Radiolucent foreign body visible on plain radiography.

Rectal foreign bodies can usually be de-tected by rectal examination, but radiog-raphy is useless for radiolucent foreignbodies. We describe a case in which a ra-diolucent foreign body was seen on plainradiography.Case reportA 51-year-old man presented with a re-tained colorectal foreign body that wasintroduced transanally for sexual stimula-tion. According to the patient, it was a15-cm long plastic tube. On physical ex-amination, a tubular-shaped mass couldbe palpated in the patient’s lower ab-domen. No foreign body was detectedon rectal examination. Initial examina-tion of the abdominal plain film (Fig. 1)revealed only a dilated loop of bowel inthe lower portion of the abdomen. How-ever, detailed examination revealed ashadow whose location corresponded tothe clinically palpable mass and that wasactually the foreign body. Colonoscopyunder mild sedation identified the lowerend of the foreign body positioned18 cm from the anal verge. However, theendoscopist failed to retrieve the foreignbody by forceps, basket, balloon or snare.Eventually, the patient was given a gen-eral anesthetic. A pair of toothed laparo-scopic forceps was inserted per anus un-der colonoscopic guidance, and theforeign body was securely grasped andremoved. It was a tubular sponge, 15 cmlong and 3 cm in diameter (Fig. 2). Thematerial was radiolucent, but the airtrapped inside it had given an interestingand characteristic appearance on the plainradiograph.DiscussionMore proximally located foreign bodiescan occasionally be palpated on abdomi-nal examination, as in this case. Plainradiography is useless for visualizing