Summarize the following:
If you are having pain across these areas, it is most likely caused by an injury to the back muscles, not the kidneys. These are common areas of back pain and it is more common for back pain to spread across this whole region than for kidney pain to spread in this way.  An injury to the back muscles can impact the function and pain levels in a variety of muscles down the backside of the body, including the gluteus muscles. If you are having widespread pain, weakness, or numbness, especially down into your legs, it is important to get medical care immediately. Kidney pain is most often located on the side or the back in the area called the flank. This is the area at the back of the body where the kidneys are located. Pain in other areas of the back, such as the upper back, is not caused by the kidneys. If the pain in your lower back is accompanied by pain in your abdomen, then it is more likely that your pain is related to your kidneys. Back pain tends to remain on the back side of the body. Enlarged or infected kidneys can cause inflammation towards the front of the body in addition to the back. If you only have abdominal pain with no back pain, that is not likely to be related to the kidneys. In many cases, kidney pain is constant. It may decrease or increase a bit throughout the day, but it never goes away completely. On the other hand, back pain will often go away completely and then come back at a later time.  Most causes of kidney pain, including urinary tract infections and kidney stones, will not stop hurting on their own without treatment. The back muscles, on the other hand, can heal themselves and the pain can go away. Some kidney stones can pass through your body on their own without treatment. However, it is still important to get the cause of your kidney pain evaluated by a doctor. If you are having pain on just one side of your flank, then it is likely that it is caused by your kidney. The kidneys are located right along the flank and a kidney stone may only cause pain in one of your kidneys.

Summary:
Identify widespread pain across the lower back and the buttocks. Feel for pain specifically between the ribs and hips. Identify abdominal pain. Assess whether the pain is constant. Feel for pain on only one side of your lower back.