Discussion
This case presented sphincter damage from a gun-shot that was not total but sufficient to cause appreciable loss of anorectal control. There was fibrous tissue joining the widely separated ends of anal sphincter (Figure 1). The case demonstrated the successful management of a traumatic anal sphincter injury following clinical assessment without the use of endoanal ultrasound to delineate the sphincter defect [6-8]. The novelty of this case were (1) the uncommon presentation of a discrete posterior anal injury involving more than 50% of the external anal sphincter caused by direct penetrating trauma. (2) With about half the sphincter ring remaining active there was satisfactory restoration of anal control without the need for a diverting stoma. Following section of the posterior sphincter muscles by the bullet, the wound had healed with much secondary epithelium and underlying scar tissue, and the sphincters had retracted to about half their circumference i.e. third degree (3b) perineal injury (Figure 2, table 1). The preoperative clinical assessment correlated well with the intra-operative assessment of the sphincter injury. Haque et al [6] had presented a similar experience following simply clinical assessment of 29 patients. Specific features in the history may point to the underlying aetiology of faecal incontinence. Often the history will give some indication as to whether the problem lies primarily within the rectum or the sphincter apparatus. There may be seepage of faeces due to sensory inattention in a proportion of patients with abnormalities purely of anal canal sensation. Patients in whom the primary presenting complaint is one of urgency of defaecation have deficiency of external anal function as in this case [8-10]. Unlike external anal sphincter injury from obstetric trauma which is always anterior and in the midline, external anal sphincter muscle injury in other sites are not so easily treated as the retracted ends are difficult to define with confidence. In addition, because of their disrupted nature any suture placed in them will tend to cut out. Thus, although the excision of the scarred tissues is essential for the mobilization of the remnant external anal sphincter muscle for an overlapping repair, it is important not to clean off all the fibrous tissue on the remnant sphincter muscle [4, 5]. At a mean follow-up of 84 months, Lamblin et al [11] reported 48% of patients maintaining good faecal continence with a satisfaction rate of 85% using the overlapping sphincteroplasty technique. Failure was attributed to mechanical dehiscence, progressive muscular atrophy or occult neuropathy. Extensive perineal injuries resulting in anal sphincter disruption often require diversion and sphincter reconstruction. However, after clear tissue viability has been established as in this case and, there was no rectal laceration, the defect can be repaired primarily without diversion of the faecal stream [2-4]. In a randomized trial to assess the need for faecal diversion at the time of sphincteroplasty, Hasegawa et al [12] concluded that there was increased morbidity from a stoma with no difference in functional outcome or wound healing . Anal stenosis requiring repeated self-dilatation was a common complication from anal disuse.