Today's Veterinary Practice

NOV-DEC 2017

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36 IMAGING ESSENTIALS PEER REVIEWED pelvic, iliac, or abdominal. 10 Ectopic kidneys are structurally and functionally normal, but they can be abnormally small, and a short ureter may be kinked, predisposing to obstruction, secondary hydronephrosis, or pyelonephritis. 11 Ectopic Ureters This congenital condition results in an abnormal vesicoureteral orifice at the urinary papilla and can be bilateral or unilateral. Ectopic ureters is the most common congenital condition causing dilated ureter and renal pelvis. 12 It is more common in female dogs. Ectopic ureters may be dilated due to ileus, concurrent infection, or partial obstruction at the point of entry to the urethra or vagina/vestibule. Autosomal Dominant Polycystic Kidney Disease This is an inherited disease reported mostly in Persian or Persian-cross cats, cairn terriers, and bull terriers. 13,14 Persian cats and bull terriers inherit this disorder as an autosomal dominant trait. In Persian cats, this disease can be detected as early as 6 to 8 weeks of age, but absence of cysts does not preclude development of cysts later on in life. Ultrasonographically, these cysts are rounded, centrally anechoic, and have smooth, sharply demarcated thin walls with distal acoustic enhancement ( Figure 2 ). The cysts are located in the renal medulla and cortex, but most are within the cortex or at the corticomedullary junction. Occasionally, these cysts may be found in the liver as well as the pancreas. Focal Abnormalities of the Renal Parenchyma Renal Cysts Renal cysts may be solitary or multiple, involving both kidneys. 15–17 This condition may be congenital, as explained previously, or acquired. Renal cysts are round to oval in contour and anechoic, and they have smooth, sharply demarcated thin walls with a distinct far wall border and distal acoustic enhancement. Cysts may deform the renal capsule if they become large enough or if autosomal dominant polycystic kidney disease is present. Also, they can contain internal echoes in association with hemorrhage or necrotic debris. Diagnostic differentials for solitary cysts include hematoma, abscess, and solid or cavitary mass. The presence of cystic lesions of the kidneys in some breeds, such as German shepherds, should raise concern for some neoplasms, such as renal cystadenocarcinoma, which can be associated with cutaneous paraneoplastic fibrotic nodular lesions (nodular dermatofibrosis). 18 Renal Hematoma Renal hematomas typically occur in a young animal with a clotting disorder or recent trauma. They may contain a mixture of anechoic, hypoechoic, and hyperechoic components within the renal cortex or medulla. Differentiation from some neoplastic lesions, such as renal hemangiosarcoma, can be ultrasonographically challenging. FIGURE 2. Long axis sagittal image of the left kidney in a ragdoll cat. Multiple smoothly marginated, rounded, anechoic foci with distal acoustic enhancement are seen throughout the entire renal parenchyma (white arrows). These cystic structures are distorting the entire internal architecture of the kidney. The caudal pole of the kidney is indicated by the white arrowhead. FIGURE 3. Short axis transverse image of the left kidney in an Alaskan malamute. This renal abscess is located within a portion of the kidney and is irregularly shaped with a thick wall containing anechoic and echogenic fluid (black arrowheads); the hyperechoic component is forming a sediment in the dependent portion of the abscess, causing a fluid-fluid line. More normal renal architecture is still present (white arrow).

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