What is the primary characteristic of nephrolithiasis?

The primary characteristic of nephrolithiasis is the presence of kidney stones. Nephrolithiasis, commonly known as kidney stones, occurs when there is a crystallization of minerals and salts in the urine that leads to the formation of solid masses in the kidneys. These stones can vary in size and may cause significant pain, particularly if they obstruct the urinary tract.

The formation of these stones can be influenced by various factors, including dehydration, certain dietary choices, or underlying medical conditions. When diagnosed, the presence of kidney stones is typically confirmed through imaging techniques like ultrasounds or CT scans, making it the defining feature of nephrolithiasis.

Other options, such as increased lung volumes, abnormal contraction of the chest wall, and difficulty in swallowing, do not relate to the condition in question. These symptoms are associated with different medical conditions and do not reflect the defining characteristic of kidney stones or nephrolithiasis.