Relationship between ultrasonographically determined renal dimensions and International Renal Interest Society stages in cats with chronic kidney disease

Gross morphological and ultrasonographic dimensions of normal feline kidney with reference to resistive index

Ultrasonography with color Doppler is the most quantitative analysis method for intra-renal parameters. There is a wide variation between authors in the measurement site and referencing the inter-lobar resistivity index (RI) in felines. Our objective is to morphometrically and ultrasonographically investigate the normal renal dimensions and vasculatures and draw up a normal reference value for the renal inter-lobar artery resistivity index (RI) using a Pulsed wave-Doppler ultrasonography. A total of twelve adult domestic cats were sedated and treated according to IACUC regulation guidelines to be examined using Doppler ultrasound. The same cats were used for morphometric investigation and divided into three groups regarding the used technique. The size difference between the right and left kidneys is slight, measuring 17 g (weight), 3.65 ± 0.06 cm (length), 2.54 ± 0.08 cm (width), and 2.21 ± 0.03 cm (thickness) for the right kidney, and about 15 g, 3.42 ± 0.06 cm, 2.32 ± 0.05 cm, and 2.13 ± 0.03 cm for the left one, respectively. There are three patterns of renal arteries' point of origin. The mean RI values of both kidneys were 0.57 ± 0.08 (0.50-0.67) in the right kidney and 0.60 ± 0.08 (0.51-0.69) in the left kidney. The gross examination and ultrasonography measurements did not have a statistically different effect on the actual renal dimensions. Moreover, 0.69 is considered the standard resistivity index (RI) threshold of the feline inter-lobar artery with no correlation to the animal's body weight.

Differentiation of stable kidney function versus progressive dysfunction in dogs

BACKGROUND

Circulating creatinine and symmetric dimethylarginine (SDMA) are biomarkers of kidney function that have been used variously to define stable vs progressive chronic kidney disease (CKD). Slope monitoring of inverse biomarker values (creatinine-1 or SDMA-1 ) has shown promise, but quantitative criteria to distinguish stable vs progressive CKD using this approach are lacking.

OBJECTIVE

Assessment of creatinine-1 and SDMA-1 slope cutoffs to distinguish stable vs progressive CKD.

ANIMALS

One hundred ten clinically healthy university staff-owned dogs and 29 male colony dogs with progressive X-linked hereditary nephropathy (XLHN).

METHODS

Retrospective analysis combining 2 prospective observational studies, 1 tracking kidney function biomarkers in healthy dogs (HDs) to a maximum of 3 years, and 1 tracking kidney function biomarkers in male colony dogs with progressive XLHN to a maximum of 1 year. The minimum slope of creatinine-1 or SDMA-1 as measured using the IDEXX SDMA test from HD was assigned as the slope cutoff for stable kidney function.

RESULTS

The stable vs progressive slope cutoff was -0.0119 week × dL/mg for creatinine-1 and -0.0007 week × dL/μg for SDMA-1 .

CONCLUSIONS AND CLINICAL IMPORTANCE

In the studied CKD population, progressive dysfunction can be distinguished from stable kidney function by using the slope of creatinine-1 or SDMA-1 . These criteria may serve to characterize CKD in other cohorts of dogs and to establish guidelines for degrees of progression rate in dogs with naturally occurring CKD.

Ultrasonographic kidney length-to-abdominal aortic diameter for the diagnosis of feline chronic kidney disease: A preliminary study

Background and Aim

Chronic kidney disease (CKD) is one of the most important diseases in cats. This study aimed to compare the ultrasonographic kidney length-to-abdominal aortic diameter (K/AO) ratio between healthy and CKD cats and investigate the correlation between K/AO and blood results.

Materials and Methods

Fifteen healthy cats and 15 CKD cats were included in this clinically prospective study. All cats were evaluated for radiographic and ultrasonographic K, radiographic K-to-second lumbar length ratio (K/L2), and K/AO, indirect systolic blood pressure and plasma creatinine (Cr), blood urea nitrogen (BUN), and symmetric dimethyl arginine (SDMA).

Results

The radiographic and ultrasonographic kidney lengths of CKD were significantly shorter than those of healthy cats (p < 0.05 and p < 0.05, respectively). The average K/L2 and K/AO were significantly lower in CKD than in healthy cats (p < 0.01 and p < 0.001, respectively). The K/AO had a strong negative correlation with plasma Cr (r = -0.7682, p < 0.0001), BUN (r = -0.6175, p < 0.001), and SDMA (r = -0.589, p < 0.001). However, K/L2 had a moderate negative correlation with plasma Cr (r = -0.5866, p < 0.001), BUN (r = -0.4884, p < 0.01), and SDMA (r = -0.5404, p < 0.01). The optimal cutoff value of K/AO (<10.71) had higher sensitivity and specificity than K/L2 for identifying feline CKD.

Conclusion

Kidney length-to-abdominal aortic diameter could be a better and more promising parameter than the K/L2 ratio for evaluating kidney size in cats with CKD.

Comparison of ultrasonographic renal measurements in kittens up to 3 months of age and young cats

OBJECTIVES

This study aimed to evaluate renal measurements by B-mode ultrasound in kittens during their first 3 months and compare them with those of young adult cats.

METHODS

Forty-eight healthy mixed-breed cats (24 males and 24 females) were enrolled in this study. The cats were divided into six age groups: groups 1-5 (kittens) and group 6 (young adult cats). Each kidney was examined using B-mode imaging and the following measurements taken: renal length (RL), renal height (RH), renal width (RW), cortical thickness (CoT), medullary thickness (MdT) and corticomedullary ratio (CMr). The ratio and correlation of RL to aortic diameter (AoD) and the length of the fifth/sixth lumbar vertebrae (LLV) were also determined.

RESULTS

Among groups, there was a statistically significant difference between RW, renal volume (RV), CoT, MdT and CMr. The smallest renal dimensions were obtained in the youngest kittens (up to 10 days of age), including RL (1.84 ± 0.40 cm), RH (1.14 ± 0.17 cm), RW (1.25 ± 0.20 cm) and RV (1.47 ± 0.68 ml). A strong correlation was observed between RL:AoD and RL:LLV, allowing for linear regression equations and reference intervals for RL:AoD and RL:LLV to be created for each age group.

CONCLUSIONS AND RELEVANCE

B-mode ultrasound showed that renal measurements in kittens differed from those in young adult cats, and that the renal dimensions, renal CoT and CMr increased with the growth of the cat. The RL-LLV ratio is a reliable method for measuring RL according to age group.

ACVR and ECVDI Consensus Statement for the Standardization of the Abdominal Ultrasound Examination

This consensus statement is designed to provide a standard of care document and describes the ACVR and ECVDI definition for performing a standard abdominal ultrasound examination in dogs and cats. The ACVR and ECVDI define a standard abdominal ultrasonographic examination as a complete exam of the abdominal organs which is appropriately documented. The consensus statement intends to provide guidance to veterinary sonographers and veterinarians for the performance and documentation of high-quality diagnostic ultrasound examination. The document may also serve as a teaching aid for veterinary students, veterinarians, and residents in diagnostic imaging who seek proficiency in diagnostic ultrasound. Finally, it may serve an additional role in educating the public as to what a high-quality abdominal ultrasound examination should entail.

Absence of renal cortical anisotropic backscattering artifact in feline chronic kidney disease

Renal cortical anisotropy backscattering artifact (CABA) is a focal hyperechoic region where the tubules are parallel to the incident ultrasound beam, reflecting most of the beams to the transducer. To investigate the association between chronic kidney disease (CKD) and the absence of renal CABA in cats. Ultrasonographic renal images of 40 cats with CKD (stage II-IV) and 36 clinically healthy cats were blindly evaluated by two observers to determine the visibility of renal CABA. Inter- and intraobserver agreements were evaluated using McNemar's test. The association between the absence of renal CABA and CKD was assessed using Fisher's exact test. Excellent intraobserver and substantial interobserver agreements were demonstrated. A significant association (P < .0001) between absent renal CABA and CKD stage was revealed in all cats. Cats with CKD had an increased risk of the absence of renal CABA (Odds ratio, 56.0; 95% CI, 13.8-227.0) compared with the clinically healthy cats. The absence of renal CABA revealed 87.5% sensitivity and 88.9% specificity to detect CKD in all cats, and 91.7% sensitivity and 83.3% specificity in aged cats. Our study demonstrated a correlation between feline CKD and the absence of renal CABA, providing a feasible and alternative method for feline CKD evaluation.

Relationship between ultrasonographically determined renal dimensions and International Renal Interest Society stages in cats with chronic kidney disease

Background

The correlation between renal dimensions and renal function in cats with chronic kidney disease (CKD) is unclear.

Hypothesis/Objectives

To investigate the relationship between renal dimensions and CKD severity in cats using ultrasound examination.

Animals

Nineteen healthy cats and 30 cats with CKD.

Methods

Renal ultrasound images obtained between 2012 and 2016 were reviewed. Severity of CKD was determined using the International Renal Interest Society CKD staging system. Renal length, cortical thickness, medullary thickness, and corticomedullary ratio were measured, and the relationship between these renal dimensions and serum creatinine concentrations as well as differences in dimensions between the control and disease groups was investigated. The sensitivity and specificity of the renal dimensions for differentiation of the CKD also were evaluated.

Results

The disease group was subdivided into stage I to II (15 cats) and stage III to IV (15 cats) groups. Cortical thickness was significantly decreased in both disease groups and negatively correlated with disease severity. Compared with other renal dimensions, cortical thickness had a stronger linear correlation with the reciprocal of the serum creatinine concentration and superior diagnostic performance (Youden index: left kidney, 90.0% sensitivity and 94.7% specificity for a cutoff of 4.7 mm; right kidney, 83.3% sensitivity and 94.7% specificity for a cutoff of 4.5 mm).

Conclusions and Clinical Importance

Decreased renal cortical thickness is observed in cats with loss of renal function. Measurement of cortical thickness using ultrasonography could be a useful method to evaluate the progression of CKD in cats.