The Anal Fistula: How Proctologists Diagnose It

Medically reviewed by: Gary H. Hoffman, MD

First, What Is An Anal Fistula?

It takes many years for a fledgling surgeon to truly understand the pathophysiology of an anal fistula.  The topic is complicated by the complexity of the anal canal and by difficulty seeing the actual path taken by the fistula, since much of the path is underneath the skin, not visible to the eye of the examiner.  However, the trained eye (and ears) of the proctologist, also known as a colon and rectal surgeon, will be able to find the fistula.

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But, what is a fistula?  Broadly speaking, a fistula is an abnormal connection between two areas not normally connected to each other.  A fistula can connect two pieces of unrealted intestine together, or can connect a piece of intestine to the skin.  Think of a fistula as a tube; but a tube that should not exist under normal circumstances.  In the case of an anal fistula,  the connection is usually between the anus and the skin of the buttocks.

A Brief Anatomy Lesson.

The anal canal is designed to store fecal matter and aid in expelling it at a convenient time.  The anal canal is about 2 to 4 centimeters in length and has several layers.  The innermost layer is the mucosa, which is a delicate lining.  The outer portion of the anal canal is the muscular sphincter complex which serves to control the timing of when we expel our bowel movements.  The sphincter has an internal component that is not under our control and which serves to involuntarily remain closed so that we do not have accidents, and an external sphincter, which is under our control and allows us to open our anal opening at a time of our choosing.

The canal is divided by the dentate line, a circumferential line between the upper and lower portions of the anal canal.  This line has glandular openings.

A Brief Pathology Lesson.

For reasons unknown, an anal gland may become infected and attempt to discharge the infection by burrowing outward to the skin.  If it cannot travel all of the way to the skin, the infection (pus) is trapped and forms an abscess.  It is at this time that the proctologist will need to lance (drain) the pus through a small incision.  It that incision does not heal, it is now termed a fistula.  Sometimes, the pus can travel to the skin and drain spontaneously, but with the same result; it may eventually heal, or may remain open as a fistula.

The Diagnosis.

Sometimes, it is easy to diagnose a fistula.  Given the history, an opening, called the external opening, is seen with the naked eye and the diagnosis is made.  This is not always the case however.  If a fistula is suspected but not seen, there are several tests available to your surgeon.  They are:

  • An exam under anesthesia at a surgical center or hospital such as Cedars-SinaiMedicalCenter.  The surgeon will be able to look into your anal canal and actually see the internal opening at or near the dentate line.
  • Fistulagram.  A radiologist (an x-ray specialist) will be able to inject contrast dye into the fistula tract form the outside and see the path of the tract by x-ray.
  • MRI is a very high tech. tool used by a radiologist to see the tract.
  • CT scan is a similar technique to an MRI.
  • Anoscopy.  In the office, your surgeon may be able to look inside of your anal canal using a small anoscope to see the internal opening.
  • Finally, in the operating room, the surgeon can place a small probe into the tract and follow the probe from inside to outside, in preparation for a curative operation.

Each of these techniques are painless or involve only mild discomfort.

Los Angeles Colon and Rectal Surgical Associates.

The board certified surgeons of Los Angeles Colon and Rectal Surgical Associates have many years of training and experience in diagnosing and treating anal fistulas.  The process begins when you schedule a consultation by calling (310)273-2310.  You will be examined, and immediately treated if possible, or scheduled for further study or an operation.  Either way, you will have a chance to ask questions and understand your problem and the proposed evaluation or treatment.  This is the first step toward feeling better.

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