Kidney stones are intense enough that rocker Vince Neil of Motley Crue had to leave a show Sunday and check into a hospital.

The story about the incident generated a lot of discussion among Internet readers who had experienced kidney stones themselves. Wrote Deaux, "I'm a mom of 4 children, and I've had 1 kidney stone. I'd rather have 4 more children than have 1 more kidney stone."

We spoke with Dr. Dianne Sacco, director of Massachusetts General Hospital's Kidney Stone Program, for more information about this condition. The following is an edited version of that interview:

How do you diagnose kidney stones?

One of the most common presentations is the flank pain on one side. It sometimes radiates down into the stomach, and it can actually radiate down into the genital area. That type of pain is pretty commonly seen in stone patients.

Sometimes there's nausea and vomiting. Those type of symptoms are something that gives us a clue that this may be a stone.

The CAT scan is the gold standard for imaging for kidney stones. That's usually the way to diagnose it. You can't do it from a blood test or anything else.

Why do people say that they are so painful?

What it does is, it blocks the flow of urine in the kidney, and it causes backup. And it's an excruciating pain. A lot of people do describe it as worse than childbirth.

When the system is trying to push urine out, what happens is: your kidney and your ureter -- they have this muscle propagation that goes down the kidney into the ureter -- when it's trying to push and the stone is blocking it, you get these intense pains. That's why we call it colicky, it comes and goes and it's extremely painful and the main reason for the pain is the backup of urine.

What's happening exactly?

Usually, if they have two kidneys, they urinate fine, because you're getting urine on the other side. The problem is, that kidney is producing urine but it can't get pushed down.

If you take a pipe and you clog it off and somehow you're still getting fluid into the other end ... if it's a pipe that can expand, it starts expanding.

The backup is like that. It causes a great deal of pain because you're expanding your system. You don't have any pop-off valve. Once it starts expanding, it's expanding unnaturally.

It's called hydronephrosis, and it's basically backup of urine into the kidney.

Are there particular risk factors?

There are certain diseases associated with kidney stones, things like hypoparathyroidism, or some bowel diseases where your absorption isn't normal.

Things like obesity and diabetes are associated with kidney stones. The main dietary factors are low water intake and high salt intake and animal protein -- anything you killed to eat. If you have high amounts of those intakes, it causes your urine to acidify and then it becomes more prone to having stones.

It just depends on the person. If you have a family history, you're more apt to get a stone.

What is the treatment?