Final answer:
Kidney stones are crystals that form in the kidney when urine becomes highly concentrated. They can vary in size and may cause symptoms like pain and bloody urine if they block the urinary tract. Large stones might need medical intervention to be removed.
Step-by-step explanation:
Renal calculi, or kidney stones, are solid masses made of crystals. These typically form when substances found in urine, like calcium, oxalate, and phosphorus, become highly concentrated and begin to crystallize. Kidney stones can range significantly in size and may pass through the urinary system without causing symptoms, or they could be large enough to block a ureter, leading to pain, possible kidney damage, and other symptoms like nausea or bloody urine. Calcium oxalate stones are the most common type of kidney stones, often developing due to dietary factors that affect crystal formation. Conditions such as hyperparathyroidism and renal tubular acidosis can lead to the formation of calcium phosphate stones. A kidney stone's movement within the kidney or ureter can cause discomfort and require medical intervention, such as high-intensity ultrasound or surgery to facilitate removal.