Anorectal Abscesses

The anal crypts can become blocked (Fig 1a), leading to abscess formation acutely (with Staphylococcus aureus the commonest cause).
Chronic infection can lead to the development of a fistula (Fig 1b). Blockage of a hair follicle in the natal cleft can lead to development of a pilonidal sinus. This sinus can become infected, leading to chronic sinus inflammation or formation of a pilonidal abscess that occurs laterally to the sinus [1-2,4].