Introduction
Materials and methods
Results
Study comparisons
Study demography and design
Paper | Design | Population | Fistulae (number, anatomy) | Location of disease | Treatment |
---|---|---|---|---|---|
Bell [24] | Retrospective cohort | Male 41 | 78 perianal | 74 colonic/ileocolonic | Rule based |
Female 46 | 27 rectovaginal | 12 small bowel | Medical (antibiotics, azathioprine, enteral, parenteral feeding) | ||
Total = 86 | 169 fistulae 135 complex (80%) | 74 colonic/ileocolonic | Simple surgery (drainage, fistulotomy, seton) [most common for simple and complex perianal] | ||
Age (mean, range) years: 35 (20–91) | ‘Simple’—superficial or intersphincteric | 12 small bowel | Complex (resection, refunctioning stoma, proctectomy) [most common for rectovaginal] | ||
‘Complex’—transsphincteric, suprasphincteric, or extraspincteric | 74 colonic/ileocolonic | Other (advancement flap, primary repair) | |||
12 small bowel | |||||
1 perianal | |||||
57 rectal involvement | |||||
Dewint [31] | RCT | Male 37 | 70 perianal (110 localisations) anatomy undefined | N/A | Random |
Female 33 | 34 allocated to ciprofloxacin (and made it to completion) | ||||
Total = 70 | 36 allocated to placebo | ||||
Age (mean, range) years: 36.1 (18–70) | Randomisation was performed through a centralised randomisation schedule in a 1:1 ratio | ||||
Smokers 22 (12 in cipro., 10 in placebo) | |||||
Loffler [25] | Prospective cohort | Male 49 | 45 rectovaginal | Anorectal/rectovaginal 144 | Rule based |
Female 98 | 101 perianal | Colon 141 | 292 operations on 146 patients | ||
Total = 147 (1 patient excluded) | Classified according to Parks et al. | 38% major surgery, 62% minor surgery | |||
Age (mean, range) years: 33 (17–68) | Extrasphincteric 34 | Minor surgery (lay open-44, fistulae excision-41, fistulae curetting-25, seton drainage-71, fibrin glue application-1) | |||
Suprasphincteric 24 | Major 1 surgery (endorectal advancement flap-34, levatorplasty/sphincteroplasty-20) | ||||
Submucosal 22 | Major 2 surgery (ostomy-17, Hartmann’s procedure-10, proctectomy/perianal resection-29) | ||||
Transsphincteric 21 | |||||
Luna-Chadid [26] | Prospective cohort | Male 57 | 59 Perianal | Ileal 33 | Rule based |
Female 51 | 12 Rectovaginal/enterovesical | Colonic 19 | All treated with infliximab | ||
Total = 108 | Ileocolonic 55 | ||||
Age (mean) years: 38 Smokers: 54 | Fistulae anatomy: Entereocutaneous or Perianal or Internal or Rectovaginal or Enterovesical 194 Localisations | ||||
Present [23] | RCT | Male 44 | 85 Perianal (anatomy not defined) | Ileum 14 | Random |
Female 50 | Colon 26 | Randomly assigned to infliximab or placebo | |||
Total = 94 | Both ileum and colon 54 | ||||
Age (mean years: 37.2) | |||||
Gaertner [27] | Retrospective cohort | Male 105 | 226 Perianal, 254 Localisations Classified by method described by Parks et al. | Ileocecal 81 | Rule based |
Female 121 | ‘Complex’—if there are multiple fistulae tracts and extension of tracks above the dentate line | Perianal 62 | Underwent operative treatment only (147) or operative treatment and infliximab (79) | ||
Total = 226 | Intersphincteric 103 | Colon 51 | |||
Age (mean, range) years: 39 (16–83) Smokers 32 | Transsphincteric 91 | Small bowel 20 | |||
Complex 35 | Terminal Ileum 12 | ||||
Extrasphincteric 14 | |||||
Suprasphincteric 11 | |||||
Angelberger [59] | Prospective cohort | Male 28 | 54 Perianal Fistulae anatomy is not defined | Ileocolonic 39 | Rule based |
Female 24 | Colonic 13 | 49 treated with ciprofloxacin | |||
Total = 54 | 3 treated with metronidazole for 7 weeks | ||||
Age (mean, range) years: 36 (22–61) | |||||
29 smokers | |||||
Bougen [32] | Retrospective cohort | Male 61 | 158 perianal 28 simple 128 complex | Ileal 19 | Rule based |
Female 95 | Colonic 63 | IFX administrated | |||
Total = 156 | Ileocolonic 70 | ||||
Age (mean) years: 30 | Upper digestive tract 8 | Episodic if administrated on relapse of symptoms | |||
Scheduled if every 8 weeks | |||||
Dejaco [29] | Prospective cohort | Male 27 | 52 Perianal classified according to Parks et al. Superficial 2 | Ileocolonic 39 | Rule based |
Female 25 | Intersphincteric 17 | Colonic 13 | All treated with ciprofloxacin and/or metronidazole | ||
Total = 52 | Transsphincteric 14 | ||||
Age (mean, range) years: 39 (22–63) | Suprasphincteric 2 | ||||
Smokers 32 | Extrasphincteric 1 | ||||
Complex fistulae 7 | |||||
Unclassified 9 | |||||
Freire [33] | Prospective cohort | Male 87 | 203 perianal Classified as ‘simple’—superficial (intersphincteric or low transsphincteric), painless, with a single external opening and no evidence of rectovaginal involvement or anorectal stricture or ‘complex’—fistulae is located high (high transsphincteric, extrasphincteric, or suprasphincteric), may be associated with pain, can potentially involve multiple external openings, and may be associated with rectovaginal fistulae and/or anorectal stricture | N/A | Rule based |
Female 116 | Antibiotic treatment; all given metronidazole and 28 also received ciprofloxacin | ||||
Total = 203 | |||||
Age (mean) years: 36.6 | |||||
Male 35.9 | |||||
Female 37.1 | |||||
Haennig [34] | Prospective cohort | Male 39 | 12 Rectovaginal | Perineum 56 | Rule based |
Female 42 | 69 Perianal | Rectum 34 | 62 had surgery, drainage with a loose seton—all given infliximab for median of 4.9 months | ||
Total = 81 | Simple or complex according to the classification of the American Gastroenterology Association | Ileum 6 | |||
Age (mean) years: 31; BMI (kg/m2) = 20 Smokers 23 | 71 Complex | Colon 32 | |||
Ileocolonic 42 | |||||
Makowiec [37] | Prospective cohort | Male 37 | 75 Perianal—14 Complex | Ileal 9 | Rule based |
Female 53 | 15 Anovaginal 50 Transsphincteric (includes 15 anovaginal) | Colitis 31 | Standard treatment was a high dose of corticosteroid therapy | ||
Total = 90 | 24 Subcutaneous | Ileocolitis 50 | 36 given prednisolone (6 also received azathioprine) | ||
4 Intersphincteric | 2 received azathioprine alone | ||||
11 Ischiorectal | These 38 were classified as receiving immunosuppressive therapy | ||||
1 Suprasphincteric | 9 were given oral metronidazole | ||||
12 received steroids | |||||
Michelassi [30] | Prospective cohort | Male 102 | 51 fistulae in ano | N/A | Rule based |
Female 122 | 20 Rectovaginal | Surgery for all patients | |||
Total = 224 | Setons used in fistulae | ||||
Age (mean, range) years: 38 (17–82) |
Paper | Previous treatment | Other perianal manifestations or stoma | Time period | Follow-up (mean, range) | Duration of CD | Statistical methods |
---|---|---|---|---|---|---|
Bell [24] | N/A | N/A | Jan 1993–Dec 1994 | 5.5 years (7 weeks–27.3 years) | 8 years (0–32 years) | Mann–Whitney U test (nonparametric comparisons). Fisher’s exact test for associations between data sets. |
Dewint [31] | Concomitant use of thiopurine derivates, methotrexate, 5-aminosalicylic, oral corticosteroids | 11 had previous stoma | Sept 2008–March 2011 | 24 weeks | N/A | Distributions between treatment groups were compared by X2 or the Fisher exact test. Continuous variables were summarised by using median and IQR or mean and SD, and their distributions between treatments were compared with Mann–Whitney test. Frequencies of response were compared between treatments using X2 or Fisher’s exact test |
Loffler [25] | 27 on immunosuppressants at time of trial | N/A | 1991–2001 | 48 months | N/A | Using SAS software, difference in no. of operations between fistulae type was calculated by Kruskal–Wallis test. Number of protectomies according to fistulae type with Fisher’s exact test |
Luna-Chadid [26] | Azathioprine 73 | N/A | Oct 1999–March 2001 | At least 4 weeks | 9 years | Comparisons between independent proportions were carried out by Chi-square test |
Corticosteroids 59 | ||||||
5-Aminosalicylates 81 | ||||||
Metronidazole 72 | ||||||
Ciprofloxacin 35 | ||||||
Present [23] | Corticosteroids 33 | Previous stoma excluded | N/A | N/A | 12.4 years | The primary analysis was performed with the intention-to-treat principle and included all patients who were assigned to treatment. 1. The Mantel–Haenszel Chi-square test for a linear dose response in the proportion of patients in whom the primary endpoint occurred. 2. If significant, Fisher’s exact test was used to compare the proportion of patients achieving the primary endpoint in each of the two infliximab groups with the placebo group. Odds ratios were used to assess the consistency of benefit of infliximab treatment. Analysis of the proportion of patients with complete response was performed with the same methods for analysis of the primary endpoint. Continuous variables were compared by analysis of variance of the van der Waerden normal scores |
Mercaptopurine or azathioprine 38 | ||||||
Aminosalicylates 52 | ||||||
Antibiotics 28 | ||||||
Gaertner [27] | 84 had previous surgery | N/A | March 1991–Dec 2005 | 30 months (6–216) | 7 years (0.08–38) | Pearson Chi-squared and Fisher’s exact tests were performed to compare baseline patient characteristics and differences in healing between treatment groups. Fisher’s exact test was performed to compare differences in healing between patients based on type of fistulae, initial site of CD, and operative treatment. p < 0.05 was considered significant. All calculations were performed by using the GraphPad InStat 3 statistics programme |
Angelberger [59] | 31 previous surgery 5-aminosalicylic acid, sulphasalazine—21 | N/A | N/A | N/A | 3.9 years (0.1–26.4) | Fisher exact test for 2 × 2 frequency tables. Comparison of the HBD-2 gene copy number and number of draining fistulae between the patient groups was performed by the Wilcoxon signed rank test and Mann–Whitney U test, respectively. All calculations were done by SAS and SPSS statistical software |
Steroids—11 | ||||||
Immunosuppressants-23 | ||||||
Bougen [32] | Major abdominal surgery 44 Purine analog 51 | N/A | Jan 1998–Sept 2011 | 5 years | 3.8 years (0–30) | Quantitative variables were described as median and percentile (IQR) Categorical variables were presented as counts and per cent of cohort. Four events were defined: events were analysed using survival analysis. Cumulative probabilities of fistulae closure, recurrence of PCD, or abscess were estimated using Kaplan–Meier method. To identify predictive factors, we performed a univariate analysis using the log-rank test. When considering the continuous variables for dichotomous analysis, cut-off values were determined using receiver operating characteristic analysis to reduce the risk of bias related to arbitrarily defined cut-off and identify the optimal cut-off using each outcome as a classification variable. To identify independent predictors of surgery using a multivariate analysis, all significant variables in the log-rank test were retained in the model and integrated into a Cox proportional hazards regression model |
Methotrexate 6 | ||||||
Adalimumab 3 | ||||||
Concomitant: | ||||||
Steroids—45 | ||||||
Purine analog—82 | ||||||
Methotrexate—8 | ||||||
Antibiotics—90 | ||||||
Dejaco [29] | Perianal surgery 32 Concomitant: Aminosalicylates | Previous stoma excluded | July 1999 –Feb 2002 | 28.1 months | 11 years (2–35) | Results are expressed as the mean ± standard deviation. Comparison of PDAI scores, leucocyte counts, and C-reactive protein levels before and during treatment was analysed by the paired exact Wilcoxon signed rank test. For the detection of differences between response rates in patients receiving different types of medication, Fisher’s exact test was used. Multivariate logistic regression analysis was performed by SAS in order to assess the simultaneous effects of smoking, azathioprine administration, and duration of fistulising disease on treatment response at week 20 |
Freire [33] | Concomitant | N/A | N/A | N/A | N/A | Categorical variables were expressed as frequency and percentage, and corresponding contingency tables were analysed with Pearson’s Chi-square test or Fisher’s exact test, OR were determined with 95% CI. Continuous variables were summarised using mean ± standard deviation. These variables were tested for normal distributions using the Kolmogorov–Smirnov test. The Student’s t test was employed to compare means of continuous variables and normally distributed data; otherwise, the Mann–Whitney U test was applied. All variants studied were in Hardy–Weinberg equilibrium. Data were analysed using the Statistical Package for Social Sciences |
5-Aminosalicylic acid = 34 | ||||||
Steroids = 6 | ||||||
Azathioprine (<3 months) = 9 | ||||||
Azathioprine (≥3 months) = 7 | ||||||
Haennig [34] | N/A | N/A | 2000–2010 | 63.8 months (2–263) | N/A | Quantitative variables are given as mean ± SD and median with range. The time to complete closure and its relation to the duration of seton drainage or infliximab treatment was determined using the Kaplan–Meier method, and significance was demonstrated using the log-rank test. Cox uni- and multivariate analysis was used to determine the effect of clinical variables on closure. Factors significantly associated with closure in univariate analysis were applied to a restricted multivariate mode |
Makowiec [37] | Previous surgery: 41 for intestinal disease | 80 had abscesses | May 1989 –Oct 1992 | 22 months (6–44) Follow-up ended Dec 1993 | 8 years (0–22) | Inactivation of perianal fistulae and abscesses, healing, reopening, and symptomatic recurrence rates were analysed using Kaplan–Meier survival estimates. Patients were considered at risk until the event occurred (inactivation, healing, recurrence) or until the last follow-up examination. Factors influencing healing or symptomatic recurrence were analysed by log-rank and Wilcoxon rank tests (univariate analysis). The data underwent further independent analysis using multiple regression according to the proportional hazard model (Cox regression analysis) |
69 for perianal fistulae or abscesses | 7 stoma | |||||
Michelassi [30] | N/A | Perianal abscesses 36 Anal stenosis 40 Incontinence 11 | Oct 1984–May 1999 | N/A | N/A | All data were transcribed on a relational database software programme for subset query extraction and analysis. Where appropriate, nominal variables were compared by using Chi-square analysis or single-tailed Fisher exact test. Statistical calculations were made with the aid of a statistical software package (Minitab 10.1 for Windows; Minitab, Inc, State College, PA, USA |
Stoma 5 |
Outcomes
Common outcome measure | Definition given in paper |
---|---|
‘Healed’/‘healing’/‘complication healed’ (n = 4) | No discharge on history or examination, with healing of the external opening [24] |
Complete closure of fistulae without sign of activity or pain for at least a month [37] | |
Complete healing or successful dilation of anal stenosis, after surgical intervention [30] | |
Non-defined [27] | |
Response (n = 3) | ≥50% reduction in fistulas [31] |
Maintained fistulae healing; PDAI 2.8 ± 2.4 [29] | |
Absence of fistulae drainage, even after compression for at least 4 weeks [33] | |
Complete response (n = 4) | The complete cessation of drainage from all fistulas despite gentle finger compression [26] |
Absence of any draining fistulas [23] | |
Absence of any drainage fistulas despite gentle finger compression [28] | |
PDAI 0.8 ± 1.0 fistulae closure or absence of any draining fistulas despite gentle finger compression [29] | |
Partial response (n = 2) | At least 50% reduction from baseline in the number of fistulas or drainage for at least 4 consecutive weeks after the discontinuation of drug infusions [26] |
Reduction of 50% or more from baseline in the number of draining fistulas [28] | |
Recurrence (n = 4) | Presence of fistulae openings among patient who experienced fistulae closure [32] |
Reopening of a former track or presence of new fistulae after primary response [34] | |
Reappearance of active perianal fistulas or associated abscesses after prior inactivation or healing [37] | |
Recurrence of the same or different complication after a period of complete healing [30] |
Bias
Overall risk of bias | 1. Study participation | 2. Study attrition | 3. Prognostic factor measurement | 4. Outcome measurement | 5. Study confounding | 6. Statistical analysis and reporting | |
---|---|---|---|---|---|---|---|
Bell [24] | Moderate | L | L | L | M | H | M |
Dewint [31] | Low | L | L | M | L | M | H |
Loffler [25] | Moderate | M | L | M | M | H | M |
Luna-Chadid [26] | Low | L | L | H | L | L | H |
Present [23] | Moderate | M | M | L | L | M | M |
Gaertner [39] | Moderate | L | L | H | H | M | M |
Angelberger [61] | Low | L | L | M | L | H | M |
Bougen [32] | Low | L | L | L | M | L | H |
Dejaco [29] | Low | L | M | M | L | L | M |
Freire [33] | Low | L | L | L | M | L | H |
Haennig [34] | Low | M | M | L | L | L | M |
Makowiec [37] | Moderate | L | M | M | L | H | H |
Michelassi [30] | Moderate | M | L | M | L | H | H |
Prognostic factors
Paper | Clinical endpoints | Significant prognostic factors | Insignificant prognostic factors |
---|---|---|---|
Bell [24] | ‘Healed’—no discharge on history or examination, with healing of the external opening | Rectal Crohn’s made proctectomy more likely than those with no rectal involvement (p = <0.001) | Complex did not take significantly longer to heal than simple (p = 0.69) |
‘Persistent fistulae’—not defined | Complex perianal took an average of 6 procedures over 2 or more years | The presence of a rectovaginal fistulae was not predictive of the need for a proctectomy (p = 0.25) | |
‘Maintenance with a seton’—not defined | This is significantly more procedures than simple (3 treatments, p = 0.002) | No association between presence of rectal CD and rectovaginal fistulae (p = 0.085) | |
‘Sepsis’—if an abscess formed at the fistulae site | This is significantly more than rectovaginal (3 treatments, p = 0.01) | ||
‘None healed’ ‘death’ | This is significantly more procedures than abdominal wall (2 treatments, p = 0.0005) | ||
This is significantly more time than internal fistulae (1 treatment, p = 0.002) | |||
Complex fistulae took on average 42.8 months to heal | |||
Rectovaginal fistulae took significantly shorter time to heal (median of 26 months) than perianal fistulae (p = 0.05) | |||
Abdominal wall fistulae took significantly shorter time to heal (median of 6.3 months) than perianal fistulae (p = 0.0001) | |||
Enteroenteric took significantly shorter time to heal (median of 9.4 months) than perianal fistulae (p = 0.03) | |||
Dewint [31] | ‘Response’ – | None | Sex (p = 0.74) |
≥50% reduction in no. of fistulae | Race, Caucasian versus other (p = 0.39) | ||
‘Remission’ – | Seton (p = 0.90) | ||
100% closure of draining fistulae | Stoma (p = 0.30) | ||
Smoker (p = 0.64) | |||
Previous treatment with infliximab (p = 0.63) | |||
Loffler [25] | ‘Long-term success’—whether or not patients have fistulae persistence or recurrence over 60 months | 98% of patients with anorectal or rectovaginal disease also had a manifestation in colon/rectum. This was significantly higher than in patients without anorectal or rectovaginal fistulae (p < 0.001) | Complex fistulae in comparison with simple fistulas, there was a strong trend to a difference in outcome of 5 years (p = 0.2113) |
Luna-Chadid [26] | ‘Complete response’—the complete cessation of drainage from all fistulas despite gentle finger compression | None | Age |
‘Partial response’—at least 50% reduction from baseline in the number of fistulas or drainage for at least 4 consecutive weeks after the discontinuation of drug infusions | Sex | ||
‘Response for rectovaginal fistulae’—closure documented by physical examination | Smokers | ||
Duration of fistulising disease | |||
(no p value given, just says the p value is not significant) | |||
Present [23] | ‘Complete response’—absence of any draining fistulae | Males (p < 0.001)are more likely than females (p = 0.28) to reach primary endpoint when in infliximab group as compared to placebo group | None |
A fistulae was considered to be closed when it no longer drained despite gentle finger compression | |||
Gaertner [27] | ‘Healing’—not defined | None | There were no significant associations found between fistulae healing and the duration of CD, initial site of CD, previous fistulae disease, and cigarette smoking |
Angelberger [59] | ‘Complete response’ -absence of any draining fistulae despite gentle finger compression | Complete fistulae response was significantly higher in patients with NOD2/CARD15 wild type | Median HBD-2 gene copy number was not significantly different between the responders and non-responders (p = 0.92) |
‘Partial response’—reduction of 50% or more from baseline in the number of draining fistulae | (p = 0.02) | Duration of perianal fistulating disease (p = 0.844) | |
Smoking (p = 0.239) | |||
Association between complete response and median number of draining fistulae (p = 0.18) | |||
Rate of patients with more than one draining fistulae (p = 0.32) | |||
Bougen [32] | (1) Fistulae closure = absence of any draining by fistulae openings at one visit | Significant predictors of perianal fistulae closure: prior abdominal surgery | Sex (p = 0.12) HR 1.46 (95% 0.89–2.35) |
(2) Recurrence of PCD = presence of fistulae openings among patient who experienced fistulae closure | (p = 0.0097) HR 0.43 (95% CI 0.21–0.8) | ||
(3) Recurrence of abscess after IFX initiation | |||
(4) Sustained fistulae closure for patients without any recurrence | |||
Dejaco [29] | ‘Response’—maintained fistulae healing, PDAI 2.8 ± 2.4 | The duration of fistulising disease was a significant prognostic factor (p = 0.04) | Smoking (p = 0.3) |
‘Complete Response’—PDAI 0.8 ± 1.0, fistulae closure or absence of any draining fistulae\despite gentle finger compression | |||
‘No response’ – | |||
PDAI 7.4 ± 3.1 | |||
Freire [33] | ‘Response’—absence of fistulae drainage, even after compression for at least 4 weeks | Clinical response of perianal fistulae to antibiotics was significantly higher in patients without the CARD15 mutation (p = 0.041) | None |
OR 8.16 (95% CI 0.97–68.74) | |||
Haennig [34] | ‘Clinical response’—complete closure of the fistulae track with no further discharge from the opening(s) on the gentle application of pressure | The time for closure of fistulae was significantly shorter for men than women (p = 0.03) HR 0.59 (95% CI 0.36–0.96) | Recurrence after initial fistulae closure—tobacco (p = 0.41) |
‘Primary response’—closure had been sustained for at least 4 months | 11.7 versus 21.0 months | Ileocolonic location of CD (p = 0.10) | |
‘Recurrence’—reopening of a former track or presence of new fistulae after primary response | The time for closure was significantly shorted for simple fistulae compared to complex fistulae (p < 0.001) HR 0.31 (0.16–0.62) | Rectovaginal fistulae (p = 0.24) | |
2 versus 15.3 months | |||
Rectovaginal fistulae took a significantly longer time to close than perianal (p = 0.02) HR 0.44 (0.22–0.91) | |||
12 versus 30.6 months | |||
Makowiec [37] | ‘Inactivation of perianal fistulas and abscesses’—cessation of purulent discharge from fistulae and disappearance of perianal pain | Ischiorectal and transsphincteric fistulae recurred more frequently than low fistulas (p = 0.007) | None |
‘Healing’—complete closure of fistulae without sign of activity or pain for at least a month | Low fistulas had a better prognosis (higher healing rate) than transsphincteric | ||
‘Reopening of fistulae’—reappearance of perianal fistulas after prior healing | or ischiorectal fistulas | ||
‘Symptomatic recurrence’—reappearance of active perianal fistulae or associated abscesses after prior inactivation or healing | (p = 0.015) | ||
The presence of rectal disease indicated that a patient was significantly more likely to have recurrence (p = 0.041) | |||
Fistulae healed better in patients without than in those with rectal disease (p = 0.017) | |||
If presence of stoma are more likely to heal (p = 0.005) | |||
Michelassi [30] | ‘Persistence’—persistence of a complication after surgical intervention | A patient is significantly less likely to heal from a perianal complication when there is rectal involvement (p < 0.05) | None |
‘Development’—development of a complication different from the original one as a consequence of surgical intervention | 49.1 versus 19.3% | ||
‘Recurrence’—recurrence of the same or different complication after a period of complete healing | A patient is significantly more likely to heal when they have a single complication compared to having multiple complications (p < 0.05) | ||
‘Complication healed’—complete healing or successful dilation of anal stenosis, after surgical intervention | 48.6 versus 28.2% | ||
‘Sepsis controlled’—anorectal sepsis controlled as consequence of surgery | Patients with rectal involvement had a significantly higher chance of proctectomy (p < 0.0001) | ||
77.6 versus 13.6% | |||
Patients with multiple complications had significantly higher chance of proctectomy (p < 0.05) | |||
23 versus 10% |
Patient characteristics
Genetics
Disease duration and location
Fistulae anatomy
Environmental characteristics
Study | Total patients (n) | Smokers (n) |
p value | Prospective/retrospective |
---|---|---|---|---|
Dewint [31] | 70 | 22 | 0.64 | Prospective |
Luna-Chadid [26] | 108 | 54 | >0.05 | Prospective |
Angelberger [28] | 54 | 29 | 0.239 | Prospective |
Dejaco [29] | 52 | 32 | 0.3 | Prospective |
Haennig [34] | 81 | 23 | 0.41 | Prospective |
Gaertner [27] | 226 | 32 | >0.05 | Retrospective |