Man Who Couldn't Urinate Discovered He Was Infected With 30 Centimeter Parasite

A man who sought medical attention after being unable to urinate discovered that he had become home to one of the largest known parasites to infect humans, a case report explains.

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The 35-year-old man showed up to the emergency department, complaining of retention of urine and a fever that had lasted for two days. Retention of urine can be a serious, painful, and sometimes life-threatening issue, particularly if it comes on suddenly or gets worse over time.

The man was admitted to the hospital at Lala Lajpat Rai Memorial Medical College, Meerut, India, where his vital signs were found to be normal, except for tachycardia, or a fast heart rate. Testing his blood and urine, the team found markers of inflammation, as well as signs of a urinary tract infection, and he was started on IV fluids, antibiotics, and drugs to treat heartburn and stomach ulcers.

He wasn't in hospital for long before the cause of his problems exited his penis. On day two, he passed a sizeable parasitic worm, along with a significant amount of blood. 

"The worm was confirmed to be a rare parasite Dioctophyme renale based on its morphology and clinical presentation," the team explains in their case report. "The worm was blood red in colour, approximately 30 cm [12 inches] in length, 3-4mm [0.12-0.16 inches] in diameter tapering at both ends."

While that doesn't sound like a "great time", it could have been significantly worse. Dioctophyme renale, sometimes simply called the "giant kidney worm", is one of the largest known parasites to infect humans, and is the largest parasitic nematode known to infect people. Adult females can reach over 1 meter (3.3 feet) in length. 

The parasite can be found worldwide, but human infections are fairly rare, with cases only being reported in 10 countries, according to a 2019 study. Generally, they are hosted by animals other than humans.

"Mustelids (particularly minks) serve as the usual definitive hosts for Dioctophyme renale, although infections with adult worms also occur in wild and domestic canids, otters, martens, and raccoons," the Centers for Disease Control and Prevention (CDC) explains. "Rarely, other mammals, including herbivores and humans can become infected."

Where humans are infected, it is usually after consuming undercooked meat such as fish.

"Although humans may serve as definitive hosts with kidney infections," the CDC continues, "often the larvae migrate aberrantly, eventually becoming encapsulated in subcutaneous nodules and ceasing further development."

Once consumed, the worms can remain within human kidneys for up to five years, sometimes requiring the removal of the infected kidney. The team monitored the patient and his urine over the next three days.

"However, microscopic examination of the urine did not show eggs of the parasite," the team explained. "Even subsequent examination of urine for next three days did not reveal any eggs neither did the patient pass more worms."

The team believes that the man, who lived in India, likely got his infection through eating raw fish. They state that, though rare, Dioctophyme renale infections should be considered in the diagnosis of urinary retention and blood in the urine.

The case report is published in the Journal of Clinical and Diagnostic Research.