Platyhelminthes are also known as flatworms because they are worms with a flat body. This is the main external morphological feature that differentiates them from nematodes (roundworms).
Even though 85 percent of kidney stones are small enough to pass during urination, fewer than 50 percent of patients chose this option. A person with a normal-size ureter can usually pass a kidney stone with a diameter less than 5 mm (about 3/16 of an inch) without significant pain or risk of kidney damage.
The Journey of a Kidney Stone. To really understand how long it takes a kidney stone to pass, you should understand exactly where it goes throughout the body. Kidney stones start in the â you guessed it â kidneys. They have to pass through the long ureter tubes and eventually make their way into the bladder.