Non contrast computerized tomography and dynamic renal scintigraphy in the evaluation of patients with renal colic: Are both necessary?

Objectives: To determine the value of the combined use of non contrast computerized tomography (NCCT) and dynamic renal scintigraphy (DRS) in the evaluation of patients with renal colic. Methods: Forty-nine consecutive patients with renal colic were evaluated with abdominal plain films (KUB), NCCT and DRS with Tc-99m DTPA or MAG-3. NCCT results showed size and location of the urolithiasis, as well as secondary signs of obstruction. DRS was used to determine the degree of obstruction in the affected renal unit. Patients were submitted to urologic intervention or followed, decision made on the basis of clinical symptoms, degree of obstruction, size, and location of the stone. Results: Three patients had other etiologies than stone for their symptoms and were excluded from the study. Of the remaining 46 patients, KUB detected stones in 24 (52.2%), while NCCT in all. NCCT showed secondary signs of obstruction in 35 patients (76%). Seven patients in this group (15%) had severe hydronephrosis on NCCT and complete obstruction on DRS. Twenty-eight patients (61%) showed moderate hydronephrosis and/or peri-renal and peri-ureteral stranding on the NCCT. In this latter group, DRS diagnosed complete obstruction in 5 (18%) patients, partial obstruction in 16 (57%) and no signs of obstruction in 7 (25%) patients. Overall 34% (12/35) of the patients with secondary signs of obstruction on NCCT had complete obstruction on DRS. NCCT revealed no secondary signs of obstruction in 11 patients (24%) with partial obstruction diagnosed by DRS in one of them (9%). All 12 patients with complete obstruction on the DRS underwent early intervention. Of the 16 patients with partial obstruction of the DRS, two patients (12.5%) necessitated ureteric stent insertion. Three patients with no obstruction on the RNS underwent elective extracorporal shock wave lithotripsy (ESWL) while the rest of the patients were followed and passed their stones spontaneously. Conclusions: The combination of non-enhanced helical CT and DRS assesses both anatomy and function. When NCCT shows no secondary signs of obstruction, NCCT as the sole imaging study performed may be adequate. If there are secondary signs of obstruction on NCCT, DRS can distinguish patients with different degrees of obstruction and together with the clinical course, size, and location of the lithiasis may help in selecting patients who need earlier intervention from those who may be safely observed.