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.
They considered any kidney stone over 2.5cm (0.98 inches) to be large, and the average size of the large stones in their study was 3cm (1.18 inches).ost sources state that the size of a kidney stone ranges from being as small as a grain of sand to as large as a golf ball. Researchers at the University of Missouri published a study about treatment for large kidney stones in the Journal of Endourology in September 2009.