What Causes Stabbing Ribs And Back Spasms?

MY 83 YR OLD MOTHER WAS DIAGNOSED OVER A YR AGO WITH A LARGE KIDNEY STONE(NOT PRESENTING ANY PROBLEMS) bUT FOR 6 WEKS NOW SHE HAS SEVERE STABBING SPASMS UNDER HER RIGHT RIBS WHICH RADIATE INTO HER BACK. ALL TESTS ARE NEG,. NO PAIN WHEN SHE LAYS DOWN, BUT HER SPASMS ARE ALL THE TIME WHEN SHE BARELY MOVES. pAIN MEDS ARE NOT HELPING AT ALL