Flow rate measurement

Flow rate measurement

For this to be meaningful, two or three voids should be recorded using a special flow meter, usually found in urology outpatient clinics; the voided volume should be in excess of 150–200 /uni00A0 mL. A typical history and a flow rate <10 /uni00A0 mL/s (for a voided volume of >200 /uni00A0 mL; Figure 84.5 ) will be su ffi cient for most urologists to recommend treatment. Usually , a flow rate measurement will be coupled with ultrasound measurement of postvoid residual urine. There are pitfalls in the measurement of flow rates. The machine must be accurately calibrated. The patient must void volumes in excess of 150 /uni00A0 mL and two or three recordings ar needed to obtain a representative measurement. Decreased flow rates and LUTS may be seen in: /uni25CF BOO; /uni25CF low voided volumes (characteristically in men with detru sor instability); /uni25CF men with weak bladder contractions (low pressure–flow voiding), also known as underactive detrusor. Details of these studies are outlined in Chapter 81 . They should be performed on the following patients: /uni25CF men with suspected neuropathy (Parkinson’s disease, dementia, longstanding diabetes, previous strokes, multi - ple sclerosis); /uni25CF men with a dominant history of irritative symptoms and men with lifelong urgency and frequency; /uni25CF men with a doubtful history and those with flow rates in the near normal range (~ or >15 /uni00A0 mL/s); /uni25CF men with invalid flow rate measurements (because of low voided volumes); /uni25CF high residual/chronic retention; /uni25CF men with recurrence of LUTS after previous BPH surgery (in the absence of urethral or bladder pathology); /uni25CF young men (<50 years) and older men (>80 years) with LUTS. -