**6. Diagnostic tests**

Although nowadays it is increasingly rare to find a patient with chronic renal failure from chronic urinary retention due to BPH, about 13,6% (range from 0,3 to 30%) of men with BPH may present with CKD defined by a baseline serum creatinine of more than 133 mmol/L (1,5 mg/dL). This is particularly true in older patients with cognitive deterioration and autonomy impairment. In order to diagnose and monitor the impact of a bladder outlet obstruction due to BPH in the upper urinary tract, some laboratory and imaging tests should be considered: standardized questionnaires, serum creatinine levels or estimated glomerular filtration rate (eGFR), urinalysis, serum prostatic specific antigen (PSA) levels, uroflowmetry with peak flow rate determination, renal ultrasonography, bladder ultrasonography with detrusor thickness evaluation, transrectal prostate ultrasonography, pre and post-void residual urinary volume, cystometry, other urodynamic studies and urethrocystoscopy.
