Application of renal microangiography to normal and diseased kidneys of cattle and mice

Use of microangiography is now essential for the study of microcirculation in various organs. Renal microangiographic studies have been reported in rats, rabbits, dogs, human beings, and mice. However, we could not find any report on use of the technique in cattle, despite high incidence of renal disease in that species. The perfusion technique used in mice was improved over that of our previous report, and was applied to normal and diseased bovine kidneys. For the microangiographic technique, composition of the contrast medium, pressure of the injection, duration of perfusion, and washing of kidneys with heparinized saline solution before perfusion are important. In cattle, 1- to 2-mm-thick sections of the kidneys were generally necessary to observe renal vasculature: arcuate and interlobular arteries, afferent arterioles, and glomerular capillaries. In normal bovine kidneys, the angiographic and microangiographic findings were easily recognized as normal, compared with those of normal mice. In affected bovine kidneys, which histologically represented glomerulonephritis and pyelonephritis, angiography and microangiography revealed corresponding findings.     

Microangiography and correlated histology: a research technique for examining renal microcirculation

A technique for radiographic delineation of the microvasculature of the canine kidney is described. The renal vasculature was perfused (at a physiologic pressure) with a finely divided barium sulfate. Microangiograms of sagittal renal slices were produced, using a special radiography machine that allows low kilovolt peak, low milliamperage, and exposure times up to 5 minutes. A special high resolution film (800 lines/mm) was used. With this technique, it was possible to delineate interlobar, arcuate, and interlobular arteries, afferent arterioles, glomerular capillaries, and peritubular vessels. The kidney slices prepared for microangiography were undamaged and available for histochemical processing. Thus, the microvascularity was correlated with the histologic appearance of the renal tissues.     

Chronic renal failure in young dogs–possible renal dysplasia

The clinico-pathological findings are described in thirteen young dogs with advanced renal disease. All but three dogs were less than 2 years old. Some had signs of renal dysfunction since birth. Presenting signs were variable but anorexia, lethargy and weight loss were most frequent. All dogs had raised blood urea levels and most passed dilute urine; proteinuria and anaemia were variable findings. At necropsy all dogs had extra-renal lesions of renal failure and finely granular or lobulated, shrunken kidneys. The microscopical appearances of the kidneys were not those of amyloidosis, inflammatory or glomerular disease but were considered likely to be of developmental origin. The renal lesions were divided into three histologically distinct groups.

• 1 Predominantly cystic and connective tissue changes, characterized by striking dilatation of glomerular capsular spaces and cortical tubules.
• 2 Atypical connective tissue changes in which there were segmental bands of fibrous tissue containing primitive glomerular and tubular structures.
• 3 Predominantly glomerular and connective tissue changes, characterized by varying degrees of glomerulosclerosis and widespread calcification of glomeruli, tubules and blood vessels.

All groups had cortical and medullary interstitial fibrosis but minimal inflammatory cell infiltrates.     

An experimental model of chronic renal disease in dogs by infusion of microspheres into the renal arterial circulation

The feasibility of renal arterial infusion of nonbiodegradable microspheres as a model of chronic renal disease in dogs was evaluated. Resin-coated, styrene-divinyl benzene copolymer microspheres were infused into the kidneys of healthy adult Beagles by direct injections of both renal arteries in a single surgical procedure. Injections of 25-microns diameter microspheres had minimal effect on either the clinical status or serum values of the dogs. Histologic examination revealed the majority of the microspheres lodged within the capillary beds of the glomeruli, and little change to the kidneys. However, injections of 50-microns diameter microspheres caused significant increases in serum concentrations of urea nitrogen and creatinine. Histologically, the larger microspheres obstructed afferent arterioles and small arteries, which caused diffuse glomerular necrosis and nephron damage. With doses ranging from 1 to 3 million microspheres/dog, a correlation between the quantity of microspheres injected and severity of renal damage was observed. The optimal dose for producing a model of moderate renal disease was determined to be 1.8 million microspheres/dog (0.9 million microspheres/kidney). During long-term studies, microsphere-injected dogs fed a moderately restricted protein ration remained relatively azotemic, compared with control dogs on the identical ration. During the 5-month postsurgical period, the serum urea nitrogen concentration averaged 18.41 +/- 1.59 mg/dl (mean +/- SE) for the microsphere-injected dogs vs 9.31 +/- 0.38 for the control dogs (P less than 0.001). Similarly, the mean serum creatinine value was significantly higher (P = 0.020) for the microsphere-injected dogs, compared with the controls (1.23 +/- 0.12 mg/dl vs 0.94 +/- 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative Histology of the Kidney of Bos taurus and Bos indicus Cattle

Twenty-six kidneys of 2–4 years old Bos indicus (zebu cattle) and twenty kidneys of 4-year old Bos taurus were examined under the light microscope. The renal tubular epithelial heights and diameters were smaller in zebu than in Bos taurus. The Bos indicus kidney had fewer vascular bundles in the outer medullary zone and a smaller number of capillaries per vascular bundle, hence a lower renal blood flow than in Bos taurus. The Bos indicus proximal tubules had broader brush borders than those of Bos taurus. The smaller renal corpuscles with smaller glomerular filtration surface and low renal blood flow are responsible for low glomerular filtration rate and urinary flow, enabling their kidneys to retain more water than those of Bos taurus.     

Effects of serial ultrasound-guided renal biopsies on kidneys of healthy adolescent dogs

Ten healthy mixed-breed dogs were used to evaluate the functional and structural effects of serial ultrasound-guided renal biopsies obtained with an automated biopsy needle. In each dog, one lateral renal cortex was biopsied at 2, 4, and 6 months of age; the other kidney was the control. Five dogs had two tissue cores and five dogs had four tissue cores taken on each biopsy occasion, and one core was examined microscopically. One week before each biopsy and a month after the final biopsy, the glomerular filtration rate (GFR) was determined by renal scintigraphy. Dogs were then euthanized for evaluation of gross and microscopic lesions attributable to the biopsies. There was no difference between GFR values for biopsied kidneys and those of control kidneys ( P >0.05). Microscopic lesions were not identified in biopsies taken at 2 and 4 months, but focal lesions were found in three of 10 specimens taken at 6 months of age. At necropsy, six of 10 biopsied kidneys had small visible capsular scars, and linear tracts <2 mm wide were observed on cut surfaces in six of 10 biopsied kidneys cut transversely into slices 5 mm thick. Discrete light microscopic lesions were observed in 25 of 452 (5.5%) of randomly selected 6-mm-diameter sections of renal cortex from biopsied kidneys. We conclude that serial renal cortical biopsies can be obtained by our method from healthy adolescent dogs with minimal risk of inducing changes that might be confused with those of a progressive renal disease.     

Progressive Juvenile Glomerulonephropathy in 16 Related French Mastiff (Bordeaux) Dogs

Background: Familial juvenile glomerulonephropathy (JGN) is reported in several breeds of dogs. The mode of inheritance and spectrum of pathological lesions vary among breeds. A progressive JGN was detected in a pedigree of French Mastiff (FM) dogs. Objectives: To describe clinical, laboratory, and histopathologic findings in related FM dogs suffering from progressive JGN and to determine the mode of inheritance of this condition. Animals: Sixteen affected and 35 healthy related FM dogs Methods: FM dogs <24 months of age and diagnosed with chronic kidney disease with evidence of proteinuria entered the study. Clinical, laboratory, histopathologic findings, and pedigree data were recorded. Results: Clinical signs were typical of progressive glomerulopathy with resultant renal failure. Increased blood urea nitrogen, creatinine and total cholesterol concentrations, and proteinuria were found in all patients. Affected dogs had abnormal kidney structure on abdominal ultrasound examination. Histopathologic examination revealed extensive cystic glomerular atrophy, glomerular hypercellularity, and capillary wall thickening without immune complex deposition when tested with immunohistochemistry or immunofluorescence. Electron microscopy did not disclose specific primary glomerular lesions. Mean age at death was 20 months and mean length of survival after diagnosis was 6 months. Both males and females from healthy parents were affected. An autosomal recessive mode of transmission is suspected, but a more complex mode of inheritance cannot be excluded. Conclusions and Clinical Importance: Progressive familial JGN occurs in FM dogs. Characterization of the pathogenesis and mode of inheritance of this disease warrants additional study.     

Scintigraphic, sonographic, and histologic evaluation of renal autotransplantation in cats.

OBJECTIVE: To determine scintigraphic, sonographic, and histologic changes associated with renal autotransplantation in cats. ANIMALS: 7 adult specific-pathogen-free cats: 5 males, 2 females, 1 to 9 years old. PROCEDURE: Renal autotransplantation was performed by moving a kidney (5 left, 2 right) to the left iliac fossa. Before and at multiple times after surgery, for a total of 28 days, cats were evaluated by B-mode and Doppler ultrasonography, scintigraphy, and renal biopsy. RESULTS: By 24 hours after surgery, a significant decrease (42%) in mean glomerular filtration rate (GFR) and an increase in mean renal size (81% increase in cross-sectional area) were evident in the transplanted kidney, compared with preoperative values. By postsurgery day 28, reduction in GFR was 23%. Significant changes in renal blood flow velocity were identified in both kidneys. Consistent changes in resistive index or pulsatility index for either kidney could not be identified. When all postoperative histologic data were combined, the histologic score, indicating degree and numbers of abnormalities detected, for the transplanted kidney was significantly higher than that for the control kidney. CONCLUSIONS: Significant changes in renal function, size, and histologic abnormalities develop secondary to acute tubular necrosis in cats after uncomplicated renal autotransplantation. CLINICAL RELEVANCE: Evaluation of renal size and function may be of benefit for clinical evaluation of feline renal transplant patients, whereas measurement of the resistive index may be of little clinical value.     

Assessment of glomerular filtration rate with dynamic computed tomography in normal Beagle dogs

The objective of our study was to determine individual and global glomerular filtration rates (GFRs) using dynamic renal computed tomography (CT) in Beagle dogs. Twenty-four healthy Beagle dogs were included in the experiment. Anesthesia was induced in all dogs by using propofol and isoflurane prior to CT examination. A single slice of the kidney was sequentially scanned after a bolus intravenous injection of contrast material (iohexol, 1 mL/kg, 300 mgI/mL). Time attenuation curves were created and contrast clearance per unit volume was calculated using a Patlak plot analysis. The CT-GFR was then determined based on the conversion of contrast clearance per unit volume to contrast clearance per body weight. At the renal hilum, CT-GFR values per unit renal volume (mL/min/mL) of the right and left kidneys were 0.69 ± 0.04 and 0.57 ± 0.05, respectively. No significant differences were found between the weight-adjusted CT-GFRs in either kidney at the same renal hilum (p = 0.747). The average global GFR was 4.21 ± 0.25 mL/min/kg and the whole kidney GFR was 33.43 ± 9.20 mL/min. CT-GFR techniques could be a practical way to separately measure GFR in each kidney for clinical and research purposes.     

Correlation of electrophoretic urine protein banding patterns with severity of renal damage in dogs with proteinuric chronic kidney disease

Background

Urine protein loss is common in dogs with chronic kidney disease (CKD). Currently available noninvasive means of evaluating CKD in dogs cannot accurately predict the severity of glomerular and tubulointerstitial damage. Electrophoretic analysis of urine proteins can indicate the compromised renal compartment (glomerular vs tubular), but extensive evaluation of protein banding pattern associations with histologic damage severity has not been performed in dogs.

Objectives

We aimed to evaluate electrophoretic banding patterns as indicators of the presence and severity of glomerular and tubulointerstitial damage in dogs with naturally occurring, predominantly proteinuric CKD.

Methods

We performed a retrospective study using urine and renal tissue from 207 dogs with CKD. Urine protein banding patterns were correlated with histologic severity of renal damage. Sensitivity and specificity of banding patterns for the detection of glomerular and tubulointerstitial damage were determined.

Results

Banding patterns were 97% sensitive and 100% specific for the detection of glomerular damage and 90% sensitive and 100% specific for the detection of tubulointerstitial damage. Correlations between composite banding patterns and the severity of renal damage were strong, while glomerular banding patterns correlated moderately with glomerular damage severity, and tubular gel scores correlated weakly to moderately with the severity of tubulointerstitial damage.

Conclusions and clinical importance

Urine protein banding patterns are useful for the detection of glomerular and tubulointerstitial damage in dogs with proteinuric CKD.     

Proteinuria as an indicator of early renal disease in bull terriers with hereditary nephritis

A group of non-azotaemic bull terriers from families with hereditary nephritis had significant subclinical renal disease. Of the renal function tests carried out, proteinuria, almost exclusively albumin, was a reliable and early indicator of glomerular abnormality. While 24-hour urinary protein excretion (24 UPE) in the bull terriers was significantly higher than in a group of normal dogs of other breeds, urinary protein excretion (UPE) was also significantly higher when measured by simple single sample tests such as the urinary protein to urinary creatinine ratio (UP/C). UPE in bull terriers was correlated with increasing age, in contrast to lack of correlation in the normal dogs. The degree of proteinuria in affected bull terriers from which renal biopsies were taken correlated with the severity of histopathological changes which mainly affected glomeruli. Light microscopic examination revealed segmentally thickened glomerular and tubular basement membranes, thickened Bowman's capsules and adhesions between glomerular capillaries and Bowman's capsules. Other renal function tests were performed but failed to detect subclinical disease. It is suggested that hereditary nephritis (HN) in bull terriers is similar to that seen in samoyeds, dober-mann pinschers and humans.     

Attenuation of ischemia-reperfusion injury by ascorbic acid in the canine renal transplantation

This study examined the effects of ascorbic acid on the attenuation of an ischemia-reperfusion (I/R) injury after a canine renal transplantation. Eight beagle dogs were subjected to a renal auto-transplantation followed by the administration of ascorbic acid (treatment group) and the same amount of vehicle (physiological saline, control group). Blood samples were collected from these dogs to perform the kidney function tests and the invasive blood pressure was measured in the renal artery at pre- and post- anastomosis. The antioxidant enzymes of level 72 h after the transplant were measured. The kidneys were taken for a histopathology evaluation at day 21. The kidney function tests showed a significant difference between the control and treatment group. The invasive blood pressure in the renal artery was similar in the groups. The activity of the antioxidant enzymes in the blood plasma was significant lower in the control group than in the treatment group. The histopathology findings revealed the treatment group to have less damage than the control group. The results of this study suggest that ascorbic acid alone might play a role in attenuating I/R injury and assist in the recovery of the renal function in a renal transplantation model.     

A comparative study of chronic kidney disease in dogs and cats: induction of cyclooxygenases

The present study investigated whether renal cyclooxygenase (COX) induction is associated with the severity of chronic kidney disease (CKD) in dogs and cats. The collected kidneys were examined histopathologically and immunohistochemically. The immunoreactivities of COX-1 and COX-2 were evaluated quantitatively, and the correlations to the plasma creatinine concentrations, glomerular size, glomerulosclerosis, interstitial fibrosis, and interstitial cell infiltration were evaluated statistically. Immunoreactivities for COX-1 were heterogeneously observed in the medullary distal tubules and collecting ducts; no correlations with the severity of renal damage were detected. Immunoreactivities for COX-2 were heterogeneously observed in the macula densa (MD) regions. In dogs, the percentage of COX-2-positive MD was significantly correlated with the glomerular size. In cats, glomeruli with COX-2-positive MD had significantly higher sclerosis scores than those with COX-2-negative MD. In conclusion, renal COX-2 is induced in canine and feline CKD, especially in relation to the glomerular changes.     

EFFECTS OF HYDRATION ON SCINTIGRAPHIC GLOMERULAR FILTRATION RATE MEASURED USING INTEGRAL AND PLASMA VOLUME METHODS IN DOGS WITH SUSPECTED RENAL DISEASE

The current standard scintigraphic method for estimating glomerular filtration rate (GFR) in dogs is the integral method, which normalizes renal GFR to body weight. The plasma volume method, that is normalizing GFR to plasma volume, has been reported to be more physiologically correct. The aim of this prospective study was to test the effect of hydration status on GFR measured by these two methods in a group of dogs with suspected renal disease. Eleven dogs were recruited. All dogs underwent standardized scintigraphic examinations before and after 15 ml/kg of fluid was administered intravenously at 5–7 ml/kg/min. Individual kidney GFR estimates (n = 22) were calculated using both methods and a consensus of two observers who were unaware of clinical findings. Individual kidney GFR increased significantly (P = 0.0008) after fluid administration using the integral method and individual kidney GFR using the plasma volume method remained constant. Percentage differences for individual kidney GFR before and after fluid administration were 31.4 ± 58.1% (change ± 95% CI) for the integral method and 0.1 ± 70% (change ± 95% CI) for the plasma volume method. Intravenously administered fluid increased individual kidney GFR from low to normal in 10 of 22 kidneys using the integral method and in 1 of 22 kidneys using the plasma volume method. Findings supported the use of the plasma volume method for scintigraphic calculation of GFR in dogs with suspected renal disease and indicated that errors of kidney status classification may more likely occur when the integral method is used.     

Measurement, interpretation, and implications of proteinuria and albuminuria.

Proteinuria is a common disorder in dogs and cats that can indicate the presence of chronic kidney disease (CKD) before the onset of azotemia or the presence of more severe CKD after the onset of azotemia. Although a direct pathogenetic link between glomerular disease, proteinuria, and progressive renal damage has not been established, attenuation of proteinuria has been associated with decreased renal functional decline in several studies. There is a need to continue to increase our understanding of the effects of proteinuria on the glomerulus, the tubule, and the interstitium in dogs and cats.     

Familial glomerulonephropathy in a litter of beagles

Membranoproliferative glomerulonephropathy was diagnosed in 5 of 7 adult Beagles from the same litter. Dogs were raised in more than 1 area of the United States. One died without evidence of renal disease when it was 3 years old. At 8 years of age, 2 dogs developed signs of uremia, including polyuria, polydipsia, and infrequent episodes of anorexia and vomiting. Serum biochemical variables and urine specific gravity values were consistent with renal azotemia. Both dogs had proteinuria. Although healthy, 3 of the 4 remaining Beagles had proteinuria. Of these 3, only 1 was azotemic. Membranoproliferative glomerulonephritis was diagnosed on the basis of results of histologic examination of renal biopsy specimens from 4 of the dogs. Electron microscopy performed on 3 of the renal biopsy specimens revealed identical lesions, consisting of an extremely thickened glomerular basement membrane with multilaminar splitting. Immunoglobulin or amyloid deposits were not detected. On the basis of similar clinicopathologic abnormalities, common genetic background, and identical histopathologic and electron microscopic findings, familial renal disease was diagnosed. Additional studies involving other related Beagles are needed to identify the hereditary nature of membranoproliferative glomerulonephropathy in Beagles.     

Idiopathic cutaneous and renal glomerular vasculopathy of greyhounds

An idiopathic disease involving skin and occasionally kidneys was seen in kenneled and racing greyhounds. Hemorrhages, fibrinoid arteritis, thrombosis, and infarction with deep, slowly healing ulcers characterized the skin lesions. Peracute renal glomerular necrosis, particularly involving afferent arterioles with intravascular coagulation in glomerular capillaries were the distinctive findings in affected kidneys. A complex pathogenesis of this disorder was suspected in which genetic predisposition plays a prominent role.     

Polycystic kidney disease in bull terriers: an autosomal dominant inherited disorder

The prevalence, mode of inheritance and urinalysis findings in Bull Terriers with polycystic kidney disease were assessed by screening 150 clinically normal dogs. The disorder was diagnosed in 39 dogs on the basis of renal ultrasound results and family history of the disease. In equivocal cases confirmation required gross and histopathological renal examination. Necropsy was performed on nine affected dogs and the kidneys from another five affected animals were also examined. Renal cysts were usually bilateral, occurred in cortex and medulla and varied from less than 1 mm to over 2.5 cm in diameter. Cysts were lined by epithelial cells of nephron origin. Abnormal urine sediment and proteinuria were common in affected dogs. The disease appears to be inherited in a highly penetrant autosomal dominant manner.     

Morphologic Peculiarities of the Renal Cortical Vasculature Connected with Blood Redistribution in the Kidney of the Domestic Pig

The cortical blood vessels from 2 to 8 month old Camborow hybrid pigs and Belgium landrace pigs were studied using histologic and semithin sections as well as corrosion casts and cleared preparations of intravascular injection. It was established that the cortical blood vessels of the porcine kidney possess peculiarities that may regulate the redistribution of blood in the cortex. These peculiarities were found in the interlobular arteries, in the efferent arterioles of midcortical nephrons, in afferent arterioles of juxtamedullar glomeruli, and in the glomerular capillary networks. It was established that the number of renal corpuscles is different in the various zones of the cortex.     

Effect of intravenous mannitol upon the resistive index in complete unilateral renal obstruction in dogs

Some studies have shown that relative to baseline, the renal resistive index (RI) remains unchanged in nonobstructed kidneys and increases in obstructed kidneys after administration of furosemide. To our knowledge, the effect of mannitol administration on the renal RI of dogs has not been reported. We evaluated the renal RI in 16 kidneys in 8 young adult dogs after administration of mannitol. The mean RI decreased significantly from baseline (P < .01). Additionally, left complete ureteral obstruction wasinduced in 5 dogs. Evaluation by Doppler ultrasonography was performed for 5 days. On the 5th day, Doppler examination was repeated at 30 and 60 minutes after administration of mannitol to obstructed dogs. After induction of left ureteral obstruction, the RI of the left kidney increased significantly over 5 consecutive days. Administration of mannitol decreased the RI in the nonobstructed contralateral kidneys, and thus the RI difference between obstructed and nonobstructed kidneys was increased above normal (P < .001). In conclusion, administration of mannitol may be useful as another diuretic agent to identify unilateral ureteral obstruction on Doppler sonographic examination.