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.
For kidney stones that do not pass on their own, a procedure called lithotripsy is often used. In this procedure, shock waves are used to break up a large stone into smaller pieces that can then pass through the urinary system. 4 mm stone has an 80% chance of passage while a 5 mm stone has a 20% chance. Stones larger than 9 mm-10 mm rarely pass without specific treatment. Some medications have been used to increase the passage rates of kidney stones.