986] and midline splitting injuries with and without hymenal involvement due to inline skating accidents [Herrmann and Crawford, 2002]. All reports stress the overwhelming importance of the history which tends to be spontaneous, acute and dramatic. It is consistent with the injuries and does not change over time or between different caretakers or between caretakers and child. Also, the immediate consultation of medical help favors the diagnosis of accidental trauma.

Dermatologic conditions which need to be differentiated from sexual abuse include erythema and excoriations in unspecific skin irritation or infection, diaper dermatitis, lack of hygiene, irritant substances (bubble bath, cosmetic care products), moniliasis, genital varicella and oxyuriasis. Recurring vaginitis is often an area of concern, especially when expressed in the context of custody debates. The child returning from the separated father after a weekend visit with red genitals may as well have experienced a paternal lack of hygiene, or his aversion to properly clean the genital area because he fears allegations of sexual abuse. Although abuse is possible and parental separation may result from nondisclosed abusive family constellations, research indicates much lower numbers of abused children in this context as commonly thought [Corwin et al., 1987].

Vaginitis is the most prevalent pediatric gynecology health problem and requires a systematic approach and broad differential diagnosis. Unclear and recurring vaginitis should warrant concern and further evaluation but is never diagnostic per se [Vandeven and Emans, 1993; Bays, 2001].

An infection caused by group A b-hemolytic streptococci may cause a fiery red, edematous and tender vaginal or perianal inflammation, sometimes accompanied by various forms of discharge: thin, thick, serous, blood tinged, creamy, white, yellow or green. Cultures have to be specifically requested as streptococci do not grow on routine media. Treatment is according to pharyngeal infections with a 10-day course of oral penicillin [Mogielnicki et al., 2000].

A frequently mistaken diagnosis of CSA occurs in children who present with anogenital lichen sclerosus et atrophicus. After initial white papules that form to white plaques, the skin becomes delicate and atrophic. It is extremely susceptible to minor trauma like wiping with toilet paper, causing fissuring or alarming subepidermal hemorrhages and spontaneous bleeding. The typical presentation is a ‘hourglass’ or ‘figure-of-eight’ configuration of decreased pigmentation around the labia majora and the anus [Jenny et al., 1989; Warrington and de San Lazaro, 1996; Young et al., 1993; Herrmann et al., 1998].

Cutaneous bleeding may also be caused by leukemia, disseminated intravascular coagulation, purpura fulminans and other coagulation disorders.

Urethral bleeding is rather caused by urethral prolapse (especially prevalent in African-American girls), polyps, hemangioma, or papilloma than by sexual abuse [Johnson, 1991]. Vaginal bleeding requires careful evaluation of the underlying causes. Most frequently it is caused by vaginitis (approx. 70%).

Other less frequent causes include precocious puberty, sarcoma botryoides (embryonal rhabdomyosarcoma), internal or external application of hormones, or unspecific, idiopathic bleeding [Bays, 2001].

Congenital conditions mistaken for sexual abuse include hemangioma of the hymen, vagina and labia. They may bleed or ulcerate. Failure of midline fusion is a congenital defect resembling scar tissue. Sometimes it is combined with an anteriorly located anus and also frequently creates confusion and misinterpretation as an abuse-related finding. Anal findings to be differentiated from abuse are fissures in chronic obstipation, Morbus Crohn, rectal prolapse or a streptococcal A cellulitis [Bays, 2001].