Objective: The aim of this study was to determine the efficacy of measuring the diameter and area of the rectum using ultrasonography as an additional parameter for the evaluation of neurogenic bowel in patients with spinal cord injury (SCI). Participants: In total, 32 patients with SCI (16 patients with upper motor neuron neurogenic bowel (UMNB) and 16 patients with lower motor neuron neurogenic bowel (LMNB)) participated in this study. We divided the patients by the type of neurogenic bowel: UMNB, patients with supraconal lesions and recovery state of spinal shock or LMNB, patients with infraconal/caudal lesions or spinal shock state). Intervention: Ultrasound was applied on the abdomen and measured the diameter and area of the rectum were measured twice each before and after defecation, respectively. Outcome measure: We compared rectal diameter and area before/after defecation between the two groups, and significant differences were found in both rectal diameter and area before/after defecation in each group. Results: After defecation, those in the UMNB group had smaller rectal diameters and areas than those in the LMNB group. Significant reduction of rectal diameter and area was observed after defecation as well. The LMNB group showed slightly increased rectal area after defecation, but the increase was not statistically significant. Conclusion: Using ultrasound to measure rectal diameter and area seems helpful for classifying neurogenic bowel types and for understanding the neurogenic bowel among SCI patients with symptoms of neurogenic bowel.