What spinal levels are associated with urinary retention?

Damage to Sacral Spinal Cord Levels (S2-S4) Causes Urinary Retention

Damage to the sacral spinal cord levels (S2-S4) is primarily responsible for urinary retention due to disruption of the micturition reflex pathway. 1, 2 This damage affects the neural control of the detrusor muscle and urethral sphincter coordination, leading to bladder dysfunction.

Spinal Levels and Urinary Function

Sacral Spinal Cord (S2-S4)

• Controls the parasympathetic innervation of the bladder detrusor muscle
• Houses the sacral micturition center that coordinates voiding reflexes
• Damage results in:
  • Detrusor underactivity or areflexia
  • External urethral sphincter denervation
  • Lower motor neuron type dysfunction 1
  • Urinary retention as the primary manifestation

Pontine Micturition Center (PMC)

• Located in the brainstem, coordinates the micturition reflex
• Lesions between the sacral spinal cord and PMC can lead to:
  • Sphincter-detrusor dyssynergia
  • Spastic bladder 3

Suprapontine Regions

• Frontal and parietal cortical areas provide voluntary control of micturition
• Damage typically causes storage dysfunction rather than retention
• Insular lesions have been associated with urinary retention 3

Clinical Presentation of Sacral Spinal Cord Damage

Primary Symptoms

• Urinary retention (inability to empty the bladder)
• Enlarged bladder capacity
• Detrusor underactivity (poor or absent bladder contractions) 1
• Denervation of external urethral sphincter

Associated Findings

• Sensory loss in "saddle" distribution
• Fecal incontinence or constipation
• Lower extremity neurological deficits
• Orthopedic abnormalities in up to 75% of patients with spinal dysraphism 2

Pathophysiology of Urinary Retention After Spinal Cord Injury

After spinal cord injury affecting sacral segments:

1. Initial phase: Bladder areflexia and urinary retention (spinal shock) 4
2. Loss of coordination between detrusor muscle and sphincter
3. Disruption of normal spinobulbospinal reflex pathway 5
4. Neuroplastic changes in bladder afferent pathways 6

Diagnostic Approach

MRI of the lumbar spine without IV contrast is the imaging modality of choice for suspected sacral spinal cord damage, as it:

• Provides superior soft-tissue visualization
• Can accurately assess the position of the conus medullaris
• Detects associated anomalies such as tethered cord syndrome 2
• Helps identify the specific level of spinal cord involvement 1

Clinical Pitfalls to Avoid

• Don't mistake urinary retention from sacral cord damage for retention from other causes (medication side effects, prostatic enlargement)
• Remember that urinary tract infection is a common complication in patients with neurogenic bladder from sacral cord damage 1
• Be aware that long-standing sacral cord damage may lead to upper urinary tract complications including hydronephrosis and renal damage if not properly managed 7
• Recognize that urodynamic studies are essential for proper characterization of the neurogenic bladder dysfunction 1

In summary, damage to sacral spinal cord levels (S2-S4) is the primary cause of urinary retention due to disruption of the neural pathways controlling bladder contraction and sphincter relaxation, resulting in detrusor underactivity and poor coordination of voiding function.