The kidneys are richly innervated by the sympathetic nervous system (Gazdar and Dammin, 1970, Muller and Barajas, 1972 in Sutters 1992).  The role of the sympathetic renal nerves in the adaptation to changes in dietary sodium intake in persons with spinal cord injury and impaired sympathetic nervous systems warrant study. 

Table: Responses to Dietary Sodium Restriction in Persons Post SCI

Discussion

In a study by Sutters et al (1992) the effects of change from a high to low sodium diet on renal sodium and water excretion and hormonal responses were studied in nine individuals with tetraplegia and dissociated sympathetic control (DS) and in six controls with paraplegia with intact sympathetic systems (IS).  Total and fractional urinary sodium excretion, supine mean arterial pressure, creatinine clearance, plasma renin activity and plasma atrial natriuretic peptide concentration were measured.  The authors reported that the results suggested that direct sympathetic control of the kidney is not required for renal sodium conservation in response to dietary salt restriction; however, is likely involved in the hemodynamic and hormonal responses.    

Conclusion

• There is level 3 evidence based on one case control study (Sutters et al., 1992) that sympathetic control of the kidney is not required for renal sodium conservation in response to dietary salt restriction.    

• Impairment of sympathetic control of the kidney secondary to SCI resulting in tetraplegia does not impact renal sodium conservation in response to dietary salt restriction.