Investigations

Any impairment of renal function must be sought by measuring urea and electrolytes (U and E) and creatinine.

A full blood count (FBC) should be obtained as a screening test and a urine sample should also be sent for microscopy.

An ultrasound scan (US) of the renal tract should be performed if any renal impairment is present. Prostate specific antigen (PSA) measurement can be falsely elevated after DRE or urethral catheterisation and should be taken prior to either of these interventions. It may not affect acute management but can be useful if immediate referral for a urological assessment is required.

PSA in this setting gives a high false positive rate and should be deferred by 2 weeks¹⁸.