Mariah Carey announced on Twitter Wednesday that her husband, rapper and actor Nick Cannon, is in an Aspen, Colo., hospital  suffering from what she called "mild kidney failure."

"Please pray for Nick as he's fighting to recover from a mild kidney failure," the singer tweeted.  On her website, Carey posted a photo of herself lying in a hospital bed with Cannon, 31.

"We're trying to be as festive as possible under the circumstances but please keep Nick in your thoughts because this is very painful," she wrote in a message on the site.

Dr. Giselle Guerra, assistant professor of clinical medicine at the University of Miami's Miller School of Medicine, isn't involved with Cannon's treatment, but said he may have a case of acute kidney failure, also known as acute renal failure.

"Acute kidney failure happens all of sudden, whereas chronic failure happens over time, often as a result of other illnesses like diabetes or high blood pressure," she said.  Acute kidney failure can range from mild to serious.  Serious cases may require dialysis and may develop into a chronic condition.

There are a number of causes of acute renal failure.  In some cases, any damage done to the kidneys is reversible.  The condition can be brought on by certain medications or other drugs, an obstruction or something that causes blood flow to the kidneys to drop, such as an infection or dehydration, Guerra explained.

"If it's caused by certain medications, once a person is off the medication, it takes some time for them to wear off, but it can be reversed," she said.  "If damage is aggressive enough, it may not be reversible."

Symptoms of acute renal failure include nausea, weakness, sluggishness and tremors.  In severe cases, the kidneys may stop producing urine.  People may also experience blood in the urine or foam in the urine.

Pain generally occurs only if there are kidney stones or an infection in the kidney, called pyelonephritis, Guerra said.

Although she joked about being stranded in Aspen, Carey asked her fans to keep the couple in their thoughts.

"I'm not trying to make light out of the situation because it's a serious moment that's very tough on all of us so please keep us and our family in your prayers. LYM."