The diagnosis of Crohn’s disease with perianal lesions as the first clinical manifestation may be more difficult or even easily overlooked. Crohn’s disease should be considered clinically if multiple perianal lesions are present at the same time, such as anal fissures, ulcerated cavities, and anal canal strictures in non-median sites. The following table compares the differences between CD perianal lesions and non-CD related perianal lesions.
The major difference between CD perianal lesions and non-CD related perianal lesions is that surgical incisions are difficult to heal! Therefore avoid using cutting hangers (tight ones) and use drainage hangers (loose ones)!
Treatment strategies for Crohn’s disease anal fistula
1.Surgical treatment
Perianal CD lesions progress slowly, are often asymptomatic, and partially heal spontaneously; poor treatment outcomes are often due to failure to use the optimal drug regimen. “As early as 1980 Alexander-Williams noted that most of the major causes of incontinence in patients with perianal Crohn’s disease are due to overly aggressive surgery rather than the lesion itself.” As medicine has evolved, the use of biological agents as well as immunomodulators has changed the treatment strategy for perianal CD. For most perianal lesions, topical treatment improves symptoms, and combined medication (antibiotics, immunomodulators, biologics, etc.) is more effective.
The treatment of perianal CD should follow the following principles.
1) advocating multidisciplinary comprehensive treatment
2)individualized treatment.
3)intestinal CD activity needs to be controlled first or simultaneously with intestinal lesion activity
4) perianal CD need not be treated if it does not cause clinical symptoms or if the symptoms are mild, and should be followed up and observed.
5) surgical procedures should be as conservative as possible
6) Asymptomatic fistulas do not require treatment.
2.Medical treatment
Medication includes metronidazole, ciprofloxacin, azathioprine (AZA) or 6-mercaptopurine (6-MP). Simple, superficial fistulas can be cured by fistulotomy and antibiotic treatment. MTX may also be of some value.
Long-term biologic therapy such as anti-tumor necrosis factor antibodies may result in complete fistula quiescence in more than half of patients. The role of infliximab and other biologic agents such as adalimumab and Certolizumab in promoting and maintaining fistula closure has been demonstrated in studies. Other immunosuppressive agents such as tacrolimus and thalidomide have been used.
Surgical approach to perianal Crohn’s disease
The ideal outcome of CD anal fistula treatment is complete and sustained closure of the fistula without abscess formation, avoidance of surgery, and improved quality of life. In actual clinical situations, most patients are unable to achieve this goal, but new drugs are emerging to achieve long-term complete fistula closure in an increasing number of patients. The current clinical focus is on reducing fistula exudate, promoting fistula healing, and improving quality of life. Surgical treatment may cause more harm than the disease itself and should be relatively conservative.
Anal fistulas are the most difficult of the perianal lesions in CD. the Parks staging of CD fistulas can be used (Figure), but clinically they are generally classified into simple and complex fistulas based on anal examination (including the presence or absence of dermatomes, fissures, fistulas, abscesses, strictures, rectovaginal fistulas, and rectal inflammation) and MR of the anal canal.
Parks typing of anal fistula
1.Low anal fistula incision
Low anal fistula can be obtained with good results by incision. However, fistulotomy should be avoided as much as possible to avoid prolonged wound healing. Most low anal fistulas without rectal inflammation can be cured by fistulotomy and or medication, but care should be taken to protect the sphincter, as partial severance may lead to fecal incontinence.
2.Complex fistula with wire drainage
Complete cure of complex fistulas is almost impossible. The aim of treatment is often not to cure the fistula but to reduce the symptoms. High-grade fistulas should be treated with a line to protect the function of the sphincter.
Drainage lines can be placed indefinitely or until the fistula lining allows removal of the line. Proctitis combined with a high complex fistula requires a combination of medication, line drainage, temporary stoma, or rectal resection. In a retrospective analysis of cases of CD combined with anal fistula at the Sixth Hospital of Sun Yat-sen University, it was concluded that non-incisional hanging wire allows for adequate long-term drainage of complex anal fistulas combined with CD and may be a better surgical procedure for Crohn’s disease combined with complex anal fistula.
3. anterior rectal flap repair
After the fistula is adequately drained and the inflammatory activity of the rectum is quiescent, transanal anterior rectal flap repair can be used to close the internal opening of the fistula. For high-grade complex anal fistula without combined proctitis, anterior rectal transposition of mucosal flap is feasible, and one-third can achieve complete healing.
Prognosis
The success of treatment of perianal abscesses and fistulas depends to a large extent on the rectal condition. If there is no inflammation in the rectum or if CD activity is reduced, the chances of cure are high. For complex fistulas with severe lesions in the rectum, anal incontinence and significant anal stenosis, rectal resection or colorectal resection, permanent colostomy or small colostomy should be performed promptly after failure of medication and local treatment to relieve the patient’s pain and improve the patient’s quality of life. Temporary stoma does not improve the final prognosis of patients with perianal Crohn’s disease, and less than 25% of patients are able to return the stoma, and most patients who successfully return the stoma also need to undergo another anal surgery.