NEW YORK (Reuters Health) – Bladder weight estimated by ultrasound doesn’t correlate with lower urinary tract obstruction, a new study suggests.

Instead, clinicians should stick with urodynamic evaluation to differentiate obstruction from bladder underactivity, investigators in Brazil advise.

Animal studies in the 1990s first suggested that outlet obstruction causes bladder hyperplasia and hypertrophy, lead author Dr. Fernando Goncalves Almeida and associates explain in BJU International published online December 16th. Trials of ultrasound-estimated bladder weight (UEBW) in men with voiding dysfunctions gave equivocal results.

To see if UEBW would be of any benefit in screening men for bladder outlet obstruction, Dr. Almeida, from Paulista School of Medicine at Federal University of Sao Paulo, and his team evaluating 50 consecutive non-neurogenic men with lower urinary tract symptoms.

After clinical examination, the doctors performed urodynamic studies, including cystometry and a pressure-flow study. They then filled the patient’s bladder with 150 mL of fluid to determine UEBW, which was used to define four groups: bladder weight < 35 g, between 35 and < 50 g, between 50 and < 70 g, and 70 g or greater. However, UEBW did not differ significantly with severity of obstruction as determined by urodynamic evaluation (p = 0.130). UEBW averaged 51.7 g in the 20 patients with mild obstruction, 54.1 g in 20 patients with moderate obstruction, and 54.8 g in 10 patients with severe obstruction. Furthermore, Dr. Almeida’s group found no differences between UEBW groups in age, prostate weight, International Prostate Score Symptoms (IPSS) questionnaire responses post-voiding residual, cystometric bladder capacity, presence of detrusor overactivity, or degree of obstruction. This lack of correlation, they suggest, may be caused by duration of bladder outlet obstruction and individual intrinsic bladder responses to obstruction. Reference:
Is the ultrasound-estimated bladder weight a reliable method for evaluating bladder outlet obstruction?

BJU Internat 2010.