A FISH swam the wrong way when it leapt upstream into a boy's PENIS and ended up in his BLADDER.

The 2cm daredevil caused all kinds of medical problems when it swam through the teenager's urethra.

The unfortunate lad was taken to hospital with complaints of pain, dribbling urine and acute urinary retention.

He claimed the fish slipped into his penis while he was cleaning his aquarium at home in India.

Professor Vezhaventhan and Professor Jeyaraman, who treated the boy and later wrote a paper on the case, said: "While he was cleaning the fish tank in his house, he was holding a fish in his hand and went to the toilet for passing urine.

"When he was passing urine, the fish slipped from his hand and entered his URETHRA and then he developed all these symptoms."

After finding the fish in the boy's BLADDER, the medics insert a special set of forceps down the patient's penis in a technique known as cystourethroscopy.

But the fish was too slippery, so the professors used a rigid ureteroscope with a tool attached - normally used for removing bladder stones.

The fish, which is thought to be a small member of the Betta genus, measured 2cm long and 1.5cm wide.

The patient was later offered counselling.