Everything you wanted to know, but were afraid to ask.
Part I: Perianal abscesses

Many of us are a little tentative when dealing with emergency presentations of ano-rectal disorders. A couple of months ago, we featured an interview by Dr. Rob Orman with Dr. Megan Cavanaugh, a colorectal surgeon in Portland, Oregon. The interview was surprisingly popular because Dr. Cavanaugh was a great sport and didn’t hesitate to weigh in candidly on our most common concerns. Admittedly, most of her recommendations are not evidence-based due to a lack of controlled studies. Nonetheless, we give considerable weight to the experience of our surgical colleagues, many of whom have an enormous wealth of experience in this area due to the common nature of these conditions and the sheer number of referrals that they receive.

Emergency physicians are often uncertain about when and how to drain perianal abscesses. We worry about abscesses being too deep and beyond our scope of practice. Although there are many complex terms and designations for abscesses in the various potential spaces of the ano-rectal region, a simple rectal examination can usually determine if an abscess requires surgical referral for drainage. Severe pain or fluctuance ascending proximally along the ano-rectal canal should alert the clinician to the presence of a deeper (perirectal) abscess. Perirectal abscesses are best drained in the operating room under general anesthesia. In some instances, these also involve other abnormalities, such as fistulae, which also require surgical repair.

Another common concern of EPs is that we may do damage to the anal sphincter and other important structures in an area of complex anatomy. In fact, the real danger to sphincter integrity comes from delay of drainage. Dr. Cavanaugh offers reassurance that if we find an area of redness and fluctuance, a place where the abscess seems to be coming to a head, it is rarely a bad idea to incise it in the emergency department. Regardless of how close it may be to the anal sphincter, incising over an area of fluctuance to relieve the pressure head of pus is unlikely to do any damage and will usually offer the patient a great deal of relief. It will also improve their overall clinical status and decrease the risk of sepsis. Provided that these patients are otherwise well and clinically stable, incision and drainage of a perianal abscess in the emergency department is usually sufficient to allow discharge home and outpatient follow-up with a colorectal surgeon. Of course, not all drained abscesses need follow-up with a specialist, especially those that are superficial and have minimal associated induration.

With respect to the technique of incision and drainage, Dr. Cavanaugh makes some further recommendations. In order to minimize the risk of incising the ano-rectal canal and its surrounding musculature, incisions should generally be made radially away from the anus, as opposed to circumferentially. Any dissection that is done beyond the initial skin incision should occur with a blunt instrument like a hemostat and should be done in a plane parallel to or away from the ano-rectal canal. Local anesthesia is often suboptimal in these cases and procedural sedation should be seriously considered. If deep dissection appears necessary to break up loculations, what appears to be a simple perianal abscess may be tracking more proximally into the perirectal realm. This should prompt surgical consultation and/or advanced imaging to determine the full extent of the abscess.

Many practitioners have moved away from gauze packing to keep wounds open because of the serious pain and discomfort that it causes patients. In larger abscesses, excising an elliptical piece of skin over the abscess is an alternative method to ensure that the abscess cavity does not close off and drainage can continue after the procedure. Antibiotics are generally not necessary but are appropriate in patients with signs of systemic infection or co-morbid conditions that result in immune compromise.

Next time we will deal with another common enigma: hemorrhoids.

Dr. Swadron is the vice-chair for education in the department of EM at the LA County/USC Medical Center. He is an assoc. prof. of clinical EM at the Keck School of Medicine. EM:RAP is a monthly audio program that can be found at www.EMRAP.org



# What on earth would cause one of these abcesses?cew 2011-11-09 04:40
That sounds horrible! What makes this happen?

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