Kidney stones less than what size have a 90% chance of passing spontaneously?

Kidney stones smaller than 4 mm have a high likelihood, about 90%, of passing spontaneously. This is important in the management of ureteral stones, as interventional treatment options may be considered for larger stones, typically those above 4 mm.

The ability for stones to pass is influenced by several factors, including their size, shape, and the patient's individual anatomy. Stones smaller than 4 mm have been shown in studies to more easily traverse the ureters and be expelled through urination without the need for surgical intervention or other treatments. In contrast, stones larger than this size often present increased difficulty in passage, leading to complications such as obstructive symptoms or infections and may necessitate additional medical or surgical procedures.

Thus, understanding that a stone size of 4 mm or smaller has a strong chance of passing spontaneously informs the decision-making process for the management of patients with renal stones.