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.
Kidney stones are often as small as grains of sand. They pass out of the body in urine without causing discomfort. However, the deposits can be much largerâthe size of a pea, a marble or even larger. Some of these larger stones are too big to be flushed from the kidney. Some kidney stones manage to travel into the ureter. This is the narrow tube between the kidney and bladder. The stones may become trapped in the ureter. Trapped kidney stones can cause many different symptoms.