Dr Jian Cheng, Nephrologist
MBBS, MPH, FRACP, FHEA, GradCert(Higher Ed), AFRACMA
This article will discuss the role of back injury in the urinary system. Key points include:
- Continence is maintained by the brain, spinal cord, nerves and bladder
- The underlying cause of incontinence is important in referring to the appropriate permanent assessor
Anatomy and physiology of the urinary system
The urinary system has two phases: storage and voiding.
The storage phase allows the bladder to fill with urine. During this time, outflow sphincters (valves) are closed. This keeps urine from leaking. When the bladder becomes full, stretch receptors in the bladder alert several areas within the brain.
The brain’s control centre then coordinates the voiding phase. The outflow sphincters relax, and the bladder muscle contracts, causing urine to be expelled.
This everyday action is an interplay between the brain, spinal cord, motor and sensory nerves (mostly from the lower nerve roots) and bladder (Figure 1). Therefore, injury to any of these pathways can cause incontinence.
Back injury and urinary incontinence
The spinal nerves as low as the sacrum level (S2-4) are involved in continence. A common memory aid used in medical school to remember this is “S2-4 keeps waste products off the floor”.
Any disruption in communications between the brain and these nerves may cause incontinence. This potentially includes injury to most parts of the spinal cord.
When a doctor is assessing a patient with back pain, they may ask questions to rule out some ‘red flags’ for incontinence. These include:
- Saddle anaesthesia – This means numbness in the area between the legs (which would be in contact riding a horse saddle). The saddle area is also innervated by the sacrum level spinal cord. Therefore, damage here may be associated with incontinence.
- History of cancer – Progressive cancer can sometimes cause back pain or compress the surrounding nerves.
- History of IV drug use – Abscesses from IV drug use can sometimes cause back pain or compress the surrounding nerves.
Impairment assessment for urinary incontinence
To assess Whole Person Impairment (WPI) under the AMA Guides, it is important to understand the underlying cause of urinary incontinence.
There are multiple chapters assigning different WPIs for incontinence in the Guides. The most appropriate assessor depends on the underlying cause. For example:
| Underlying cause of incontinence | Most appropriate assessor/field |
| Bladder injury | Urinary and reproductive systems |
| Brain injury | Nervous system |
| Back injury | Spine |
Concrete examples include:
- Case 1: A worker suffered bladder trauma after a machinery accident, which has caused stress incontinence. This claimant should be reviewed by an assessor with urinary and reproductive systems accreditation. This is because the underlying cause of incontinence is direct trauma. The claimant may be assessed up to 70% WPI under Chapter 11 of the Guides.
- Case 2: A patient who suffered a stroke now has ongoing urinary incontinence and needs to use incontinence pads, as well as having arm and leg weakness. This claimant should be reviewed by an assessor with nervous system accreditation. This is because the underlying cause of incontinence is the brain. The claimant may be assessed up to 60% WPI under Chapter 4 of the Guides.
- Case 3: A patient who became tetraplegic after a car accident suffered vertebral fractures and a spinal cord injury. This resulted in total bowel and bladder incontinence. This claimant should be reviewed by an assessor with spine accreditation. This is because the underlying cause of incontinence is related to the spinal cord injury. The claimant may be assessed up to 60% WPI under Chapter 3 of the Guides.
The three cases above demonstrate that even though the claimants all have incontinence, the medicolegal assessor should be assigned based on the underlying cause, which ensures the most accurate WPI calculation.
Summary
Urinary continence is preserved by a complex system involving the brain, spinal cord, nerves and bladder. There are various underlying conditions, including back injuries, that disrupt this system and result in incontinence. To choose an appropriate medicolegal assessor, it is important to understand the underlying cause of incontinence.
