What Causes Increase In Creatinine Levels While On Cefspan?

Hi My father is 82 years old and he is suffering from benign prostatic hyperplasia (BPH) since 2005. BPH of size 68 grams with vesical stone of size 37 mm. Last month he was attacked by hydronephrosis with UTI and his creatinine was 3.1 which was reduced to 1.7 after 30 days by inserting foley catheter. After 30 days his renal DTPA scan revealed that “markedly reduced blood flow to both kidneys scintigraphically. The cortical phase images show markedly reduced tracer uptake in both kidneys. The delayed images show minimal clearance of tracer from both the kidneys in response to Lasix stress.” Right Kidney GFR 15.7ml/min 42% Left kidney GFR 21.5 ml/min 58% after next 15 days creatinine was reduced to 1.2mg/dl and BUN was normal (before surgery). then doctor performed open surgery to remove stone.after surgery he was attacked by chest infection with wheezing cough and mucus.father was feeling so weakness even cannot sit. after 15 days of surgery he can walk and go washroom to pass stool but cathete is still inserted due to weakness. after 1 month of surgery last day father labs reports are these. serum urea is normal but his creatinine is elevated slightly 1.4mg/dl. his urine is cloudy with pus cells many 300 HPF, red cells 20-25 HPF and epithelial cells are a few. crystals are amorphous urates+ and protein is + question is why his creatinine elevated again? is thats because of UTI? he is taking medicine cefspan 400mg tablet daily since after surgery prescribe by Doctor.