Objective: To determine the role of bedside renal ultrasonography (US) and plain radiography of the kidneys, ureters, and bladder (KUB) as the initial investigative modality for those patients presenting to the ED with unilateral flank pain and hematuria. The hypothesis was that the renal US + KUB may obviate the need for emergent i.v. pyelography (i.v.P) in a majority of patients.
Methods: Prospective study over an 8-month period of all consecutive adult patients between the ages of 18 and 65 years presenting with unilateral flank pain and hematuria to the ED at LAC + USC Medical Center. Patients received KUB followed by a 500-mL bolus of normal saline. Bedside US was then performed by emergency physicians (EPs). Hydronephrosis of the kidney was graded as mild, moderate, or severe. All patients then underwent i.v.P. The results of the bedside US + KUB were then compared with those of i.v.P (the criterion standard).
Results: Of a total of 139 eligible patients, 108 were enrolled. The combination of US and KUB correctly identified pathology consistent with nephroureterolithiasis with a sensitivity of 97.1% (95% CI = 93.1-100%) when compared with i.v.P. The KUB + US results were falsely positive in 16 patients, resulting in a specificity of 58.9% (95% CI = 43.5-74.3%). The positive predictive value of the combined modality was 80.7%, the negative predictive value was 92.0%, and the overall accuracy was 83.3%.
Conclusion: The bedside US + KUB has a high sensitivity and can be performed rapidly at the bedside by the EP when compared with i.v.P. This combined modality is an effective screening tool in the initial evaluation of ureteral colic.