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.
In about 85% of patients, the kidney stones are small enough (about 5 mm) that they pass through normal urination, usually within 2 - 3 days. In some cases, a stone may take weeks to months to pass, although the pain usually goes away before that.