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.
These muscles begin to spasm; they're trying to push the kidney stone out. This is what causes pain in your flank, back and stomach. Once the stone has come through the ureter, the pain usually abates. Anywhere from hours to weeks later, the kidney stone will pass, probably during urination. On average, stones take between one and three weeks to pass. Most stones that pass on their own will do so within a month of their first beginning to cause pain. If the stone doesn't pass within this time, it may be stuck, and could cause infection or other problems if it isn't removed.