Lumbar pain radiated to the hip, exacerbated by movements

Dear Ask The Doctor: Hello, I have pain in the right side of my back, right where the kidneys are supposed to be, on the right of my back right above where my hip is. I was worried that it might be a kidney infection derived from a UTI, but I read somewhere that kidney pain is constant and comes in waves regardless of movement. When I move in certain ways, my back hurts in that same spot. The area where my back hurts is not tender to the touch either. The pain is internal. There are a few neutral positions in which no pain occurs so I think it may be muscular. My guess is I might have slept in an awkward position and pulled my deep back muscles. So I've been taking Advil to help with the pain. It hurts the least when I stand upright or lay down flat. While sitting (even as I type this out), it mildly hurts. My pain ranges from 1-5 on a scale of 1-10, 10 being excruciating pain. If I lay down or stand upright, the pain is practically 0. I also noticed numbness on the right side of my stomach. It's a patch of numbness the size of a closed fist just to the right of my belly button. I don't feel it if my fingers touch the skin, but I do feel cold and hot on it. I tested the feeling of pressure also by pressing the area with my fingernail and I can feel that after it becomes painful to the skin. But I feel no strokes of touch. I've also gotten an itch or two on the numb spot that goes away but if I scratch it, I can't feel it so there's no relief... just waiting for the itch to subside instead. This is my 3rd day with these two symptoms coexisting. So my question is, are they related and what could be causing them? Is renal infection still a possibility? I've had no frequent urination, nor pain during urination, nor fever or any other symptoms. Thank you very much for your help.

Dear Austin: Most likely the kind of pain that you described is due to a lumbar sprain that is producing a local inflammatory response, muscle contracture and is affecting the sensitive nerves that supply the part of the skin where you have problems with the sensation or paresthesia. In the view that the pain is modified with the movements and you do not have any urinary symptoms (fever,urgency,burning) a UTI is not likely, but for your peace of mind you may go to your PCP and get some lab tests done to rule out completely any kidney problem associated. Probably you are experiencing, as I said before a Mechanical low back pain (LBP)  . Mechanical low back pain is the second most common reason for seeing a physician in the United States. Of the US population, 85% will experience an episode of mechanical LBP at some point during their lifetime. The LBP tends to resolve within some weeks if you follow these conservative measures: a physical therapy program aimed to control the pain and the inflammatory process and teach you flexion and extension exercises of the spine to reduce the nerve tension, these exercises will improve the muscular strength and endurance of your lumbar muscles. Also is very important to keep a good posture at all times and practice low-impact activities such as swimming, walking, and bicycling, these can increase overall fitness without straining your low back. While standing, keep your head up and stomach pulled in. If you are required to stand for long periods of time, you should have a small stool on which to rest one foot at a time. Do not wear high heels and keep your weight under control. The use of anti-inflammatory medication (i.e.: “motrin”, “advil”, “aleve”) can be beneficial to manage the pain if you are not lactating. Nearly everyone improves within a month following these conservative measures if it is a mechanical back pain. Otherwise, if the back pain persists for more than 2 months, in despite of the above mentioned measures, the evaluation by a physician to rule out other possible causes than just mechanic or postural is recommended.

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