Are the unenhanced and excretory CT phases necessary for the evaluation of acute pyelonephritis?

Abstract

Background The most widely accepted computed tomography (CT) protocol for diagnosis of acute pyelonephritis (APN) includes at least a pre- and post-contrast scan, which may expose patients to higher doses of ionizing radiation. Purpose To establish the accuracy, reproducibility, and degree of confidence in CT diagnosis of acute pyelonephritis (APN) and urolithiasis using only images obtained during the nephrographic phase. Material and Methods A retrospective study of 100 consecutive patients (88 women; age range, 19-70 years) with clinical and laboratory suspicion of APN and who underwent triphasic abdominal CT scans (non-contrast, nephrographic, and excretory phases) was performed. Two readers first evaluated independently only the nephrographic phase of scans, and, in a second session, the entire study. The diagnostic reference standard was settled by a third experienced radiologist who reviewed all triphasic scans and clinical data. Results The accuracy of only nephrographic phase for diagnosis of APN and urolithiasis was in the range of 90.3-91.78% and 96.27-99.25%, respectively. There was no significant difference in comparison with the triphasic reading (z: -0.4 - 0.2; P = 0.34-0.83). The average degree of confidence for APN also showed no significant variation for both readers ( P = 0.4 and 0.08). Almost perfect inter-observer agreements for the diagnosis of APN (k = 0.86, P < 0.001) and for urolithiasis (k = 0.84, P < 0.001) were observed when considering only the nephrographic phase. Conclusion CT assessment of APN and urolithiasis can be accurately performed using only the late nephrographic phase, with consequent dose reduction.

CT Grading in Upper Urinary Tract Calculi with Kidney Infection

“…Acute in ammatory reactions occur in the renal parenchyma, showing aggregation and in ltration of in ammatory cells, telangiectasia, edema of localized or patchy tissues, presence of edema and slight ischemic areas and presence of diffuse or punctate distribution [19]. On plain CT images, these features are manifested as kidney enlargement, thickened renal parenchyma, decreased density, and unclear decomposition of renal cortex and medulla [19,20]. Multiple abscesses or infarct focuses are visible, characterized by one or more wedge-shaped banded lowdensity focuses extending from the renal papilla to the renal cortex, in striated signs [19,20].…”

“…On plain CT images, these features are manifested as kidney enlargement, thickened renal parenchyma, decreased density, and unclear decomposition of renal cortex and medulla [19,20]. Multiple abscesses or infarct focuses are visible, characterized by one or more wedge-shaped banded lowdensity focuses extending from the renal papilla to the renal cortex, in striated signs [19,20]. Thus, we classi ed the patients with CT manifestations of local thickening of the renal parenchyma, decreased density, unclear boundary of the renal cortex medulla, and local wedge swelling of the renal parenchyma and low-density foci as CT grade 3.…”

ACR Appropriateness Criteria® Acute Pyelonephritis

“…Other authors have recommended the use of two phases, namely precontrast and nephrographic, unless obstruction is suspected [2,8]. A recent retrospective study by Taniguchi et al [20] showed that scans using only the nephrographic phase had similar accuracy with triphasic scans (which also included precontrast and excretory phases) for the diagnosis of acute pyelonephritis and urolithiasis. This study reported an accuracy of nephrographic phase only CT of 90% to 92% in the diagnosis of acute pyelonephritis and 96% to 99% in the diagnosis of urolithiasis.…”

Acute Renal Infection in Adult, Part 1: An Overview of What the Radiologist Needs to Know

“…Craig et al 19 and Stunell et al 26 have studied pyelonephritis by only precontrast and nephrographic phase CT in cases where obstruction is not suspected. Taniguchi et al 27 reported that scans using only the nephrographic phase had high accuracy with triphasic scans (which also included precontrast and excretory phases) for the diagnosis of AP and urolithiasis. This study reported an accuracy of nephrographic phase only CT of 90 to 92% in the diagnosis of AP and CT of 96 to 99% in the diagnosis of urolithiasis.…”