Urinary N-acetyl-beta- d-glucosaminidase concentration in patients with spinal cord injury: relationship with urodynamic parameters

Abstract

Objectives. To investigate the relationships between urinary N-acetyl-beta- d-glucosaminidase (NAG) concentrations and urodynamic parameters in patients with spinal cord injury (SCI). NAG has been proposed as a marker of renal damage. Methods. Twenty-three patients with SCI were evaluated with urodynamic studies. Urine samples were collected from the 23 patients and 10 healthy volunteers, the NAG levels were evaluated, and the urodynamic parameters were compared with the urinary NAG levels. The patients were divided into two groups according to the amplitude of the hyperreflexic detrusor contractions (HDCs): group A, patients with an HDC amplitude of 40 cm H 2O or greater, and group B, patients with an HDC amplitude of less than 40 cm H 2O; group C was composed of healthy volunteers. The urinary NAG concentrations in the three groups were compared. Results. A positive correlation was found between the urinary NAG levels and the HDC amplitude and detrusor leak point pressure ( P = 0.015 and 0.007, respectively). The urinary NAG concentration was 3.38 U/g in group A, 2.14 U/g in group B, and 2.12 U/g in group C. The differences in the urinary NAG concentrations between groups A and B and between groups A and C were statistically significant ( P = 0.03 and P <0.001, respectively). The concentrations between groups B and C were comparable. Conclusions. In our experience, the only urodynamic parameters that clearly and positively correlated with the urinary NAG levels were those expressing the amplitude of intravesical pressure. This result stresses the importance of reducing the intravesical pressure in patients with SCI using alternative treatments or surgical procedures if the usual conservative therapies are not effective.