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Renal imaging is best performed with the animal in lateral recumbency, with the kidney to be imaged uppermost. The longitudinal axis of the left kidney is located by use of survey scan. Sagittal scans are begun at the medial margin of the kidney, and a serial sequence of a sagittal scans are made at 0.5 cm intervals until the most lateral margin of the kidney is no longer visible. The scan-arm is then rotated. 90° cross-sectional transverse images are obtained, beginning at the cranial pole of the left kidney and a serial sequence of transverse scans is made at 0.5-cm steps until the caudal pole is no longer visible. Brightest echoes are those of the capsules, whereas the pelvic diverticula and vasculature seemed slightly less bright. The renal sinus epithelium, fat and vasculature are less echogenic than were the diverticula and the cortical echoes are markedly less echogenic. The plane in which the sound beam traverses the organ profoundly influences the ultrasound structural anatomy of the kidney. Feline kidney is extremely mobile. The slightest pressure on the abdominal wall by the transducer may be sufficient to displace the kidney or alter the orientation of kidney. A true sagittal or transverse scan of kidney is important, because measurement of renal geometric determinants may be inaccurate and the renal architecture misinterpreted if the beam slices the kidney at an obtuse angle. The renal capsule and sinus and the pelvic diverticula are most echogenic structures. The cortex is echoic but was less echogenic than the renal capsule and sinus and the pelvic diverticula. Renal corpuscles (glomerulus and glomerular capsule) and convoluted tubules provides the collagen tissue interfaces that generate the echoes. The medulla contains only thin walled, straight tubular loops and therefore is less echoic than the cortex. It may be difficult to see the whole of right kidney at once because of rib shadowing. Two ultrasonographic images are mandatory for the evaluation of renal size and structural integrity.
Abnormal findings: Dilatation of renal pelvis causes the normal echogenic knot to become a ring or "C" shape, with a central anechoic area. As the dilatation progresses, the central anechoic area expands, and the surrounding parenchyma becomes compressed until, in extreme cases, a thin walled bag of fluid is seen. Renal calculi, irrespective of its mineral composition, appear as echogenic foci that cast acoustic shadows. Cysts are anechoic and of various sizes and the pelvic sinus echo is retained. Infected cysts containing debris have echogenic contents and somewhat less distant enhancement than urine filled cysts. The use of ultrasonography in diagnosis of renal parenchymal diseases is particularly applicable in differentiating cavitating from solid mass lesions. The ultrasonographic patterns for diffuse infiltrative disease are somewhat less specific.
Normal Left Canine Kidney Normal Right Canine Kidney
PHYSICS OF ULTRASOUND| MERITS| LIMITATIONS| EYE| HEART| LIVER| SPLEEN| KIDNEY| BLADDER AND PROSTRATE| PANCREAS| GI TRACT| TESTIS| REPRODUCTION AND OBSTETRICS