Ultrasonographic evaluation of renal size in dogs with acute allograft rejection

Computed tomographic measures of renomegaly vary among dogs with different types of congenital portosystemic shunts

Renomegaly has been reported in dogs with congenital portosystemic shunts (PSS). However, no study has objectively evaluated the degree of renomegaly in dogs with different types of PSS. The purpose of this retrospective, analytical, cross-sectional study was to determine kidney size (renal length-to-L2 vertebral body ratio; RL/L2 ratio) using CT in dogs with different types of PSS and correlate with clinical information. A medical record search for dogs with a PSS diagnosed using CT between 2016 and 2020 was conducted. Breed, age, sex, body weight, and biochemistry results were recorded. Kidney and L2 vertebral body lengths were measured using multiplanar reformatted CT images, and the RL/L2 ratio was calculated. Dogs were categorized into four groups based on PSS morphology for comparisons: intrahepatic (IH; n = 19), extrahepatic portocaval (EHPC; n = 20), extrahepatic portoazygos (EHPA; n = 7), or extrahepatic portophrenic (EHPP, n = 7). The RL/L2 ratio (mean ± SD) was largest in IH (3.55 ± 0.38) and EHPC (3.55 ± 0.38), followed by EHPP (3.10 ± 0.23), and EHPA (2.78 ± 0.18). RL/L2 ratio was significantly larger in EHPC and IH (vs. EHPA and EHPP [P < .01]). Significant correlations between kidney size and creatinine, alkaline phosphatase, albumin, total protein, and ammonia were present. Renomegaly was observed in 86.8% of dogs with PSS overall, but it was uncommon in dogs with EHPA and less common in dogs with EHPP, as these two groups showed clinical signs later in life, made evident by older age at presentation. The authors suggest that the severity of hepatic dysfunction and the shunted blood volume may influence the development of renomegaly in dogs with PSS.

Kidney and cystic volume imaging for disease presentation and progression in the cat autosomal dominant polycystic kidney disease large animal model

BACKGROUND

Approximately 30% of Persian cats have a c.10063C > A variant in polycystin 1 (PKD1) homolog causing autosomal dominant polycystic kidney disease (ADPKD). The variant is lethal in utero when in the homozygous state and is the only ADPKD variant known in cats. Affected cats have a wide range of progression and disease severity. However, cats are an overlooked biomedical model and have not been used to test therapeutics and diets that may support human clinical trials. To reinvigorate the cat as a large animal model for ADPKD, the efficacy of imaging modalities was evaluated and estimates of kidney and fractional cystic volumes (FCV) determined.

METHODS

Three imaging modalities, ultrasonography, computed tomography (CT), and magnetic resonance imaging examined variation in disease presentation and disease progression in 11 felines with ADPKD. Imaging data was compared to well-known biomarkers for chronic kidney disease and glomerular filtration rate. Total kidney volume, total cystic volume, and FCV were determined for the first time in ADPKD cats. Two cats had follow-up examinations to evaluate progression.

RESULTS

FCV measurements were feasible in cats. CT was a rapid and an efficient modality for evaluating therapeutic effects that cause alterations in kidney volume and/or FCV. Biomarkers, including glomerular filtration rate and creatinine, were not predictive for disease progression in feline ADPKD. The wide variation in cystic presentation suggested genetic modifiers likely influence disease progression in cats. All imaging modalities had comparable resolutions to those acquired for humans, and software used for kidney and cystic volume estimates in humans proved useful for cats.

CONCLUSIONS

Routine imaging protocols used in veterinary medicine are as robust and efficient for evaluating ADPKD in cats as those used in human medicine. Cats can be identified as fast and slow progressors, thus, could assist with genetic modifier discovery. Software to measure kidney and cystic volume in human ADPKD kidney studies is applicable and efficient in cats. The longer life and larger kidney size span than rodents, similar genetics, disease presentation and progression as humans suggest cats are an efficient biomedical model for evaluation of ADPKD therapeutics.

Ultrasonographic evaluation of the renal dimensions in captive tigers

Ultrasonographic measurements of kidney size are useful in the practical diagnosis of kidney diseases in animals. In tigers, there is a lack of information regarding the ultrasonography methods used to measure the kidney size of the tiger. Thirty-three healthy captive tigers (Panthera tigris) were placed in lateral recumbency for ultrasonography. The measurements obtained from the ultrasonography were computed, and the results showed that there was a statistically significant difference between genders in terms of body weight and renal length. The length of the right kidney was significantly different from that of the left kidney (10.23 ± 0.76 cm in males versus 9.94 ± 0.80 cm in females; P<0.05). Interestingly, this study demonstrated that kidney length was statistically significantly associated with the body weight, and it also had a positive linear relationship with the body weight. Therefore, ultrasonographic renal dimensions could prove to be beneficial and modality for use in the evaluation of kidneys in unconscious tigers. However, kidney size evaluation must be performed using not only ultrasound but other clinical forms of technology and parameters.

Reestablishment of radiographic kidney size in Miniature Schnauzer dogs

Kidney size may be altered in renal diseases, and the detection of kidney size alteration has diagnostic and prognostic values. We hypothesized that radiographic kidney size, the kidney length to the second lumbar vertebra (L2) length ratio, in normal Miniature Schnauzer dogs may be overestimated due to their shorter vertebral length. This study was conducted to evaluate radiographic and ultrasonographic kidney size and L2 length in clinically normal Miniature Schnauzers and other dog breeds to evaluate the effect of vertebral length on radiographic kidney size and to reestablish radiographic kidney size in normal Miniature Schnauzers. Abdominal radiographs and ultrasonograms from 49 Miniature Schnauzers and 54 other breeds without clinical evidence of renal disease and lumbar vertebral abnormality were retrospectively evaluated. Radiographic kidney size, in the Miniature Schnauzer (3.31 ± 0.26) was significantly larger than that in other breeds (2.94 ± 0.27). Relative L2 length, the L2 length to width ratio, in the Miniature Schnauzer (1.11 ± 0.06) was significantly shorter than that in other breeds (1.21 ± 0.09). However, ultrasonographic kidney sizes, kidney length to aorta diameter ratios, were within or very close to normal range both in the Miniature Schnauzer (6.75 ± 0.67) and other breeds (7.16 ± 1.01). Thus, Miniature Schnauzer dogs have breed-specific short vertebrae and consequently a larger radiographic kidney size, which was greater than standard reference in normal adult dogs. Care should be taken when evaluating radiographic kidney size in Miniature Schnauzers to prevent falsely diagnosed renomegaly.

Ultrasonographic measurement of kidney-to-aorta ratio as a method of estimating renal size in dogs

Renal size is an important parameter in the assessment of renal disease in dogs. However, because of the great variability in body conformation, absolute renal measurements cannot solely be used when evaluating kidneys with ultrasonography. The use of a ratio comparing renal length and aortic luminal diameter (K/Ao) was investigated. After confirming the reproducibility of these measurements, K/Ao ratios were obtained in 92 dogs without clinical evidence of renal disease. Left and right K/Ao ratios were statistically similar. Based on 95% confidence intervals, renal size should be considered reduced if the K/Ao ratio is < 5.5 and increased when > 9.1.

Indicators of Acute Rejection on Tc-99m DTPA Renal Scintigraphy

INTRODUCTION

Specific criteria for diagnosing an acute rejection episode (ARE) are not present on renal scintigraphy. However, a deterioration in renal function observed on serial imaging is suggestive of an ARE during the early posttransplantation period. In this study, we evaluated Tc-99m DTPA renal scintigraphy findings among patients with renal allograft dysfunction. The aim was to define criteria for ARE on a single imaging study alone.

MATERIALS AND METHODS

This study included 82 patients with renal allograft dysfunction, each of whom had a specific biopsy-proven pathology. From the background-corrected Tc-99m DTPA renal time-activity curves, the following parameters were computed: the ratio of counts at peak perfusion to that at plateau (P:PL) and the ratio of counts at peak perfusion to that at peak uptake (P:U). The images were inspected visually for excretion patterns and other morphological changes.

RESULTS

A specific renogram pattern, that is an increase in perfusion to uptake ratio together with a nearly flat uptake curve and preserved peak/plateau pattern, was observed in 67% of low-grade AREs. In contrast, a flat uptake curve usually occurred together with a loss of peak/plateau pattern in a high-grade ARE. The findings that were highly specific for ARE on visual inspection were little or no collecting system activity, pelvic hypoactivity, and indistinctness of the corticomedullary junction.

CONCLUSIONS

Our results indicate that in low-grade ARE, there is decreased filtration relative to perfusion as evidenced by a decrease in the perfusion-to-uptake ratio with loss of a peak/plateau pattern. A hypoactive pelvis with little activity in the collecting systems may be due to edema in the renal interstitium and pelvicalyceal structures.

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 evaluation of renal autografts in normal cats

The purpose of this study was to determine changes in resistive index (RI) and renal size that occur in normal feline kidney autografts in the immediate post-transplant period. Qualitative changes in renal parenchymal echogenicity and pelvic dilation were also noted, although this was not a major focus of the study. Fourteen domestic short-haired cats underwent bilateral nephrectomies followed by an autograft of the right kidney to either the aorta or external iliac artery. Due to post-operative complications, only nine of these cats completed the study. Ultrasonographic determination of the RI and renal size was made before transplantation and on days 1, 4, 7, 10, and 13 following transplantation. No significant changes in renal RI were identified during the study. Renal size increased significantly, peaking at 63% above baseline on day 7, and stayed elevated at 50% above baseline on day 13. There was no evidence of rejection or other abnormalities found on histologic evaluation of the transplanted kidneys. It was concluded that the RI of normal feline renal autografts does not significantly change in the immediate post-operative period. However, significant renal enlargement, likely due to a combination of post-operative edema and hypertrophy, does occur. This study provides baseline information for comparison with feline allografts in the immediate post-transplant period.

Effects of diet and aging on renal measurements in uninephrectomized geriatric bitches

Under controlled, but varied dietary conditions among geriatric, uninephrectomized Beagle bitches (dogs) observed for 4 years, renal size increase as assessed radiographically and ultrasonographically occurred at variable rates, but on a seemingly continuous basis. The maximum observed mean renal linear parameter increase found was approximately 15%. However, a 10 and 15% increase is a more representative expectation among the 4 parameters (sonographic length, radiographic length, sonographic width, radiographic width) under consideration. The rate of renal size increase was rapid during the first 2 to 3 months following uninephrectomy. Thereafter, the rate of increase was slow, but occurred to varying degrees in both the length and width as assessed radiographically or ultrasonographically. The mechanism creating the size change was hypertrophy, not hyperplasia. Within limits of the 3 diets used in the study, no significant diet effect was found on the rate or degree of long term compensatory hypertrophy. Radiographically and ultrasonographically measured renal length had the greatest correlation with each other as well as with post mortem measurements and are, therefore, the recommended parameter for imaging assessment of compensatory hypertrophy. When the prenephrectomy, radiographic renal lengths and widths were normalized as a ratio of the second lumbar vertebral body length (L2) measured from ventrodorsal radiographs, the diet group means across dogs (approximately three L2 lengths for renal length; two L2 lengths for renal width) were in the middle of the respective previously published normal radiographic ranges for mature dogs (e.g. 2.5 L2 < or = length < or = 3.5 L2; 1.58 L2 < or = width < or = 2.38 L2 lengths). Even after the hypertrophic changes occurred, the radiographic group mean lengths and widths across dogs were still within the specified normal ranges, although toward the upper end of the respective range. This information provides background for clinical interpretation of potential compensatory hypertrophy that may be encountered following uninephrectomy for spontaneous disease in aged dogs. In addition, it appears that available radiographic renal linear ranges for normal mature dogs are applicable to geriatric dogs as well.

Comparison of kidney weight and volume to selected anatomical parameters in the adult female rhesus monkey (Macaca mulatta)

In this study, the normal distribution of renal weight and volume was determined and the correlation between the weight and volume and various skeletal measurements taken from radiographs and at necropsy was assessed. Values from 136 female monkeys with complete data (including all bone, radiographic, and kidney measurements) were analyzed. The mean kidney weight was 13 g with a standard deviation (SD) of 2 g. The mean kidney volume was 12 ml, SD 2 ml. The estimation of kidney weight and volume from bone length, age, or body weight was not reliable according to statistical analysis of our data. We did find that all apparently normal adult female rhesus monkeys typically have similar sized kidneys. This information is useful in that it reduces concerns about consistency in experimental subjects.