Despite completing 6 years of residency and a subsequent 2-year Female Pelvic Medicine and Reconstructive Surgery fellowship, I often have found that my treatments for neurogenic bladder (NGB) are based on the anecdotal knowledge I have accrued in my 10 years as an attending urologist rather than what can be found in a textbook. To me, health service research, the integration of epidemiology, sociology, economics and other analytical sciences, is a means to identify the scope of patient issues, provide ideas to optimize clinical practices (if not change them completely) and answer unknown clinical questions. In this way, abstract concepts in oft-misunderstood areas (such as NGB care) are made more concrete and inform clinical practice guidelines (based on the best available evidence combined with expert opinion) for the next generation to build upon.

As the primary urological practitioner who provides NGB care for many patients after discharge from our hospital’s spinal cord injury (SCI) rehabilitation center, a significant portion of my career has been spent serving the SCI population. While the 4 I’s (urinary tract Infection, urinary Incontinence, bladder management Independence and bladder management Inconvenience)¹ are often a focus in my established patients, the question I am most asked by those with a new SCI is “what is the chance I can urinate on my own again?” For the first several years of my career, I was not able to answer this simple yet life altering question, only knowing that those with less complete injuries were more likely to void over time.

My ability to answer this important question changed in 2016 with the publication of “Prediction of Bladder Outcomes after Traumatic Spinal Cord Injury: A Longitudinal Cohort Study.”² In this work, the authors described a robust prediction model of volitional voiding after SCI based on a standard neurological examination grading scale of the L2-S1 myotomes bilaterally (ranging in each myotome from 0’total paralysis to 5’active movement with full range of motion against gravity and full resistance). The corresponding lower extremity motor score (LEM), ranging 0–50, is then used to predict the estimated probability of a return of volitional voiding ranging from 6.7% (LEM=0) to 93.5% (LEM=50; see Figure).² The published prediction tool, which was generated using the data of 1,250 patients in the European Multicenter Spinal Cord Injury Study, was subsequently examined by our group using the data of 4,327 patients from the United States National Spinal Cord Injury Database, where we confirmed the almost unheard-of performance of LEM scores to predict volitional voiding (area under the curve=0.912).³

Figure. Prediction of volitional void based on LEM scores (adapted).2

Taking this to the clinic, I found that I could now answer a patient’s question about their chance of ever voiding again with much greater clarity, though I found that not all patients came to me with a neurological examination that contained an LEM score. For this reason, our group went back to the National Spinal Cord Injury Model Systems Database and worked to calculate the chance of volitional voiding using a variable that was simpler to find (albeit not as granular), the American Spinal Injury Association Impairment Scale (AIS) classification.⁴ With this, a provider can provide an approximate estimate of the chance of volitional void (AIS A=2%, AIS B=5%, AIS C=25% and AIS D=75%) without the aid of a prediction tool in front of them (see Table). In my specific practice, I find that these prediction tools (either using LEM scores or AIS classification) set the tone for conversations on realistic expectations, allow me to decide if and when formal urodynamic testing is necessary and alert me to potential outlier patients who may have subclinical bladder dysfunction that might become problematic down the road (ie the AIS A or AIS B patient who says they are voiding volitionally, where the chances of that occurring are very low). I think that these conversations are immensely helpful, not only from a patient understanding of where they stand, but also in establishing that I am a credible resource who knows the SCI landscape.

In addition to improving patient care discussions, NGB outcomes studies also provide the building blocks for future investigations. For instance, our group has found the predictive ability of LEM scores on volitional voiding to be of assistance when trying to identify other factors that might augment recovery of volitional voiding after SCI. Specifically, LEM scores afford us more granular and accurate subgroupings of patients to improve prognostication on bladder outcomes. In our latest work using LEM scores to predict chance of volitional voiding, we demonstrated that early infection during the rehabilitation phase after SCI may reduce the chance of volitional void, a finding that hopefully will lead to further investigation on the subject (either basic or clinical science based).⁵ Likewise, any future studies on therapeutic interventions to aid recovery of volitional voiding will benefit from an understanding of LEM scores as a prediction tool to properly stratify participants based on expected neurological recovery.