In medicine, foreign bodies are objects lying partially or wholly within the body that originated in the external environment. Foreign body placement is voluntary or involuntary. Common voluntary acts will include cosmetic reasons, e.g. earrings (or other body piercings) and iatrogenic e.g. surgical clips; occasionally however the object has been inserted into natural and unnatural cavities for sexual or nefarious purposes. Conversely involuntary placement is usually as a result of an accident e.g. motor vehicle collisions, stepping on broken glass, gunshot wounds, or explosions 1-7.
Most rectal foreign bodies are inserted via the anus, although occasionally the foreign body has been ingested and has passed through to lie in the rectum. Commonly, rectal foreign bodies are used for sexual purposes 1-3. Rectal foreign bodies have a large variety from sex toys to light bulbs to vegetables. The main problem with this is the often delayed presentation due to the reluctance of patients to present to emergency departments. Patients may suffer from extraperitoneal mucosal injuries or suffer from a more severe complication such as perforation 1-5.
Two plain radiographs are recommended to accurately demonstrate the size, shape and location of the rectal foreign body. This should be performed before a digital examination to prevent staff-related injuries from sharper foreign bodies.
Ingested foreign bodies range from children putting whatever they want in their mouths, mental-health related issues of swallowing strange objects (pica), to bones stuck in the pharynx or gastrointestinal tract. Coins account for 70% of paediatric ingested foreign bodies; coins will typically become ‘stuck’ at the level of the cricopharyngeus muscle 8,14. As a rule of thumb, coins visualised in the sagittal plane (acquired while entering through vocal cords) on anteroposterior radiographs are in the trachea, whereas coins in the oesophagus will have a coronal orientation on frontal chest radiographs.
An important alternative to consider when assessing coin-like objects are button batteries. These are very similar in appearance to coins, but typically have a slight step in profile with an inner ring when viewed en face. Button batteries can be potentially fatal when in contact with surrounding tissue as they can generate an electric current that will lead to the formation of sodium hydroxide resulting in severe, potentially fatal mucosal damage 6,13,14.
Sharp ingested foreign bodies can be potentially problematic when lodged in the oesophagus, patients will often require emergency endoscopy, more often than not if the sharp object is within reach of endoscopy it will be removed before it progresses further 12.
Plastic bread clips are diagnostically challenging, the limited literature on this foreign body suggests they are invisible on both plain radiography and CT, and the rigid shape can cause bowel perforations or gastrointestinal haemorrhage 15,16.
Most soft tissue foreign bodies are involuntary, resulting from an accident. The most commonly reported soft tissue foreign bodies are glass, metal and splinters from wood 5. It is imperative to locate foreign bodies before they become infected or worse damage close by organs.
Metal, glass and stone can be visualised very well using conventional plain film radiography, whereas more organic structures, such as wood, may require further imaging such as ultrasonography 5-7.
Commonly, aspirated foreign bodies will have a clear clinical correspondence: choking, coughing, neck pain or struggling to breathe. The right main bronchus is the most common site of obstruction due to the anatomy of the bronchial tree favouring the right side (larger diameter, more vertical orientation). Often two orthogonal plain radiographs are the primary investigation of choice 12.
Drug packing is a well-documented foreign body; it is also one of the most common recorded anal foreign bodies. Often drugs are placed within condoms, or wrapped in foil, latex or cellophane, then swallowed or inserted anally or vaginally. These should be considered hazardous to the patient until evacuated due to the possibility of the containment method rupturing.
The investigation of foreign bodies relies heavily on radiology and every foreign body will have an optimal modality for investigation 17.
The radiological appearance in plain radiography of foreign bodies is dependent on three factors: the x-ray attenuation of the foreign body, the surrounding structures and any overlying structures that may veil the object.
The anatomical location will not only affect the radiopacity of the suspected foreign body, but the rate of magnification as the object is placed further or closer to the detector, lateral cervical radiographs can have a magnification rate of up to 21.6% 9-11.
Most foreign bodies are hyperechoic.
The density of the foreign material in the body can range markedly, so use of multiple window settings is crucial in identifying the presence of the objects. Routinely soft issue, lung, and bone windows should be assessed. Certain plastics may be occult on CT.
The signal intensity of the foreign material in the body can range markedly, but most objects cause artefact of some sort. Certain objects may be occult on MRI, such as those made of wood or plastic.
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