While browsing the Internet, you may have read strange tales of a fish that’s known for swimming up the male urethra, becoming painfully lodged there. This fish is called the candiru and is a member of the genus Vandellia.

While the stories may sound shocking, there’s some doubt surrounding their truthfulness.

Read on to learn more about the alleged “penis fish.”

The candiru is found in the Amazon region of South America and is a type of catfish. It’s about an inch long and has a thin, eel-like appearance.

The fish is actually parasitic. It uses spines located on the covers of its gills to attach itself to the gills of other, larger fish. Once positioned, it’s able to feed on the other fish’s blood.

Accounts of candiru attacks on humans aren’t a recent development. They can be traced back to the 19th and early 20th centuries.

The gist of these stories is that the fish is attracted by human urine in the water. When someone urinates in the water, according to these stories, the fish swims into and lodges itself in the urethra of the unsuspecting individual.

Once inside, the fish uses the spines on its gill covers to hold itself in place, which is painful and makes removal difficult.

Over the years, more extreme tales of the candiru fish have emerged. Some of these claim that the fish:

  • can jump up out of the water and swim up a stream of urine
  • lays eggs in the bladder
  • eats away at the mucous membranes of its host, eventually killing them
  • can only be removed through surgical methods, which may include penis amputation

Despite all of these claims, there’s very little credible evidence that the candiru fish has ever invaded the human urethra.

The most recent reported case occurred in 1997. In a report made in Portuguese, a Brazilian urologist claimed to have removed a candiru from a person’s urethra.

But inconsistencies in the account, such as the actual size of the extracted fish and the history given by the affected person cast doubt on the truth of the report.

In addition, a 2001 study found that the candiru might not even be attracted to urine. When researchers added chemical attractants, including human urine, to a tank of candiru, they didn’t respond to it.

There are very few reports of candiru attacks in scientific or medical literature. Additionally, many of the historical reports are anecdotal accounts relayed by early explorers or travelers to the region.

If a candiru has ever entered a human urethra, it was likely by mistake. The limited space and lack of oxygen would make it almost impossible for the fish to survive.

While the candiru’s reputation as the “penis fish” is likely based on myths, some tiny organisms can indeed travel up the urethra.

This usually results in either a urinary tract infection (UTI) or sexually transmitted infection (STI).

UTIs

UTIs happen when bacteria enter the urinary tract via the urethra and cause an infection. Fungal infections can also sometimes cause a UTI.

A UTI can affect any part of the urinary tract, including the kidneys, bladder, or urethra. When a UTI affects the urethra, it’s referred to as urethritis. This condition can cause discharge and a burning feeling when urinating.

STIs

STIs are spread via sexual contact. Although these infections often affect the outer genitals, they can also affect the urethra.

Some examples of STIs that can involve the urethra include:

  • Gonorrhea. Caused by the bacterium Neisseria gonorrhoeae, this infection can cause discharge and painful urination when it affects the urethra.
  • Chlamydia. Caused by the bacterium Chlamydia trachomatis, this infection can also cause discharge and painful urination.
  • Genital herpes. Caused by the herpes simplex virus, this infection causes painful sores to develop on the genitals, anus, and urethra.
  • Trichomoniasis. Caused by the parasite Trichomoniasis vaginalis, this infection can impact the urethra and cause itching, discharge, and discomfort while urinating.

The candiru, sometimes known as the “penis fish,” is a small Amazonian catfish. It’s reported to lodge itself in the urethra of people who may be urinating in the water.

Despite the unsettling stories surrounding this fish, there’s skepticism about whether the fish actually attacks humans. There’s very limited credible evidence in medical literature about this happening.