In my case (after ruling out gall bladder, ulcers, kidney stones) this turned out to be a severe torn oblique abdominal muscle. The muscle healed with scar tissue, making it weaker and shorter.
Try to remember back if you suffered an injury at some point to the abdominal muscles. In my case it was lifting something in the garden over a year ago - and I'm still suffering pain and weakness in that side.
Good News! I've started to get better with a regime of physio and improved posture. Use a lumbar support to prevent tilting the pelvis forward and contracting the abdominal muscles. Do GENTLE sit ups and stretches on a yoga ball - building up slowly.
It will take months - but you will get there.
The first onset of it was two months after I recovered from rupturing my right Achilles. Despite PT, I developed a compensatory outward turn with my right foot / leg that puts strain on my right hip and abdomen when I'm physically active. Because of this, I strain this muscle group with some regularity, hence why it crops up every few weeks to greater or lesser degrees.
I'd recommend that anyone who's done the legwork on being tested for stones, tumors and other medical conditions that normally affect this area to stop and think about when it started and if you experienced any trauma to your right side / right leg as it can be directly related to the lower abdomen and lower back - often presenting as kidney or appendix issues.
I'm having the same medical issues but they say it's my olverie on the right side but yet they hand me a bottle of 800 MG of Ibuprofen n say goodbye they don't understand this pain is horrible please email me if you find out any more about your case because my blood work is also fine n checks out healthy n it's not my gallbladder that's gone already. So, they can't finger it out they just say my olvers must be giving me problems but I had a hysterectomy too. Everyone doctors clueless.
The muscle related piece is apparently very common but it took me a year to find a site that mentioned this.
I started out with pain over about where the right kidney is, and thought it was a stone (felt like the beginning of one due to past experience). Docs agreed. Went on for months off and on, though, and began shifting to go across my right lower back and occasionally zing into the groin like a stone normally would as it moves without the sharper pain. So I had an xray and ultrasound done, no stones. Urologist said a CT might find a small stone but nothing could be done for tiny stones even though they can be the source of such pain, so he wasn't much help. Then I /did/ have a stone a couple of months later - blood in urine, severe sharp pain, typical stone symptoms per the ER. After a couple days it passed. Yet, the pain in my back persisted. Eventually my doc realised it was a muscular knot and gave me cyclobenzaprine which seemed to stop it in two days. Since then everyone I see agrees... The psoas may have been in spasm first, and now because of an exercise I was doing for that, I may have pulled an oblique so the pain has shifted to just under the ribs. The abdominal muscles are very touchy things and the psoas doesn't have its own nerve endings so the pain can seem to shift and move around as the fascia and other muscles that /do/ have nerve endings are disrupted by the spasming of the psoas. All the muscles are interactive, as in, one spasms, it can set others off as well at times. Also, it is suspected that a kidney stone, which causes uretal spasms, can set off the psoas or other nearby muscles, which then doesn't help the ureter any so you can get into a cycle of stones and spasms. The other thought is that psoas spasms are easily induced by a very sedentary lifestyle (sitting). So if you sit at work a lot, and/or at home, you're far more prone to psoas and oblique spasms. Also, I find that the cyclobenzaprine stops the worst of the symptoms, but the tenderness in the right obliques and sometimes the iliacus and nearby area can persist on an annoying but manageable (advil or ignoring it) level.
As for me, it's been about a year since this started and I've been getting (hopefully properly) treated for it for the past two months or so. I'm still doing stretches for both muscle groups (on both sides, lest my left side start in on me next) and the basic premise is that you stretch out the hamstrings if they're short, because they pull on the opposite side of your back which irritates muscles there. You also stretch the affected muscle groups very gently a few times a day after applying heat, and do core strengthening exercises a few times a day, too. The idea is that everything is very interrelated so you have to treat everything nicely for a long time and slowly stop sitting all the time, standing in one place all the time, slouching, etc... but not all at once, that also doesn't help, it just causes new things to start compensating. My chiropractor seemed to think under two months should fix the psoas spasm issue, but after weeks of working on it, going off the cyclobenzaprine would result in a full spasm which means I have to lie on my back on the floor and not move. Sometimes all day. The pain is horrendous. Certain yoga positions seemed to help it at first, but since then a twisting motion sent my oblique area into a similar spasm so be careful and follow instructions if you /do/ try stretches and such. Build up gradually and don't re-injure yourself or injure a new area. Use heat beforehand and ice to reduce swelling in between, heat to relax and help it heal.
To get proper stretch instructions, best to see a PT. They can work with you to get the right routine put in place. And yes, it will take a long time to get back to normal, regardless of what websites say about things. And remember there are a LOT of muscles in the back. Sidenote: My xray did show that the lumbar region of my spine is bowing out toward the right side. Any sort of curvature in the spine is called scoliosis and is very common in people as they age. It is also common in people with tight psoas and other abdominal muscles because of the pulling on the spine and hip areas. These are /strong/ muscles!!
this could be my story. i hurt so bad some times i just cry. i have a very bad back the kidney doc said that it must be my back because the stone i have is in the 'meat' of the kidney, in other words it is not floating around and causing pain, it is stationary in the kidney. sweet jesus, it feels like i must be croaking. to sit is excruciating in the lower right quadrant. sometimes near my waist, some times really low in front. it kind of moves. the constant is the back pain, getting worse for last 10 years.
it helps to lie down. i pray for all people with pain.