Most kidney cancers detected today do not in fact cause any symptoms.
This is because cancers are often diagnosed as incidental abnormalities when a scan is performed of the abdomen to investigate abdominal pain or other non-specific symptoms. Most kidney cancers detected in this way are often quite small and would not be the cause of any symptoms. Even larger kidney cancers often grow without causing symptoms. If kidney cancers grow to a very large size before they are detected they may cause pain as well as blood in the urine and if they are very large sometimes they can even be felt by the examining physician. It is quite rare for kidney cancers to have spread at the time they are diagnosed.
If you ever do see blood in the urine you must see your doctor urgently. The most common cause of blood in the urine would be infection or possibly kidney stones but tests will need to be performed to exclude a cancer.