Bladder Height to Width Ratio as a surrogate marker for non-physiological storage pressures in children with spinal dysraphism

Abstract

Abstract Introduction : Spinal dysraphism is the most frequent cause of neurogenic bladder. Urodynamic study (UDS) is an important component of the follow up of a child with neurogenic bladder. However, it suffers from a lack of widespread availability and is further hampered by technical difficulties along with difficulty in its interpretation in children. A neurogenic bladder often appears vertically elongated, sparce literature is available regarding objectively defining the bladder shape and the urodynamic parameters in the cohort. Objectives The aim of this study was to investigate the usefulness of the height to width ratio (HWR) of the bladder on cystogram as a screening tool for identifying “non-physiological” bladder in children with spinal dysraphism. A prospective study was undertaken to evaluate children operated for spinal dysraphism. Cystogram, ultrasonography and UDS evaluation was performed. HWR was calculated by the ratio of the maximum height to the maximum width of the bladder at maximum cystometric capacity. The children were categorised into groups based on maximum detrusor pressure (MDP) into two groups (MDP ≥ 30 cmH2O and MDP < 30 cmH2O). A receiver-operative characteristic curve was constructed to analyse the sensitivity and specificity of HWR in predicting the MDP. Results A total of 53 children, operated for spinal dysraphism, met the study criteria. The median age of children was 4 years (IQR – 3-5.5 years). The HWR ratio was compared between the two groups and was significantly higher for the non-physiological pressure bladders than for physiological pressure bladders (median 1.55 vs 1.3, p = 0.001). On evaluating the sensitivity and specificity of HWR for discerning children with non-physiological bladder pressures were 87.5% and 48.28%, respectively. The area under curve (AUC) was 0.781 with a cut off value of 1.3. Discussion We attempted to objectively evaluate the HWR based on bladder shape. We demonstrated that there was a moderate correlation between the bladder shape and the bladder pressures. A HWR of 1.3 or higher could be considered significant for identifying a non-physiological bladder storage pressure. Conclusion The height to width ratio of the bladder on cystogram is a useful tool as a surrogate marker for non-physiological storage pressures in bladders of children with spinal dysraphism.