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Ultrasonography of the kidneys

Sarah Tibbs, BVetMed, DACVR

April 2017

Outline

Imaging kidneys overview

Basic how to image kidneys

Imaging anatomy

review

Ultrasonographicanatomy review

Advanced imaging techniques

Specific ultrasound kidney descriptors

Disease

– Congenital dysplasia

– Acquired

Kidneys can be imaged by

– Radiographs +/- IV/pyelographic contrast

▪ Kidneys are not always visible on radiographs

▪ Contrast media can impact kidney function and the risk:benefit ratio may preclude use

– Ultrasound

▪ Excellent kidney visualization

▪ Available with variable user confidence

▪ Non invasive

▪ Interpretation of findings can be difficult

Imaging Kidneys

Renal tubular cyst adenocarcinoma9 yo M(N) Flat coat retriever

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Imaging Kidneys

Kidneys can be imaged also by – CT +/- CE and MRI

▪ Can be cost prohibitive

▪ Limited availability

▪ Requires anesthesia

▪ CT contrast can have negative side effects

▪ MRI contrast can have negative side effects related to kidney function (reported in humans)

– Scintigraphy

(give injection of radioactive material that is filtered through kidneys, watch with gamma camera)

▪ Scintigraphy has poor spatial resolution

▪ Great functional information (GFR)

▪ Very limited availability

Diagnostic utility for ultrasound has expanded

Konde LJ et al. Ultrasonographic anatomy of the normal canine kidney. Vet Radiol Ultrasound 1984; 25:173-178.

Image from 2013Image from 1984

Veterinary academic use in 1970’s

B Mode scans

Static Real Time

Probe placement

Left kidneyRight kidney

Kidney disease is a common cause of morbidity and mortality

Ultrasound is commonly one of the first steps in evaluating kidneys

– Size and shape and internal architecture

Most kidneys can be sufficiently imaged with

the patient dorsally recumbent

Lateral approach

However…

Intercostal and lateral approach

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Probe placement Lateral recumbency can also be used to

image kidneys▪ Very dorsal approach needed

▪ Approach just caudal to the ribs on the left

▪ Over the last couple of ribs on the right

Homco LD: Ultrasound scanning techniques. In: Green RW (ed): Small Animal Ultrasound. Lippincott Williams & Wilkins: Philadelphia, 1996; 35.

•Evaluate fully in two planes (90° to each other)

➢Longitudinal➢Transverse

•Fanning across the tissue in in both directions

LongitudinalTransverse(at the hilus)

Fundamental ultrasound technique

Imaging Parameters

Röentgen findings

1. Position

2. Size

3. Shape

4. Margin

5. *Opacity

6. Number

7. Additional ultrasonographic findings

– Internal architecture

– Renal pelvis evaluation

– Parenchymal echogenicity

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Normal Position - DOG

Right kidney in renal fossa of caudate lobe of liver

Left kidney is caudal to the fundus and dorsomedial to the spleen

The kidneys are described as ventrolateral to vertebral bodies, and in the retroperitoneal space

radiographically seen as soft tissue, surrounded by retroperitoneal fat

Normal Position - CAT

Cat kidneys are in basically the same place as dogs, however,the tend to be more at the same level

Kidney disease

There any many kidney diseases, however, the kidneys ability to respond to disease is limited

Kidneys – Change size and shape– Deposit mineral or cysts– Have abnormal urine flow

There is a lot of overlap in DDx list Diagnosing kidney disease can be a challenge

– non specifically systemically ill patients– and non specific imaging findings

True kidney diagnosis generally requires cytology or histopathology/biopsy

Using imaging information requires inferences and clinical correlation

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Kidney size

Important indicator of disease

Radiographic size descriptions – on the VD view– Dogs 2.5 - 3.5 x L2

– Cats 2.4-3 x L2 (as 1.9 x L2 in older cats)

– Obliquity can decrease measurement

There is correlation between renal length and body weight

Length seems to be the most useful

Compensatory hypertrophy occurs

Burk RL and Feeney DA. Small animal Radiology and Ultrasonography, 3rd ed. WB Saunders: Philadelphia, 2003; 360-399.

Boag BL et al. Renal sonographic measurements in the dog preceding and following unilateral nephrectomy.Vet Radiol Ultrasound 1993; 34:112-117.

Kidney size - ultrasound Ultrasound size measurement have been less

well accepted and established You can measure length, height and width

Volume is stated to correlates to renal function – prolate ellipsoid methods – Not easy or simple– And may be limited to being useful when used for

serial evaluation of a single kidney in a patient– Studied predominately to evaluate renal transplant

rejection▪ hypertrophy post transplant up to about 20%▪ rejection volume increased 130%

Nyland TG et al. Ultrasonographic evaluation of renal size in dogs with acute allograft rejection. Vet Radiol Ultrasound 1997; 38:55-61.

Nyland TG et al. Ultrasonic determination of kidney volume in the dog. Vet Radiol Ultrasound 1989; 30:174-180.

Kidney to Aorta Ratioan attempt to standardize ultrasonographic kidney

measurements

Mareschal A, et. al. Ultrasonographic measurement of kidney to aorta ratioas a method of estimating renal size in dogs. Vet Radiol Ultrasound 2007; 48:443-438.

A K/Ao ratio has been described as between 5.5 – 9.1

– Measure the kidney length

– Measure the aortic diameter

near the kidney at maximal diameter

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They are smoothly margined and have a hilus with the renal artery, vein, and ureter

The kidneys of dogs are “bean” shaped

The kidneys of cats are more round

Basic AntomyShape

DOG

CAT

Owens JM and Biery DN. Radiographic Interpretation for the Small

Animal Clinician, 2nd ed. Williams & Wilkins: Baltimore, 1992; 262.

Anatomy - Shape Kidneys

– Smooth, sharp margin with an echogenic capsular line because fibrous capsule

– Cranial and caudal edges can be indistinct from edge-shadowing artifact▪ Associated with sound wave refraction (no sound makes it

around the bend of the kidney to be echo’ed back to make the image)

Size and Shape and Margin

These are the radiographic differentials

They can be extended to ultrasound as well, although ultrasound findings often narrow the differentials

Feeney DA and Johnston GR. The kidneys and ureters. In: Thrall DE (ed): Textbook of Veterinary Diagnostic Radiology, 4th ed. WB Saunders: Philadelphia, 2002; 566-571.

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Inner medulla

Outer medulla

Renal peripelvic tissue

Renal papilla Cortex

Diverticula andInterlobar vessels

Arcuate vessels

Anatomy- Internal Architecture– cortex and medulla– medullary papillae– arcuate vessels– pelvic recess interfaces– renal vessels and pelvic fat in the renal hilus

Anatomy –Cortex

Cortex is defined as finely granular and smooth in echotexture

SLinKy –– Spleen brightest– Liver less

IN

– Kidney leastY

Echogenicity of the cortex is used to eval the kidney and compare to other organs

Anatomy- Cortex However, recent papers describe that the kidney cortex

may also be mildly hyperechoic compared to the liver It should not be iso or hyperechoic to the spleen Cats kidney: can have very hyperechoic cortex

(especially in fat patents increase number of fat vacuoles in the tubular epithelium)

Ivančić M and Mai W. Qualitative and quantitative comparison of renal vs. hepatic ultrasonographic intensity in healthy dogs. Vet Radiol Ultrasound 2008; 49: 368-373.

Right liver Right kidney

Fat cat normal kidney

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Anatomy- Medulla

Inner medulla

Outer medulla

Cortex

The medulla is defined as hypoechoic to nearly anechoic (may be iso to hypoechoic to the liver)

However, it can have an echogenic outer layer, that can be hyperechoic to the cortex– Probably due to increased

vessels in this area

It is divided into papillae by the diverticular recesses

Hart DV et al. Ultrasound appearance of the outer medulla in dogs without renal dysfunction. Vet Radiol Ultrasound 2013.

Renal peripelvic tissue

Renal papilla

Diverticula andInterlobar vessels

Dyce KM, et al. Textbook of Veterinary Anatomy, 3rd ed. Saunders: Philadelphia, 2002; 175-179.

Renal papilla

Diverticula andInterlobar vessels

Renal peripelvic tissue

Anatomy - Renal pelvis

Renal pelvis

The renal pelvis is a line of hyperechoic tissue corresponding to connective tissue of the pelvis and surrounding hilar fat– In transverse seen as a V shaped line

– In longitudinal as a central straight line

– The actual pelvis is not seen without diuresis

Although…High frequency probes and improved imaging capabilities allow for visualization of– Normal renal pelvis in some animals

– Physiologic dilation (IV fluids, diuresis, PU/PD state)

Longitudinal

Transverse

D’Anjou, M et al. Clinical significance of renal pelvic dilatation on ultrasound in dogs and cats. Vet Radiol Ultrasound 2011; 52: 88-94.

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Renal pelvis dilation

Renal pelvis dilation – anechoic pelvis with near and far walls that are hyperechoic and distinct

Pyelectasia – term for mild to moderate non obstructive pelvic dilation

Hydronephrosis – greater degree of renal pelvis and diverticular dilation

Pelvis dilation can be seen with– Renal insufficiency

– Pyelonephritis

– Outflow obstruction (also with ureteral ectopia)

Greater than 13mm – 100% predictive of obstruction

Felkai CS et al. Lesions of the renal pelvis and proximal ureter in various nephro-urological conditions: an ultrasonographic study. Vet Radiol Ultrasound 1995; 36: 397-401.

Pyelectasia

Hydronephrosis

mild moderatemarked

moderate marked

Renal pelvis dilation

Advanced kidney imaging techniques

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Resistive Index (RI) Pulsed-wave Doppler ultrasound

– Doppler effect - sound wave frequency changes with movement of the reflector (RBC)

– Pulsed wave – a “gate” is used to sample only the lumen of the blood vessel for ultrasound information

– Angular correction and vessels size cancel out

– A spectral trace is created, that displaced the flow signal over time

RI

Indirect measurement of blood flow resistance

can be very useful to evaluate renal blood flow characteristics because renal function (glomerular, tubular and urine flow) needs blood flow

Used in the kidney, at either the renal artery, interlobar, or arcuate arteries

Usually used in smaller vessels as this is the region of most interest pathologically

Measurement of arteriole vascular resistance –calculation to express resistance to blood flow

Unitless value

RI

Elevates with several diseases and is suggestive of tubulointerstitial or vascular disease– Transplant rejection– Pyelonephritis– Ureteral obstruction – Acute renal failure

Glomerular dysfunction may not affect RI

Prone to artifact– Affected by cardiac output

and rate– Level of kidney in relation

to the heart– Respiratory compromise

due to dorsal recumbency– Stress levels– Sedatives or other

medications can affect blood flow through kidney

Transducer pressure can artificially elevate RI

Should not be used alone

Morrow KL et al. Comparison of the resistive index to clinical parameters in dogs with renal diseaseVet Radiol Ultrasound 1996; 37: 193-199.

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RI Different reports on normal

– Morrow KL et al

▪ if RI greater than >0.7 is abnormal

▪ normal range 0.56-0.67 (humans N – 0.58-0.63)

– Chang YJ et al

▪ RI normal upper limits 0.73

– Novellas R et al

▪ Normal cat RI - 0.7

▪ Normal dog RI - 0.72

Chang YJ et al. Relationship between age, plasma renin activity, and renal resistive index in dogs.Vet Radiol Ultrasound 2010; 51: 335-337.

Novellas R et al. Doppler ultrasonographic estimation of renal and ocular resistive and pulsatilityindices in normal dogs and cats. Vet Radiol Ultrasound 2007; 48: 69-73.

RI to detect urinary tract obstruction

Used cut off RI 0.7 Surgically induced obstruction and relief of

obstruction

Invasive studies detected rise in renal vascular resistance with urinary obstruction

High false negative rate (up to 27%) limits clinically usefulness, especially as the condition becomes chronic– Because the RI drops back off– Renal tissue may be being obliterated by

hydronephrosis as well

Nyland TG et al. Diagnosis of urinary tract obstruction in dogs using duplex Doppler ultrasonography.Vet Radiol Ultrasound 1993; 34: 348-352.

Renal biopsy

Determine specific disease to target therapy

High skill set needed Invasive, requires anesthesia Requires appropriate sample handling Complications

– Hematuria– Hemorrhage– Non diagnostic sample– Infection– AV fistula

However, Dogs: multiple biopsies episodes

– No complications– No affect on GFR– Scars and tracts were noted at gross

pathology– Microscopic mild fibrosis or

tubulointerstitial atrophy – One infarct was noted

▪ Small wedge shaped lesion- in k of dog with an arcuate art noted on a biopsy sample

Cats: one episode, with two samples– Next day after biopsy minimal drop in

GFR, with likely no clinical significance– Overall minimal effect, all stayed within

90% of baseline GFR– Worse complications if medulla and

bigger vessels biopsied

Groman RP et al. Effects of serial ultrasound-guided renal biopsies on kidneys of healthy adolescent dogs. Vet Radiol Ultrasound 2004; 45: 62-69.

Drost WT et al. The effects of unilateral ultrasound-guided renal biopsy on renal function in healthy sedated cats. Vet Radiol Ultrasound 2000; 41: 57-62.

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Percutaneous Pyelography Direct injection of contrast media into the renal

pelvis, percutaneously with ultrasound guidance, across the renal parenchyma

Nephropyelonecentesis is performed and an equal amount of contrast is injected into the pelvis

Followed by radiographs Renal pelvis dilation is necessary to a degree

that facilitates needle placementComplications

• Leak of contrast out and around the kidney• Hemorrhage –Perinephric or intrapelvic (which has the potential to cause obstruction)

Percutaneous ethanol ablation

Tissue can be ablated with ethanol injections in humans and dogs

A paper report case with this procedure performed in a renal cyst in a dog

Generally cyst are clinical insignificant, however, if they cause pain, infection, or obstruction they may require intervention

Historically the are treated with draining, however, they often return

Ethanol ablates the cyst lining, preventing recurrence

Risk of peri cyst damage, hemorrhage, and incomplete ablation

Agut A. et al. Imaging Diagnosis – Ultrasound-guided ethanol sclerotherapy for a simple renal cyst. Vet Radiol Ultrasound 2008; 49: 65-67.

Specific ultrasound kidney descriptors

“See the signs”

Corticomedullary Rim SignHalo Sign

Subcapsular Hypoechoic Rim SignMedullary Band Sign

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CM distinction

Corticomedullary distinction

– Because the cortex is hyperechoic to the

medulla

– Lose this distinction when

▪ Medulla is hyperechoic

– Increased distinction when

▪ cortex is hyperechoic

– Both are non specific and can be present with acute, chronic, and inflammatory disease

Corticomedullary Rim Sign Curvilinear echogenic line parallel

to the corticomedullary junction Mineral in the tubular epithelium

and basement membrane ?able significance Seen with

– Ethylene glycol induced Ca oxalate nephrosis

– Hypercalcemia nephropathy/nephrocalcinosis(LSA)

– FIP (pyogranulamatous vasculitis)– Idiopathic tubular necrosis – Chronic interstitial nephritis

Although it may indicate poor prognosis when seen with some disease

Tends persist even if kidney disease appears to resolve

Biller DS et al. Renal Medullary rim sign: ultrasonographic evidence of renal disease. Vet Radiol Ultrasound 1992; 33: 286-290.

Halo Signunclear usefulness

Seen with (presumed) ethylene glycol toxicity and secondary oxalate nephrosis

The cortex and medulla are described as having increased echogenicity, with a hypoechoic zone at the corticomedullary junction– is this normal hypoechoic medulla

between two hyperechoic regions– does this represent a different

description of the corticomedullary rim sign or even the medullary band

Two additional images included here one confirmed (a second presumed) end stage kidneys with medullary fibrosis and mineralization – the one on the left had a hypoechoic zone between the cortex and the bright medulla – is this a halo sign?

Adams WH et al. Abstract: Ultrasonographic findings in dogs and cats with oxalate nephrosis attributed to ethylene glycol intoxication: 15 cases (1984-1988). J Am Vet Med Assoc. 1991; 199: 492-6.

Adams WH et al. Abstract: Early renal ultrasonographic findings in dogs with experimentally induced ethylene glycol nephrosis. Am J Vet Res. 1989; 50: 1370-6.

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Subcapsular Hypoechoic Rim Sign Hypoechoic subcapsular thickening Why – lymphatic drainage for the kidney is formed by a

superficial capsular system of capillaries Significant association between this and renal LSA Extra nodal renal LSA 5-20% of LSA in cats Can have renal LSA without rim Non specific findings that indicate renal LSA

– Renomegaly +/- irregular shape– Focal nodules/masses (usually hypoechoic)– Hyperechoic cortices– Subcapsular effusion (? fluid or tissue)

DDX– undifferentiated neoplasia– renal anaplastic carcinoma– FIP

Valdes-Martinez A, et al. Association between renal hypoechoic subcapsular thickening and lymphosarcoma in cats. Vet Radiol Ultrasound 2007; 48: 357-360.

Medullary Band Sign The medullary band is

described as a hyperechoic zone, in the (inner) medulla

Caused by medullary– Congestion/Edema– Hemorrhage– Necrosis

20 cases of Leptospirosis– 3 had normal kidneys– 17 had abnormal kidneys

▪ Renomegaly▪ Pyelectasia▪ Peri-renal effusion▪ Increased cortex echogenicity

– 6 had medullary band sign (only seen in the lepto dogs?!)

Forrest LJ et all. Sonographic findings in 20 dogs with leptospirosis. Vet Radiol Ultrasound 1998; 39: 337-340.

Hart DV et al. Ultrasound appearance of the outer medulla

in dogs without renal dysfunction. Vet Radiol Ultrasound 2013.

Ultrasonographic appearance of some kidney diseases

•Congenital•Acute•Chronic•Pseudocyst•Pyelonephrosis•Neoplasia

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Congenital renal dysplasia Renal dysplasia (also called juvenile nephropathy, and

familial renal disease)– disorganized development of the renal parenchyma leading to

small, irregular, fibrosed kidneys

– Primary differential is end stage chronic kidney disease

Caused by imperfect inductive interaction between the mesonephric duct and the metasnephric blastema, that leads to failure of complete differentiation

Hereditary versus from neonatal infection (can also see hypoplasia, agenesis and congenital cyst)

Causes renal failure in

young animals with a

chronic disease

appearance

Congenital renal dysplasia Microscopic changes

– Persistence of primitive kidney form▪ Mesenchyme▪ Tubules/Ducts▪ Nephrons▪ Glomeruli

– Secondary chronic disease ▪ Mineral in the parenchyma (dystrophic)▪ Obstruction/infarction

– Fibrous tissue– Degenerative and inflammatory tissue

▪ Lipid in renal tubular epithelium from anoxic or toxic change

Gross pathology findings – Small kidneys– Irregular to lobulated from fibrosing bands

Additional descriptions include – A thin cortex– Incomplete lobulation of the medulla and

pelvic structures

Top Image from: Bruder MC et al. Renal dysplasia in Beagle dogs: four cases. Toxicologic Pathology 2010; 38:

1051-1057.Bottom Image from:Kerlin RL and Van Winkle TJ. Renal dysplasia in Golden Retrievers. Vet Pathol. 1995; 32: 327-329.

Congenital renal dysplasiacase examples

5 year old M(N) Labrador RetrieverAzotemic, post HBC and fractured hind limbAzotemia persisted, pain, and clinical signs associated with renal failureShort period of stabilization of clinical signs with supportive care for chronic kidney disease

1 year old M Shih TzuAzotemia and unthrifty through entire lifeA few years of stable diseasePTS at 5 years old

Main findings:Small sizeLack of normal corticomedullary lobulations

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Acute kidney disease

Includes– Leptospirosis (see earlier slide re the

Medullary Band sign)

– Lyme nephritis (poorly understood pathology and poor prognosis)

– Toxins▪ Lilly ingestion

▪ Grape/Raisin intoxication

▪ Non steroidal drugs

▪ Ethylene glycol (anti-freeze)

Ultrasonographic appearance of acute kidney disease

Normal

Often ultrasound is used to rule out chronic disease and help make the presumptive diagnosis of acute disease

Increased renal echogenicity– Cortical

– Medullary

Renomegaly

Pyelectasia

Perirenal fluid/retroperitoneal effusion

OR

Holloway A and O’brien R. Perirenal effusion in dogs and cats with acute renal failure. Vet Radiol and Ultrasound 2007: 48; 574-579.

Chronic disease Ultrasonographic appearance

– Small and irregular

– Thick and hyperechoic cortices

– Poor corticomedullary distinction

– Infarcts

▪ Wedge shaped hyperechoic areas (narrow toward the pelvis)

– Cysts

15 1/2 yo M(N) Min Pin

16 yo F(S) DSH

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Perirenal pseudocyts Radiographic appears as a smoothly margined

renomegaly– DDX: LSA, FIP, hydronephrosis, pyelonephritis, amyloidosis and

less likely polycystic kidney disease (usually irregular)

Cause is unknown– In human – trauma, surgery, neoplasia, venous congestion

– In veterinary – associated with chronic renal disease or idiopathic

Azotemia is usually from primary renal disease but can be from compression of the renal pelvis and proximal ureters

Treat ASAP to preserve renal function– manage underlying renal disease

– Ultrasound guided Percutaneous drainage (may recur or have hemorrhage)

– surgical capsulectomy

12 yo F(S) DSHBilateral

12 1/2 yo M(N) DSHLeft only

12 M(N) DSHRight only

Post draining

Perirenal pseudocytscase examples

Pyelonephritis/pyonephrosis

Common ultrasonographicappearance

– Pyelectasia hydronephrosis

– Irregular shape to the renal pelvis/diverticula

– Proximal ureteral dilation/wall thickening

– Hyperechoic tissue around the renal pelvis

– Acute kidney disease changes

– Perirenal/retroperitoneal fluid

– Pain on probe pressure

9 yo F(S) Pomeranian mix

chronic hind limb paralysis

5 ½ yo German Shepherd

systemic Aspergillosis

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Neoplasia Often renomegaly is note on radiographs

Usually unilateral lesions

Can have bilateral tumors – multifocal primary neoplasia

▪ Carcinoma, nephroblastoma, tubular adenocarcinoma, others

– multicentric/metastatic neoplasia▪ Hemangiosarcoma, lymphoma

Hypoechoic, cavitated and heteroechoic mass lesions

DDx – Cyst, abscess/granuloma, hematoma

Case examples– LSA (multicentric disease)

– Carcinoma

– Hemangiosarcoma

– Tubular adenocarcinoma

Multicentric LSAInnappetanceStranguiria/hematuria

PPHX: SC LSAChronic pancreatitis

Right kidney mass (3cm)

Right kidney

Left kidney mass (2cm)

Marked bladder wall thickening

Baldder post LSpar

15.5 yo M(N) Maine Coon

Suspect carcinoma14 yo F(S) Toy poodle

Chronic kidney disease

7 yo M(N) Puggle

Lethargy, PD, pain

Left Kidney too!

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Hemangiosarcoma6 ½ yo MN Cocker spaniel

perirenal HSA grade 2

Renal tubular cyst adencarcinoma9 yo M(N) Flat coat retriever

References Konde LJ, Wrigley RH, Park RD, and Lebel JL. Ultrasonographic anatomy of the normal canine kidney. Vet

Radiol Ultrasound 1984; 25:173-178.

Burk RL and Feeney DA. Small animal Radiology and Ultrasonography, 3rd ed. WB Saunders: Philadelphia, 2003; 360-399.

Boag BL, Atilola M, and Pennock P. Renal sonographic measurements in the dog preceding and following unilateral nephrectomy. Vet Radiol Ultrasound 1993; 34:112-117.

Nyland TG et al. Ultrasonographic evaluation of renal size in dogs with acute allograft rejection. Vet Radiol Ultrasound 1997; 38:55-61.

Nyland TG, Kantrowitz BM, Fisher P, Olander HJ and Hornof WJ. Ultrasonic determination of kidney volume in the dog. Vet Radiol Ultrasound 1989; 30:174-180.

Mareschal A, D’Anjou M, Moreau M, Alexander K, and Beauregard G. Ultrasonographic measurement of kidney to aorta ratio as a method of estimating renal size in dogs. Vet Radiol Ultrasound 2007; 48:443-438.

Feeney DA and Johnston GR. The kidneys and ureters. In: Thrall DE (ed): Textbook of Veterinary Diagnostic Radiology, 4th ed. WB Saunders: Philadelphia, 2002; 566-571.

Dyce KM, Sack WO, and Wensing CJG. Textbook of Veterinary Anatomy, 3rd ed. Saunders: Philadelphia,

2002; 175-179.

Ivančić M and Mai W. Qualitative and quantitative comparison of renal vs. hepatic ultrasonographic intensity in healthy dogs. Vet Radiol Ultrasound 2008; 49: 368-373.

• Hart DV, Winter MD, Conway J, and Berry CR. Ultrasound appearance of the outer medulla in dogs without renal dysfunction. Vet Radiol Ultrasound 2013.

D’Anjou M, Agathe B, and Dunn ME. Clinical significance of renal pelvic dilatation on ultrasound in dogs and cats. Vet Radiol Ultrasound 2011; 52: 88-94.

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References

Felkai CS, Vörös K, and Fenyves B.. Lesions of the renal pelvis and proximal ureter in various nephro-urological conditions: an ultrasonographic study. Vet Radiol Ultrasound 1995; 36: 397-401.

Morrow KL, Salman MD, Lappin MR, and Wrigley R. Comparison of the resistive index to clinical parameters in dogs with renal disease. Vet Radiol Ultrasound 1996; 37: 193-199.

Chang YJ. Chan IP, Cheng FP, Wang WS, Liu PC, and Lin SL.. Relationship between age, plasma renin activity, and renal resistive index in dogs. Vet Radiol Ultrasound 2010; 51: 335-337.

Novellas R, Espada Y, and Ruiz De Gopegui R. Doppler ultrasonographic estimation of renal and ocular resistive and pulsatility indices in normal dogs and cats. Vet Radiol Ultrasound 2007; 48: 69-73.

Nyland TG, Fisher PE, Doverspike M, Hornof WJ, and Olander HJ. Diagnosis of urinary tract obstruction in dogs using duplex Doppler ultrasonography. Vet Radiol Ultrasound 1993; 34: 348-352.

Groman RP, Bahr A, Berridge BR, and Lees GE. Effects of serial ultrasound-guided renal biopsies on kidneys of healthy adolescent dogs. Vet Radiol Ultrasound 2004; 45: 62-69.

Drost WT, Henry GA, Meinkoth JH, Woods JP, Payton ME, and Rodebush C. The effects of unilateral ultrasound-guided renal biopsy on renal function in healthy sedated cats. Vet Radiol Ultrasound 2000; 41: 57-62.

Agut A, Soler M, Laredo FG, Pallares FJ, and Seva JI. Imaging Diagnosis – Ultrasound-guided ethanol sclerotherapy for a simple renal cyst. Vet Radiol Ultrasound 2008; 49: 65-67.

Biller DS, Bradley GA,and Partington BP. Renal Medullary rim sign: ultrasonographic evidence of renal disease. Vet Radiol Ultrasound 1992; 33: 286-290.

Valdes-Martinez A, Cianciolo R, and Mai W. Association between renal hypoechoic subcapsular thickening and lymphosarcoma in cats. Vet Radiol Ultrasound 2007; 48: 357-360.

References

Nyland TG, Mattoon JS, and Wisner ER. Ultrasonography of the urinary tract and adrenal glands. In: Nyland TG and Mattoon JS. Veterinary Diagnostic Ultrasonography. WB Saunders: Philadelphia, 1995; 95-111.

Barr F, Diagnostic ultrasound In: Lee R (ed): BSAVA Manual of Small Animal Diagnostic Imaging, 2nd ed. BSAVA: England, 1995; 162-163.

Owens JM and Biery DN. Radiographic Interpretation for the Small Animal Clinician, 2nd ed. Williams & Wilkins: Baltimore, 1999; 261-276.

Adams WH, Toal RL, and Breider MA. Abstract: Ultrasonographic findings in dogs and cats with oxalate nephrosis attributed to ethylene glycol intoxication: 15 cases (1984-1988). J Am Vet Med Assoc. 1991; 199: 492-6.

Adams WH. Toal RL, Walker MA, and Brieder MA. Abstract: Early renal ultrasonographic findings in dogs with experimentally induced ethylene glycol nephrosis. Am J Vet Res. 1989; 50: 1370-6.

Forrest LJ et all. Sonographic fidnings in 20 dogs with leptospirosis. Vet Radiol Ultrasound 1998; 39: 337-340.

Holloway A and O’brien R. Perirenal effusion in dogs and cats with acute renal failure. Vet Radiol and Ultrasound 2007: 48; 574-579.

Bruder MC, Shoieb AM, Shirai N, Boucher GG, and Brodie TA. Renal dysplasia in Beagle dogs: four cases. Toxicologic Pathology 2010; 38: 1051-1057.

Kerlin RL and Van Winkle TJ. Renal dysplasia in Golden Retrievers. Vet Pathol. 1995; 32: 327-329. Ohara K, Kobayashi Y, Tsuchiya N, Furuoka H, and Matsui T. Renal dysplasia in a Shih Tzu dogs in Japan. J

Vet med Sci. 2001; 63: 1127-1130. Essmand SC, Drost WT, Hoover JP, Lemire TD, and Chalman JA. Imaging of a cat with perirenal

pseudocysts. Vet Radiol and Ultrasound 2000; 41: 329-334.

QUESTIONS

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