Can Low Grade Fever Be A Symptoms Of Having Kidney Stone ?

my mom 79 was having low grade fever every 2/3 weeks, she was diagnosed for kidney stones and left kidney was25% of its size and had two stones and one stone in the right kidney ureter . all stones were of the size of 1cm to 1.5 cm. the right kidney stone was taken out and left kidney a stent was used. this was done on 30th April. the stent is still there. still low grade fever is thee and ESR is 120 and creatnine is 1.9. her tests are coming negative. TB test is also negative. she had taken TB medication in 2003. Cant understand where is the infection. do you think removing the stent used for left kidney will remove the low grade fever. Her hbaic is 6.1, she takes med for thyroid, cholestrol, BP