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Kidneys and proximal ureters

image of Kidneys and proximal ureters
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Abstract

Common indications for renal ultrasonography include: gross or microscopic haematuria; pyuria; proteinuria; suspected urolithiasis; bilateral or unilateral renomegaly/renal mass; acute renal failure; congenital renal dysplasia of familial nephropathy; polyuria/polydipsia; loss of retroperitoneal detail radiographically; chronic renal failure. This chapter examines indications and the value of ultrasonography compared with radiography and computed tomography. Imaging technique and normal ultrasonographic appearance are explained before the chapter goes on to cover system conditions, diffuse parenchymal disease, neoplasia and peri-renal disease. This chapter contains eight video clips.

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Figures

Image of 10.1
10.1 Colour Doppler ultrasonogram of a normal left kidney showing the presence of multiple large vessels within the organ. The veins are larger than the arteries. Venous flow is shown as blue, indicating flow below the baseline or away from the transducer. Arterial flow is shown as red/orange, indicating flow towards the transducer. Power Doppler ultrasonogram of a normal left kidney. Power Doppler is more sensitive to the presence of flow, but includes no information about flow direction or velocity. Transverse images of the hilus of the right kidney without and with colour flow Doppler. The greyscale image shows the renal artery (arrowhead) and renal vein (arrowed) at the renal hilus. The renal vein is much wider than the corresponding artery. The colour Doppler ultrasonogram shows flow within these vessels. Doppler evaluation and RI in an arcuate artery. The arcuate artery was identified using colour flow Doppler, and a small (1–2 mm) PW Doppler sample volume was then placed over the artery. Normal flow within the arcuate arteries is characterized by rapid acceleration at the beginning of systole followed by gradual deceleration. Flow is present even during diastole. The RI in this patient is <0.70 and thus is normal.
Image of 10.2
10.2 Lateral abdominal radiograph of an ultrasound-guided pyelogram in a cat. The contrast medium was injected into the renal pelvis following urine aspiration. Some contrast medium has accumulated between the renal cortex and capsule, creating a halo around the kidney. The renal pelvis and pelvic diverticula are moderately dilated and there is mild to moderate dilatation of the ureter. There is a small air bubble within the ureter just distal to the ureteropelvic junction. An obstructive calculus (arrowed) is present in the dorsal mid-abdomen. On subsequent radiographs there was no evidence of the contrast medium passing beyond the calculus.
Image of 10.3
10.3 Sagittal plane image of a normal left kidney in a dog. The cortex has a uniform granular echotexture and medium echogenicity. The medulla is hypoechoic in comparison to the cortex. There is good distinction between the cortex and medulla. Dorsal plane image of a normal left kidney in a dog. The lateral cortex is in the near-field. Note the hyperechoic appearance of the renal pelvis and peripelvic fat at the renal hilus (arrowed). Transverse plane image at the mid-body of a normal left kidney in a dog. The renal artery is seen as two parallel slightly irregular lines (arrowed). The renal vein is much larger and positioned slightly deeper (arrowhead). The papilla of the renal medulla is almost anechoic and protrudes slightly into the renal pelvis, which is hyperechoic and concave.
Image of 10.4
10.4 Sagittal plane image of a normal right kidney (RK) and the caudate lobe of the liver in a dog. The cranial two-thirds of the right kidney is seen. The cranial pole of the kidney sits in the renal fossa of the caudate lobe of the liver. The renal cortex is comparable in echogenicity and echotexture to the liver parenchyma.
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10.5 Sagittal plane image of a normal left kidney and spleen in a dog. The spleen is in the upper left corner of the image, in close contact with the cortex of the kidney. The splenic parenchyma is hyperechoic in comparison with the renal cortical parenchyma.
Image of 10.6
10.6 Dorsal plane image of a normal left kidney in a cat. The kidney is somewhat shorter and rounder than a normal canine kidney. The cortex is moderately echogenic, whilst the medulla is hypoechoic in comparison. The hyperechoic structure of the renal pelvis and hilar fat is seen at the medial aspect of the mid-body of the kidney.
Image of 10.7
10.7 Dorsal plane image of the left kidney. The renal pelvis is mildly dilated, measuring slightly <2 mm in depth. There is increased cortical and medullary echogenicity with some loss of normal corticomedullary distinction. Transverse plane image of the left kidney in a 17-year-old cat. The renal pelvis is mildly dilated, measuring slightly >1 mm in depth. It appears as a hypoechoic half moon-shaped structure, outlining the renal papilla at the renal hilus. The echogenicity of the cortex and medulla is comparable with little corticomedullary distinction. This is a non-specific indicator of chronic renal disease. Transverse plane image of the right kidney in a cat. There is mild to moderate dilatation of the renal pelvis (arrowheads) and proximal ureter (arrowed). The urine within the pelvis and proximal ureter appears anechoic and outlines the renal papilla.
Image of 10.8
10.8 Dorsal and transverse plane images of the left kidney in a 1-year-old Golden Retriever. There is moderate to severe dilatation of the renal pelvis (✩) and similar dilatation of the ureter (◊). The urine within the collecting system is quite echogenic. There is atrophy of the medulla and increased cortical echogenicity. These abnormalities were the result of a partial obstruction caused by ureteral ectopia and chronic secondary pyelonephritis.
Image of 10.9
10.9 Sagittal plane image of the left kidney in an elderly dog. There is a large calculus within the renal pelvis, seen as a curved hyperechoic interface with a distal acoustic shadow. A small calculus is present within one of the pelvic recesses, just above the large calculus. The renal pelvis is moderately dilated. A cyst (indicated by the cursors) is present at the corticomedullary junction of the kidney. There is increased cortical and medullary echogenicity with loss of corticomedullary distinction. Transverse plane image of the left kidney in a cat. A small calculus is present within the renal pelvis, appearing as a hyperechoic structure with a well defined distal acoustic shadow. Sagittal plane image of the right kidney in a 12-year-old Pomeranian. There is a large calculus within the renal pelvis. The calculus has an irregular shape and extends into the pelvic diverticula, giving a so-called ‘staghorn’ appearance. The calculus is quite large and generates a wide complete acoustic shadow.
Image of 10.10
10.10 Dorsal plane image of the left kidney in a dog. There is moderate dilatation of the renal pelvis and proximal ureter with echogenic urine. The renal medulla is partly atrophied. A large calculus (arrowed) is present within the proximal ureter just distal to the ureteropelvic junction. There is no evidence of ureteral dilatation distal to the calculus, which indicates at least partial obstruction. Sagittal plane image of the left ureter in the mid-abdomen. The ureter (arrowed) is mildly dilated and the ureteral wall appears mildly to moderately thickened. There are multiple small calculi within the ureter (arrowheads), which are too small to cause an acoustic shadow. There was similar dilatation of the ureter distal to these calculi, indicating that they are unlikely to be obstructive.
Image of 10.11
10.11 Sagittal plane image of the right kidney and caudate liver lobe in an 8-month-old Shih Tzu. The kidney is markedly hyperechoic in comparison with the caudate lobe of the liver. There is poor corticomedullary distinction and the cortical surface is irregular. Mild dilatation of the renal pelvis is also seen (indicated by the cursors). The final diagnosis was renal dysplasia.
Image of 10.12
10.12 Sagittal plane image of the right kidney in a 12-year-old Yorkshire Terrier. There is increased echogenicity of the cortex and medulla with near complete loss of normal corticomedullary distinction. Multiple small, pinpoint hyperechoic foci are seen within the medulla, consistent with nephrocalcinosis. These findings are non-specific and indicate chronic acquired renal disease. The patient was azotaemic and the final diagnosis was chronic interstitial nephritis. Note also the large calculus in the renal pelvis causing a well defined acoustic shadow. Dorsal plane image of the left kidney in an elderly cat. The kidney is small measuring slightly less than the lower limit of the normal range (3.0–4.5 cm). The cortex is markedly hyperechoic and has an irregular contour. The medulla appears atrophied. These findings are consistent with chronic acquired renal disease such as chronic interstitial nephritis.
Image of 10.13
10.13 Sagittal plane image of the right kidney and caudate liver lobe of an 11-year-old Dachshund. The renal cortex is hyperechoic in comparison with the adjacent liver tissue. There are multiple small cysts (arrowed) within the cortex. The medulla is also increased in echogenicity with reduced corticomedullary distinction. These findings are consistent with chronic renal disease. However, this patient had no evidence of renal insufficiency and was diagnosed with a linear foreign body of the pylorus and descending duodenum.
Image of 10.14
10.14 Sagittal plane image of the body of the stomach in a 10-year-old mixed-breed dog. A thin hyperechoic line (arrowed) is seen at the mucosal surface consistent with mineralization of the gastric mucosa, indicating uraemic gastropathy and chronic severe renal insufficiency.
Image of 10.15
10.15 Dorsal plane image of the left kidney in a cat. The patient had been treated 1 week earlier for acute, complete urethral obstruction and presented with acute onset dullness, lethargy and abdominal pain. On physical examination the left kidney was palpably enlarged and appeared painful. Ultrasonography showed that the left kidney was larger than at the examination 1 week earlier. A thin hypoechoic rim is visible adjacent to the outer cortex (arrowheads), the cortex is hyperechoic, and a hypoechoic defect is seen within it in the near-field. There were large numbers of neutrophils in the urine and the patient had a marked leucocytosis. The diagnosis was acute pyelonephritis superimposed on chronic renal disease.
Image of 10.16
10.16 Dorsal plane image of the left kidney in a middle-aged cat. There is a thin, well defined hyperechoic line in the upper medulla close to the corticomedullary junction. This abnormality may be seen with hypercalcaemia, acute tubular necrosis and chronic renal disease. However, the patient had no evidence of renal insufficiency.
Image of 10.17
10.17 Sagittal plane image of the left kidney in a 1-year-old Australian Cattle Dog. The patient presented in acute renal failure. There is a marked increase in echogenicity of the renal cortex. An ill defined hyperechoic band is also present within the medulla. These abnormalities are the result of ethylene glycol poisoning.
Image of 10.18
10.18 Sagittal plane image of the left kidney in a 12-year-old Schnauzer. The caudal half of the kidney has been replaced by a well defined, thin-walled cyst-like lesion with echogenic contents. The patient had no evidence of renal insufficiency. The lesion was presumed to be a benign renal cyst.
Image of 10.19
10.19 Sagittal plane image of the left kidney in a Himalayan cat. There are several cysts within the renal cortex. The cyst at the lower left of the image contains some echogenic debris. The other cysts have anechoic contents, are well defined and the cyst walls blend with the renal cortex. These abnormalities are consistent with polycystic kidney disease. Sagittal plane image of the left kidney in an 8-year-old Persian cat. There is gross enlargement of the kidney, which extends beyond the field-of-view. There are multiple, variably sized cysts within the kidney. These cysts have effaced all normal renal architecture. This patient had bilateral palpable renal enlargement and was azotaemic.
Image of 10.20
10.20 Transverse plane image of the right kidney in a dog. There is a wedge-shaped hypoechoic lesion within the renal cortex in the near-field. The colour Doppler sample volume demonstrates absence of flow within this lesion consistent with an acute renal infarct. Sagittal plane image of the left kidney in a dog. There are several well defined hyperechoic lesions within the renal cortex of the cranial pole of the kidney. These are wedge-shaped with the base at the cortical surface and apex at the corticomedullary junction. A shallow concave depression is seen in the cortical surface (arrowed), overlying the lesion in the near-field. The abnormalities are consistent with chronic renal infarcts. Transverse plane image of the right kidney in a cat. There is a broad, well defined concave defect (arrowed) within the cortex in the near-field. This is consistent with local atrophy of the cortex as a result of a chronic infarct.
Image of 10.21
10.21 Sagittal plane image of the left kidney in a 12-year-old Shetland Sheepdog. All normal renal architecture has been effaced by a mass. The mass lesion has a hypoechoic outer rim and an irregular hyperechoic centre with a few small cavitated areas. The mass was determined to be renal in origin based on the absence of a normal kidney and its location. The final diagnosis was renal carcinoma. Dorsal plane image of the left kidney in a cross-breed German Shepherd Dog. There is a mixed echogenic mass slightly >5 cm in diameter at the caudal pole of the left kidney. The mass lesion has effaced the cortex in this area and expanded beyond the renal capsule. The histological diagnosis was haemangiosarcoma. Sagittal plane image of the right kidney in a dog. There is a well defined mass lesion of uniform echogenicity and echotexture originating from the cranial and ventral aspects of the right kidney. The mass lesion appears slightly hyperechoic in comparison with the normal renal cortex. The normal architecture of the renal medulla and pelvis have been partly preserved. This mass was diagnosed as lymphoma.
Image of 10.22
10.22 Dorsal plane image of the left kidney in a Domestic Shorthaired cat. There is gross enlargement of the kidney, which measures 7 cm in length. The medulla is expanded and the renal cortex is hyperechoic. In the near-field, an irregular hypoechoic rim can be seen between the renal capsule and cortex. This rim of hypoechoic tissue adjacent to the cortex is frequently seen in feline renal lymphoma. Lymphoma was confirmed by FNA.
Image of 10.23
10.23 Sagittal plane image of the left kidney in a 15-year-old Domestic Shorthaired cat. The field-of-view is nearly completely filled by a large cyst-like lesion with anechoic contents. The left kidney is contained within the cyst and is seen in the near-field. The kidney is small (2.28 cm long; normal 3.0–4.5 cm), has increased cortical and medullary echogenicity and an irregular cortex. This is a perinephric pseudocyst.

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Normal kidney in a dog.

The left kidney of an adult Jack Russell Terrier is shown in this clip. The kidney is a smooth oval shape. The echogenic focus in the central part of the kidney represents fat within the renal pelvis. There is good distinction between the renal cortex and medulla. (Courtesy of F. Barr)

Normal kidney in a cat.

This clip shows the right kidney in an adult male Domestic Longhaired cat with normal renal function. The kidney is smoothly rounded, with a narrow echogenic line representing fat in the renal pelvis. There is good definition between the renal cortex and medulla. In the second half of the clip, the echogenicity of the renal cortex can be compared with that of the liver, which lies adjacent to the right kidney, on the left of the screen. In this case the renal cortex is hyperechoic compared with the hepatic parenchyma. (Courtesy of F. Barr)

Hydronephrosis.

This clip shows enlargement of the right kidney in a young Exotic Shorthaired cat. There is severe fluid distension of the renal pelvis and diverticula centrally. A band of renal parenchyma surrounds the distended pelvis with little discernible distinction between the cortex and the medulla. Towards the end of the clip, an echogenic focus with acoustic shadowing is seen within the renal pelvis. Although there may well have been transient ureteric obstruction in this cat, the pelvic dilatation resolved over a period of a week with treatment for urinary tract infection. (Courtesy of F. Barr)

Renal calculi.

This clip shows the left kidney of the same cat as in Hydronephrosis. Multiple echogenic foci are seen within the central part of the kidney, and these cast clear acoustic shadows. The foci were judged to be multiple small renal calculi. Mild fluid distension of the renal pelvis is also present. (Courtesy of F. Barr)

Chronic renal disease in a cat.

The right kidney of an elderly cat with azotaemia is shown in this clip. Although the kidney is a reasonably normal size, the margins are mildly irregular and rather indistinct. Corticomedullary definition is present but is subjectively reduced. (Courtesy of F. Barr)

Renal infarction (1).

The kidney of this adult crossbred dog is a normal shape and size, and has normal architecture. However, an ill defined region of increased echogenicity is visible in the cortex of the caudal pole (on the right of the screen). (Courtesy of F. Barr)

Renal infarction (2).

Same dog as in Renal infarction (1). This clip, using Power Doppler, shows very limited perfusion of the peripheral region. The appearance is consistent with a small, organized infarct of the renal cortex. (Courtesy of F. Barr)

Renal lymphoma.

This clip shows the left kidney of an adult Golden Retriever. The kidney is enlarged and irregular in outline. There is mild fluid distension of the renal pelvis and diverticula centrally. The renal parenchyma shows loss of the normal corticomedullary definition. In the second half of the clip, a rounded hypoechoic mass is seen cranial to the kidney, representing an enlarged lymph node. The final diagnosis was lymphoma. (Courtesy of F. Barr)

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