Novel imaging techniques in acute kidney injury

Abstract

Imaging of the kidneys can provide valuable information in the work up and management of acute kidney injury. Several different imaging modalities are used to gather information on anatomy of the kidney, to rule out obstruction, differentiate acute kidney injury (AKI) and chronic kidney disease and to obtain information on renal blood flow and GFR. Ultrasound is the most widely used imaging modality used in the initial work up of AKI. The utility of contrast enhanced computerized tomography and magnetic resonance imaging is limited because of toxicities associated with contrast agents used. In this review the basics of ultrasonography are reviewed with an emphasis on findings in AKI. The new developments in different imaging modality and their potential uses in AKI are reviewed as well.

Fig. 1

B-mode ultrasound images of (A) normal kidney, (B) enlarged and echogenic kidney with loss of differentiation between cortical, medullary and sinus fat compartments in a case with acute kidney injury, (C) small, slightly echogenic kidney with thin cortex in a patient with chronic kidney disease and (D) normal size but echogenic kidney with a single simple cyst in a patient with chronic kidney disease secondary to diabetic nephropathy.

Fig. 2

B-mode ultrasound image of the kidney demonstrating hydronephrosis. Dilated calices (thin arrows) and renal hilum and the origin of ureter (thick arrow) are seen in this image.

Fig. 3

Unehanced computerized tomography (CT) images of (A) distal right ureteral stone (arrow) with periureteric stranding and (B) large kidney stone (arrow). B = bladder.

Fig. 4

B-mode (A), and contrast-enhanced (B) ultrasound images of the kidney. Note the marked improvement in image quality especially in clear distinction between the cortex and medulla in the contrast enhanced image. This technique can provide useful information on the quantity and pattern of blood flow, volume and velocity to different regions within the kidney tissue.

Fig. 5

Sequential contrast-enhanced images of kidney with frames selected from (A) steady state during infusion of contrast agent, (B) high energy pulse and destruction of tissue microbubbles within the kidney, (C) replenishment of the kidney tissue with contrast agent observed first in the main, interlobar and arcuate arteries in a fraction of a second and later in the renal cortex (after about 1 second) (D).