In an episode of "Friends," Joey is passing a gallstone while Phoebe is giving birth to triplets. Their yowls of pain are pretty similar (Joey's might be a bit louder). That's how painful passing a large gallstone can be.

Gallstones develop (80 percent of the time) because cholesterol in the bile, which is produced in your liver and stored in your gallbladder, causes the formation of pellets that range in size from a speck to a golf ball. When they block a gallbladder's bile duct, they trigger excruciating pain on the right side of the abdomen. Left untreated, obstructive stones can cause jaundice, fever, even death.

More than 25 million North Americans contend with gallstones - twice as many women as men. There are 1 million new cases every year. In fact, there's a good possibility that everyone has gallstones, but only a small percentage cause problems.

The go-to diagnostic tool is ultrasound, and to put an end to an attack, the stones can be extracted via laparoscope. If you have two or more attacks, you may need to have your gallbladder removed. Fortunately, your digestive system can work pretty well without it, if you follow the doctor's dietary advice.

Good news? You can avoid problem gallstones by keeping your cholesterol in check, maintaining a healthy weight (lose weight slowly if you're on a diet; rapid weight loss can trigger stone formation), walking 10,000 steps a day and avoiding the Five Food Felons, especially fried food. If you can eat fried food without pain, you probably don't have gallstones.