Secondary Healing of Horseshoe Perianal Abscess in a Patient With Morbid Obesity: Experience at a Rural Hospital

Perianal abscess is a local collection of pus in the perianal tissues, and it is among the most common anorectal problems encountered by surgeons. The most frequent etiology is glandular infection arising from the anal crypts, and perianal abscess is associated with anal fistula in approximately 40% of cases.¹ According to Sahnan et al,² 90% of perianal abscesses are caused by cryptoglandular infection. The remaining 10% are the result of etiology other than anal gland infection, such as Crohn disease, tuberculosis, trauma, chronic inflammation, hidradenitis suppurativa, HIV, sexually transmitted diseases, radiotherapy, malignancy, and foreign bodies.^3,4 Further extension of this infection into the unilateral or bilateral ischiorectal fossa through the conjoint longitudinal muscle in the anterior or posterior midline, or through the deep anterior or posterior anal space, leads to a horseshoe abscess.⁵

Perianal abscess is one of the most common anorectal diseases that occurs in males aged 30 to 50 years.⁵ The incidence is 16.1 to 20.2 per 100 000 per year, and the rate of subsequent fistula formation following an abscess is 15.5%.^2,6 Perianal abscess may spread alongside the rectum (ischiorectal), above the pelvic floor (supralevator), or between the muscles of the anal canal (intersphincteric).⁷

If the perianal abscess is not drained spontaneously or surgically, the infection may spread rapidly and result in extensive tissue loss. Even if the abscess is drained, fistula-in-ano may occur.⁶ The goal of surgical management of anal fistula is to eradicate sepsis and promote healing of the tract while preserving the sphincters and the mechanism of continence; surgery is also performed to prevent recurrence.⁸ Management of fistula-in-ano remains challenging.^5,8

The authors’ experience of managing a case of horseshoe perianal abscess with secondary healing process in a 35-year-old male with morbid obesity is reported to broaden the knowledge and perspective of diagnosis and management of an extending perianal abscess.

A 35-year-old male with a BMI of 35.5 kg/m² (height, 175 cm; weight, 108 kg) presented to the surgery outpatient clinic at RS PTPN VIII in Subang, West Java, Indonesia, with continuous severe pain and swelling around the anal area of approximately 7 days’ duration. The patient also presented with a high-grade fever, appeared agitated, and was mildly obese per BMI measurement; although the BMI was below the threshold of morbid obesity, obesity-related type 2 diabetes was also present, which could warrant the designation of morbid obesity. The medical history did not include a significant chronic condition such as primary hypertension, any type of heart disease, disturbed microcirculation, peripheral neuropathy, diabetes, impaired immune system, malignancy, leukemia, long-term administration of corticosteroids, liver cirrhosis, renal failure, urinary tract infection, or hemodialysis. He also reported no history of infectious diseases such as tuberculosis or AIDS. The patient’s medical history revealed no trauma or any other surgical intervention. He had no contact history of toxicity or radioactive exposure. No family history of any inherited cancer was reported, and he reported no history of smoking or alcohol consumption. The patient worked as an engineer in a private manufacturing company and preferred a sedentary lifestyle.

General physical examination revealed a high-grade fever (39.1 °C), tachycardia (pulse rate of 122 bpm), and tachypnea (respiratory rate of 24/min), both blood pressure and oxygen saturation were within normal limits. Physical examination of the anogenital region, including inspection, palpation, and digital rectal examination, revealed perianal abscess extending to the ischiorectal fossa, approximately 1 cm from the anal verge and measuring 7.5 cm × 4.5 cm × 10 cm. Tenderness; presence of blood, pus, and necrotic tissue; and fluctuance were noted (Figure 1). Laboratory tests revealed leukocytosis (leukocyte count, 35 900 cells/µL; percentage of granulocytes, 87%) and thrombocytosis (thrombocyte count, 675 000 cells/µL). Other complete blood test values were within the normal limit, including random blood glucose of 133 mg/dL, hemoglobin of 13.3 g/dL, and hematocrit of 41%. Renal function as measured by levels of urea and epithelial cells was within normal limits. Computed tomography and MRI were not performed due to resource and facility limitations at the hospital.

Initial resuscitation with crystalloids, IV broad-spectrum antibiotics (1000 mg cefoperazone twice daily), IV NSAIDs (1000 mg ketorolac twice daily), IV proton-pump inhibitor (1000 mg once daily), and oral antipyretic (500 mg acetaminophen twice daily) was followed by examination under general anesthesia. Prior to the induction of general anesthesia, the patient received counseling regarding the emergency procedure and written informed consent was obtained. In the operating room, thorough inspection and washout of the bilateral ischiorectal spaces were performed through the surgical incisions.

Intraoperative finding

Incision and dissections were performed with scalpel, scissors, and electrocautery, and the entire surface and tract of the abscess were traced up to the limit of healthy tissue. Primary treatment of the horseshoe abscess consisted of surgical incision and drainage. Drainage was performed as close to the anus as possible to shorten the length of any subsequent fistula tract, should one arise.

After observing that the abscess had reached the ischiorectal area and formed a horseshoe abscess, necrotomy, debridement, and evacuation of pus were performed. The perianal abscess was found to extend to the ischiorectal fossa and to have formed a posterior horseshoe abscess approximately 1 cm from the anal verge and 7.5 cm × 4.5 cm × 10 cm in size. Necrotic tissue was excised, and approximately 1000 mL of pus mixed with blood was drained. The internal and external sphincters were intact (Figure 2).

The surgical procedure lasted approximately 45 minutes. The deep postanal space was packed with moist (normal saline-soaked) gauze and surgical drainage made from a thin, flexible rubber tube placed in the surgical site to prevent the buildup of fluid, and an external wound dressing was applied.

Postoperative care and follow-up

During the first 2 postoperative days, the moist gauze packing and external wound dressing were changed once to twice daily. Sitz bath, regular cleaning with normal saline, and emptying of the tract were also done once or twice per day. It was recommended that the patient eat a hard-texture diet low in fiber to decrease the frequency of defecation. Because of the possibility of frequent fecal contamination exposure to the wound, the patient was advised to undergo colostomy surgery but declined. Instead of colostomy, the patient chose wound healing by secondary intention.

After adequate drainage of the blood and pus, postoperative wound care was continued by using hydrocolloid dressing as the internal (primary) wound dressing and aluminum silicate-microporous ceramic as the external (secondary) wound dressing. This combination was chosen to maintain moisture balance, minimize the frequency of dressing changes to prevent further exposure to the outer environment, and avoid infection. The dressings were changed every 3 to 5 days when they were sufficiently saturated with pus and blood.

Length of stay in the hospital was 9 days. Laxatives were prescribed to soften the stool and ease defecation. Paracetamol was used as the primary analgesic; higher-potency analgesic NSAIDs (diclofenac) did not need to be given. The patient was also prescribed antibiotics (levofloxacin) for 14 days. Follow-up was conducted twice weekly for wound dressing changes every 3 to 5 days until complete healing was achieved. The patient sat in a sitz bath with warm water and antiseptic twice daily. Follow-up included monitoring the patient’s vital signs and the wound for the presence of necrotic tissue, slough, granulation tissue, pus, and fecal contamination (Figure 3).

After healthy granulation tissue began to form, alginate dressing was used as the internal (primary) dressing, with aluminum silicate-microporous ceramic as the external (secondary) dressing. Healing time, defined as the period from the date of surgery to the date of complete healing, was 8 weeks (Figure 4).

According to Hsieh et al,⁹ the 1-year recurrence rate of perianal abscess in patients who survived during hospitalization was 13.9%. Inadequate drainage, failure to break up loculations, and/or failure to reveal multiple fistulous tracts increase the rate of persistence.¹⁰ To achieve a satisfactory response to treatment, it is important to understand the etiopathogenesis of the disease.

Infections of the anal glands (ie, cryptoglandular infection) in the intersphincteric plane cause the majority of anorectal suppurative disease. At the level of the dentate line of the anal canal, the excretory ducts of the anal glands pass through the internal sphincter and empty into the anal crypts. An abscess forms when an anal gland is infected, and the abscess then enlarges and spreads along one of many planes in the perianal and perirectal areas. The anus is surrounded by the perianal area, which laterally merges with the buttock’s fat. The internal and external anal sphincters are separated by the intersphincteric gap. The intersphincteric gap is cephalad to the rectal wall and is contiguous with the perianal region distally.^11,12

The ischiorectal space (ischiorectal fossa) is located lateral and posterior to the anus and is bounded medially by the external sphincter, laterally by the ischium, superiorly by the levator ani, and inferiorly by the transverse septum. The inferior rectal arteries and lymphatics are in the ischiorectal area. The deep postanal space is formed when the 2 ischiorectal spaces unite posteriorly above the anococcygeal ligament but below the levator ani muscle. The supralevator spaces, which are located above the levator ani on either side of the rectum—and which communicate posteriorly—are located above the levator ani on either side of the rectum. The location and spread of cryptoglandular infections are influenced by the anatomy of these areas.^11,12

Simple anorectal abscess is usually diagnosed by physical examination alone in patients experiencing intermittent pain and purulent, often bloodstained, perianal discharge with a common history of anorectal abscess drainage. Although physical examination is usually sufficient for assessment in uncomplicated abscess fistula disease, imaging studies such as contrast fistulography, US, or MRI may be useful in the evaluation of complex or recurrent disease.¹² However, owing to limitations of the imaging facility in the current case, passage of a probe and hydrogen peroxide injection technique were used to identify the internal opening; the pressure created by the bubbles may be sufficient to penetrate even a stenotic tract.

Passage of a probe through both the external and the internal opening of the fistula is the most reliable technique to demonstrate the course of the fistulous tract. In a 2014 study, MRI had a positive predictive value of 93%, a negative predictive value of 90% for anorectal abscess, and a sensitivity of greater than 90% for fistula-in-ano.¹³ The TPUS had a sensitivity of 85% and a positive predictive value of 86% for anal fistulas and was of similar value to EUS for the diagnosis of anorectal abscess and delineating fistula tracts; it is especially effective in identifying horseshoe abscess extensions.¹⁴ Three-dimensional US techniques provide even better imaging, especially in patients with complex perianal sepsis or high-riding tracts.¹⁰ Combining 3-D US with hydrogen peroxide injection through the external opening has demonstrated accuracy rates comparable to MRI, with close to 90% concordance.¹⁰ Tomography can be useful for patients with complex suppurative anorectal conditions, and it is especially helpful in identifying supralevator abscesses, or for those patients who would otherwise be difficult to examine without anesthesia.¹⁰

Most perianal abscesses can be managed in the outpatient setting. Some conditions, such as cellulitis without fluctuance, failed drainage in the outpatient setting, abscesses with associated systemic signs of sepsis, or extensive abscesses, are more appropriately managed in an operating room where thorough examination under anesthesia can ensure optimal diagnostic evaluation and drainage.¹¹ For superficial abscesses, drainage under local anesthesia is feasible. It should be performed as close as possible to the anal verge to achieve adequate drainage and breakdown of loculations.¹⁴ For a more complex abscess, drainage should be performed in the operating room under general anesthesia, sedation, or local anesthesia.¹⁵

Pain relief is usually immediate. Patients are instructed to use sitz bath, bulk-forming fiber laxatives, and analgesics. Bleeding and drainage usually subside within a few days. The wounds should heal in a few weeks. Surgical follow-up is encouraged because acute abscess recurs in 13.9% of patients and development of chronic fistula-in-ano occurs in up to 40% of patients.^1,9

Antibiotics are unnecessary with routine incision and drainage of an uncomplicated abscess, as they have not been shown to improve healing times or reduce recurrence rate. However, antibiotics should be considered for patients with high-risk conditions such as immunosuppression, diabetes, extensive cellulitis, prosthetic devices, and high-risk cardiac, valvular, and anatomic conditions.^11,16 The patient was given antibiotics in the current case because the last random blood glucose level, measured before the patient was discharged from the inpatient ward, was slightly high (200 mg/dL).

Colostomy is performed for fecal diversion and is indicated in patients with severe perineal involvement or extensive resection of the sphincter, as well as in those at high risk of fecal contamination in the anorectal area and sphincter for whom wound management may be difficult. After complete wound healing is achieved, anastomosis of colostomy may be performed.^11,17,18 The advantage of using colostomy is that it prevents fecal contamination in the anorectal area. Colostomy is associated with several complications, however, such as improper stoma site selection; vascular compromise; retraction; peristomal skin irritation; peristomal infection, abscess, or fistula; acute parastomal herniation and bowel obstruction; and technical errors (pure human error).¹⁹ Due to patient preference to avoid colostomy in the current case, laxatives were prescribed to soften the stool and ease defecation; the patient was also advised to eat a soft-texture diet after the first postoperative day.

Many surgical options for definitive management of horseshoe fistulae originating from cryptoglandular sepsis have been described, including posterior midline sphincterotomy/fistulotomy with and without counter incisions, wide debridement and unroofing, incision and drainage, endorectal advancement flap, fibrin glue injection, collagen plug, and fecal diversion.²⁰ However, because of resource and facility limitations, as well as patient preference in this case, wound healing by secondary intention with the principal of moisture balance was chosen. The authors of this case report preferred open wound care to better control the progression of wound healing. The patient was followed up weekly until complete wound healing was observed based on the following parameters: vital signs and the presence of necrotic tissue, slough, granulation tissue, pus, and fecal contamination. Granulation tissue formation was expected in this case, but all parameters were considered.

Skin graft was indicated based on the extensive wound area. However, the treating clinicians chose open wound care to promote healing with secondary intention based on the patient’s comorbidities (obesity), the patient’s refusal of skin graft, and the availability of a good wound care facility at the authors’ center.

The ideal wound dressing should maintain moisture balance, provide hydration (if the wound is dry or desiccated), allow drainage of excessive exudates, prevent desiccation and be nontraumatic, allow for gaseous exchange, and be impermeable to microorganisms. In addition, a wound dressing should be free of toxic particles or irritants, should not release particles or nonbiodegradable fibers into the wound, should be associated with minimal pain during application and removal, and should be easy to use and cost-effective.²¹

For the patient in this case report, wet-to-moist gauze with drainage was applied during the first 2 postoperative days. Gauze is familiar to hospital staff, inexpensive, reliable, available, and highly absorbent. It is highly permeable, is nonocclusive, and can be used as a primary or secondary wound dressing. It is commonly used on both infected and noninfected wounds, large or irregularly shaped wounds, or in packing strips to prevent premature closure or to keep exudates away from the surrounding skin.²⁰ Removal of a wet-to-moist dressing that has dried may cause reinjury of the wound, resulting in pain and delayed wound healing.²² Thus, for the patient in the current case report, this wound dressing method was used only for the first 2 postoperative days with the primary aim of optimizing the drainage of pus and blood. Use of wet-to-moist gauze also allowed the treating clinicians to routinely monitor pus drainage and the wound healing process.

In this case, after the pus had sufficiently drained, hydrocolloid dressing was chosen as the internal (primary) wound dressing. Hydrocolloid dressings consist of 2 layers. The inner, hydrocolloid adhesive layer has particles that absorb exudate to form a hydrated gel over the wound, creating a moist environment that promotes healing and protects new tissue. The outer layer (film, foam, or both) forms a seal to protect the wound from bacterial contamination, foreign debris, urine, and feces. The outer layer also maintains a moist environment and helps prevent shearing. In the chronic setting, hydrocolloid dressings are advantageous because they do not have to be changed frequently and they can be used on wounds in various stages of healing. They are suitable for use on necrotic, sloughy, granulating, or epithelializing wounds; however, they are not the dressing of choice in wounds with copious amounts of drainage. Hydrocolloid dressing can be replaced after 3 to 5 days.²³

In this case, alginate dressing was applied after granulation tissue began to form. Alginates, which are extracted from seaweed, are thought to have hemostatic properties suitable for heavily draining wounds and bleeding wounds owing to their high absorbency.^21,23 An ion-exchange interaction occurs between the calcium ions in the dressing and sodium ions in serum or wound fluid once it comes into contact with an exuding wound. The fiber swells and partially dissolves when a sufficient fraction of the calcium ions on the fiber are replaced by sodium, generating a gel-like substance.²³ Patients report less pain during application and removal of alginate dressing compared with gauze (P <.02).^20,23

This case report is limited in that it discusses a single patient. Due to resource and facility limitations, diagnostic imaging to better visualize the anatomical tract of the horseshoe abscess was not conducted. Monitoring the patient’s blood glucose level should also be performed during wound management.

Horseshoe abscesses have long been a challenging condition to manage, mainly owing to the risk of postoperative incontinence and the high rates of recurrence. Thorough and careful diagnosis is required, along with prompt resuscitation, a properly planned surgical approach, and individualized postoperative care.

Wound healing by secondary intention may be successfully achieved with careful consideration and selection of the appropriate wound dressing based on the wound healing phase and condition of the wound. Wet-to-moist gauze is appropriate for an infectious wound that requires adequate drainage and for which routine monitoring is possible. Hydrocolloid dressing is useful to maintain moisture balance and decrease the frequency of wound dressing replacement. Alginate dressing, with its hemostatic properties, is suitable for the exudative wound; significantly (P <.02) reduced pain during the application and removal of this dressing has been reported.