Conservative versus operative management of perianal abscess and fistula-in-ano in infants: a narrative review

Introduction

Perianal abscesses (PAs) are defined as a collection of purulent material that is superficially located close to the anus. Fistula-in-ano (FIA) is defined as an abnormal fibrinous tract connecting the perianal skin to the anal canal. Most physicians consider these two conditions to be closely related if not sequential and arising from a similar origin. Supportive of this view, the incidence of FIA formation from PAs ranges from 20-80% among infants (1). Interestingly, the incidence of PA/FIA in pediatric patients peaks during infancy and seems to predominantly occur in males (2-4). The relative absence of adult predisposing factors such as diabetes, sexually transmitted infections, and inflammatory bowel disease (IBD) makes infant PA/FIA unique. Abnormal anal gland development, infected fissures and hormonal effects are proposed factors contributing to the development of infant PA/FIA.

Surgical management with incision and drainage (I&D) has been historically utilized to achieve source control. However, observation with or without antibiotic therapy has been adopted by some practitioners likely reflecting recent literature that purports the safety, efficacy and possible superiority of conservative management. Critics of conservative management argue the risks of PA/FIA recurrence can be mitigated or reduced when a fistulous tract is identified and opened at the time of surgical drainage. Given the absence of long-term data examining cure rates, PA recurrence, and fistula development between different treatment strategies, no consensus exists on the optimal management of PA in infants. Using the currently available literature, this narrative review aims to characterize the pathogenesis, clinical presentation, and management options of PA and FIA in infants. We also seek to highlight the inherent problems with current retrospective comparative studies and offer insights towards better study design. We present this article in accordance with the Narrative Review reporting checklist (available at https://tgh.amegroups.com/article/view/10.21037/tgh-25-73/rc).

Methods

The primary literature was assessed using the methodology outlined in Table 1. The National Institute of Health Library of Medicine MEDLINE, PubMed, Embase, and Cochrane Library databases were queried for articles related to PA or FIA in infants until April 30, 2025. MeSH search terms are listed in Table 1. All article types including opinion pieces, case series, retrospective reviews, review articles, retrospective cohort, and meta-analyses were initially included. Articles with patients 18 years old or older, no full-text options, or no English translations were excluded from this narrative review. Those articles meeting inclusion/exclusion criteria were then read and summarized for the narrative review. From the remaining articles, retrospective cohort studies were chosen based on study design and subjected to critical appraisal using the Newcastle-Ottawa Scale (NOS) which allocates nine points over three domains: selection, comparability and outcome. Articles were appraised using the specific selection criteria in Table S1 (5). Biorender was used to create figures.

Discussion and summary

Pathogenesis of PA and FIA in neonates

The underlying etiology of PA and FIA in the infant population remains unclear. However, the early onset during infancy, male predominance, and lack of classical risk factors supports a distinct infant etiology of PA and FIA.

One possible theory relates to the congenital development of the anal canal. Around 8 weeks of gestation, the anal portion of the cloacal membrane breaks down to form the anal canal. The remnant of this membrane forms the dentate line which contains posteriorly located longitudinal mucosal folds. The crypts of Morgagni exist between these folds and typically lead to an anal gland (Figure 1A) (6). The cryptoglandular theory suggests obstruction of these anal glands within crypts leads to inflammation and infection with progression to PA and FIA (Figure 1B). In the 1980s, Shafer et al. provided surgical management for a small cohort of infants with FIA (7). Intraoperatively, they observed a thickened dentate line containing abnormal deep crypts of Morgagni. This anatomic anomaly was hypothesized to predispose the development of cryptitis and eventual progression to PA and FIA. Other surgeons have also observed these deep crypts (Poenaru, Serour) but only see them in approximately 39.3–47% of surgical cases (8,9). Given the deep crypts are not a universal observation, the mechanism is likely multifactorial.

Figure 1 The anal canal anatomy and cryptoglandular theory of disease development. (A) Depicts a schematic illustration of the anal canal with key anatomical features noted. (B) Blockage or abnormally developed anal crypts (crypts of Morgagni) lead to an obstruction of the anal gland which leads to the development of perianal abscesses and fistula-in-ano. Created in BioRender. Lab, W. [2025] https://BioRender.com/411o94k.

Hormonal imbalance or excessive androgen production has also been thought to contribute to the observed male predilection for PA in this population. This sexual dimorphism has been observed consistently from multiple studies (3,4,9,10). While the exact mechanism is unclear, experts have theorized that the surge of androgens during the first year of life in male infants may stimulate the growth of anal sebaceous glands causing abnormal hyperplasia and secretions thus making them susceptible to PA and FIA development. Two studies have correlated the age of PA/FIA diagnosis with a standard serum testosterone curve. Christison-Lagay et al. considered infants less than 12 months of age and found the peak of disease incidence coincided with the peak of infant serum testosterone around 1-2 months of age (3). Gong et al. replicated this visualization; however, their study included individuals up to 15 years of age (4). In their dataset, testosterone demonstrated a bimodal distribution with a peak during the first few months of life and a second peak around 14 years of age. Interestingly, the peak incidence of PA/FIA was only during the infantile period, and no uptick was observed during the second androgen surge. Given the lack of true mechanistic experimentation and the absence of a second peak of PA and FIA during adolescence, the hormonal contribution is unlikely to be the sole factor.

Furthermore, in the adult population, perianal disease is a known entity within the context of IBD. The role of IBD in infant PA/FIA is conflicting. In one series, nearly 10% of pediatric patients 1 month to 16 years old with PA and FIA went on to be diagnosed with Crohn’s disease (11). However, another cohort study found no link between isolated PA in those under two years old and later diagnosis of Crohn’s disease (12). Taken together, IBD does not appear to explain the majority of cases.

Finally, there are unique attributes of infants that may increase their risk for PA and FIA. First, their anal canal is shorter. As a result, the intestinal mucosa can be easily exposed during defecation leading to ultimate trauma from wiping and/or diaper friction (13). Furthermore, infants tend to have frequent liquid bowel movements. This thickened liquid has been postulated to easily block the crypts with resultant obstruction. A recent retrospective case-control study of 41 infants and toddlers with FIA compared to 41 healthy controls found four risk factors of FIA in infants: born to mothers with previous deliveries, high defecation frequency, loose stools, and repeated wipes (14).

Clinical presentation and diagnosis

The most common clinical scenario involves an infant, predominantly male, after their caregivers notice a concerning area around the anus. The clinical features of a PA are a raised area of skin near the anus with overlying erythema and palpable fluctuance. These abscesses may be associated with surrounding tissue swelling, induration, or drainage. While generally thought to be the consequence of PA, FIA presents as an area of skin ulceration with anal secretions. The location of PA/FIA can be anywhere around the circumference of the anus; however, there is a predilection for these abscesses to be located at the right and left lateral regions (Figure 2) (15,16). Clinical history and physical exam should be sufficient to make the diagnosis of PA/FIA. However, ultrasound has gained some traction in certain clinical settings (17,18).

Figure 2 Most common location of infant perianal abscesses. Infant perianal abscess are typically located in the lateral locations with equal right and left distribution. Created in BioRender. Lab, W. [2025] https://BioRender.com/ivztzfm.

Additionally, various studies have sought to evaluate the microbiology of infant PAs. With relative agreement across studies, enteric pathogens such as E. coli and Klebsiella spp. and skin pathogens such as Staphylococcus spp. are typically cultured from abscess contents (19-22). In a retrospective Turkish cohort of mostly infant patients, they found 42% of microbial isolates possessed beta-lactamases and 37.5% were methicillin-resistant (22). Nevertheless, there is no consensus on the clinical utility of abscess cultures in this population.

Management strategies

The management of PAs has long been debated. However, management typically falls into two paradigms—conservative and surgical.

Conservative treatment

Conservative management is often difficult to define. Most clinicians consider anal hygiene and sitz baths with or without antibiotics as mainstays of conservative management. However, some authors consider needle aspiration or I&D under local anesthesia as conservative measures. The addition of these office procedures obfuscates the distinction between conservative and surgical management thereby making interpretation of primary literature difficult.

Nevertheless, advocates for conservative management in infants’ dates to the late 1990s. Between 1990–1999, Rosen et al. implemented a practice change where infants presenting with a PA were management with a trial of conservative management without antibiotics (23). Out of 18 male infants with PA, 14 were managed conservatively. Notably, 13 of these patients developed a FIA that was successfully managed expectantly. Rosen concluded infant PA&FIA could be considered self-limiting. Since then, multiple studies have sought to determine the relative risk and benefits of conservative management. A recent systematic review of the literature defined conservative management as those procedures that lack general anesthesia (24). They found nine studies that assessed conservative management of infant PA. All studies included hygiene and sitz baths in their definition. Six studies included antibiotics, and seven studies considered I&D under local anesthesia as conservative measures. Other less studied measures included needle aspiration and drain insertion as well as topical medications such as hainosankyuto and basic fibroblast. In their cohort of 1,049 patients, 790 (75.3%) had resolution of PA without the use of general anesthesia. The remaining 243 infants (23.2%) developed a recurrence or FIA of which only 59 underwent a procedure involving general anesthesia. While this meta-analysis suggests that most infants can receive management without the need for general anesthesia, it highlights the heterogeneity of conservative therapy definitions.

Recently, Yin et al. completed a retrospective review of all conservatively treated infant PAs between 2014 and 2020 (25). They identified 153 infants treated with conservative measures based on parental preference. Conservative was defined as sitz baths and anal hygiene with optional adjuncts such as topical traditional Chinese medicine and antibiotic ointment. After at least 2 months of conservative management, 119 (78%) of infants were cured with 34 (22%) experiencing some failure defined as fistula formation, recurrence, or new-abscess formation. Twenty-three of these infants who failed initial conservative management elected for another round of conservative management of which 20 infants were cured.

Overall, while the current literature has differing definitions of what constitutes conservative management, there seems to be a consensus that most infants can be managed without maximally invasive procedures that would require general anesthesia. Predictors of conservative management failure include increased inflammatory markers and abscess size (17). Advocates state the complications of conservative management are relatively minor and can be controlled with another trial of conservative therapy and/or surgical management.

Adjuncts to conservative management

The utility of antibiotics in conservative therapy remains unclear. The options typically include local ointments and/or oral antibiotics. Application of local antibiotic ointment seems to the general practice of some published studies (25,26). However, the direct comparison of conservative management with and without oral antibiotics is lacking. Christison-Lagay et al. found that antibiotic use reduced the risk of FIA (3). Similarly, Afsarlar et al. found that individuals who received oral antibiotics regardless of overall treatment management developed fewer FIA compared to individuals who did not receive antibiotics (19). In contrast, other groups found that antibiotics do not appear to significantly alter clinical courses (27,28). In a sub-analysis from a retrospective cohort study, Neville et al. compared oral antibiotics alone to operative management and found a higher rate of recurrence and fistula formation in the antibiotic alone cohort (28). Taken together, in the absence of dedicated prospective trials, clear evidence for oral antibiotics is lacking.

Other groups have explored the utility of novel topical agents. Kubota et al. used a spray form of basic fibroblast growth factor (bFGF) for the treatment of PAs and FIAs (29). bFGF is a polypeptide, which functions as a multipotent cytokine and regulates angiogenesis, mitogenesis, cellular differentiation, cell migration and tissue injury repair. In an initial proof of concept study, Kubota et al. treated nine infants with topical bFGF, seven were cured while two had recurrence that was successfully treated with a second administration of bFGF (29). Despite the lack of proper controls, bFGF appears to be safe and may be a promising agent for the conservative treatment approach.

Additionally other studies have explored the use of traditional herbal Japanese medicines, hainosankyuto and juzentaihoto, in the setting of infant PA (30). While the exact mechanism of action for these agents remains unclear, they are generally thought to have properties that promote resolution of various inflammatory and infectious processes. A retrospective study found hainosankyuto to be associated with faster resolution of purulent drainage and induration compared to upfront I&D (31). In a subsequent four-arm drug administration study, Sueyoshi et al. found that combination therapy with hainosankyuto and juzentaihoto resulted in complete resolution of infant PAs that were conservatively treated (32). Taken together these agents may be effective but have not gained widespread support.

Surgical drainage

Surgical management of PA and FIA consists of I&D, fistulotomy, and fistulectomies. Advocates of initial surgical management may disagree on how invasive interventions should be; however, most agree that drainage of the abscess is necessary. Whereas opponents of initial surgical intervention state the risk of damage to the anal-sphincter complex is prohibitive and warrants initial conservative management.

I&D procedures can be performed in the clinic under local anesthesia or the operating room under general anesthesia. The overarching goal of drainage is to extract infected material and promote healing of the abscess cavity. Stab incisions under local anesthesia may be advantageous in avoiding the side effects of general anesthesia; however, risk incomplete drainage and creation of a FIA. Conversely operative I&D allows the surgeon to thoroughly excavate the cavity and assess the presence of a FIA but incurs risks of general anesthetic in the infant period. Charalampopoulos et al. retrospectively reviewed 98 children less than 2 years old who underwent an operative procedure for PA/FIA (33). In their series (n=98), 47% had PA and underwent I&D. 13% of these patients developed a recurrence of PA. The authors concluded that I&D for PA was safe and effective with minimal adverse effects.

Other authors support the use of more invasive measures such as fistulotomy or fistulectomy (34,35). These authors deem the recurrence rate and FIA formation rate to be a significant downside to conservative measures and I&D. In a small case series, Balaz et al. observed that patients who had upfront fistulotomy/fistulectomy had lower recurrence compared to infants who received I&D (36). Similarly in other retrospective reviews of operative PA cases, both Buddicom et al. and Karlsson et al. found an association of lower PA recurrences if a fistulotomy was initially performed (16,37) Recently a retrospective comparative study between I&D only and I&D with fistulotomy (IDF) found that IDF had a superior cure rate (98.46% vs 80.82%) with lower postoperative fistula formation (38).

An adjunct to surgical management includes the placement of seton which is consistently used in adults. The effective use of the seton in infantile FIA has been reported as early as 2007 (39). In a retrospective review of children ages 0–16 years [median 16 (min, max: 3, 156) months] with prior operative drainage or spontaneous rupture of a PA who presented with a FIA, Yang et al. studied a cohort of 103 patients who underwent seton placement for FIA treatment (40). They found 94.2% of patients achieved complete healing defined by closure of the fistula with no skin breakdown or residual granulation tissue. In another retrospective review, Inuoe et al. found that 35/36 infants who developed a FIA after a PA or presented concurrently exhibited complete healing after seton placement with no complications reported for up to 49.4 months post seton (1). Both authors argue for the safety and efficacy of the seton method in infants.

Another adjunctive interventional approach is the injection of N-utyl Cyanoacrylate (histoacryl) into infants with FIA (41). In an initial study, the use of Histoacryl injection was found to be safe with successful closure of the fistula in 15/17 patients at the two month follow up. No studies have been published comparing the use of Histoacryl to conservative or surgical management.

Overall, surgical management has generally been shown to be an acceptable method of management. Prior abscess and purulence noted at the time of surgery have been found to be risks of recurrence (17,42). However, prospective trials directly comparing surgical techniques are lacking.

Comparison of operative vs. nonoperative management

Multiple studies have demonstrated the efficacy and safety of both conservative and surgical management paradigms. Many researchers have sought to determine the optimal management. Notable comparative studies are summarized in Table 2. All studies are retrospective cohort studies. The main outcomes measured across studies were overall successful cure rate, PA recurrence, and FIA development post management. Of the ten listed studies, two suggested conservative management was associated with better outcomes (3,4), three found that operative management had better outcomes (17,26,28), three found no difference (18,19,31), and two were underpowered to statistically assess the relevant outcomes (9,35).

Each of these studies were independently assessed for quality by the NOS. Most studies did not formally control for potential confounders such as age, use of antibiotics, center, or size of the abscess. As such, confidence in the cohort’s homogeneity between treatment arms is difficult to ascertain. Additionally, four studies define their study population as those with PA and/or FIA at presentation (4,17,18,28). In fact, Neville et al. found the operative group to have a higher proportion of FIA compared to the conservative management (CM) group (28). While considered part of the same disease entity, the FIA presentation may be considered a more severe phenotype. Without controlling for the initial presence of FIA or separating the phenotypes, mixing these two presentations may create unbalanced treatment arms and explain the heterogeneity in results.

Another major confounder is the differing definitions of conservative management and its consistent application across all patients within the conservative management cohort. Neville et al. and Kang et al. considered bedside procedures such as I&D and needle aspiration as conservative management (18,28). Interestingly, they observed a trend towards higher rates of conservative management failure (PA recurrence or FIA formation). Whereas Boenicke, Gong, and Christison-Lagay considered these procedures to be an operation, defining conservative management as strictly non-invasive. Gong et al. found strict conservative management had improved cure rates and less recurrence than I&D alone (4). While Christison-Lagay found that strict conservative management had less risk of FIA formation compared to surgery (3). Interestingly, Boenicke et al. found the opposite trend noting that most patients receiving conservative management ultimately required surgical management (17). Overall, these discrepancies in patient populations and definitions of management highlights the need to develop consensus definitions to conduct robust studies that are comparable.

Despite the limitations of these studies, all studies found that conservative management was safe and demonstrated acceptable levels of cure albeit to varying success. Interestingly, Wang et al. found that I&D with fistulotomy had the highest cure rate (97.9%) and lowest recurrence and FIA formation compared to I&D and conservative management (26). Yet despite this finding, the authors argue a trial of conservative management is prudent given the 80.4% cure rate for conservative management.

Conclusions

Taken together, the current literature seems to support the efficacies of both conservative and operative management. Clinical management tends to be center-specific with either management option resulting in relatively good outcome and low morbidity. Current retrospective cohort studies fail to convincingly demonstrate the superiority of one treatment method. The current management strategy of PA and FIA is summarized in Figure 3.

Figure 3 Summative overview of clinical management schema. Created in BioRender. Lab, W. [2025] https://BioRender.com/cfrpmvl.

Future prospective cohort or randomized control trial are needed to determine evidenced based management. However, there are multiple challenges to such endeavors. First, and possibly most important, the heterogeneity of clinical practice and definitions of conservative management make defining treatment arms difficult. Consensus of conservative management strategies must be established before reproducible clinical trials are employed. Secondly, the relatively uncommon rate of these events would make recruitment challenging. Adding multiple centers would be needed; however, coordinating consistent conservative care would be challenging. At present there are two clinical trials registered aimed at PA in infants. First is a prospective randomized clinical trial in Germany aimed to assess the duration of a cutting seton in pediatric patients 0–18 years old who have a fistula in-ano (NCT05666609) (43). Additionally, while not a comparative trial, a prospective observational study of conservative management is currently underway in China (ChiCTR2300077406) (44). Results from these studies will hopefully add to our knowledge and help delineate the optimal clinical practice for this vulnerable patient population.

Acknowledgments

We thank Biorender.com for providing the platform to create science figures.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://tgh.amegroups.com/article/view/10.21037/tgh-25-73/rc

Peer Review File: Available at https://tgh.amegroups.com/article/view/10.21037/tgh-25-73/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tgh.amegroups.com/article/view/10.21037/tgh-25-73/coif). E.A.P. serves as an unpaid editorial board member of Translational Gastroenterology and Hepatology from January 2022 to December 2026. D.M.A. reports salary comes from the Pediatric Gastro T32 NIH grant (#DK077653). No NIH funds from this grant were used in this project. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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