Limited added utility of performing follow-up contrast-enhanced CT in patients undergoing initial non-enhanced CT for evaluation of flank pain in the emergency department.

In our emergency department (ED), patients with flank pain often undergo non-enhanced computed tomography (NECT) to assess for nephroureteral (NU) stone. After immediate image review, decision is made regarding need for subsequent contrast-enhanced CT (CECT) to help assess for other causes of pain. This study aimed to review the experience of a single institution with this protocol and to assess the utility of CECT. Over a 6 month period, we performed a retrospective analysis on ED patients presenting with flank pain undergoing CT for a clinical diagnosis of nephroureterolithiasis. Patients initially underwent abdominopelvic NECT. The interpreting radiologist immediately decided whether to obtain a CECT to evaluate for another etiology of pain. Medical records, CT reports and images, and 7-day ED return were reviewed. CT diagnoses on NECT and CECT were compared. Additional information from CECT and changes in management as documented in the patient's medical record were noted. Three hundred twenty-two patients underwent NECT for obstructing NU stones during the study period. Renal or ureteral calculi were detected in 143/322 (44.4 %). One hundred fifty-four patients (47.8 %) underwent CECT. CECT added information in 17/322 cases (5.3 %) but only changed management in 6/322 patients (1.9 %). In four of these patients with final diagnosis of renal infarct, splenic infarct, pyelonephritis and early acute appendicitis in a thin patient, there was no abnormality on the NECT (4/322 patients, 1.2 %). In the remaining 2 patients, an abnormality was visible on the NECT. In patients presenting with flank pain with a clinical suspicion of nephroureterolithiasis, CECT may not be indicated. While CECT provided better delineation of an abnormality in 5.3 % of cases, changes in management after CECT occurred only in 2 %. This included 1 % of patients in whom a diagnosis of organ infarct, pyelonephritis or acute appendicitis in a thin patient could only be made on CECT.