Pyelonephritis/renal abscess are different spectrum of infection. Treatment is based on symptoms, general condition, organism is culture report  and imaging findings. If renal abscess, it may require drainage. Also a pus culture is needed here Control of underlying sugar along with prevention from low sugar by regular monitoring Abnormal renal function (high urea/creatinine) will not happen if one kidney is involved, either her both kidney's function are temporarily affected by ongoing infection or her kidneys are affected due to diabetes. Some drugs can also cause abnormal renal function but they are mostly avoided is patient like your mother.