Madhavi is caught by surprise at the intensity of the pain that she is feeling. She is doubled up and feels like somebody has punched her. The pain is cramping in nature and she feels it travelling down from the left side of her back, along the side and into the lower abdomen. She feels waves of nausea as the pain makes her writhe.

Madhavi is feeling the effects of a kidney stone. Though more men have kidney stones (also known as renal calculi) than women, women can suffer from this most painful condition. Kidney stones are one of the most common disorders of the urinary tract.

What is a kidney stone?

A kidney stone is a solid mass made up of tiny crystals. It forms in the kidney and then can start travelling down the ureter, which is the tube that empties the urine from the kidney into the bladder. One or more stones can be in the kidney or ureter at the same time. The most common type of stone contains calcium in combination with either oxalate or phosphate. A less common type of stone is caused by repeated infection in the urinary tract. This type of stone is called a struvite stone and is more common in women.

Who gets kidney stones?

Stones occur more frequently in men. The prevalence of kidney stones rises significantly as men enter their 40s and continues to rise into their 70s. For women, the prevalence of kidney stones peaks in their 50s. Women who have a kidney stone are prone to getting more stones.

What causes kidney stones?

It is not quite clear why stones form. Some people have an inherited condition called hypercalciuria. In this condition, calcium is absorbed excessively from food and is excreted into the urine. This high level of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys. This condition may be the cause of renal stones in more than half of patients.  

A person with a family history of kidney stones may be more likely to develop stones. In women, repeated urinary tract infections may result on stones in the urinary tract.

What are the symptoms of kidney stones?

Most commonly, renal stones manifest themselves in the hot summer months when people do not drink enough water and get dehydrated. Pain usually occurs when the stone is dislodged from the kidney and starts travelling down the ureter. The pain may be due to two reasons. First, the stone can block the ureter and the kidney gets distended with urine, leading to pain. The second reason is that if the stone is too large to pass easily, the muscles in the wall of the narrow ureter try to squeeze the stone into the bladder.