Ultrasonography and plain film versus intravenous urography in ureteric colic

Urography (IVU) is considered the best first investigation in patients with suspected ureteric colic, but recently ultrasonography (US), combined with a plain film of the abdomen (KUB), has been suggested as an alternative. We have undertaken a prospective study to see if this approach can be used in an Emergency Department by radiologists with different amounts of ultrasound experience. Some 180 patients with suspected ureteric colic presenting to the Emergency Department over an 8-month period were studied. They had a plain abdominal film (KUB) and US examination of the kidneys, ureters and bladder following hydration. Some 120 patients subsequently underwent IVU at a mean interval of 3.5 days after the ultrasound examination. Of these, 15 patients passed a stone before their IVU. Of the remaining 105 patients, 44 had an IVU positive for stone and 61 had a negative IVU. Fifty of the 60 patients who did not have an IVU had clinical follow-up and 31 had ultrasound. Our findings in this prospective study suggest that in the hydrated patient the combination of KUB plus US is a sensitive but not very specific screening test (sensitivity 95%, specificity 67%). Because of the high negative predictive value of KUB plus US (95%), urography is not likely to be helpful when KUB plus US are negative. Urography is indicated only if KUB plus US findings are equivocal or if intervention is necessary. If we had used KUB plus US alone as the first test in our patients, urography would have been unnecessary in approximately 60%. Twenty per cent of our patients passed a stone in the first 48 h.