Use of sonography and radioisotope renography to diagnose hydronephrosis in patients with spinal cord injury

Objective: To study the accuracy of sonography and radioisotope renography in detecting hydronephrosis in patients with spinal cord injury (SCI). Design: Prospective, blinded comparison study. Setting: Rehabilitation hospital affiliated with a medical college. Participants: One hundred and nine patients with SCI (21 women, 88 men) participated. Interventions: Comprehensive urologic examinations including clinical evaluation, laboratory tests, intravenous urography (IVU), sonography, radioisotope renography (renal scan), voiding cystourethrography, and cystometry. The findings at sonography and renal scan were separately compared with the final diagnosis interpreted by IVU and clinical findings. Main Outcome Measures: Effective renal plasma flow, pyelocaliectasis, and positive and negative predictive value. Results: A total of 235 kidneys were analyzed. Sonography correctly excluded the presence of hydronephrosis in 173 of 192 nonobstructed kidneys. Sonograms were interpreted as positive in 41 of 43 kidneys with documented hydronephrosis. Renal scan correctly excluded 161 nonobstructed kidneys. The renal scan detected 39 of 43 kidneys with hydronephrosis. The sensitivity of sonography was .96 with a specificity of .90. Renal scan reached a sensitivity of .91 with a specificity of .84. Conclusion: Sonography and renal scan are safe, sensitive, and specific for detecting hydronephrosis. Combined use of both methods appears to be a reliable alternative to IVU in the long-term follow-up for patients with SCI with neurogenic bladder dysfunction.