J Korean Soc Radiol.  2016 Dec;75(6):487-494. 10.3348/jksr.2016.75.6.487.

Detection of Parenchymal Abnormalities in Experimentally Induced Acute Pyelonephritis in Rabbits Using Contrast-Enhanced Ultrasonography, CT, and MRI

• Ryu JA
• Kim B
• Kim SK
• Seo JW
• Kim JS

• KMID: 2360437
• DOI: http://doi.org/10.3348/jksr.2016.75.6.487

Abstract

PURPOSE
We evaluated the efficacy of contrast-enhanced ultrasonography (CEUS) in detecting acute pyelonephritis (APN) using the rabbit kidney model and compared it with CT and MRI.
MATERIALS AND METHODS
This study was approved by the Institutional Review Board. In a total of 20 New Zealand White rabbits, APN was induced experimentally. CEUS, CT, and MRI were performed on the first, third, and seventh postoperative days. After imaging studies, the subjects were sacrificed and the pathological diagnosis of APN was confirmed in each animal by a pathologist.
RESULTS
Imaging studies were obtained in eight animals, including eight CEUS, four computed tomography (CT), and four magnetic resonance imaging (MRI) images. CEUS depicted diffuse renal enlargement (7), diffuse heterogeneous parenchymal enhancement (6), and focal areas of decreased parenchymal enhancement (6). These findings were well correlated with the CT and MRI findings in five cases in which these studies were available. CT and MRI showed diffuse renal enlargement, diffuse heterogeneous parenchymal enhancement, focal areas of decreased parenchymal enhancement, focal contour bulging, and the finding of perinephric spread of infection.
CONCLUSION
In a rabbit model, CEUS could depict the parenchymal lesions of APN similar to CT or MRI; however, it was limited in depicting the perinephric extension of inflammation.

MeSH Terms

Animals
Diagnosis
Ethics Committees, Research
Inflammation
Kidney
Magnetic Resonance Imaging*
Pyelonephritis*
Rabbits*
Ultrasonography*

Figure

• 

  Fig. 1 Acute pyelonephritis involving the left kidney of a rabbit on the first post-inoculation day. A. In the CEUS longitudinal image, the kidney shows diffuse heterogeneous enhancement. The large perfusion defect in the near field seems to be an artifact (arrowheads); however, the parenchyma on the opposite side and bilateral renal poles show multifocal areas of parenchymal perfusion abnormality (arrows). Renal hilum is not enhanced (asterisk). B. T2-weighted axial image shows a normal right kidney of this rabbit having a normal renal size, cortical signal intensity and clear perinephric fat. C. T2-weighted axial image of the left kidney shows increased parenchymal signal intensity, diffuse renal enlargement, hydronephrosis, and perinephric strands due to renal inflammation (arrows). D. Delayed phase contrast enhanced CT axial image of the normal right kidney shows normal excretion. E. In the same phase of (D), the left kidney shows diffuse decreased parenchymal enhancement and delayed renal excretion. Renal enlargement and hydronephrosis are also noted in the axial image. CEUS = contrast-enhanced ultrasonography, CT = computed tomography, MRI = magnetic resonance imaging

• 

  Fig. 2 Acute pyelonephritis involving the left kidney of a rabbit on the third post-inoculation day. A. The CEUS longitudinal image shows diffuse heterogeneously decreased parenchymal enhancement. Renal hilum is not included in this view. B. In the T2-weighted coronal image, the kidney shows a focal area of increased signal intensity in the lower pole (arrows). There is an adhesion between the renal capsule at the upper portion and small bowel loops (arrowheads). C. Gadolinium enhanced T1-weighted coronal image also shows the loss of corticomedullary differentiation in the lower portion (arrows). D. Delayed phase contrast enhanced CT axial image shows a large, sharply demarcated area of decreased enhancement. Renal enlargement and adhesion between the upper renal pole and small bowel loops are visualized (arrowheads). CEUS = contrast-enhanced ultrasonography, CT = computed tomography

• 

  Fig. 3 Acute pyelonephritis involving the right kidney of a rabbit on the seventh post-inoculation day. A. In the CEUS longitudinal image, a large, sharply defined wedge shaped perfusion defect is noted in the mid portion of the kidney (arrows). Renal hilum is not included in this view. B. Delayed phase contrast enhanced CT axial image shows a large, sharply demarcated area of decreased enhancement in the midportion of the right kidney (arrow). The renal pelvis shows markedly increased enhancement, suggestive of acute pyelitis (arrowheads). Right renal enlargement is definite in contrast to the normal sized left kidney. C. In the T2-weighted axial image, the right kidney shows diffusely increased cortical signal intensity. CEUS = contrast-enhanced ultrasonography, CT = computed tomography

• 

  Fig. 4 Parenchymal abnormalities of acute pyelonephritis in rabbits. A. In the CEUS longitudinal image of the kidney in a rabbit on the third post-inoculation day, multifocal areas of decreased parenchymal enhancement are noted in the upper pole and deep side of the parenchyma (arrows). Calyceal dilatation is noted in the lower pole (arrowheads). A portion of the renal pelvis is noted (asterisk). B. In the CEUS longitudinal image of the same kidney, a sharply demarcated focal parenchymal perfusion defect in the lower portion is noted, and it seems to be an abscess (arrows). Calyceal dilatation (arrowhead) and dilated renal pelvis (asterisk) are also visualized. C. In the CEUS longitudinal image of the kidney in the other rabbit on the first post-inoculation day, diffuse heterogeneous parenchymal perfusion is noted along the kidney. Renal hilum is not visualized in this view. CEUS = contrast-enhanced ultrasonography

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