Clinical Presentation
Most anorectal infections originate in the crypto glandular area located in the anal canal at the level of the dentate line. Abscesses within these glands can then penetrate the surrounding sphincter and track in a variety of directions. This leads to larger abscesses within the perianal, intersphincteric, ischiorectal, and supralevator spaces. A small number of anorectal abscesses have a non-crypto glandular etiology such as Crohn's disease, atypical infection (e.g., tuberculosis, lymphogranuloma venereum), malignancy, or trauma. Particularly virulent organisms, immunologic deficiency in the patient (e.g., poorly controlled diabetes, human immunodeficiency virus [HIV]), or localized scarring from previous operations can make the diagnosis more challenging. Fever, rigors, and shock may occur before more subtle localized findings. Pain and swelling are the most frequent complaints. Bleeding, purulent discharge and fevers may also be present. A perianal abscess is usually evident at the anal verge. An inflammatory process in the soft tissues of the buttock would more commonly indicate a perirectal abscess. Pelvic pain and dysuria may herald a supralevator abscess. The majority of patients with a fistula-in-ano have a history of abscess development with persistent drainage, pain and possibly bleeding. The external opening on the skin is evident and digital rectal exam, anoscopy or proctoscopy may reveal an indurated area in the anal canal corresponding to the internal opening. Fistulae are categorized according to their relationship with the external sphincter complex. The majority of these fistulae are intersphincteric and about one fourth are transsphincteric. If there is any suspicion of an underlying disease such as Crohn’s or immune suppression, this should be thoroughly evaluated prior to the formal treatment of the fistula. Pilonidal cysts initially present as an abscess and/or cellulitis in the sacrococcygeal area. Spontaneous drainage often occurs followed by chronic drainage from the secondary sinuses. Some of these may track toward the anus, potentially being confused with a fistula-in-ano or hidradenitis suppurativa. The latter is a chronic suppurative disease of the epidermal apocrine sweat glands. Consequently, it can occur in the perineal/perianal region, in the areolar area of the breasts and quite frequently in the axillae. It is most commonly seen in the second through fourth decades of life and is thought to be hormonally influenced.
In primary pruritus ani, impaired sphincter function predisposes this area to moisture and inflammatory fecal elements from such dietary elements as caffeinated and acidic dietary products. Excessive cleansing or poor hygiene will also initiate an irritative process. Intertrigo, a mixed bacterial infection associated with obesity, may also be involved. Pinworms should be considered in children and exposed adults. Pruritus vulvae, resulting from urinary incontinence or vaginal discharge may spread to the perianal region, and mycotic infections should also be considered in the differential diagnosis.
Treatment
Anorectal pain that prevents a digital examination necessitates an examination under anesthesia. Needle aspiration can demonstrate a collection of pus that is accessible to percutaneous drainage. As with any abscess, incision and drainage is the definitive form of therapy. Antibiotics should also be considered when there is significant cellulitis surrounding the abscess or when the patient is immunocompromised or has cardiac valvular pathology. Perianal and ischiorectal abscesses can usually be drained using local anesthesia if they have tracked to the subcutaneous area. A cruciate incision or an elliptical excision of skin overlying the area of fluctuance is recommended to avoid premature closure of the drainage site during the period of resolution. The surgical incision should be as close to the anal verge as possible, so as to minimize the length of a potential fistulous tract. If the abscess cavity is large, and the procedure is being performed under general anesthesia, digital exploration should be performed to break up any loculations. Packing of the wound is only necessary for initial hemostasis. Adequate drainage, followed by frequent sitz/tub baths, especially after bowel movements, will reduce the risk of continued infection and recurrence. If there is palpable crepitus, a Gram stain of the tissue/fluid can be helpful in identifying clostridia.
Established operative goals for an anal fistula are to open the tract and remove the epithelial lining by curettage, electrocautery, etc. There has been some success in the use of fibrin glue for these fistulas. Several methods of determining the configuration of a fistulous tract are possible. Any resistance to the passage of a probe should be avoided so as to prevent the creation of false passages. If the internal opening is not evident, injection of dilute methylene blue dye, milk or hydrogen peroxide into the external opening with an angiocatheter may facilitate the visualization. Judicious unroofing of the observable tract may also allow better recognition of the entire tract. Preoperative transanal ultrasound and fistulography are useful diagnostic modalities to be considered. If little or no external sphincter muscle is involved, the external opening and skin overlying the tract may be excised. When greater than half of the external sphincter muscle is involved, or in the patient where sphincter integrity is already at risk, a seton can be applied. In this setting, after the skin and involved internal sphincter are opened, a strip of material is inserted around the overlying external sphincter component and tied snugly. Setons can be fashioned from silk sutures, vessel loops or Penrose drains. During the 1-2 months following the operation, the seton will erode into the muscle and cause an inflammatory response, which prevents significant retraction of the sphincter ends. Either the seton will completely erode through, or the remaining smaller amount of external sphincter can then be transected. A newer alternative, after the seton stabilization period, is the instillation of fibrin glue into the tract after the internal opening is closed with a suture. Treatment in the acute phase of a pilonidal cyst/abscess involves simple incision and drainage. Antibiotics are used if there is significant cellulitis. Any septations should also be disrupted. Because hair and particulate matter are often found within the cavity/sinuses, the use of depilatory cream should be considered to lower the risk of recurrence. The development of chronic sinuses will require further operative intervention for removal.
For hidradenitis suppurativa, unless there are abscesses that need operative drainage, local symptomatic therapy and antibiotics for the cellulitis is initially adequate. Unfortunately, chronicity is common and the drainage and pain can be debilitating. Because the etiology involves the epidermal sweat glands, the only definitive treatment is the excision of involved tissue. Wound healing by secondary intention is frequently chosen, but very large areas may need coverage with surrounding tissue transfers. In order to optimize the healing of complicated wound closures, a temporary diverting colostomy should be considered.
With pruritus ani, patient education, reassurance and close follow-up are imperative. The goal is to attain clean, dry, intact skin. Overzealous cleansing, scratching and colored or perfumed toilet papers should be avoided. Secondary pruritus ani can result from anatomical pathology of the anorectum such as fistulae, fissures and hemorrhoids. Infectious processes, radiation damage and neoplasms can also be responsible.
Qualifications for Performing Surgery on Perineal Suppurative Processes
The qualifications of a surgeon to perform any operative procedure should be based on education, training, experience and outcomes. At a minimum, the surgical treatment of perineal suppurative processes should be carried out by surgeons who are certified or eligible for certification by the American Board of Surgery, the American Board of Colorectal Surgery, the Royal College of Physicians and Surgeons of Canada, or their equivalent.
