Follow-up imaging of the urinary tract in spinal injury patients: is a KUB necessary with every ultrasound?

Study Design: Prospective study of 100 consecutive patients.

Objectives: To evaluate the diagnostic usefulness of the urinary tract (KUB) radiograph routinely performed as part of spinal injury patient urinary tract screening with ultrasound (US) and the KUB radiograph.

Setting: Orthopaedic and District General Hospital with spinal injuries unit, UK.

Methods: Prospective study of the urinary tract of 100 consecutive routine follow-up spinal injury patients with KUB (kidneys, ureters, bladder) radiograph and US of the urinary tract. The percentage of the visualised area of kidneys and urinary bladder and relevant abnormal findings were recorded. Relevant patient history was recorded.

Results: In all, 80 men 20 women were examined (average age 46 years, average time since injury 11 years). A total of 199 kidneys and 99 urinary bladders were examined. On average, less than 50% of the renal area and about 70-75% of the urinary bladder area were visualised. Five patients had renal stones identified on the KUB radiograph, and of these two were seen on US. There were no stones seen on US only. The patient history was not helpful to identify patients with renal stones. Significant further renal abnormalities were identified with US in 14 patients, and with the KUB radiograph in 0 patients. Significant urinary bladder abnormalities were identified with US in 20 patients, and with the KUB radiograph in 0 patients.

Conclusion: On average, less than 50% of the kidney area is visualised on the KUB due to overlying bowel markings making the KUB radiograph a poor tool to assess the kidneys. The KUB radiograph and US are poor tools to assess urinary tract stones. In the absence of a therapeutic consequence, the KUB radiograph does not seem justified in the routine follow-up of the urinary tract in spinal injury patients.