UTI and complex renal cysts

[R4062]

My mum  is 65 years old and has been getting urinary tract infections quite often nowadays. Whenever she is given antibiotics- she gets better and the urge to go to the bathroom subsides. She did a scan and they found that she has complex renal cysts ( level 2). After 7 months another scan was done but the cysts were not to be seen.However last month she did another scan ( after about 6 months from the second one) and they found the cysts again( at the same level). She went for a urine test last week ( during  a routine medical check up)and they found that she has infection -UTI ( the chit was not very clear-- but it stated something like 810) and they suggested medication.I was just wondering, is the infection caused by the cysts or something else- because it is like happening rather often now? She has rheumatoid arthritis too
(Sjogren).What would you suggest?Is complex renal cysts (level 2)serious and is it curable?She gets up once in the middle of the night to go to the bathroom.
Thank you.