LAUSR

Dear editor, I read with interest the article by Ortega et al. [1]. The article reviews the anatomy and pathophysiology of anorectal suppuration in a lucid manner. However, there are few points which merit discussion. The supralevator anorectal abscess has been classified in four categories out of which type II, III, and IV are extrasphincteric supralevator abscesses. Extrasphincteric fistulas and abscesses are extremely rare these days [2]. The authors have not listed their own experience regarding the incidence or prevalence of supralevator and extrasphincteric abscesses in the article [1]. In 1976 Parks et al. found extrasphincteric fistulas in only 5% (out of 400) patients, whereas recent large studies analyzing fistula-in-ano on MRI imaging found no extrasphincteric fistula in those series [2, 3]. Morris et al. [3] found no extrasphincteric fistula in 300 patients, and Garg et al. [2] found no extrasphincteric fistula and abscess in 229 fistula-in-ano patients assessed and correlated by MRI scans and operative findings. The category of extrasphincteric fistula/abscess could be possibly erroneous or extremely rare as supralevator extension of fistula-in-ano is almost always in intersphincteric plane [4]. Extrasphincteric fistulas were reported few decades back when accurate imaging modalities like MRI and endoanal ultrasound (EUS) were not available. With the availability of these imaging modalities, the delineation and understanding of high fistulas (especially supralevator) have improved considerably. Secondly, as most extrasphincteric fistulas are iatrogenic, improved understanding and awareness among surgeons has perhaps led to decrease in this iatrogenic complication. Extrasphincteric abscesses (which are extremely rare) have been given three out of four categories of supralevator anorectal abscess classification (type II, III and IV) in the published article [1], and all other supralevator abscesses (which are far more common) have been clubbed in a single category (type I). Secondly, the authors have given impression that CT scan is better suited for anorectal abscess and fistula-in-ano imaging than MRI and EUS [1]. This is quite contrary to the current evidence in literature. MRI, closely followed by EUS, is considered gold standard to analyze and study complex fistula-in-ano and abscess [2]. Both these modalities are superior to CT scan as far as fistula-in-ano imaging is concerned [2]. Thirdly, authors have greatly emphasized the role of deep postanal space (DPAS) in causation of ischioanal abscesses, horseshoe abscesses and supralevator abscesses [1]. Therefore, they have advocated the opening up of deep postanal space by dividing anococcygeal ligament to manage these fistulas. Though DPAS, also known as Courtney’s space, was considered as the prime source of pathology in pre-MRI era, the latest evidence emerging clearly indicates that deep posterior intersphincteric space (DPIS) is more important than DPAS in pathogenesis of all the above abscesses [5]. In recent studies involving large number of patients, DPIS was the site of primary lesion in up to 97% of patients and surgeons had to open up DPIS rather than DPAS to treat the primary lesion for the fistula management. In an MRI-based study analyzing 513 patients in 2016, Zhang et al. [5] found that DPAS was involved in only 13.3% patients, whereas DPIS was involved in 79.2% patients which included 85.5% in horseshoe and 93.5% in supralevator fistula.