Hi i am Dr Ahmed Aly  
  thanks for using HealthcareMagic site ,
I had gone through your question and understand your concerns ..
   In my opinion it is probably a renal stone or gravel and the pain is usually referred to lower back , it is very rare to have such pathology on both kidneys at the same time unless she have a past history .
    She may increase her fluid intake , avoid high protein and salty meals , proximol or 
allopurinol  sachets  ,phosphorus solutions and eating 
oxalate rich food will be helpful in most of cases .
   If pain persists i recommend laboratory investigations like urine analysis , BUN ( blood , urea and nitrogen ) , 
creatinine levels to diagnose these stones , the best diagnostic tool is U/S abdomen and pelvis to know site and size of such crystals .
    Hope your mother feels better soon and if her symptoms propagates visit her 
nephrologist for proper evaluation and management . 
Please click and consider a 5 star rating with some positive feedback if the information was helpful. Wish you good health,
Any further clarifications feel free to ask.