Perianal and Perirectal Abscesses 

  • Author: Nelson G Rosen, MD, FACS, FAAP; Chief Editor: Marleta Reynolds, MD   more...
 
Updated: Jan 14, 2010
 

Background

Perianal abscess is a relatively common condition in children. It occurs most often in male infants younger than 1 year but can occur in either sex and at any age. The exact incidence and prevalence of perianal abscesses is not well established. The treatment approach varies somewhat by age and, in most instances, differs from that used in adults.

A perianal abscess is an infection characterized by a collection of pus that has formed under the skin within the soft tissue just outside the anus. The abscess often appears as a raised red lesion under the skin lateral to the anus, where it may grow and become painful. Some abscesses may spontaneously drain pus and heal, whereas others may require surgical intervention. Some perianal abscesses may heal incompletely, with or without surgery, and result in a tiny opening at the site of drainage, called an anal fistula, or fistula-in-ano. This may or may not require an additional surgery.

The vast majority of perianal abscesses develop spontaneously in completely healthy children and are self-limited; however, in older children, the condition can be associated with inflammatory bowel disease (IBD) or other conditions in which the immune system is compromised.

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Epidemiology

Frequency

The overall incidence of perianal and perirectal abscesses in children is unknown. It is a relatively common condition seen in a general pediatric or pediatric surgical practice. In infants, in whom the condition is most prevalent among pediatric patients, the incidence is estimated at between 0.5% and 4.3%, overwhelmingly in males. In older children, perianal and perirectal abscesses have no sexual predilection. No racial predilection is reported in any age group.

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Etiology

The etiology of perianal abscess and fistula-in-ano remains unclear. The prevailing theory implicates small glands in the wall of the anal canal, called the crypts of Morgagni. It is believed that a small infection, or cryptitis, forms in one of these crypts, leading to perianal abscess.

Some authors have suggested that some infants have abnormal crypts, which predispose them to cryptitis and abscess formation. One study showed that the crypts of infants with fistulas tend to be deeper (3-10 mm) than those in healthy infants (1-2 mm).[1] Some have suggested that androgen excess or androgen-estrogen imbalance might predispose to the formation of these abnormal crypts.[2]

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Pathophysiology

The prevailing theory is that an infection in an anal crypt progresses and erodes through the wall of the anal canal into the surrounding soft tissue, where a collection of pus accumulates. This is the perianal abscess.

When a perianal abscess drains spontaneously by eroding through the skin or is surgically drained, a communication is formed between the abscess cavity and the skin. If the infection truly originated in an anal crypt, the abscess cavity must communicate with the lumen of the anal canal. The hole in the skin would therefore also communicate all the way into the anal lumen. When this communication persists over several weeks, it is called a fistula. It is unclear why some individuals form fistulas while others do not.[3]

If the etiology of fistula is abscess drainage, either spontaneously or through surgical incision, it is a logical conclusion that efforts to cure the abscess before it drains, thereby avoiding completing the communication from the anal canal to the skin, may decrease the risk of fistulization. Recent studies have followed this line of thinking and are discussed in the Treatment section.

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Presentation

Perianal abscesses often present within the first few months of life. A perianal abscess, which in many ways is the same as a small pimple, appears as a red swollen area located just outside the anus; this is usually first noticed during a diaper change and may be tender to the touch. Affected children may appear to be irritable but are commonly asymptomatic. Differentiating an upset baby from true tenderness due to perianal abscess can be a challenge for the clinician but is important to reassure parents.

Infants with perianal abscesses generally do not have underlying medical conditions that predispose them to abscesses. Perianal abscess and fistula-in-ano are unrelated to diaper rash.

Older children with perianal abscesses fall into two roughly equally sized categories. The first category is otherwise completely healthy children who have no significant risk factors or history of symptoms suggestive of IBD. Many children are constipated; constipation is a risk factor for anal fissure but not for perianal abscess. The second category of older children with perianal abscesses are those with IBD. Some children with a known history of Crohn disease present with a new abscess or fistula. In many cases, the first manifestation of IBD or Crohn disease in a child is perianal abscess or fistula. Elements in the history that suggest IBD include weight loss, failure to thrive, diarrhea, and chronic abdominal pain.

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Indications

Abscess

In infants younger than one year who present with a small perianal abscess, it is reasonable to try to attain full resolution with an antibiotic regimen and no drainage. Such an approach may decrease the likelihood of fistula formation.[3]

More aggressive treatment is indicated in children younger than one year who present with a large, red, bulging perianal abscess and who appear to be in significant distress. The abscess should be drained, most commonly in the office, and oral antibiotics initiated. Although exceedingly rare, signs of true systemic illness (weakness, lethargy, fever) secondary to the infection in children require admission for intravenous antibiotics.

Routine perianal abscesses in babies do not require operative intervention and do not require general anesthesia for examination or drainage.

An identical approach can be followed in older children without a history of inflammatory bowel disease (IBD), with perhaps a shorter threshold to perform drainage in any patients initially deemed suitable for antibiotics alone. Older children with complex fistulas and/or in extreme pain during the examination require general anesthesia for examination and treatment.

Fistula

Babies who present with a fistula after surgical or spontaneous drainage of an abscess should undergo a period of nonoperative observation and should be observed until age 18 months provided that they remain otherwise happy and healthy.[4] After this time, it is reasonable to consider surgical fistulotomy for resolution.

Older children with fistulas secondary to Crohn disease should be referred to a pediatric surgeon with significant IBD experience or to an adult colorectal surgeon.

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Relevant Anatomy

The anal canal and the skin around it are the site of perianal abscesses and fistulas. Just inside the anal canal, about 1-2 cm from the anal verge in most babies, are small pits in the wall of the anal canal called anal crypts or the crypts of Morgagni. It is believed that these abscesses and fistulas originate as an infection in these anal crypts. The infection then erodes through the wall of the anal canal and extends into the fat beneath the perianal skin. Here it can go in one of two directions: (1) The infection can head toward the skin (most common), or (2) it can track deeper into what is referred to as the ischiorectal fossa, bounded superiorly by the levator ani muscles. Infections in the ischiorectal fossa are rare in the pediatric population.

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Contributor Information and Disclosures
Author

Nelson G Rosen, MD, FACS, FAAP  Assistant Professor of Surgery and Pediatrics, Albert Einstein College of Medicine; Attending Pediatric Surgeon and Director, Pediatric Trauma Center, Department of Pediatric General Surgery, Schneider Children's Hospital

Nelson G Rosen, MD, FACS, FAAP is a member of the following medical societies: American Academy of Pediatrics, American College of Surgeons, American Pediatric Surgical Association, American Trauma Society, Association of Military Surgeons of the US, Canadian Association of Pediatric Surgeons, and Eastern Association for the Surgery of Trauma

Disclosure: Nothing to disclose.

Specialty Editor Board

Kurt D Newman, MD  Vice Chairman, Department of Pediatric Surgery, Children's National Medical Center; Professor, Departments of Surgery and Pediatrics, George Washington University School of Medicine

Kurt D Newman, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Surgeons, American Pediatric Surgical Association, and Society of Surgical Oncology

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Andre Hebra, MD  Chief, Division of Pediatric Surgery, Professor of Surgery and Pediatrics, Medical University of South Carolina College of Medicine; Surgeon-in-Chief, Medical University of South Carolina Children's Hospital

Andre Hebra, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Surgeons, American Medical Association, American Pediatric Surgical Association, Children's Oncology Group, Florida Medical Association, International Pediatric Endosurgery Group, Society of American Gastrointestinal and Endoscopic Surgeons, Society of Laparoendoscopic Surgeons, South Carolina Medical Association, Southeastern Surgical Congress, and Southern Medical Association

Disclosure: Nothing to disclose.

H Biemann Othersen Jr, MD  Professor of Surgery and Pediatrics, Emeritus Head, Division of Pediatric Surgery, Medical University of South Carolina

H Biemann Othersen Jr, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Association for the Surgery of Trauma, American Burn Association, American Cancer Society, American College of Surgeons, American Medical Association, American Pediatric Surgical Association, American Society for Parenteral and Enteral Nutrition, American Surgical Association, American Thoracic Society, British Association of Paediatric Surgeons, Society for Surgery of the Alimentary Tract, Society of Critical Care Medicine, South Carolina Medical Association, Southeastern Surgical Congress, Southern Medical Association, Southern Society for Pediatric Research, and Southern Thoracic Surgical Association

Disclosure: Nothing to disclose.

Chief Editor

Marleta Reynolds, MD  Professor of Surgery, Northwestern University, The Feinberg School of Medicine; Head, Department of Surgery and Surgeon in Chief, Head, Division of Pediatric Surgery, Children's Memorial Hospital of Chicago

Marleta Reynolds, MD is a member of the following medical societies: American Pediatric Surgical Association

Disclosure: Nothing to disclose.

Acknowledgments

The author wishes to acknowledge Dr. Alberto Pena and the late Dr. James Warden. Dr. Warden was an eminent pediatric surgeon, and, on a visit to his friend and fellow eminent pediatric surgeon (and the author's mentor) Dr. Pena, Dr. Warden communicated his technique of nonoperative management of fistula-in-ano. This radical concept led to a study in this regard in which the author extensively participated and thereby inherited Dr. Pena's passion for this subject and for the optimal care of children with this condition.

The author would also like to thank Dr. Peter Masiakos and his colleagues for their further efforts to advance the nonoperative treatment of children with perianal abscess with the thought that avoiding fistula-in-ano is better than treating it.

The authors and editors of eMedicine also gratefully acknowledge the contributions of prior authors Asma Al Mannaie, MBBS, and Pramod S Puligandla, MD, MSc, FRCSC, FACS, to the development and writing of this article.

References
  1. Shafer AD, McGlone TP, Flanagan RA. Abnormal crypts of morgagni: The cause of perianal abscess and fistula-in-ano. J Pediatr Surg. March/1987;22:203-204. [Medline].

  2. Fitzgerald RJ, Harding B, Ryan W. Fistula-in-ano in childhood: a congenital etiology. J Pediatr Surg. February/1985;20(1):80-81. [Medline].

  3. [Guideline] Christison-Lagay ER, Hall JF, Wales PW, et al. Nonoperative management of perianal abscess in infants is associated with decreased risk for fistula formation. Pediatrics. September 2007;120(3):e548-52. [Medline]. [Full Text].

  4. [Guideline] Rosen NG, Gibbs DL, Soffer SZ, Hong AR, Sher M, Pena A. The Nonoperative Management of Fistula-in-Ano. J Pediatr Surg. June 2000;35(6):938-939. [Medline].

  5. Abercrombie JF, George BD. Perianal abscess in children. Ann R Coll Surg Engl. Nov 1992;74(6):385-6. [Medline].

  6. Festen C, van Harten H. Perianal abscess and fistula-in-ano in infants. J Pediatr Surg. May 1998;33(5):711-3. [Medline].

  7. Ho YH, Tan M, Chui CH, et al. Randomized controlled trial of primary fistulotomy with drainage alone for perianal abscesses. Dis Colon Rectum. Dec 1997;40(12):1435-8. [Medline].

  8. Laberge JM. Perianal abscess and fistula-in-ano in infants. J Pediatr Surg. Dec 1998;33(12):1848. [Medline].

  9. Macdonald A, Wilson-Storey D, Munro F. Treatment of perianal abscess and fistula-in-ano in children. Br J Surg. Feb 2003;90(2):220-1. [Medline].

  10. Murthi GV, Okoye BO, Spicer RD, et al. Perianal abscess in childhood. Pediatr Surg Int. Dec 2002;18(8):689-91. [Medline].

  11. Nix P, Stringer MD. Perianal sepsis in children. Br J Surg. Jun 1997;84(6):819-21. [Medline].

  12. Serour F, Gorenstein A. Characteristics of perianal abscess and fistula-in-ano in healthy children. World J Surg. March 2006;30(3):467-472. [Medline].

  13. Serour F, Somekh E, Gorenstein A. Perianal abscess and fistula-in-ano in infants: a different entity?. Dis Colon Rectum. February 2005;48(2):359-64. [Medline].

  14. Tang CL, Chew SP, Seow-Choen F. Prospective randomized trial of drainage alone vs. drainage and fistulotomy for acute perianal abscesses with proven internal opening. Dis Colon Rectum. Dec 1996;39(12):1415-7. [Medline].

  15. [Guideline] Watanabe Y, Todani T, Yamamoto S. Conservative management of fistula in ano in infants. Pediatr Surg Int. Apr 1998;13(4):274-6. [Medline].

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