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Foreign bodies within the rectum are the result of an ingestion from above or are placed into the anus from below.1 Fortunately, the majority of items ingested from above that pass the pylorus and ileocecal valve also pass the anal sphincter. The most frequent types of items found in the anus from above are undigested fish or chicken bones. Foreign bodies that are placed into the rectum from the anus are placed iatrogenically (e.g., enema tips and thermometers), inserted by the patient in an attempt to remove impacted stool, inserted by the patient or their partner as a form of anorectal auto-eroticism, forcibly placed in the anus during a rape, or placed in the rectum to smuggle objects across a border illegally.
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The items placed into the rectum from the anus seem to be limitless and represent all the shapes and sizes imaginable.2 This makes their removal more difficult. It is important to attempt to identify the characteristics of the foreign body in order to devise the safest way of removal. As an example, consider the typical electric lightbulb. The glue that attaches the metal base to the glass loosens with moisture and time. Pulling off the metal base exposes a thin, sharp glass edge. The glass globe is very thin and breaks very easily. If the glass breaks, it may take a long time to remove the fragments and cause considerable damage to the surrounding rectal mucosa or the examining finger. The idea is to remove the foreign body without causing further damage to the rectum or the anal sphincter muscle. The more knowledge the Emergency Physician has about the foreign body and how it was inserted, the more likely it is that it will be removed safely.
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The significant anatomy of the anal canal is discussed in Chapter 70, describing the anatomy for anoscopy. Important anatomic considerations in removing rectal foreign bodies include the axis of the lumen of the anus. The anus is pointed toward the patient's umbilicus, while the curve of the sacrum forms a posterior arc. If the length of the foreign body is longer than the curve of the sacrum, such as a long vibrator or dildo, the sacral promontory causes the distal end of the foreign body to be directed toward the tip of the sacrum or coccyx. When the object is being removed by bringing the distal end anteriorly, the middle portion may push anteriorly (i.e., into the prostate, uterus, or bladder) and cause considerable discomfort.
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The important physiologic considerations include the anal sphincter muscles, edema, and the creation of a vacuum. The anal sphincter is a complex group of muscles. The external anal sphincter muscle is made up of voluntary muscle fibers. The internal anal sphincter muscle is made of smooth muscle fibers. The reflex response to dilatation of the rectum is contraction of the external anal sphincter muscle. The normal tone of the anal sphincter ...