I've been having the same problem? Have you found out what it is? I'll be going to the doctors soon to find out, if you find anything out please post it.
Hi, this could be muscle strain, renal stone, swollen kidney etc. Try heat application, pain killers and topical counterirritants for 3-4 days, if pain still persists, do get ultrasound and urine routine microscopy done.
Have a test called an IVP done(standing). It could be nephroptosis, sagging kidney. It's nothing to be concerned about, and the main symptom is colicky flank pain, usually on the rt side. It took me 5 years to figure out what I had just b/c they couldn't find it! Good luck.
As a side note. I was in the ER about a month ago for an unrelated matter, and they ran some tests. Kidney function was fine and all blood work was normal. Thx.