The Associated Press has a story about a 52 year-old who spent 65 days swimming all 3,272 miles of the Amazon River. Note the following paragraph:
He said he was lucky to have escaped encounters with piranhas, the dreaded toothpick fish, which swims into body orifices to suck blood, and even bull sharks that swim in shallow waters and can live for a while in fresh water.
–Slovenian man ends 65-day swim down Amazon River. Associated Press, April 7, 2007
The ‘toothpick fish’ (candiru) preys upon larger fish by detecting urea and ammonia as well as subtle changes in the water current generated by exhaling gills. When its prey exhales, it swims into the gill and starts sucking on its blood. The candiru has poor visual acuity, so it cannot differentiate between an exhaling fish and… injudicious urination into the Amazon waters. What happens next?
A detailed description of the horrific events, from the Straight Dope (see here, and the update here):
On 28 October 1997, one of us (Samad) attended a 23-year-old man from the town of Itacoatiara on the Amazon River who sought medical attention with obstruction of the urethra, having been attacked by a candirú. Prior to being attended, the patient remained untreated for three days and was only administered medication for pain. By the fourth day the patient presented with fever, intense pain, scrotal edema [swelling of the scrotum], and extreme abdomen distention from urine retention. Surgical removal of the fish was considered, but rejected in favor of endoscopy [insertion of a TV-equipped tube into the urethra]. The patient was anesthetized with 5% lidocain and the procedure was performed. The fish was grasped using an alligator-clip attachment on the endoscope and removed in one piece. Fortunately the fish was dead, and decay was beginning to soften its tissues. Tension on the spines had relaxed in death, and they no longer gripped. Had the candirú been alive, its removal would have been more difficult and resulted in greater trauma to the patient.
The fish penetrated the victim’s urethra while he was standing in the river urinating, actually emerging from the water and entering his penis, filling the entire anterior urethra. He reported trying to grab hold of the fish, but it was very slippery, and it forced its way inside with alarming speed. The candirú’s forward progress was blocked by the sphincter separating the penile urethra from the bulbar urethra. With the passage blocked, the fish had made a lateral turn and bitten through the tissue into the corpus spongiosum, creating an opening into the scrotum. Perfusion [flushing] of the urethra with sterile distilled water prior to endoscopy induced further immediate and pronounced scrotal edema, making it evident that the opening had allowed the perfusate to enter the scrotum. Although the patient had remembered the fish as being small, after extraction it measured 134 mm (51/2 in) [long], with a head width of 11.5 mm (7/16 in). . . . Some coagulated material was removed, revealing a wound on the bulbar urethra of 1 cm in diameter and associated with a small amount of local bleeding. Although the patient suffered immediate trauma, no long term effects of the attack were noticed 1 year after the incident.
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