Comparing the role of renal ultrasound vs MAG3 renal scans for evaluation of neurogenic bladder after spinal cord injury

Abstract

Objective

Compare ability of renal ultrasound and Tc-99m mercaptoacetyltriglycine (MAG3) renal scan to identify upper urinary tract stasis.

Design

Retrospective chart review.

Setting

Outpatient Neuro-urology clinic serving a large SCI population.

Participants

One hundred and sixty-five individuals with spinal cord injury, presenting for annual evaluation.

Interventions

Renal ultrasound, MAG3 renal scan.

Outcome Measures

Radiologic evidence of upper urinary tract stasis as reviewed by independent radiologist. For renal ultrasounds, this included: mild hydronephrosis, dilation of collecting systems, pelviectasis, or caliectasis. For MAG3 renal scans, this included evidence of slow drainage of radioisotope, dilation of collecting systems, or reverse peristalsis.

Results

Forty-five individuals with spinal cord injury demonstrated upper tract stasis, with 12 identified by renal ultrasound and 43 identified by MAG3 renal scan. There was a strong relative correlation between test results (Yule’s Q = 0.90), though MAG3 renal scan identified a significantly higher rate of upper tract stasis within the same patients (P < 0.0001). The odds ratio of improved identification using MAG3 renal scan was 16.5 (95% CI 3.96–68.76).

Conclusions

While renal ultrasound is more effective at evaluating renal anatomy, MAG3 renal scan identifies significantly more upper urinary tract stasis than renal ultrasound and should be considered for SCI individuals with risk factors of upper tract injury.

Keywords:

• Spinal cord injury
• Neurogenic bladder
• Renal insufficiency