Magnetic resonance evaluation of recurrent disc herniation - Is gadoliniumnecessary?

Study Design. Evaluation of magnetic resonance images (MRIs) with surgical reference standard. Objectives. To determine whether the addition of contrast-enhanced MRI scan s increases diagnostic efficacy in the evaluation of recurrent disc herniat ion. Summary of Background Data. Many centers now routinely use gadolinium-enhan ced examinations in the evaluation of recurrent disc herniation. Others, no ting the additional expense of contrast injection, advocate a more limited role for contrast injection and emphasize the importance of T-2-weighted ax ial sequences. Methods. The study included 165 consecutive patients who were referred to t he authors' outpatient imaging center and had a history of previous lumbar discectomy and recurrent back and/or leg pain. The scanning protocol includ ed sagittal and axial T-1-weighted spin-echo pre- and postcontrast injectio n images and sagittal and axial T-2-weighted fast spin-echo images. Twenty- eight patients (32 vertebral levels) had subsequent surgical exploration of a disc margin that had previously undergone discectomy. The surgical findi ngs formed the reference standard. Three spine radiologists interpreted the MRI examinations without knowledge of the surgical results. They first int erpreted the unenhanced studies, indicated whether they felt contrast injec tion would be helpful in further evaluation, and then (regardless of this d etermination) read the postcontrast study, Results. On pre- and post-contrast examinations Reader 1 had a sensitivity of 95% (20/21), a specificity of 100% (10/10), and an accuracy of 97% (30/3 1). Reader 2 had a sensitivity of 95% (20/21), a specificity of 90% (9/10), and an accuracy of 94% (29/31). Reader 3 had a sensitivity of 90% (19/21), a specificity of 100% (10/10), and an accuracy of 94% on the precontrast e xaminations. His post-contrast performance demonstrated a sensitivity of 86 % (18/21), a specificity of 100% (10/10), and an accuracy of 90% (28/31). I n the nine interpretations wherein the readers thought that a contrast-enha nced examination might provide useful additional information, they did not change their interpretations in three cases, improved their interpretations in two, and made their interpretations worse in four on the basis of addit ion of the enhanced images, Conclusions. Routine use of contrast-enhanced examinations in patients who have had prior lumbar surgery probably adds little diagnostic value and may be confusing.