Contrast-enhanced diagnostic ultrasound causes renal tissue damage in a porcine model

Abstract

Objective: Glomerular capillary hemorrhage (GCH) has been reported and confirmed as a consequence of contrast-enhanced diagnostic ultrasound (CEDUS) imaging of rat kidney. This study assessed renal tissue injury in the larger porcine model.

Methods: The right kidneys of anesthetized pigs were imaged in 8 groups of 4 pigs. A Vingmed System Five ultrasound machine (General Electric Co, Cincinnati, OH) was used at 1.5 MHz in the B-mode to intermittently scan the kidney at 4-second intervals. An Acuson Sequoia 512 machine (Siemens Medical Solutions, Mountain View, CA) was used in the 1.5-MHz Cadence contrast pulse sequencing mode with intermittent agent clearance bursts at 4-second intervals. Kidneys were scanned transabdominally or after laparotomy through a saline standoff. The second machine's probe was placed in contact with the kidney for 1 group. A perflutren lipid microsphere contrast agent (Definity; Lantheus Medical Imaging, Inc, North Billerica, MA) was infused at 4 μL/kg/min (diluted 33:1 in saline) for 4 minutes during scanning.

Results: Blood-filled urinary tubules were evident on the kidney surface for all groups except the group with the probe in contact with the kidney. Glomerular capillary hemorrhage was found by histologic processing in 31.7% ± 9.8% (mean ± SD) of glomeruli in the center of the scan plane for 1.7-MPa transabdominal scanning and 1.5% ± 2.9% of glomeruli in sham samples (P < .05). In addition, hematuria was detected after scanning, and tubular obstruction occurred in some nephrons.

Conclusions: Renal tissue damage was induced by CEDUS in the porcine model. This result, together with previous studies in rats, support a hypothesis that GCH would occur in humans from similar CEDUS exposure.

Figure 1

The band of marks seen on the kidney surface, resulting from hemorrhage into urinary tubules, on a group 5 kidney with closed abdomen image-exposure (a), and a cross-section cut through the band to show the penetration of tissue injury through the cortex (b). Scale bars are 5 mm (a) and 2 mm (b).

Figure 1

The band of marks seen on the kidney surface, resulting from hemorrhage into urinary tubules, on a group 5 kidney with closed abdomen image-exposure (a), and a cross-section cut through the band to show the penetration of tissue injury through the cortex (b). Scale bars are 5 mm (a) and 2 mm (b).

Figure 2

The mean percentage with standard error bars of glomerular capillary hemorrhage (GCH) induced by the Vingmed System Five machine in the center of the scan plane for the groups 1, 2, 3 and 5 listed in Table 1 with the specified peak rarefactional pressure amplitude (PRPA) for the scans.

Figure 3

Measurements of the width of Bowman’s urinary space (between the glomerular tuft and capsule) for samples from group 3 pigs. Exposed Bowman’s spaces were measured for erythrocyte content categorized as empty, partially full and essentially full of hemorrhage. The enlargement of Bowman’s space is indicative of intratubular obstruction by the hemorrhage into the urinary space and tubules.

Figure 4

Serial sections of a glomeruli found in a kidney from group 4 with normal hematoxylin (blue) and eosin staining (a) and with hematoxylin and immunohistological staining for fibrinogen/fibrin, which stains clots dark brown (b). The clot (C) in (b) extends from the glomerular capsule (G) into the neck of the first convoluted tubule (T). Scale bars: 50 μm.

Figure 4

Serial sections of a glomeruli found in a kidney from group 4 with normal hematoxylin (blue) and eosin staining (a) and with hematoxylin and immunohistological staining for fibrinogen/fibrin, which stains clots dark brown (b). The clot (C) in (b) extends from the glomerular capsule (G) into the neck of the first convoluted tubule (T). Scale bars: 50 μm.

Figure 5

A band of marks from hemorrhage into tubules on a group 6 kidney with open-abdomen scanning with the Sequoia 512. Note the regular pattern of maxima in the marks with a spacing of about 4 mm. Scale bar: 10 mm.

Figure 6

Images obtained with the Sequoia 512 for the probe in contact with the kidney (left) and for the probe with saline standoff and closed abdominal wall (right). The images were obtained with the tissue harmonic mode (top row), and with the contrast mode (bottom row) which shows contrast agent gas bodies in the renal circulation. The contrast mode utilized balance setting 1 (contrast agent only) in (left lower), and setting 0 (contrast plus B mode background) in (right lower).

Figure 7

Ultrasonic pressure plots for the clearance burst of the Sequoia 512 in contrast mode at two lateral positions about 2 mm apart in the focal zone at the same 4 cm image depth. The pulse pressure amplitudes vary in a regular way with five peaks. However, note that the sequence in the upper panel starts (on the left) with a maximal pulse followed by decreasing pulse heights, while the sequence in the lower panel starts with a minimal pulse followed by increasing pulse heights. Sequences displayed a transition between the two extreme cases as the hydrophone was moved transversely along the scan plane.