Kidney computed tomography perfusion in patients with ureteral obstruction.

INTRODUCTION: Kidney perfusion on CT is an encouraging surrogate for renal scintigraphy in assessing renal function. However, data on dynamic volumetric CT in patients with kidney obstruction is lacking. Thus, the aim of this study is to determine the feasibility of CT-based renal perfusion using a dynamic volume to assess renal hemodynamics at different degrees and durations of obstruction. MATERIALS AND METHODS: We included patients with unilateral kidney obstruction in our single-center, prospective study. The patients were divided into three groups. Patients without dilatation of the pelvicalyceal system (PCS) and normal parenchyma thickness were included into Group 1; patients with PCS dilatation and parenchyma thickness 1.8-2.4 cm-into Group 2; and patients with ureteropyelocalicoectasia and parenchyma thickness less than 1.8 cm-into Group 3. RESULTS: Total of 56 patients were enrolled. In Group 1 mean values of cortical and medullar arterial blood flow, blood volume, and extraction fraction were within the normal range. Changes in contralateral kidney were not determined. Patients from Group 2 showed significant differences in blood flow parameters in the cortical and medulla of the obstructed kidney. No changes in perfusion values in the contralateral kidney was observed. In patients from Group 3 there was a marked decrease in perfusion on the side of obstruction compared to Group 2, indicating that the degree of expansion of the PCS directly correlates with the change in blood flow. However, in the contralateral kidney, these indicators exceeded the normal values of perfusion. CONCLUSION: CT perfusion allows to objectively assess changes in blood flow in the setting of renal obstruction. The degree of obstruction directly affects the measured rate of blood flow.

Dual-Energy Computed Tomography for Stone Type Assessment: A Pilot Study of Dual-Energy Computed Tomography with Five Indices.

Purpose: To assess the efficacy of dual-energy CT (DECT) in predicting the composition of urinary stones with a single index (dual energy ratio [DER]) and five indices. Methods: Patients undergoing DECT before active urolithiasis treatment were prospectively enrolled in the study. Predictions of stone composition were made based on discriminant analysis with a single index (DER) and five indices (stone density at 80 and 135 kV, Zeff [the effective atomic number of the absorbent material] of the stone, DER, dual-energy index [DEI] and dual-energy difference [DED]). After extraction, stone composition was evaluated by means of physicochemical analyses (X-ray phase analysis, electron microscopy, wet chemistry techniques, and infrared spectroscopy). Results: A total of 91 patients were included. For calcium oxalate monohydrate (COM) stones, the sensitivity, specificity, and overall accuracy of DECT with one index (DER) were 83.3%, 89.8%, and 86.8%, respectively; for calcium oxalate dihydrate (COD) and calcium phosphate stones-88.2%, 92.9%, and 91.2%, respectively; for uric acid stones-0%, 98.8% and 97.8%, respectively; for struvite stones-60%, 95.3%, and 93.4%, respectively. Discriminant analysis with five indices yielded the following sensitivity, specificity, and overall accuracy: 95.2%, 89.8%, and 92.3% for COM stones, 85.3%, 96.4%, and 92.3% for COD stones, and 100% in all three categories for both uric acid and struvite stones. Conclusions: DECT is a promising tool for stone composition assessment. It allowed for evaluation of chemical composition of all stone types with specificity and accuracy ranging from 85% to 100%. Five DECT indices have shown much better diagnostic accuracy compared to a single DECT index.