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Bladder Diameter Ratio: A Measure Of Bladder Elongation And Correlation To Bladder Trabeculation in Children with Spina Bifida


To date, there is no widely accepted objective measure to help quantify the shape of the normal urinary bladder in the literature. Patients with spina bifida are a potentially complex population who can present with a spectrum of upper and lower urinary tract derangements. Better understanding of the link between bladder shape in patients with normal bladders and those with spina bifida would greatly add to this understanding. Herein I attempt to shed like on this subject and evaluate a new measure, bladder diameter ratio (BDR), used to quantify the shape of bladders in children with and without evidence of vesicular neurologic pathology.

A small retrospective pilot study evaluated all voiding cystourethrograms (VCUGs) that were performed at our institution in 2010. Those that were performed in children without known bladder pathology or underlying neurologic condition, and read as normal, were included. Patients with spina bifida with and without were also evaluated. A BDR was calculated in a standard fashion and defined as the ratio of maximal bladder length to width on cystography at cystometric capacity. Mean difference was compared using an independent samples t-test.

Seventy-five children with normal bladders and 63 patients with SB were included with mean ages at time of VCUG of 6.2(0.3-17.6) and 7.2(0.1-21) years respectively, (p=0.2). Children with normal bladders had a BDR of 1.03(95%CI 0.99-1.07). Patients with spina bifida and no trabeculation had no difference in BDR compared to those with normal bladders (BDR=1.04(95%CI 0.96-1.12;p=0.78)), unlike patients with spina bifida and trabeculation (BDR=1.44(95%CI 1.33-1.55;p<0.001).

A larger retrospective study was performed to confirm the findings in a larger cohort of patients with spina bifida and to include ultrasounds, as a possible non-invasive imaging modality to measure BDR and follow patients. A similar analysis was performed which confirmed the similarities with regards to mean BDR between the 3 groups both on both x-ray contrast studies and ultrasound.

There was also a positive correlation between the presence of an elevated BDR and upper tract changes on ultrasound in both studies.

BDR, as a measure of bladder shape in children with normal bladders, can be a useful tool. It provides the first objective measure of normal bladder shape. It can be used as a marker of disease progression. Further studies are needed to correlate BDR with hostile bladder pressures in a prospective fashion.

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