Bacteriology of anal fistulae

Perianal fistulizing Crohn's disease: Current perspectives on diagnosis, monitoring and management with a focus on emerging therapies

Crohn's disease (CD), a chronic inflammatory bowel disorder, manifests in various phenotypes, with fistulizing perianal CD (CD-PAF) being one of its most severe phenotypes. Characterized by fistula formation and abscesses, CD-PAF impacts 17% to 34% of all CD cases and with a significantly deleterious impact on patient's quality of life, while increasing the risk for anorectal cancers. The pathogenesis involves a complex interplay of genetic, immunological and environmental factors, with cytokines such as tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) playing pivotal roles. Diagnostic protocols require a multi-disciplinary approach including colonoscopy, examination under anesthesia and magnetic resonance imaging. In terms of treatment, biologics alone often prove inadequate, making surgical interventions such as setons and fistula surgeries essential. Emerging therapies such as mesenchymal stem cells are under study. The South Asian context adds layers of complexity, including diagnostic ambiguities related to high tuberculosis prevalence, healthcare access limitations and cultural stigma toward perianal Crohn's disease and ostomy surgery. Effective management necessitates an integrated, multi-disciplinary approach, especially in resource-constrained settings. Despite advances, there remain significant gaps in understanding the disease's pathophysiology and a dearth of standardized outcome measures, underscoring the urgent need for comprehensive research.

Microbiomic signatures of anal fistula and putative sources of microbes

Anal fistula is a common perianal disease that typically develops from an abscess caused by in-flammation in the area. It has long been believed that intestinal microbes play a significant role in its development, considering its close relation to the intestinal environment. This work attempts to identify the microbiomic signatures of anal fistula, and putative sources of microbes by analyzing microbiomes of 7 anal fistula-associated sites in 12 patients. This study found that microbes in anal fistulas may originate from the skin surface in addition to the intestinal tract. This finding was further validated by NMDS analysis, which also indicated that the microbial communities in the inner and outer openings of the fistula were more similar to their surrounding environments. Using MaAslin2, the characteristics of the microbiome were examined, demonstrating a higher similarity between the abundant bacteria in the anal fistula samples and those found on the skin surface. Moreover, pin-to-pair analysis conducted on all subjects consistently showed a higher abundance of skin-sourced bacteria in anal fistulas. This study identifies the microbiomic signatures of anal fistula, and provides novel insights into the origin of microorganisms in anal fistulas.

Management of Perianal Fistulizing Crohn's Disease

Perianal fistulizing Crohn's disease (CD) represents a severe phenotype of CD that is associated with significant morbidity and reduction in quality of life. Perianal fistulizing CD is caused by a complex interplay of genetic predisposition, immune dysregulation, gut dysbiosis, and various unknown physiological and mechanical factors. A multidisciplinary approach is hence required for optimal management . A detailed anatomical description and classification of perianal fistula, including comprehensive clinical, endoscopic, and radiological diagnostic workup, is an important prerequisite to treatment. For simple perianal fistulas, use of antibiotics and immunomodulators, with or without fistulotomy, are appropriate measures. The medical management of complex perianal fistula, on the other hand, requires adequate control of infection before initiation of therapy with immunomodulators. In active complex perianal fistula, anti-tumor necrosis factors remain the most accepted therapy, with concomitant use of antibiotics or immunomodulators enhancing the efficacy. For patients refractory to anti-tumor necrosis factors, treatment with anti-integrins, anti-interleukins, and small molecules is being evaluated. Mesenchymal stem cells, hyperbaric oxygen therapy, and exclusive enteral nutrition have also been investigated as adjunct therapies. Despite the expansion of the medical armamentarium, a large proportion of the patients require surgical interventions. In this review, we provide an up-to-date overview of the pathophysiology, clinical presentation, diagnosis, and medical management of perianal fistulizing CD. A brief overview of the surgical management of perianal fistulizing CD is also provided.

Diagnosis and Classification of Fistula from Inflammatory Bowel Disease and Inflammatory Bowel Disease-Related Surgery

Fistula in inflammatory bowel disease (IBD) is a well-known yet poorly understood phenotype. Pathophysiology is largely based on the activation of the epithelial-mesenchymal transition (EMT); however, interactions with the microbiome, genetics, mechanical stress and the presence of stricturing disease, and surgical complications play a role. Perianal penetrating disease represents a more severe phenotype in IBD. Pouch-associated fistula can arise as a result of an anastomotic leak, surgical complications, or Crohn's disease (CD) of the pouch. Classification is site-dependent, includes a range of severity, and informs management. It is important to determine associated symptoms and recognize the complex interplay of underlying etiologies to form the basis of appropriate care.

A Microbial Signature for Paediatric Perianal Crohn's Disease

BACKGROUND AND AIMS

Perianal fistulising disease can affect up to 25% of patients with Crohn's disease [CD] and lead to significant morbidity. Although the role of the gut microbiota in inflammatory bowel disease [IBD] has been increasingly recognised, its role in fistula development has scarcely been studied. Here, we aimed to define the microbial signature associated with perianal fistulising CD in children.

METHODS

A prospective observational study including children age 6-18 years with a diagnosis of perianal fistulising CD was conducted. Stool samples and rectal and perianal fistula swabs were collected. Stool samples and rectal swabs from children with CD without perianal disease and healthy children were included as comparison. Whole shotgun metagenomic sequencing was performed.

RESULTS

A total of 31 children [mean age 15.5 ± 3.5 years] with perianal CD were prospectively enrolled. The fistula-associated microbiome showed an increase in alpha diversity and alteration in the abundance of several taxa compared with the rectal- and faecal-associated microbiome with key taxa belonging to the Proteobacteria phylum. Genes conferring resistance to the clinically used antibiotic regimen ciprofloxacin and metronidazole were found in the three sample types. In comparison with children without the perianal phenotype [N = 36] and healthy controls [N = 41], the mucosally-associated microbiome of children with perianal CD harboured a reduced butyrogenic potential. Linear discriminant analysis identified key taxa distinguishing the rectal mucosally-associated microbiome of children with perianal CD from children without this phenotype.

CONCLUSIONS

The microbial community within CD-related anorectal fistula is compositionally and functionally unique. Taken together, these findings emphasise the need to better understand the ecosystem of the fistula milieu to guide development of novel microbiome-based strategies in this CD phenotype.

Time to Revisit Disease Classification in Inflammatory Bowel Disease: Is the Current Classification of Inflammatory Bowel Disease Good Enough for Optimal Clinical Management?

Inflammatory bowel disease (IBD), historically subdivided into Crohn's disease and ulcerative colitis, is a very heterogeneous condition. While the tendency in medicine is to try to reduce complexity, IBD is a disease that cannot justify a one-size-fits-all principle. Our current clinical classification tools are suboptimal and need further refinement to capture, at least in part, the variety of phenotypes encountered in daily clinical practice. Although these revised classification tools alone will not be sufficient and should be complemented by more detailed molecular subclassifications, optimized clinical phenotypes can contribute to improved trial designs, future translational research approaches, and better treatment outcomes. In the current review, we discuss key clinical features important in IBD disease heterogeneity, tackle limitations of the current classification systems, propose some potential improvements, and raise priorities for future research in this domain.

Does Anti-TNF-α Therapy Affect the Bacteriological Profile of Specimens Collected from Perianal Lesions? A Retrospective Analysis in Patients with Crohn's Disease

Anal abscesses and fistulas are potential complications of Crohn’s disease (CD). Chronic immunosuppression, loose stools, and poor wound healing in this population present challenges to the management of perianal diseases. The purpose of the study was to determine the predominant bacterial species found in specimens from perianal lesions causing anal abscess and/or fistula drainage in hospitalized patients, and to compare the number and type of microorganisms isolated from samples taken from patients undergoing biological therapy or traditionally treated. The outcomes of studies of patients treated for anal abscesses or fistulas from 2017 to 2019 were evaluated. Data obtained from medical records included culture and antibiotic sensitivity results of swabs from perianal lesions of isolated microorganisms. A total of 373 swabs were collected from perianal lesions during the analysis period, including 51 (49 positive samples) from patients with CD. The predominant pathogen was Escherichia coli (55%, p < 0.001), the second most common microorganism was Staphylococcus aureus (14.3%, p < 0.001). In vitro susceptibility testing showed E. coli, ESBL (strain with Extended Spectrum Beta-Lactamase) in five cases, S. aureus, MRSA (methicillin-resistant S. aureus -resistant to all beta-lactam antibiotics: penicillins with inhibitors, cephalosporins, monobactams, carbapenems, except for ceftaroline) in one sample. Biologic therapy does not affect the type of microorganisms isolated from perianal abscesses in patients with CD.

Differences in amino acid and lipid metabolism distinguish Crohn's from idiopathic/cryptoglandular perianal fistulas by tissue metabonomic profiling and may offer clues to underlying pathogenesis

INTRODUCTION

Few studies have investigated perianal fistula etiopathogenesis, and although the cryptoglandular theory is widely accepted in idiopathic cases, in Crohn's disease, it is thought to involve the interplay between microbiological, immunological and genetic factors. A pilot study was conducted to assess for metabolic variations in Crohn's perianal fistula tissue that might differ from that of idiopathic (cryptoglandular) perianal fistula tissue as a comparator. The goal was to identify any potential biomarkers of disease, which may improve the understanding of pathogenesis.

AIMS AND METHODS

Fistula tract biopsies were obtained from 30 patients with idiopathic perianal fistula and 20 patients with Crohn's anal fistula. Two different assays were used in an ultra-high-performance liquid chromatography system coupled with a mass spectrometric detector to achieve broad metabolome coverage. Univariate and multivariate statistical data analyses were used to identify differentiating metabolic features corresponding to the perianal fistula phenotype (i.e. Crohn's disease vs. idiopathic).

RESULTS

Significant orthogonal partial least squares discriminant analysis predictive models (validated with cross-validated-analysis of variance P value <0.05) differentiated metabolites from tissue samples from Crohn's vs. idiopathic anal fistula patients using both metabolic profiling platforms. A total of 41 metabolites were identified, suggesting alterations in pathways, including amino acid, carnitine and lipid metabolism.

CONCLUSION

Metabonomics may reveal biomarkers of Crohn's perianal fistula. Further work in larger numbers is required to validate the findings of these studies as well as cross-correlation with microbiome work to better understand the impact of host-gut/environment interactions in the pathophysiology of Crohn's and idiopathic perianal fistulas and identify novel therapeutic targets.

Significant presence of biofilm-producing gut-derived bacteria in anal fistula of chronic duration

Fistula-in-ano though not a life-threatening condition, yet its symptoms often significantly impact patients' social, intimate, and work lives. There is an established role of bacterial microflora in acute infections. However, we proposed that biofilm-forming organisms might be present in the microflora of anal fistula of prolonged duration. This aspect has rarely been studied earlier. Therefore, the study describes the microbiology of anal fistula and the biofilm-forming capacity of the isolated organisms. A total of 30 patients were included in the study as per the criteria. Anal fistula tissue sample, tissue fluid, and blood samples were collected from each individual. The collected specimens were detected for the presence of aerobic and anaerobic microflora through standard microbiological method and polymerase chain reaction. Furthermore, the role of biofilm formation by microtitre plate assay and serum matrix metalloproteinases-9 was also studied. The result showed significant predominance of gut-derived microflora with high-to-moderate biofilm-producing ability in anal fistulas of prolonged duration. The study emphasises the presence of biofilm-forming bacteria in chronic, non-healing fistula.

Evaluation of animal models of Crohn's disease with anal fistula (Review)

Anal fistula is a common and serious complication of Crohn's disease (CD). A sufficiently suitable animal model that may be used to simulate this disease is yet to be established. The aim of the present review was to summarize the different characteristics and experimental methods of commonly used animal models of CD with anal fistula. Electronic databases were searched for studies reporting on the use of this type of animal model. A total of 234 related articles were retrieved, of which six articles met the inclusion criteria; these were used as references for the present review article. The characteristics of the animal models, the advantages and disadvantages of the modeling methods and the similarities with patients with CD and anal fistula were summarized and analyzed. The evidence suggests that a sufficiently suitable animal preclinical model requires to be established.

Clinical, microbiological, immunological and imaging characteristics of tunnels and fistulas in hidradenitis suppurativa and Crohn's disease

Hidradenitis suppurativa (HS) tunnels and Crohn's disease (CD) fistulas are a challenge to treat. Although pathogenic similarities have been described between HS and CD, recent studies indicate that clinical, microbiological, immunological and imaging characteristics differ between these diseases. This review highlights the differences between HS tunnels and CD fistulas. Next-generation sequencing studies demonstrate a microbiome in HS tunnels dominated by Porphyromonas spp., Prevotella spp. whereas no specific bacteria have been associated with cutaneous CD. Immunologically, TNF has been found upregulated in HS tunnels along with various interleukins (IL-8, IL-16, IL-1α and IL-1β). In CD fistulas, Th1, Th17, IL-17, IFN-ɤ, TNF and IL-23 are increased. US imaging is an important tool in HS. US of HS tunnels depict hypoechoic band-like structure across skin layers in the dermis and/or hypodermis connected to the base of a widened hair follicle. In CD, MR imaging of simple perianal fistulas illustrates a linear, non-branching inflammatory tract relating to an internal opening in the anus or low rectum and an external opening to the skin surface. An increased awareness of the immediate potential differences between HS tunnels and CD fistulas may optimize treatment regimens of these intractable skin manifestations.

Review article: pathogenesis of Crohn's perianal fistula-understanding factors impacting on success and failure of treatment strategies

BACKGROUND

Evidence from groups who have studied fistula aetiology and extrapolation from interventional studies supports a multifactorial hypothesis of Crohn's perianal fistula, with several pathophysiological elements that may contribute to fistula formation, persistence and resistance to treatment.

AIM

An evidence synthesis of current understanding of pathophysiological factors underlying Crohn's perianal fistula is presented, exploring the fundamental reasons why some treatments succeed and others fail, as a means of focussing clinical knowledge on improving treatment of Crohn's perianal fistula.

METHODS

Evidence to support this review was gathered via the Pubmed database. Studies discussing pathophysiological factors underpinning perianal fistula, particularly in Crohn's disease, were reviewed and cross-referenced for additional reports.

RESULTS

Pathophysiological factors that impact on success or failure of interventions for Crohn's perianal fistulae include the high-pressure zone, obliterating the dead space, disconnecting the track from the anus, removing epithelialisation, eradicating sepsis and by-products of bacterial colonisation, correcting abnormalities in wound repair and removing the pro-inflammatory environment which allows fistula persistence. Most current interventions for Crohn's perianal fistulae tend to focus on a single, or at best two, aspects of the pathophysiology of Crohn's anal fistulae; as a result, failure to heal fully is common.

CONCLUSIONS

For an intervention or combination of interventions to succeed, multiple factors must be addressed. We hypothesise that correct, timely and complete attention to all of these factors in a multimodal approach represents a new direction that may enable the creation of an effective treatment algorithm for Crohn's anal fistula.

The treatment of anal fistula: second ACPGBI Position Statement - 2018

It is over 10 years since the first ACPGBI Position Statement on the management of anal fistula was published in 2007. This second edition is the result of scrutiny of the literature published during this time; it updates the original Position Statement and reviews the published evidence surrounding treatments for anal fistula that have been developed since the original publication.

Perianal fistulizing Crohn's disease: pathogenesis, diagnosis and therapy

Perianal fistulizing Crohn's disease has a major negative effect on patient quality of life and is a predictor of poor long-term outcomes. Factors involved in the pathogenesis of perianal fistulizing Crohn's disease include an increased production of transforming growth factor β, TNF and IL-13 in the inflammatory infiltrate that induce epithelial-to-mesenchymal transition and upregulation of matrix metalloproteinases, leading to tissue remodelling and fistula formation. Care of patients with perianal Crohn's disease requires a multidisciplinary approach. A complete assessment of fistula characteristics is the basis for optimal management and must include the clinical evaluation of fistula openings, endoscopic assessment of the presence of proctitis, and MRI to determine the anatomy of fistula tracts and presence of abscesses. Local injection of mesenchymal stem cells can induce remission in patients not responding to medical therapies, or to avoid the exposure to systemic immunosuppression in patients naive to biologics in the absence of active luminal disease. Surgery is still required in a high proportion of patients and should not be delayed when criteria for drug failure is met. In this Review, we provide an up-to-date overview on the pathogenesis and diagnosis of fistulizing Crohn's disease, as well as therapeutic strategies.

Pathogenesis and persistence of cryptoglandular anal fistula: a systematic review

Anal fistulas continue to be a problem for patients and surgeons alike despite scientific advances. While patient and anatomical characteristics are important to surgeons who are evaluating patients with anal fistulas, their development and persistence likely involves a multifaceted interaction of histological, microbiological, and molecular factors. Histological studies have shown that anal fistulas are variably epithelialized and are surrounded by dense collagen tissue with pockets of inflammatory cells. Yet, it remains unknown if or how histological differences impact fistula healing. The presence of a perianal abscess that contains gut flora commonly leads to the development of anal fistula. This implies a microbiological component, but bacteria are infrequently found in chronic fistulas. Recent work has shown an increased expression of proinflammatory cytokines and epithelial to mesenchymal cell transition in both cryptoglandular and Crohn's perianal fistulas. This suggests that molecular mechanisms may also play a role in both fistula development and persistence. The aim of this study was to examine the histological, microbiological, molecular, and host factors that contribute to the development and persistence of anal fistulas.

Immunopathological characterization of cryptoglandular anal fistula: a pilot study investigating its pathogenesis

AIM

The pathogenesis of cryptoglandular anal fistula (AF) is still under debate. Tissue inflammation could play a primary role. The pathological process of epithelial mesenchymal transition (EMT) might be involved but has never been investigated.

METHOD

In a prospective pilot study, 12 patients with an AF had a fistulectomy. The excised track was divided into proximal (intrasphincteric) and distal (extrasphincteric) parts which were subjected to standard histopathological examination. The cytokines IL-8 and IL-1beta were analysed as markers of inflammation, while EMT was evaluated by expression of TGF-beta, Vimentin, Zeb-1, Snail and E-cadherin. The mRNA and protein expression of these molecules was investigated by real-time PCR (RT-PCR), Western blot analysis and immunohistochemistry and was compared with that of the normal adjacent tissue.

RESULTS

Chronic inflammation and granulation tissue and a stratified epithelium were evident on standard histopathological examination. The cytokine IL-8 was more expressed in the proximal than the distal part of the track (fold increase 4.34 vs 3.60), while the reverse was found for IL-1beta (fold increase 1.33 vs 2.01); both were more intensely expressed compared with the normal anal mucosa. EMT was demonstrated, in both proximal and distal parts of the track, with an increase of TGF-beta, Vimentin, Zeb-1 and Snail and a mean decrease of E-cadherin. Western blot analysis and immunohistochemistry confirmed the protein expression.

CONCLUSION

The study suggests that chronic inflammation is present in cryptoglandular fistulas. The inflammatory pattern might be different in the proximal than in the distal part of the fistula track. The cytokines IL-1beta and IL-8 could play a possible role in fistula formation. The study demonstrates for the first time the potential importance of EMT in the pathogenesis of cryptoglandular AF.

Results of the Fifth Scientific Workshop of the ECCO (II): Pathophysiology of Perianal Fistulizing Disease

The fifth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on the relevance of fistulas to the disease course of patients with Crohn's disease (CD). The objectives were to reach a better understanding of the pathophysiological mechanisms underlying the formation of CD fistulas; to identify future topics in fistula research that could provide insights into pathogenesis; to develop novel therapeutic approaches; and to review current therapeutic strategies (with clarification of existing approaches to prevention, diagnosis and treatment). The results of the workshop are presented in two separate manuscripts. This manuscript describes current state-of-the-art knowledge about fistula pathogenesis, including the roles of epithelial-to-mesenchymal transition and cytokine matrix remodelling enzymes, and highlights the common association between fistulas and stenosis in CD. The review also considers the possible roles that genetic predisposition and intestinal microbiota play in fistula development. Finally, it proposes future directions and needs for fistula research that might substantially increase our understanding of this complex condition and help unravel novel therapeutic strategies and specific targets for treatment. Overall, it aims to highlight unanswered questions in fistula research and to provide a framework for future research work.

What role do bacteria play in persisting fistula formation in idiopathic and Crohn's anal fistula?

AIM

The aetiology of Crohn's disease-related anal fistula remains obscure. Microbiological, genetic and immunological factors are thought to play a role but are not well understood. The microbiota within anal fistula tracts has never been examined using molecular techniques. The present study aimed to characterize the microbiota in the tracts of patients with Crohn's and idiopathic anal fistula.

METHOD

Samples from the fistula tract and rectum of patients with Crohn's and idiopathic anal fistula were analysed using fluorescent in situ hybridization, Gram staining and scanning electron microscopy were performed to identify and quantify the bacteria present.

RESULTS

Fifty-one patients, including 20 with Crohn's anal fistula, 18 with idiopathic anal fistula and 13 with luminal Crohn's disease and no anal fistula, were recruited. Bacteria were not found in close association with the luminal surface of any of the anal fistula tracts.

CONCLUSION

Anal fistula tracts generally do not harbour high levels of mucosa-associated microbiota. Crohn's anal fistulas do not seem to harbour specific bacteria. Alternative explanations for the persistence of anal fistula are needed.

CT of acute perianal abscesses and infected fistulae: a pictorial essay

Computed tomography (CT) is an effective, readily available diagnostic imaging tool for evaluation of the emergency room (ER) patients with the clinical suspicion of perianal abscess and/or infected fistulous tract (anorectal sepsis). These patients usually present with perineal pain, fever, and leukocytosis. The diagnosis can be easy if the fistulous tract or abscess is visible on inspection of the perianal skin. If the tract or abscess is deep, then the clinical diagnosis can be difficult. Also, the presence of complex tracts or supralevator extension of the infection cannot be judged by external examination alone. Magnetic resonance imaging (MRI) is the best imaging test to accurately detect fistulous tracts, especially when they are complex (Omally et al. in AJR 199:W43-W53, 2012). However, in the acute setting in the ER, this imaging modality is not always immediately available. Endorectal ultrasound has also been used to identify perianal abscesses, but this modality requires hands-on expertise and can have difficulty localizing the offending fistulous tract. It may also require the use of a rectal probe, which the patient may not be able to tolerate. Contrast-enhanced CT is a very useful tool to diagnose anorectal sepsis; however, this has not received much attention in the recent literature (Yousem et al. in Radiology 167(2):331-334, 1988) aside from a paper describing CT imaging following fistulography (Liang et al. in Clin Imaging 37(6):1069-1076, 2013). An infected fistula is indicated by a fluid-/air-filled soft tissue tract surrounded by inflammation. A well-defined round to oval-shaped fluid/air collection is indicative of an abscess. The purpose of this article is to demonstrate the usefulness of contrast-enhanced CT in the diagnosis of acute anorectal sepsis in the ER setting. We will discuss the CT appearance of infected fistulous tracts and abscesses and how CT imaging can guide the ER physician in the clinical management of these patients.

Diagnosis and treatment of perianal Crohn disease: NASPGHAN clinical report and consensus statement

Inflammatory bowel disease is a chronic inflammatory disorder of the gastrointestinal tract that includes both Crohn disease (CD) and ulcerative colitis. Abdominal pain, rectal bleeding, diarrhea, and weight loss characterize both CD and ulcerative colitis. The incidence of IBD in the United States is 70 to 150 cases per 100,000 individuals and, as with other autoimmune diseases, is on the rise. CD can affect any part of the gastrointestinal tract from the mouth to the anus and frequently will include perianal disease. The first description connecting regional enteritis with perianal disease was by Bissell et al in 1934, and since that time perianal disease has become a recognized entity and an important consideration in the diagnosis and treatment of CD. Perianal Crohn disease (PCD) is defined as inflammation at or near the anus, including tags, fissures, fistulae, abscesses, or stenosis. The symptoms of PCD include pain, itching, bleeding, purulent discharge, and incontinence of stool. In this report, we review and discuss the etiology, diagnosis, evaluation, and treatment of PCD.

Assessment of microbiota and peptidoglycan in perianal fistulas

Transanal advancement flap repair has been advocated as the treatment of choice for high transsphincteric perianal fistulas, but fails in 1 of every 3 patients. Persistence of the fistula after flap repair might be the result of ongoing disease in the remaining fistula tract. In 10 specimens of the distal part of the fistula, microbiota was assessed by means of conventional microbiological culture and 16S rRNA gene sequencing. Proinflammatory bacterial peptidoglycan and recognition proteins were assessed by immunohistochemistry. Bacterial species were bowel derived, skin derived, or a combination of both. No mycobacterium species were identified. 16S rRNA gene sequencing failed to identify bacteria in all but 1 specimen, most likely as a result of low numbers of organisms. Peptidoglycan was detected in 90% of the patients, and a host response to peptidoglycan in 60%. Therefore, we suggest that peptidoglycan might play a role in the ongoing inflammation in perianal fistulas.

Anal fistula: an unusual presentation of tuberculosis in a migrant health care professional

We present a case of a young health care professional from the Indian subcontinent, who presented with a low anal fistula and underwent exploration, debridement and fistulotomy twice. The initial working diagnosis was Crohn's disease. However, Mycobacterium tuberculosis, fully sensitive to all first-line drugs was cultured from the specimens sent from the second surgical procedure. On initiation of anti-tubercular therapy the symptoms improved within 5 weeks. The origin of the patient, high index of suspicion for non-infectious reactivation of tuberculosis in migrant health care workers, importance of a proper history taking including previous exposure and diagnostic workup is stressed.

Thread-dragging therapy in treatment of a rat model of infected subcutaneous fistula

OBJECTIVE

This study was to develop an experimental rat model of subcutaneous fistula induced by bacteria infection and treat it with thread-dragging therapy.

METHODS

A spring-gauze was surgically implanted into 24 male Sprague-Dawley rats' dorsal muscles, respectively, then mixed Staphylococcus aureus and Escherichia coli were injected into the spring-gauze. After 45 d, all the spring-gauzes were removed from the rats under anesthesia. X-ray and ultrasound were performed to assess the fistula tract. Each rat was examined by a fistula probe and four rats were randomly selected for histological assessment. The residual rats were randomly divided into two groups. Group A was treated with thread-dragging therapy, and group B was treated with fistulotomy. The healing time and body weight of the two groups were compared.

RESULTS

On the 45th day of the spring-gauze implantation, imaging assessment proved a tract with two openings in all rats and histological results proved that lumen and surrounding granulation tissue with epithelium were similar to the features of fistula in human beings. The mean healing time of rats in group A was shorter than that of the rats in group B (P<0.01). The body weight of rats in group A was heavier than that of the rats in group B on the 7th and 14th day after surgery, respectively (P<0.05).

CONCLUSION

A rat model of subcutaneous fistula induced by mixed Staphylococcus aureus and Escherichia coli infection was successfully established. Traditional Chinese medicine thread-dragging therapy is less invasive and safer than fistulotomy.

Etiology of perianal Crohn's disease: role of genetic, microbiological, and immunological factors

Perianal fistulation is a common complication of Crohn's disease (CD). Fistulating perianal CD appears to represent a distinct phenotype of CD, separate from luminal fistulating disease, with differing disease behavior and which often requires different therapeutic strategies. The etiology of Crohn's perianal fistulae appears to have genetic, microbiological, and immunological components. Relationships with IBD5, which codes for the organic/cation transporter and IRGM, important in the autophagy pathway, have been identified but further genetic associations remain elusive. The partially efficacious use of antibiotics and fecal diversion imply a microbiological component and, similarly, the partial efficacy of immunosuppressants and anti-tumor necrosis factor alpha (TNFalpha) treatments suggest not only that an immunological process is taking place, but also that microbiota alone cannot account for the pathogenesis. Recent work implicates failures in the tissue injury/repair process with myofibroblasts, matrix metalloproteinases, and an epithelial-to-mesenchymal transition being possible culprits. We examine these areas in a review of the current understanding of the etiology of Crohn's perianal fistulae.

An experimentally successful new sphincter-conserving treatment for anal fistula

PURPOSE

A new sphincter-conserving treatment was evaluated in a porcine model.

METHODS

A total of 36 fistulas were created by procedures that have been published previously. At fistula induction a skin biopsy was taken from which to culture fibroblasts. Four weeks after induction, when fistulas were well established, the fistula tracks were cored out. Collagen paste modified from Permacol injection (Covidien, Mansfield, MA) was then used as a solitary infill material in 11 tracks, cultured autologous fibroblasts being added to this in a further 18 tracks. The track was cored out in seven controls, but these tracks were not treated with infill material. All of the internal and external openings were closed. Anorectal excision was then carried out under terminal anesthesia at 2 to 12 weeks. Histologic examination of individual tracks was performed by an experienced pathologist.

RESULTS

In this quadruped all of the infilled tracks healed, autologous fibroblasts having the best tissue integration, but only two of seven control tracks healed.

CONCLUSIONS

Removal of the fistula track followed by injection of collagen healed all of the cases. The addition of autologous fibroblasts improved the histologic appearance of the tracks. A pilot study in human fistula patients is in progress.

Assessment of antimicrobial microspheres as a prospective novel treatment targeted towards the repair of perianal fistulae

BACKGROUND

None of the proposed materials tested for the management of perianal fistulae has proven to be a definitive treatment.

AIM

To assess a new repair scaffold and drug delivery device conceived to target perianal fistula repair.

METHODS

Poly(D,L-lactide-co-glycolide) porous microspheres containing either antibacterial silver-releasing degradable phosphate glass or metronidazole were prepared using thermally induced phase separation.

RESULTS

Ion- and drug-release profiling of the microspheres revealed continued release of silver ions from microspheres filled with silver-doped phosphate glass and high encapsulation efficiency for metronidazole [78% and 82% for microspheres loaded with 2.5% and 1.3% (w/w), respectively]. Microbicidal activity was confirmed by growth inhibition of bacterial species (Staphylococcus aureus, Escherichia coli and Bacteroides fragilis), which characteristically dominate the colonization of perianal fistula tracts. Microspheres containing >3 mol% silver or metronidazole resulted in strong bacterial inhibition/kill against B. fragilis; the presence of one sphere containing >3 mol% silver had a potent inhibitory effect against all the microbes studied. Microspheres became rapidly integrated with host tissue following subcutaneous implantation into a rodent wound model.

CONCLUSION

The study demonstrates a novel scaffold for guided tissue regeneration providing local release of antimicrobial agents sufficient to counter bacterial colonization and warrants further investigation.

Antimicrobial peptides in chronic anal fistula epithelium

OBJECTIVE

Anal fistulas are the result of chronic infection of an intersphincteric gland. Despite the passage through mesenchymal tissue, fistulas seldom lead to systemic infection. Antimicrobial peptides are secreted by a variety of epithelia, belonging to the innate immune system and are potential factors contributing to infection control. The aim of this study was to investigate whether epithelium is present in the fistulas and what the origin might be.

MATERIAL AND METHODS

Forty-seven chronic anal fistulas from patients, excluding Crohn's disease, were compared with healthy rectal and perianal control tissue. Expression of antimicrobial peptide mRNA was analysed by real-time polymerase chain reaction (RT-PCR) and immunohistochemistry. Tissue was further studied by cytokine and cytokeratin staining.

RESULTS

Chronic anal fistulas express high levels of hBD-2 and hBD-3 and the newly identified antimicrobial peptides RNase7 and psoriasin compared to rectal mucosa from control patients. Perianal skin has almost identical levels of RNase7 and psoriasin expression to those in fistulas. IL-1b and IL-8 were the only cytokines detectable in fistulas. Fistulas are lined with squamous epithelium that expresses identical cytokeratines as skin.

CONCLUSIONS

Epithelialization and local production of antimicrobial peptides in anal fistulas serve as defence mechanisms to prevent local and systemic infection by microbes from faeces passing through the fistula tract.

Perianal fistulas in Crohn's disease are predominantly colonized by skin flora: implications for antibiotic treatment?

In this study we aimed to determine the microorganisms found in perianal fistulas in Crohn's disease and whether treatment with ciprofloxacin affects these microorganisms. Thirteen patients (males/females, 7/6; median age, 34 years; range, 18-61 years) with fistulas were treated with infliximab, 5 mg/kg intravenously, at weeks 6, 8, and 12 and randomized to double-blind treatment with ciprofloxacin, 500 mg bd (n = 6), or placebo (n = 7) for 12 weeks. Samples were taken at baseline and at weeks 6 and 18. In the ciprofloxacin group 10 different genera of microorganisms were identified, while 13 genera could be identified in the placebo group. Gram-negative enteric floras were present in a small minority. The genera found in patients with perianal fistulas were predominantly gram-positive microorganisms. Therefore, antimicrobial treatment should be directed toward these microorganisms.

Pilot study: fibrin sealant in anal fistula model

PURPOSE

The aim of this study was to investigate the failure of fibrin sealant treatment for fistula-in-ano in an experimental porcine model and to determine histologic changes associated with the sealant and setons.

METHODS

Three surgically created fistulas were treated by seton drainage in each of eight male pigs. After 26 days, magnetic resonance imaging was performed and setons were removed. Two pigs were killed as controls for stereologic histologic fistula track assessment. In six, fistulas were curetted, and in four the fistulas were treated with fibrin sealant. In these four sealant and two seton pigs, magnetic resonance imaging was repeated a median of 47.5 days after fistula formation. The pigs were killed and stereologic histologic fistula track examination was performed to determine granulation tissue and fistula lumen volumes. These values were compared among control, seton, and sealant groups over time, and related to fistula volumes derived from magnetic resonance imaging.

RESULTS

Sealant was not visible microscopically within tracks, although some sections revealed a foreign body-type reaction. On stereologic assessment, granulation tissue volumes were smaller in sealant and seton groups than in controls (median, 88 vs. 187 vs. 453 mm3, respectively; P = 0.002) and decreased over time (median, 408 and 152 mm3 (Day 42) vs. 88 and 75 (Day 53), respectively; P = 0.002). Fistula lumen (P < 0.001), and granulation tissue combined with fistula lumen volumes (P = 0.002) were similarly smaller. Magnetic resonance imaging of fistula intensity was less in the sealant group than in the seton group and controls (mean, 777 vs. 978 vs. 1214 units/mm2, P = 0.003). Magnetic resonance imaging fistula volumes were least in sealant and seton groups vs. controls (P = 0.024), decreasing significantly in the sealant group over time (P = 0.018). No direct relationship was found between imaging and histologic volumes.

CONCLUSIONS

In an experimental porcine model of anal fistula, granulation tissue was still present, albeit diminished, following track curettage combined with seton or sealant therapy, and was minimal in the sealant group, confirming some benefit from this procedure. Eradication of all longstanding granulation tissue may ensure complete success of fibrin sealant therapy.

Tuberculous anal sepsis: report of clinical features in 20 cases

INTRODUCTION

Tuberculosis is a neglected cause of anal sepsis, often is not recognized, and therefore is not treated properly.

METHOD

All patients were reviewed who had tuberculous anal sepsis diagnosed by histology reports of fistulectomy specimens or abscess scrapings from January 1990 to April 1999.

RESULTS

Twenty patients (median age, 53 years; 18 males) with anal tuberculous sepsis were identified. They presented with abscesses (n = 2), abscesses and fistulas (n = 6), or fistulas (n = 12). All patients had a long history of anal complaints (3 months to 20 years), for which 15 patients were operated on previously. Nearly all fistulas (17/18) were complex, and secondary tracks or additional complicating features were common, even at first presentation. Eight patients had active concurrent pulmonary tuberculosis, and six showed evidence of previous pulmonary tuberculosis. Six patients had no signs of concurrent or previous tuberculosis elsewhere. Recurrence was observed only in cases where tuberculosis was initially not recognized, and antitubercular treatment therefore was not started.

CONCLUSION

Contrary to views held previously, anal tubercular sepsis seems to have characteristic clinical features. It should be considered in cases of known pulmonary or extrapulmonary tuberculosis or if anal sepsis is persistent, recurrent, or complex in nature.

Anorectal abscess and fistula

Anorectal abscesses and fistulas are seen commonly in the primary care practice. An abscess forms as the result of obstruction of an anal gland, with resulting retrograde infection. An anal fistula simply represents the chronic phase of a perianal abscess. The history generally is diagnostic, and special studies usually are not required. Treatment is surgical, with good results.

Does HIV status influence the anatomy of anal fistulas?

PURPOSE

Although anorectal disease is common in human immunodeficiency virus-positive patients, little is known about the type and anatomic distribution of anal fistulas in this patient group. The aim of this study was to compare anatomic characteristics of anal fistulas in human immunodeficiency virus-positive patients with those in human immunodeficiency virus-negative patients by use of a retrospective chart review.

METHODS

The charts of 146 male patients younger than 50 years with an anal fistula were reviewed. Incomplete fistulas referred to those tracts arising from an internal opening into either a blind sinus or an undrained abscess cavity.

RESULTS

There were 60 human immunodeficiency virus-positive patients and 86 human immunodeficiency virus-negative patients. Mean age of the human immunodeficiency virus-positive patient group was 37 years vs. 40 years for the human immunodeficiency virus-negative patient group. Thirty-one human immunodeficiency virus-positive patients (52 percent) were classified as having AIDS, and the remaining 29 patients (48 percent) were asymptomatic. Mean T helper cell count in the human immunodeficiency virus-positive patient group was 277 cells per microliter. Fistulous tracts were intersphincteric (n = 56), transsphincteric (n = 41), suprasphincteric (n = 2), and incomplete (n = 47). Incomplete fistulas were identified in 33 (55 percent) human immunodeficiency virus-positive patients vs. 14 (16 percent) human immunodeficiency virus-negative patients (P < 0.001). Of the 47 incomplete fistulas, 37 (79 percent) were found in association with an abscess cavity. All ten patients with an incomplete fistula into a blind sinus were human immunodeficiency virus-positive. The incidence of an incomplete fistula without an abscess was significantly higher in the human immunodeficiency virus-positive patient group (17 percent) compared with the human immunodeficiency virus-negative patient group (0 percent; P < 0.001).

CONCLUSIONS

Anal fistulas in HIV-positive patients arise from the dentate line in similar locations to human immunodeficiency virus negative patients. However, human immunodeficiency virus-positive patients were more likely to have incomplete anal fistulas than human immunodeficiency virus-negative patients. Furthermore, human immunodeficiency virus-positive patients are predisposed to incomplete fistulas leading into a blind sinus.

Rectal submucosal tumor-like lesion originating from intestinal tuberculosis

We present the case of a 55-year-old man who underwent transsacral local excision for a rectal submucosal tumor-like lesion suspected to originate from tuberculosis. The lesion, 2 cm in size, was found incidentally in the posterior wall of the lower rectum during anal fistulectomy. The lesion was apart from the primary crypt of the anal fistula. Barium enema and colonoscopy revealed a protuberant submucosal growth with a shallow depression of the overlying mucosa. Although computed tomography and magnetic resonance imaging showed a well defined round mass within the rectal wall, digital rectal examination suggested extramural origin. Since repeated endoscopic biopsies were negative, we selected the transsacral approach for excisional biopsy to achieve histological diagnosis. The lesion was confined to the rectal wall and the full-thickness rectal wall was excised. Histologically, a foreign-body granuloma with acute inflammation was the main component of the lesion. Caseating granulomas and Langhans' giant cells, consistent with tuberculosis, were also found.

Persistence of idiopathic anal fistula may be related to epithelialization

Anal fistulas may fail to heal because of continuing disease within the intersphincteric anal glands. Histological studies of the intersphincteric component of 18 consecutive idiopathic anal fistulas show that fistula persistence may be caused by epithelialization of the fistula track from internal or external openings. Some fistulas are lined by epithelium similar to that of anal gland ducts, but this may also represent epithelium derived from the transitional zone of the anal canal. Persistence may be related more to non-specific epithelialization of the track than to a chronically infected anal gland.

Anovaginal fistulae

Anovaginal fistulae are an uncommon type of anal fistulous disease. The symptoms can be minimal but frequently are disabling. Obstetric injury is the most common cause, but many other disease states can produce this communication. It is important to completely evaluate the patient before any consideration is given to surgical correction. This includes evaluation of the function of the anal sphincter, involvement of any other organ systems, and tissue diagnosis if the cause is uncertain. It is also important to delay surgical correction until any inflammation and infection have subsided. Many different surgical procedures have been reported in the literature for repair of these fistulae, most with success rates of at least 75%. It is important to remember the physiologic high-pressure zone in the anal canal when planning surgical correction. Fistulae secondary to inflammatory bowel disease have a markedly reduced success rate, and the presence of anal Crohn's disease should be suspected, especially when a previous surgical repair has failed. Medical management should be used either to heal the fistula nonoperatively or to improve the surgical result. Finally, some fistulae secondary to neoplasia, radiation, anastomotic leaks, or inflammatory bowel disease require diversion of the fecal stream either as an adjunct to repair or as definitive treatment. Proper preoperative evaluation of the patient and selection of the operation provide the optimum result.

Results of a policy of selective immediate fistulotomy for primary anal abscess

A prospective study of a policy of selective immediate fistulotomy in the management of acute primary anal abscesses was performed. Eighty-nine patients (74%) underwent simple drainage only, as no internal openings were found during drainage of pus (group A). Thirty-one patients (26%) had drainage of pus and immediate fistulotomy (group B). Follow up for groups A and B occurred at a median of 122 weeks (104-136 weeks) and 121 weeks (104-136 weeks), respectively. No patient in group A had residual problems with anal continence whilst two patients (6.5%) from group B had minor anal incontinence following the initial procedure (p = 0.07). Ten patients from group A (11%) and four patients from group B (13%) developed recurrent anal sepsis. The overall rate of recurrent sepsis was 11.7%. In those patients who had incision and drainage alone, 90% of those who developed a recurrence and 71% of those who did not develop a recurrence grew gut-associated organisms from pus obtained during the initial drainage of the acute abscess, giving a positive predictive value for recurrence of 13.8% for a culture of gut-associated organisms. The positive predictive value for recurrent sepsis for both groups taken together for a culture of gut-associated organisms was 28.2%. Patients with acute primary anal abscess should be treated with simple drainage.

Anal fistula

Anal fistula is a common cause of chronic irritation to both patients and surgeons. Treatment failure rates may be decreased by a good appreciation of normal anorectal anatomy and fistula pathoanatomy, as well as a wide and practical knowledge of the possible treatment regimens. The various treatment options available for acute abscesses as well as simple and complex anal fistulae are presented and discussed. Identification of the patient at risk of postoperative anal incontinence or of the difficult or high fistula may allow treatment in a specialized proctology unit.