Defecating proctogram
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The defecating proctogram is an imaging study performed by a radiologist in which the mechanics of a patient's defecation are visualized in real time.
History
Defecating proctography is a technique first pioneered in 1945 during the second world war. Due to a rash outbreak of hookworm, which is known to cause rectal prolapse, defecating proctography gained popularity during this time. It has since become the gold standard for diagnosis of any of a number of rectal contractility disorders.
Since then, however, it has fallen out of favor due to inadequate training in the technique, and it is now only performed at a few select institutions around the country. Many radiology residents affectionately refer to the procedure as the "Def Proc", "Defogram", or "Stool Finale".
Technique
In females, as well as in certain males, pre-procedural preparation involves smearing a small amount of barium contrast in the vagina with careful avoidance of the rectum. This can often prove to be somewhat challenging in certain body habitus individuals.
The technique itself involves insertion of a caulk gun device into the rectum with subsequent manual infusion of barium paste until there is adequate distension. The patient is then transferred to a toilet which is situated next to an x-ray camera with recording of the defecation. Positioning of the x-ray camera is of paramount importance as visualization of the buttocks, rectal vault and lower pelvis is mandatory.
More recent techniques involve the use of advanced, cross-sectional imaging modalities such as magnetic resonance imaging. The following video is an example of MR defecating proctography: [1]. This is considered by many to be an outrageous waste of medical resources.
Advanced Techniques
Due to the high technical demand required of the operator during the procedure, there have been several advanced techniques described:
- The Zaki technique involves usage of an electric caulk gun for operators with weak wrists. The use of a mechanically assisted barium introduction device makes the infusion of the barium paste much less technically challenging. However, this technique is not preferred, as it eliminates the variable resistance that the operator would otherwise use to gauge the degree of distension of the rectum. Very few cases of rectosigmoid injury (rupture, barium overdose, and rarely endotracheal aspiration) have been reported in cases of the Zaki technique being attempted by an untrained operator.
- The Chang protocol is used to help guide the operator during the introduction of the barium paste into the rectum. As the radiologist introduces the barium paste into the rectum, the patient is instructed to inform him when he or she has a strong, painful urge to defecate. Historically, at this point, the patient would be transferred to the commode for defecation and image acquisition. However, the Chang protocol calls for the additional infusion of one-third to one-half of the volume of the caulk gun, after the patient indicates the painful urge to defecate, ensuring adequate distension of the rectum. This markedly improves both the sensitivity and specificity of the examination.
- The Abe Assist is a not infrequently utilized method for patients who are unable to initiate defecation despite usage of the previously described techniques. Often the embarrassment of the procedure can be overwhelming and the previously noted urge to defecate quickly dissipates upon being seated on the plastic commode. Certain rectal contractility disorders are also associated with difficulty in the initiation of defecation. The Abe Assist entails the operator placing a finger in the rectum of the patient in order to assist with initiation of defecation. This may sometimes be performed using fluoroscopic guidance.
References:
- Bristol Laparoscopic Surgery, http://www.bristolsurgery.com/article.aspx?articleid=100709
- ASCRS: Pelvic Floor Dysfunction, http://www.fascrs.org/patients/conditions/pelvic_floor_dysfunction/