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

Ionic Liquid-Reinforced Multifunctional Hydrogel for the Treatment of Enterocutaneous Fistula

Enterocutaneous fistulas (ECFs) profoundly impact patients' quality of life, contributing to high morbidity rates and increased mortality due to ineffective treatment options. To address this challenge, ECFGel, a multifunctional, tissue adhesive injectable hydrogel, designed to occlude, sterilize, and promote healing of ECF tracts, is developed. ECFGel is formulated using gelatin and oxidized dextran (O-Dex) as base components, which form chemical crosslinks within the hydrogel and with surrounding biological tissues, ensuring tissue adhesiveness. A choline and geranate-based ionic liquid (IL) is incorporated to provide dual functionality, potent antimicrobial activity, and mechanical enhancement. By optimizing IL concentration, ECFGel achieves rapid gelation, enhanced mechanical strength, and improved elastic recoverability. Additionally, iohexol (IOH) is added for radiopacity, enabling real-time imaging and further strengthening the hydrogel's mechanical properties. ECFGel demonstrates antiswelling properties, biodegradability, and effective tract occlusion in porcine soft tissues. It shows strong antimicrobial activity against highly resistant, patient-derived pathogens isolated from clinical ECF cases. In a porcine perianal fistula model, ECFGel enables rapid occlusion and complete healing, promoting tissue maturation, reducing bacterial load, and increasing markers of cell proliferation and vascularization compared to untreated controls. These promising results highlight ECFGel's potential as a new therapeutic option for treating infected ECFs.

Global trends in surgically based treatment of anal fistula in Crohn's disease: a bibliometric and visualization analysis

BACKGROUND

Crohn's disease (CD) is a chronic, recurrent gastrointestinal disorder characterized by a complex etiology. Among its perianal complications, anal fistulas represent a challenging comorbidity. With the increase of surgical options, a comprehensive bibliometric analysis was deemed necessary to consolidate the vast array of research in this field.

METHODS

We extracted 1608 articles spanning from 1 January 1994, to 1 May 2024, from the Web of Science Core Collection. Using VOSviewer, CiteSpace, and Scimago Graphica for visual analytics, we synthesized key trends across multiple bibliometric indicators, encompassing geographic and institutional contributions, individual authorship, journal prominence, citation metrics, and thematic prevalence.

RESULTS

From the delineated corpus, we identified publications from 325 countries and 5110 research institutions, with the US and UK at the forefront of publication volume and academic impact. The data indicated a leading role for institutions like the Cleveland Clinic and Imperial College London. "Diseases of the Colon and Rectum" emerged as a central journal due to its high publication and citation frequency. Distinctly, the analysis uncovered trending keywords, signifying the field's prioritization on surgical intervention, biologic therapy, imaging modalities, and emerging biological treatments.

CONCLUSION

Our findings elucidate a trajectory toward prominent advancements in CD fistula research. This analysis underscores the field's shift towards integrative treatment strategies, spotlighting the pressing need for comprehensive comparative studies of surgical approaches. It underscores the imperative for robust clinical trials to standardize treatments and extend care to a broader CD patient population.

Microbial and Transcriptomic Landscape Associated With Neutrophil Extracellular Traps in Perianal Fistulizing Crohn's Disease

BACKGROUND

Perianal fistulizing Crohn's disease (pfCD) poses significant healing challenges, closely associated with neutrophil extracellular traps (NETs). This study aimed to investigate the microbe-host interactions influencing NETs in pfCD.

METHODS

From January 2019 to July 2022, patients with pfCD were screened at Ren Ji Hospital. Patients in remission following comprehensive treatment were recruited. We documented clinical characteristics, medication regimens, healing outcomes, and infliximab levels in fistula tissues. NET positivity was confirmed by positive results in citrullinated histone H3 (CitH3) enzyme-linked immunosorbent assay (ELISA) and dual immunofluorescence staining for myeloperoxidase and CitH3. Microbial and transcriptomic profiles from fistula tissues, obtained during surgery, were analyzed using 16S rRNA gene sequencing and RNA sequencing. Differences in microbiome and transcriptomic profiles were evaluated, and their relationships were assessed using Mantel's and Spearman's coefficients.

RESULTS

Significant differences in microbial communities were found between groups (P = .007). Representatively differential microbes such as Prevotella bivia, Streptococcus gordonii, and Bacteroides dorei were enriched in NETs-positive fistulas (P < .05). Functional analysis of microbes revealed reduced ubiquinol biosynthesis and butanoate production in NETs-negative fistulas (P < .05). Transcriptomic analysis indicated increased neutrophil and monocyte infiltration in NETs-positive fistulas, associated with pathways involving bacterial response, neutrophil chemotaxis, secretory processes, and peptidase activity (P < .05). Species prevalent in NETs-positive fistulas correlated positively with immune responses and wound healing pathways, whereas bacteria in NETs-negative fistulas correlated negatively. NETs were negatively associated with tissue infliximab levels (P = .001) and healing outcomes (P = .025).

CONCLUSIONS

Our findings reveal unique microbial and transcriptomic signatures associated with NETs in pfCD, highlighting their profound influence on clinical outcomes.

Antimicrobial PVA Hydrogels with Tunable Mechanical Properties and Antimicrobial Release Profiles

Hydrogels are broadly employed in wound healing applications due to their high water content and tissue-mimicking mechanical properties. Healing is hindered by infection in many types of wound, including Crohn's fistulas, tunneling wounds that form between different portions of the digestive system in Crohn's disease patients. Owing to the rise of drug-resistant infections, alternate approaches are required to treat wound infections beyond traditional antibiotics. To address this clinical need, we designed a water-responsive shape memory polymer (SMP) hydrogel, with natural antimicrobials in the form of phenolic acids (PAs), for potential use in wound filling and healing. The shape memory properties could allow for implantation in a low-profile shape, followed by expansion and would filling, while the PAs provide localized delivery of antimicrobials. Here, we developed a urethane-crosslinked poly(vinyl alcohol) hydrogel with cinnamic (CA), p-coumaric (PCA), and caffeic (Ca-A) acid chemically or physically incorporated at varied concentrations. We examined the effects of incorporated PAs on antimicrobial, mechanical, and shape memory properties, and on cell viability. Materials with physically incorporated PAs showed improved antibacterial properties with lower biofilm formation on hydrogel surfaces. Both modulus and elongation at break could be increased simultaneously in hydrogels after both forms of PA incorporation. Cellular response in terms of initial viability and growth over time varied based on PA structure and concentration. Shape memory properties were not negatively affected by PA incorporation. These PA-containing hydrogels with antimicrobial properties could provide a new option for wound filling, infection control, and healing. Furthermore, PA content and structure provide novel tools for tuning material properties independently of network chemistry, which could be harnessed in a range of materials systems and biomedical applications.

Management of Pelvic Pain in Patients with Crohn's Disease-Current Overview

Crohn's disease (CD) is a subtype of chronic inflammatory bowel diseases (IBD) with characteristic skip lesions and transmural inflammation that may affect the entire gastrointestinal tract from the mouth to the anus. Persistent pain is one of the main symptoms of CD. This pain has multifactorial pathogenesis, but most often arises from intestinal inflammation itself, as well as from gut distention or partial intestinal obstruction. Some current evidence also suggests sensitization of sensory pathways, as well as modulation of those signals by the central nervous system, which highlights the impact of biopsychosocial factors. To date, most studies have focused only on the pain located in the abdomen, while pelvic pain has rarely been explored, despite it being a common symptom. The aim of this study is to provide an abbreviated summary of the current state of knowledge on the origins and treatment of pelvic pain in CD.

Pathogenesis of Fistulating Crohn's Disease: A Review

Sustained, transmural inflammation of the bowel wall may result in the development of a fistula in Crohn's disease (CD). Fistula formation is a recognized complication and cause of morbidity, occurring in 40% of patients with CD. Despite advanced treatment, one-third of patients experience recurrent fistulae. Development of targeting treatment for fistulae will be dependent on a more in depth understanding of its pathogenesis. Presently, pathogenesis of CD-associated fistulae remains poorly defined, in part due to the lack of accepted in vitro tissue models recapitulating the pathogenic cellular lesions linked to fistulae and limited in vivo models. This review provides a synthesis of the existing knowledge of the histopathological, immune, cellular, genetic, and microbial contributions to the pathogenesis of CD-associated fistulae including the widely accredited contribution of epithelial-to-mesenchymal transition, upregulation of matrix metalloproteinases, and overexpression of invasive molecules, resulting in tissue remodeling and subsequent fistula formation. We conclude by exploring how we might utilize advancing technologies to verify and broaden our current understanding while exploring novel causal pathways to provide further inroads to future therapeutic targets.

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.

Epidemiological profile of patients with fistula in ano

Rationale There is a lack of consistent national data on the evaluation of the epidemiological profile of patients with anal fistula.

Objective To evaluate the epidemiological profile of patients with anal fistula at a center specialized in coloproctology.

Method A cross-sectional, retrospective study was carried out between 2016 and 2018 of patients who underwent surgical procedures for the treatment of fistula in ano by the Department of Coloproctology of the Regional Hospital of Mato Grosso do Sul. Age, gender, disease duration, number of procedures, association with Crohn's disease and other comorbidities were evaluated. The data were tabulated and submitted to statistical treatment considering p < 0.05.

Results 93.2% of the patients were less than 60 years old, 66.7% were male, 88.9% had the disease less than one year, the most frequent procedures were fistulotomy (55.6%) and fistulectomy (36.8%), with a greater percentage of patients having undergone only one procedure (74.4%), 8.5% had Crohn’s disease, 7.7% systemic hypertension and 3.4% had diabetes mellitus.

Conclusion In the studied group, there was a predominance of anal fistulae in men under 60 years old and without comorbidities, diagnosed for up to one year, most of them submitted to fistulotomy or fistulectomy at one time. Patients operated after one year of illness and also those with Crohn’s disease were submitted mainly to curettage + seton and multiple procedures.

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.

Cx601 (darvadstrocel) for the treatment of perianal fistulizing Crohn's disease

Introduction: Given the well-documented difficulty to treat perianal fistulizing Crohn's disease (pCD), with 40% of patients experiencing recurrence even after reiterative surgery and advanced medical therapy, research in this field has focused on the role of mesenchymal stem cells (MSC). Areas covered: The aim of this article is to furnish an overview of the pathogenetic mechanisms, clinical applications and evidences for the use of MSC for pCD with particular focus on adipose-derived allogenic MSC including darvadstrocel. Expert Opinion: The effect of MSC on fistula healing is probably mediated by their anti-inflammatory properties more than by their ability to engraft and trans-differentiate in the healthy tissue. A holistic treatment of pCD, addressing different pathophysiological factors, may represent the key for an improvement in the healing rate. In this setting, MSC might play a role as 'augmentation' therapy in combination with more conventional treatments. Whether MSC have benefit in non-complex fistula in biological naïve patients, in complex fistula with many tracts and/or in rectovaginal fistulas, are unexplored fields that need further investigation. A central registry of pCD patients undergoing treatment with MSC should be created in order to elucidate the efficacy, safety and costs of stem cells treatment on long term follow up.

A Distinct Gut Microbiota Exists Within Crohn's Disease-Related Perianal Fistulae

BACKGROUND

Gut bacteria are strongly suspected to play a key role in the pathogenesis of Crohn's disease (CD). Studies have demonstrated alterations in the gut microbiota in this patient population. The purpose of this study was to characterize the gut microbiota of fistulizing perianal CD.

MATERIALS AND METHODS

Stool and fistula samples were obtained from patients undergoing surgery for CD-related anorectal fistulae. Microbial compositions of matched stool and fistula samples were characterized using 16S rRNA gene profiling. The effect of sample type, patient gender, disease classification (Montreal A/B), disease activity (Harvey Bradshaw Index), antibiotic use, and presence of active proctitis on microbial composition was assessed.

RESULTS

Samples were obtained from 18 patients. Bacteroides was the most abundant genera across all samples collected, followed by Streptococcus and Bifidobacterium. Bifidobacterium was present at significantly higher levels in fecal samples than fistula samples, whereas Achromobacter and Corynebacterium were present at significantly higher levels in fistula samples. Antibiotic, but not thiopurine or antitumor necrosis factor medication, exposure affected the gut microbial composition. Patient gender, disease classification, disease activity, and presence of active proctitis did not alter stool or fistula microbiota.

CONCLUSIONS

Our data show that the gut microbiota within CD-related anorectal fistulae is distinct from that in stool samples obtained from the same patients. We also observe a dysbiosis in patients treated with antibiotics compared with those not treated with antibiotics.

Efficacy of Medical Therapies for Fistulizing Crohn's Disease: Systematic Review and Meta-analysis

BACKGROUND & AIMS

Fistulas are debilitating complications of Crohn's disease (CD) that affect up to 50% of patients. We conducted a systematic review and meta-analysis of randomized controlled trials to assess the efficacy of treatments for fistulizing CD.

METHODS

We searched publication databases from inception through December 13, 2016 for trials comparing the efficacy of a therapeutic agent (single or combination) with placebo or another active therapy in adult patients with any form of fistulizing CD. The Cochrane risk of bias tool was used to assess the methodological quality of trials; the overall quality of evidence was evaluated using GRADE. Primary outcomes included induction and maintenance of fistula response and remission. Pooled risk ratios (RRs) and 95% CIs were calculated for each outcome.

RESULTS

We analyzed data from 27 trials; most studies (21/27) focused on patients with perianal fistulizing CD. We found moderate-quality evidence to support the efficacy of tumor necrosis factor (TNF) antagonists (RR, 2.01; 95% CI, 1.36-2.97), particularly infliximab, ustekinumab (RR, 1.77; 95% CI, 0.93-3.37), and mesenchymal stem cell therapy (RR, 1.31; 95% CI, 0.98-1.73) for induction of fistula remission. We found low-quality evidence for the efficacy of vedolizumab and immunosuppressives. There was also low-quality evidence to support the efficacy of combination therapy with TNF antagonists and antibiotics vs a TNF antagonist alone.

CONCLUSION

In a systematic review and meta-analysis of 27 controlled trials, we found TNF antagonists to be effective for induction and maintenance of perianal fistula response and remission. There are few data on the effects on internal fistulae. Further studies are needed, particularly for ustekinumab, vedolizumab, and stem cell therapies, in patients with fistulizing CD.

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.

Infectious Diseases Perspective of Anorectal Abscess and Fistula-in-ano Disease

BACKGROUND

Anorectal abscess and fistula-in-ano is a rare disease with an exemplary prognosis. Most patients are diagnosed with cryptoglandular disease but unusual infections raise difficult antimicrobial management challenges.

METHODS

All primary references identified in PubMed, EMBASE, the ISI Web of Knowledge database and the Cochrane Library, published between 1960 and 2015, using the keywords "anorectal abscess," "fistula-in-ano," "perianal abscess," or "perianal fistula" or all, were uploaded into a database. The databases were also interrogated using keywords specific for each infection type studied.

RESULTS

In all, 52 relevant primary medical publications were identified. There were also 4 relevant organizational standards guideline publications, 1 relevant review and 4 historical publications about the diagnosis and outcomes of anorectal abscess and fistula-in-ano with data derived primarily from prospective and retrospective trials as well as institutional case series to provide an evidence level opinion. The use of antimicrobial therapy in combination with surgical incision and drainage in the treatment of cryptoglandular disease has failed to improved healing times or reduce recurrences or both. Based on limited data, routine antimicrobial therapy may benefit patients with significant comorbid conditions, extensive cellulitis and systemic symptoms. For patients with unusual infecting pathogens (eg, Mycobacterium tuberculosis, Actinomyces species and Chlamydia species) outcomes are favorable with selected antimicrobial therapy agents of various durations.

CONCLUSION

Surgical incision and drainage is the main treatment for anorectal abscess and fistula-in-ano, but a select group of patients with unusual infections benefit from tailored prolonged antimicrobial therapy with the overall recurrence rate remaining low.

Medical Therapy of Perianal Crohn's Disease

Background

Development of perianal fistulas are a common feature of Crohn's disease (CD). Consequences are severe impairment of quality of life as well as potentially life-threatening complications like abscess formation or bacterial sepsis. Therefore, appropriate treatment is an important task in the management of CD.

Methods

This review describes the epidemiology, pathogenesis, diagnosis, and conservative medical treatment of perianal CD with regard to the available literature. In February 2015, a PubMed search was performed with the following terms (combined and separate): ‘Crohn's disease management’, ‘Crohn's disease complications’, ‘perianal Crohn's disease’, ‘fistulizing Crohn's disease’, ‘perianal fistulas’, ‘fistula healing’, ‘fistula closure’. From the search results, 36 articles were chosen as core elements of this review.

Results

Pelvic magnetic resonance imaging and rectal endosonography are established diagnostic approaches to evaluate perianal fistulas in conjunction with endoscopy. Antibiotics, thiopurines, and calcineurin inhibitors are useful agents in the management of perianal CD. The availability of anti-TNF-alpha therapies has substantially changed the prospects and goals of medical treatment, and fistula healing seems to be possible in a substantial proportion of patients.

Conclusion

Antibiotics and several immunosuppressive drugs have improved the treatment of fistulizing CD and should be combined with surgical measures.

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.

Improving the outcome of fistulising Crohn's disease

Fistulas are a frequent manifestation of Crohn's disease (CD) and can result in considerable morbidity. Approximately 35% of all patients with CD will experience one fistula episode during their disease course of which 54% is perianal. The major symptoms of patients with perianal fistulas are constant anal pain, the formation of painful swellings around the anus and continuous discharge of pus and/or blood from the external fistula opening. The exact aetiology of perianal fistulas in CD patients remains unclear, but it is thought that a penetrating ulcer in the rectal mucosa caused by active CD forms an abnormal passage between the epithelial lining of the rectum and the perianal skin. Genetic, microbiological and immunological factors seem to play important roles in this process. Although the incidence of perianal fistulas in patients with CD is quite high, an effective treatment is not yet discovered. In this review all available medical and surgical therapies are discussed and new treatment options and research targets will be highlighted.

A comprehensive review of inflammatory bowel disease focusing on surgical management

The two main diseases of inflammatory bowel disease are Crohn's disease and ulcerative colitis. The pathogenesis of inflammatory disease is that abnormal intestinal inflammations occur in genetically susceptible individuals according to various environmental factors. The consequent process results in inflammatory bowel disease. Medical treatment consists of the induction of remission in the acute phase of the disease and the maintenance of remission. Patients with Crohn's disease finally need surgical treatment in 70% of the cases. The main surgical options for Crohn's disease are divided into two surgical procedures. The first is strictureplasty, which can prevent short bowel syndrome. The second is resection of the involved intestinal segment. Simultaneous medico-surgical treatment can be a good treatment strategy. Ulcerative colitis is a diffuse nonspecific inflammatory disease that involves the colon and the rectum. Patients with ulcerative colitis need surgical treatment in 30% of the cases despite proper medical treatment. The reasons for surgical treatment are various, from life-threatening complications to growth retardation. The total proctocolectomy (TPC) with an ileal pouch anal anastomosis (IPAA) is the most common procedure for the surgical treatment of ulcerative colitis. Medical treatment for ulcerative colitis after a TPC with an IPAA is usually not necessary.

Managing Perianal Crohn’s Disease

Perianal Crohn’s Disease (CD) is a significant cause of morbidity in CD patients. Accurate identification of perianal involvement requires advanced imaging techniques in addition to physical exam. Treatment of the disease is aimed at improving both the perianal and intestinal manifestations. Proper treatment depends upon the severity of the disease and combines current medical and surgical therapies to maximize response. The ability to improve perianal disease has grown significantly since the introduction of anti-TNF agents which are now a mainstay of treatment along with antibiotics and immunomodulators. New experimental therapies are limited by lack of research to support their use.

CARD15 mutations and perianal fistulating Crohn's disease: correlation and predictive value of antibiotic response

BACKGROUND

CARD15 mutations alter bowel immunity and increase susceptibility to Crohn's disease (CD). However, the relation between these mutations and Crohn's perianal fistulas has not been fully clarified.

AIMS

To assess whether CARD15 mutations are associated with risk of developing Crohn's perianal fistulas and whether these mutations are predictors of the response of perianal fistulas to antibiotics.

METHODS

CARD15 mutations were investigated in 203 consecutive CD patients. Presence/absence of history of perianal fistula was recorded. Patients with history of perianal fistula were divided into two groups (with/without CARD15 mutations), and response to antibiotics was evaluated in both groups.

RESULTS

Of the 203 patients, 60 (29.6%) showed at least one CARD15 mutation and 55 (27.1%) had history of perianal fistula. History of perianal fistula was identified in 13 (21.7%) patients with mutations and in 42 (29.4%) patients without mutations (P = 0.260). Mean age at diagnosis of first perianal fistula was similar in patients with/without CARD15 mutations (28.7 ± 9.8 versus 29.7 ± 10.1 years, P = 0.758). Average time between disease onset and diagnosis of first perianal fistula was also similar in the two groups (4.6 ± 5.1 versus 5.0 ± 5.9 years, P = 0.816). Response of perianal fistulas to antibiotics (metronidazole alone or combined with ciprofloxacin) was significantly higher in patients without CARD15 mutations (7.7% versus 40.5%, P = 0.041).

CONCLUSIONS

In CD, CARD15 mutations are not associated with risk of developing perianal fistulas or with time of their outbreak. Nevertheless, patients with perianal fistulas and CARD15 mutations showed worse response to antibiotics.

Perianal fistulae in Crohn's Disease: current and future approaches to treatment

: affecting sphincter integrity and continence. Traditional surgical and medical approaches are not without their limitations and may result in either comorbidity, such as fecal incontinence, or incomplete healing of the fistulae. Over the last 2 decades these limitations have led to a paradigm shift toward the use of biomaterials, and more recently cell-based therapies, which have met with variable degrees of success. This review discusses the traditional and current methods of treatment, as well as emerging and possible alternative approaches that may improve fistula healing.

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.

Diagnosis and management of fistulizing Crohn's disease

The transmural inflammation characteristic of Crohn's disease predisposes patients to the formation of fistulas. Up to 50% of patients with Crohn's disease are affected by fistulas, which is a major problem given the considerable morbidity associated with this complication. Appropriate treatment of fistulas requires knowledge of specific pharmacological and surgical therapies. Treatment options depend on the severity of symptoms, fistula location, the number and complexity of fistula tracts, and the presence of rectal complications. Internal fistulas, such as ileoileal or ileocecal fistulas, are mostly asymptomatic and do not require intervention. By contrast, perianal fistulas can be painful and abscesses may develop that require surgical drainage with or without seton placement, transient ileostomy, or in severe cases, proctectomy. This Review describes the epidemiology and pathology of fistulizing Crohn's disease. Particular focus is given to external and perianal fistulas, for which treatment options are well established. Available therapeutic options, including novel therapies, are discussed. Wherever possible, practical and evidence-based treatment regimens for Crohn's disease-associated fistulas are provided.

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.

Perianal Crohn's disease

Crohn's disease is commonly complicated by perianal manifestations. The surgeon plays a pivotal role in caring for these patients; a detailed history along with a thorough clinical exam provides the treating physician with invaluable information upon which to base further investigations and management decisions. Other than abscess drainage, medical management to control proximal disease often precedes any surgical attempt to cure the disease. Surgical interventions are indicated in selective patients, but are often complicated by poor wound healing and recurrences. A sizable percentage of these patients may need a proctectomy.

Review article: Medical therapy for fistulizing Crohn's disease

BACKGROUND

Fistulae will develop in approximately one-third of patients with Crohn's disease. With an expected spontaneous healing rate of only 10%, fistulizing Crohn's disease requires a comprehensive strategy with a medical and possible surgical approach.

AIM

To summarize the current literature evaluating various medical options for treating patients with fistulizing Crohn's disease.

METHODS

A literature review was conducted using PubMed (search terms: Crohn's disease and fistula) and manual search of references among the identified studies and relevant review papers to identify papers that present data on medical treatment of fistulizing Crohn's disease.

RESULTS

The first line of medical therapy remains antibiotics (metronidazole and ciprofloxacin). Mercaptopurine and azathioprine are medications that are effective in treating fistulizing Crohn's disease. The current gold standard of medical treatment to induce and maintain remission for fistulizing Crohn's disease is infliximab. Used as induction therapy, infliximab produced a 62% clinical response, and a complete closure rate of 46%. A maintenance therapy trial demonstrated at 54 weeks, 46% of patients receiving infliximab continued to respond to treatment, compared with 23% in the placebo group (P = 0.001).

CONCLUSION

Further research to find new therapies and to improve our existing medical treatment of fistulizing Crohn's disease is required.