Postoperative lumbar CT: technique, results, and indications.

Seventy-seven patients with recurrent radicular symptoms after operation for lumbar disk herniation were examined by plain computed tomography (CT) and by intravenously enhanced CT. With the latter technique, scar tissue and recurrent disk herniation can be distinguished: scar tissue shows definite contrast enhancement whereas recurrent disk herniation remains unenhanced. Nerve roots surrounded by scar tissue are often visualized on the postcontrast scan as rounded lucencies. Symmetrical undisplaced nerve roots were identified in 88% of cases of hypertrophic scar formation; this finding excludes recurrent disk herniation. Dural calcifications were found in five patients with hypertrophic scar formation. The authors conclude that CT with contrast enhancement should be the method of choice for evaluating patients with recurrent radicular symptoms after operation for disk herniation.