Madarite Leeches are a species of leeches that within less than a day lay their eggs in the bladder of living beings, and then die.
These leeches enter through a physical wound and lay eggs in the bladder. It takes them at least a day to reach the bladder, lay their eggs, and die. The hatched eggs would be then excreted along with urine, but the process is too painful and would cause immediate death to the living being. However, the eggs need a strong and stable concentration of ammonia to hatch. A body with a low ammonia in the urine would prompt the eggs to evacuate painlessly. An easy method to accomplish this is to keep drinking beer and peeing often until the urine turns from black to white.
Yorknew City arcEdit
The Shadow Beast Leech injects the Madarite Leeches into Uvogin's gaping wound, but is instantly killed by Uvogin after detailing what they're capable of. When Uvogin finishes off the remaining Shadow Beasts, Shalnark explains in further detail about the leeches and the remedy to expel them from his body, before the leech eggs in his body hatch.
Before his fight with Kurapika, Uvogin manages to urinate all of the leech eggs safely out of his system.