Today's Veterinary Practice

NOV-DEC 2017

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42 IMAGING ESSENTIALS PEER REVIEWED from the urinary bladder. Ultrasonographic changes associated with pyelonephritis include: • Mild renal enlargement and mild to moderate pelvic and ureteral dilation 34 • Hyperechoic mucosal margin parallel to the wall of the renal pelvis and proximal ureter 24 • Echogenic medullary band at the corticomedullary junction • Focal hyperechoic areas in the renal medulla and patchy, focal hypoechoic or hyperechoic areas in the renal cortex 24 Urine echogenicity may increase and even contain sedimentation due to pyuria. In chronic cases, renal pelvic and diverticula distortion and a hyperechoic rim can be seen. Hydronephrosis Hydronephrosis occurs when the renal pelvis and diverticuli become dilated, distorting and compressing the renal parenchyma. 33 The renal diverticuli become rounded and appear as anechoic finger-like projections extending from the anechoic renal pelvis ( Figure 12 ). Possible causes of hydronephrosis include congenital malformation, lower urinary tract obstruction, and ureteral or renal pelvic obstruction from a calculus, stricture, or trigonal or retroperitoneal mass. In chronic cases, the renal pelvis is distended, and the renal parenchyma can atrophy. Hydroureter is often seen in combination with hydronephrosis. Hydronephrosis may progress to pyonephrosis, caused by urinary stasis and subsequent infection. 35 Hydroureter If ureters are filled with fluid, they are easily identified beginning at the renal hilus. Ureters can be abnormally distended secondary to ectopia, ureteritis, obstruction, or congenital conditions. 36 In chronic obstructions, the distended ureters can become severely enlarged and tortuous, making it possible to follow them caudally to the level of the obstruction. If ureteroliths (ureteral calculi) are suspected to be the inciting cause, smoothly to irregularly marginated, hyperechoic foci with distal acoustic shadowing can be identified within the abnormally distended ureteral lumen. Other tubular structures are also located in the renal hilus, such as the renal vein and artery. To differentiate FIGURE 12. Long axis sagittal image of the left kidney in a domestic shorthaired cat. The renal pelvis (P) and proximal ureter (U) are moderately distended with anechoic fluid. Note the rounded renal diverticuli (white arrowheads). This cat was diagnosed with obstructive hydronephrosis and hydroureter secondary to ureteral calculi. FIGURE 13. Long axis sagittal image of the right ureter at the level of the apex of the urinary bladder in a domestic shorthaired cat. The ureter is distended with anechoic fluid. Note the lack of color Doppler flow within the ureter and the subjectively thickened ureteral wall. FIGURE 11. Short axis transverse image of the right kidney in a domestic shorthaired cat. The retroperitoneal fat is hyperechoic. There is poor corticomedullary distinction. The renal pelvis is mildly distended with slightly echogenic fluid. This cat was diagnosed with presumptive pyelonephritis.

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