ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE KIDNEY*

Radiographic and ultrasonic examinations were performed in 12 normal dogs. Initial ultrasound examinations were performed in normally hydrated dogs. The ultrasonic appearance of the diuresed kidney was evaluated after excretory urography and intramuscular administration of furosemide. The dogs were euthanized for anatomic correlation with the sonographic appearance of the kidneys. Renal cortex, medulla, pelvic diverticula, intrarenal vessels, renal pelvis, and renal sinus fat were identified sonographically. Kidney enlargement during diuresis was due to increase renal medullary size. Veterinary Radiology, Vol. 25, No. 4, 1984; pp 173–178.     

IMAGING DIAGNOSIS—ULTRASOUND-GUIDED ETHANOL SCLEROTHERAPY FOR A SIMPLE RENAL CYST

Solitary renal cysts are benign and in the majority of instances asymptomatic and do not require treatment. Nevertheless, treatment may be required if abdominal discomfort or pain, hypertension, infection or renal outflow obstruction occur. Under these circumstances, percutaneous management of the cyst is the easiest and fastest procedure, and no major complications are generally encountered. In this report we describe a patient with a solitary renal cyst treated successfully by a single injection of ethanol into the cyst. The sonographic appearance of the cyst changed from a well-defined hypoechoic structure to an ill-defined hyperechoic region. Canine renal cysts may be successfully managed in some instances by a single ethanol injection.     

Imaging diagnosis--Ultrasound-guided ethanol sclerotherapy for a simple renal cyst.

Solitary renal cysts are benign and in the majority of instances asymptomatic and do not require treatment. Nevertheless, treatment may be required if abdominal discomfort or pain, hypertension, infection or renal outflow obstruction occur. Under these circumstances, percutaneous management of the cyst is the easiest and fastest procedure, and no major complications are generally encountered. In this report we describe a patient with a solitary renal cyst treated successfully by a single injection of ethanol into the cyst. The sonographic appearance of the cyst changed from a well-defined hypoechoic structure to an ill-defined hyperechoic region. Canine renal cysts may be successfully managed in some instances by a single ethanol injection.     

EFFECT OF SEVOFLURANE ANESTHESIA AND BLOOD DONATION ON THE SONOGRAPHIC APPEARANCE OF THE SPLEEN IN 60 HEALTHY CATS

The aims of this prospective study were to describe the normal sonographic size and appearance of the feline spleen, and to test effects of sevoflurane anesthesia and blood collection on sonographic characteristics. Sonographic evaluations were performed in 60 healthy blood donor cats prior to anesthesia and blood collection (baseline), after anesthesia induction, after completion of blood collection while under anesthesia, and 7–10 days after blood collection. Transverse sonographic images of the splenic mid‐body were made. Splenic height, width, cross‐sectional area, echogenicity relative to the left renal cortex, and echotexture were recorded. Height, width, and cross‐sectional area were compared across time periods using linear‐mixed effects models. Holm's method was applied to adjust for multiplicity and control the overall Type 1 error rate at α = 0.05. Normal transverse sonographic splenic measurements (mean ± standard deviation) at baseline were: height 8.2 ± 1.4 mm; width 26.7 ± 4.4 mm; and CSA 1.6 ± 0.5 cm². While there were statistically significant differences in splenic height, width, and cross‐sectional area after sevoflurane anesthesia and/or blood collection, differences were of low magnitude. The spleen was diffusely homogenous and subjectively isoechoic or mildly hyperechoic relative to the left renal cortex. In 77% of castrated male cats, the spleen was isoechoic to the left renal cortex. We conclude that sevoflurane anesthesia and blood donation do not subjectively alter splenic dimensions, echogenicity and echotexture in normal cats.     

ULTRASOUND CORNER SONOGRAPHIC EVALUATION OF PERITONEAL EFFUSION IN SMALL ANIMALS

Abdominal effusion is a common sonographic finding. The sonographic appearance of the fluid is affected by its cellular content. Transudates and modified transudates have a low cellular content, and usually are anechoic or mildly echogenic while exudates containing a high cellular content and fibrin strands are usually echogenci. Using history, laboratory values, sonographic appearance of the effusion, an estimate of the type of effusion and probable cause can be determined.     

Comparative sonographic appearance of nephroliths and associated acoustic shadowing artifacts in conventional vs. spatial compound imagingm

Spatial compound sonography improves visualization of tissue details and allows clearer delineation of structural margins. Improved image clarity is due to reduced speckling artifact; however, other types of acoustic shadowing artifacts may be unchanged or variably altered when conventional and spatial compound sonographic images are compared. Because intrarenal distal shadowing artifacts in conventional sonographic images are oftentimes the first or only evidence that a nephroliths is present, we compared the appearance and associated artifacts of nephroliths examined with both imaging modes. Consensus evaluation by two evaluators confirmed differences in appearance of nephroliths based on imaging mode. Nephroliths with conventional imaging mode were less hyperechoic and had better margin delineation while nephroliths were more hyperechoic and had less distinct margins with spatial compound imaging mode. Distal acoustic shadowing artifacts were present in 43% of spatial compound imaging mode vs. 86% of conventional imaging mode. When present in both imaging modes, intensity of these artifacts was weaker and the distance traveled was shorter in spatial compound imaging mode. Multiple diverging acoustic shadowing artifacts originating from a single source, the nephroliths were occasionally noted in spatial compound but not conventional imaging mode. These results demonstrate that the absence of distal acoustic shadowing cannot be used to exclude the presence of a nephrolith in dogs and cats. Optimal diagnosis of nephroliths, margin delineation, and visualization of the distal renal parenchyma requires paired radiography and sonography, and alternating between sonographic imaging modes is therefore suggested.     

SONOGRAPHIC APPLICATION IN THE DIAGNOSIS OF INTRAABDOMINAL ABSCESS IN THE DOG

The sonographic appearance of intraabdominal abscess, excluding prostatic abscess, is presented. The most common sonographic pattern identified for intraabdominal abscess is an irregularly defined, hypoechoic mass with minimal to no through transmission. Definitive diagnosis of intraabdominal abscess using only sonography is not possible, as variations of this common sonographic pattern are imaged. Sonography is best utilized to scan an animal when there is a high suspicion of intraabdominal abscess with no overt physical or radiographic evidence, and to better characterize intraabdominal masses. Sonography can be used to assist in percutaneous aspiration, catheterization, and intraoperative localization of abscessation.     

SONOGRAPHIC AND SCINTIGRAPHIC EVALUATION OF ACUTE RENAL ALLOGRAFT REJECTION IN CATS

The sonographic features of acute renal allograft rejection in humans and dogs are manifested by increase in renal cross-sectional area and reduction in renal cortical blood flow. These changes have not been investigated in cats. The objectives of this study were to evaluate sonographic and scintigraphic changes during acute renal allograft rejection in cats. Eight SPF, intact, adult, male cats received heterotopic renal allotransplantations. Immunosuppressive doses of cyclosporine and prednisolone were administered for 14 days and then discontinued to allow acute allograft rejection to occur. Serial measurements of renal cross-sectional area, resistive index (RI), echogenicity, and glomerular filtration rate (GFR) were performed to evaluate changes during acute rejection. Upon sonographic confirmation of absent diastolic blood flow or a 20% increase in cross-sectional area of the allograft, a nephrectomy and histopathologic evaluation were performed. Acute allograft rejection was confirmed histologically in all cats. Significant increases in renal cross-sectional area (P < 0.001) occurred postoperatively and during rejection. There were no significant changes in RI (P = 0.43) at any time. A subjective increase in medullary echogenicity and a decrease in corticomedullary demarcation were observed in the rejection period. While GFR decreased significantly in the immediate postoperative period (P < 0.001), no further change occurred during rejection (P = 0.42). Changes in RI and GFR do not appear to be sensitive indicators of acute renal allograft rejection in cats. Serial measurements of renal cross-sectional area appear to be a sensitive method for the early diagnosis of allograft rejection in feline renal transplant recipients.     

ULTRASONOGRAPHIC FEATURES OF PYONEPHROSIS IN DOGS

Pyonephrosis refers an infected hydronephrotic kidney which arise from pyelonephritis followed by exudate accumulation in a dilated renal pelvis or hydronephrosis followed by ascending infection. Pyonephrosis may cause serious systemic complications, making prompt and reliable diagnosis critical. Clinical and ultrasonographic findings are used for the diagnosis of pyonephrosis in humans, but these findings have not been investigated in dogs. We reviewed ultrasonographic features in pyonephrosis in 18 dogs. Ten dogs with hydronephrosis were also evaluated to compare with the pyonephrosis patients. In most dogs with pyonephrosis, hyperechoic contents completely filled the dilated renal pelvis (n=8) or a fluid‐debris level was observed (n=8). Hyperechoic contents were dispersed in renal pelvis in only two of the 18 dogs. Hyperechoic, edematous mesentery, and peritoneal and retroperitoneal effusion, which represented peritoneal and retroperitoneal inflammation, were observed in the perinephric region in 11 dogs. Compared with pyonephrosis, and as expected, hydronephrosis was characterized by anechoic contents within the urine‐filled collecting system and there were no definitive findings to suspect peritonitis. Thus, there is a distinct difference in the sonographic appearance of pyonephrosis vs. hydronephrosis in dogs.     

PERIRENAL EFFUSION IN DOGS AND CATS WITH ACUTE RENAL FAILURE

Perirenal fluid accumulation has been described as an ultrasonographic feature of urine leakage, hemorrhage, abscessation, or neoplasia. The purpose of this retrospective study was to report perirenal effusion as an additional ultrasonographic finding in canine and feline patients with acute renal failure. The causes of acute renal failure in 18 patients included nephrotoxicity (4), leptospirosis (3), ureteral obstruction (2), renal lymphoma (2), ureteronephrolithiasis (2), prostatic urethral obstruction (1) and interstitial nephritis and ureteritis (1). An underlying cause was not identified in three patients. The sonographic finding of perirenal fluid was bilateral in 15 patients. Unilateral perirenal fluid was identified ipsilateral to the site of ureteric obstruction in two patients. Large effusions extended into the caudal retroperitoneal space. Additional sonographic findings suggestive of renal parenchymal disease included mild (5), moderate (5) or severe (2) pyelectasia, increased renal echogenicity (11), increased (9) or decreased renal size (2) and ureteral and/or renal calculi (3). There did not appear to be an association between the volume of perirenal fluid and the severity of renal dysfunction. All patients with large effusions underwent euthanasia. Perirenal fluid developing in acute renal failure is thought to be an ultrafiltrate associated with tubular back-leak into the renal interstitium that overwhelms lymphatic drainage within the perirenal and retroperitoneal connective tissues although obstruction to urine flow may also play a role. Localized perirenal retroperitoneal free fluid may be a useful ultrasonographic feature to assist with the characterization of, and determination of prognosis in, patients with suspected renal disease.     

URINARY BLADDER MURAL HEMORRHAGE ASSOCIATED WITH SYSTEMIC BLEEDING DISORDERS IN THREE DOGS

The sonographic appearance of three dogs with diffuse bladder wall thickening due to mural hemorrhage is described. Two dogs were diagnosed with immune-mediated thrombocytopenia and the third dog with vitamin K antagonist toxicity. Urinary bladder wall thickening ranged from 5 to 12 mm on initial sonographic examination. In the two surviving dogs, the bladder wall returned to normal thickness. One dog, euthanatized for refractory hematuria, had submucosal hemorrhage in the urinary bladder at necropsy. Urinary wall thickening sonographically resolved at a rate of approximately 1 mm per day. Mural hemorrhage should be considered in patients with concurrent bleeding disorder and urinary bladder wall thickening.     

Evaluation of oxidative stress markers for the early diagnosis of allograft rejection in feline renal allotransplant recipients with normal renal function

The purpose of this study was to identify oxidative damage to renal allografts during graft rejection by evaluating changes in oxidative markers and plasma lactate levels in feline renal allotransplant recipients. Heterotopic renal allotransplantations were performed between 8 adult feline cross-matched donors. Following 14 d of immunosuppression, the drugs were discontinued to allow allograft rejection. Baseline and serial postoperative evaluations of serum creatinine, plasma lactate, plasma thiobarbituate reactive substances (TBARS), plasma creatol, urine creatol, and renal sonographic cross-sectional area were performed. When sonographic evaluation revealed the absence of blood flow to the allograft, the rejected kidney was nephrectomized and evaluated histopathologically. Allograft rejection occurred in all cats by day 26. A significant elevation in body temperature occurred during the rejection period. No significant change was observed between any of the time periods for plasma TBARS, creatol, or urine creatol. There was a significant decrease in plasma lactate levels throughout the study. Markers of oxidative stress from venous blood did not reflect renal allograft rejection in cats with a normally functioning native kidney. Renal allograft rejection may be associated with significant increases in body temperature and warrants further investigation.     

ULTRASOUND-ASSISTED DIAGNOSIS OF RENAL DYSPLASIA IN A 3-MONTH-OLD QUARTER HORSE COLT

A 3-month-old foal was presented for correction of bilateral angular limb deformities. Azotemia was detected as an incidental finding. Small, misshapened, hyperechoic kidneys with decreased corticomedullary demarcation were noted with ultrasonography. Additionally, the internal renal architecture was abnormal in that the intrarenal vessels and distant collecting system were not clearly seen in either kidney. Ultrasound-guided renal biopsy was suggestive of congenital renal dysplasia, which was later confirmed at necropsy. Clinical, sonographic, and pathologic features of equine renal dysplasia are discussed.     

RENAL SONOGRAPHIC MEASUREMENTS IN THE DOG PRECEDING AND FOLLOWING UNILATERAL NEPHRECTOMY

The purpose of this study was to establish sonographic baseline values for normal kidneys initu and to document sonographic changes following unilateral nephrectomy. Normal canine renal measurements were determined sonographically prior to and following unilateral nephrectomy. These included: cortical thickness (cranial, caudal, dorsal, ventral, lateral and medial), medullary measurements (cranial and caudal) and measurements of the renal silhouette (length, height and width). The latter group of measurements was obtained to determine renal volume. Normal parameters were obtained from sixteen healthy dogs prior to nephrectomy; the unilateral nephrectomy group was comprised of eight of these animals, the remaining eight dogs were part of an allo-transplant study.¹ The mean sonographic value for the length of the kidney was 60.3 mm ± 6.4 (n = 26) while the widths and heights were 34.7 ± 3.8 (n = 27) and 27.8 mm ± 3.3 (n = 26) respectively. Renal cortical measurements were found to be smallest dorsally and ventrally on sagittal and transverse sonograms. The largest volumes were the cranial pole on sagittal scans and the lateral pole on the transverse scans. Pearson correlation coefficient for volume resulted in r values of 0.88, 0.78 and 0.72 for length, height and width (n = 25, dif = 24) respectively.     

A REVIEW OF SONOGRAPHIC IDENTIFICATION OF ABDOMINAL BLOOD VESSELS AND JUXTAVASCULAR ORGANS

Abdominal vasculature can be evaluated non-invasively using 2-D ultrasound imaging and Doppler ultrasonography.^5,6,12 The identification of abdominal vessels using ultrasound is based on knowledge of their normal location, appearance and relationship to specific organs. Because anatomic location of major abdominal vessels is fairly consistent, finding and following vessels is a useful aid when attempting to locate and evaluate juxta-vascular organs. Sonographic vascular evaluation may be beneficial in providing information regarding central cardiovascular abnormalities, detection of abnormalities involving the vessel interrogated, or detection of abnormalities of the parenchymal bed that the vessel supplies,^5–12 Knowledge of the location and appearance of the vessels is necessary for this information to be of diagnostic value.
In this paper, abdominal vessels in the dog are reviewed and a sonographic map of major abdominal vessels is described. This includes the sonographic appearance of the aorta, caudal vena cava, and portal vein, their major branches and their anatomic relationship with adjacent organs.
Identification of the medial iliac lymph nodes, mesenteric lymph nodes, abdominal esophagus, duodenum, spleen, kidneys, pancreas, adrenal glands and liver lobes are assisted by recognizing specific vascular landmarks. The locations and appearances of pertinent organs as pertains to abdominal vasculature (caudal vena cava and aorta) are described.     

COMPARISON OF THE RESISTIVE INDEX TO CLINICAL PARAMETERS IN DOGS WITH RENAL DISEASE

The resistive index (RI) is a measurement of arteriole vascular resistance and is obtained by pulsed-wave Doppler interrogation. The diagnostic potential of the renal resistive index (RI) was retrospectively investigated in 142 kidneys from 81 dogs. The resistive index of each kidney was compared to clinical laboratory parameters, clinical diagnoses, and sonographic findings. The mean renal resistive index (RI) for 22 normal kidneys was 0.61 (standard deviation = 0.06). An elevation in the mean renal RI (>0.70) was found for the clinical diagnoses of acute renal failure and congenital dysplasia. When a RI of greater than 0.70 was considered abnormal, the sensitivity and specificity of the RI in determining normal vs, abnormal kidneys were 38% and 96% respectively.     

SONOGRAPHIC RENAL FINDINGS IN 20 DOGS WITH LEPTOSPIROSIS

Abdominal ultrasound examinations of 20 dogs with confirmed leptospirosis were reviewed retrospectively for renal abnormalities. Three dogs had a normal ultrasound examination. The remaining 17 dogs had sonographic abnormalities of the kidneys. These abnormalities, seen either alone or in combination, included renalmegaly (n=10), pyelectasia (n=9), increased cortical echogenicity (n=15), perinephric effusion (n=5), and a medullary band of increased echogenicity (n=6). At our institution, the medullary band of increased echogencity has only been seen in dogs with leptospirosis and may therefore be a specific sonographic sign for this disease.