Is dark urine a sign of ruptured spleen with mono?

NO: The darker urine is likely due to bilirubin from the liver also being bothered by the mono. If you have not already seen a physician and had blood work done, you should do that. Make sure to drink lots of water. If the spleen ruptures, it is life threatening due to severe bleeding in the abdomen.

Probably not: May be bilirubin from jaundice with liver effects of mono. Or concentration if dehydrated. Easily determined by urinalysis exam.