To predict the development of a neurogenic bladder based on an analysis of the clinical and radiological findings in patients with lumbar disc herniations.

Twenty-six patients, who were suspected of having neurogenic bladders, underwent urodynamic testing. The anteroposterior diameters and the cross-sectional areas of the dural sacs at the herniated disc levels were measured by magnetic resonance imaging. Clinically, we evaluated lower back pain, radiating pain, saddle anesthesia, bladder function, motor weakness of the lower limbs, and the Japanese Orthopaedic Association (JOA) score.

Thirteen (50%) of the 26 patients were diagnosed with positive neurogenic bladders. The average anteroposterior diameters of the dural sacs in group I (13 cases) with positive neurogenic bladders and in group II (13 cases) with negative neurogenic bladders, were 6.8 (range, 4-9) mm and 9.0 (range, 8-10) mm, respectively (p<0.001). When an anteroposterior diameter of 7 mm was used as the threshold value for differentiation between the anteroposterior diameter of the dural sac and a neurogenic bladder, the sensitivity and specificity were 61.5% and 100%, respectively. The average cross-sectional areas of the dural sacs in group I and group II were 74.9 (range 50-96) mm² and 86.2 (range 60-103) mm², respectively (p=0.069). When a cross-sectional area of 77 mm² was used as the threshold value for differentiation between the cross-sectional area of the dural sac and a neurogenic bladder, the sensitivity and specificity were 61.5% and 84.6%, respectively. All 9 patients who had saddle anesthesia were diagnosed with positive neurogenic bladders. However, there was no statistical significance between the preoperative JOA score and the development of a neurogenic bladder.

The anteroposterior diameter of the dural sac and saddle anesthesia might be important factors in predicting the presence of a neurogenic bladder in patients with lumbar disc herniation.