Hi Megster, I'm sorry I'm just getting around to answering your question. I hope all has gone well with your mom.
Basically, creatinine is a byproduct of broken down creatine, which is a part of muscle. Kidneys are the organs that clear creatinine from the body. When creatinine levels are high it can mean that the kidneys are not functioning properly, for a number of reasons. Some reasons can include dehydration, rhabdomyolysis, heart failure, kidney failure, and a number of others. Because I cannot see your moms other lab levels, I really can't give you a definitive answer-nor can I because I am not a physician.
If you still have questions please do not to hesitate asking the nurses and physicians on your mom's case.
Thank you for reading and asking a question!