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A woman in Michigan, United States recently went to the doctors complaining about abdominal pain on her right side and feeling like "a ball was rolling inside of her" when getting up from lying down.

Doctors were baffled by what the "ball" actually was – her right kidney.

The 28-year-old woman, who felt the pain for nearly six years, was suffering from a condition known as a floating or "wandering" kidney, medically known as "nephroptosis", in which one of the kidneys falls into the pelvis when a person stands up.

Case report author Dr. Akshay Sood, a urologist at Henry Ford Hospital in Detroit, who treated the woman, said that her right kidney fell more than 2 inches (almost 6 centimeters) down when she changed positions, according to Live Science.

The patient underwent a procedure called "nephropexy," to fix her floating kidney. Nephropexy is the process by which the kidney is tied back to the wall of the body. After a month, she said that she was pain-free.

Women are generally at a higher risk of the rare disease and it involves body fat. Kidneys have a lot of fat around them for support. In thin women, kidneys sometime fall into the pelvis when the person stands up as they don't have enough fat to support the organs.

When this happens, it causes a hooking or kinking of the blood vessels attached to the organ, reported Live Science. It also causes a bend in the ureter(the duct that passes urine from the kidney to the bladder), due to which urine cannot be drained properly and it flows back and gets collected in the kidney. The condition can cause the kidney to swell up like a balloon.

However, men are not totally exempted from the disease.

"A floating kidney is a hard condition to diagnose, and it's not that common," Sood said by pointing out that CT scans, which are taken in a lying down position, cannot give away the disease, according to the website.

He also added that there has been some controversy surrounding the diagnosis of the rare disease.