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.