Evaluation of renal cortical echogenicity in healthy cats using anisotropic backscatter artifacts and echogenicity differences among internal organs

Figures & data

Figure 1. The presence (A, B) and absence (C, D) of renal CABA in median longitudinal (A, C) and transverse (B, D) plane of the feline kidney. Magnified images of the presence of renal CABA from the rectangular dotted region of (A) and (B) are shown in (a) and (b), respectively. The arrowheads indicate focal hyperechogenic trapezoid regions with indistinct or faded margins at 3 and 9 o’clock of the renal cortex compared with the rest of the cortex.

Figure 2. Illustration of echo scores within urinary bladder. The urinary bladder with anechoic urine was scored as 0 (A); less than 10 echoes was scored as 1(B); echoes that occupied less than 25% of the lumen was scored as 2 (C); echoes that occupied 25–50% was scored as 3 (D); echoes that occupied more than 50% was scored as 4 (E).

Figure 3. Illustrations of the tissue comparisons between CABA (*) and non-CABA region (#). Hepatic versus splenic echogenicity (A), renal cortex versus splenic echogenicity (B), and renal cortex versus hepatic echogenicity (C). CABA, cortical anisotropic backscatter artifact.

Table 1. Clinical data of all included cats.

Clinical data
Age (years)	4.5 (1–10; IQR, 2.0–6.0)
Gender
Intact female	14
Intact male	5
Female spayed	3
Male neutered	8
Breed	10 mixed cats, 5 Persians, 4 Ragdolls, 4 Munchkins, 3 American shorthairs, 2 British shorthairs, 1 Exotic shorthair, 1 Norwegian forest
Body weight (kg)	3.8 ± 1.4
Serum creatinine (µmol/L)	97.2 (53.0–141.4; IQR, 88.4–132.6)
Serum SDMA (µmol/L)	0.55 (0.40–0.69; IQR 0.45–0.64)
Body condition score	4.0 (3–9; IQR 4–5)

Note: Age, serum creatinine, serum SDMA and body condition score were present as median (range). Body weight was presented as mean ± SD. IQR: Interquartile range.

Table 2. Associations among the variables with the presence of renal CABA from different observers.

	The presence of renal CABA
	Observer 1	Observer 2
Gender	p = 1.00	p = 0.49
Reproductive state	p = 1.00	p = 0.54
Presence of lipid droplets in urine	p = 0.29	p = 1.00
Presence of echoes within bladder	p = 1.00	p = 1.00
Age	p = 0.72	p = 0.35
Body weight	p = 0.87	p = 0.41
BCS	p = 0.78	p = 0.70
Serum SDMA	p = 0.71	p = 0.93
Serum creatinine	p = 0.88	p = 0.56

Gender, reproductive state, presence of lipid droplets in urine and presence of echoes within bladder were analyzed by Fisher’s exact test. Age, body weight, BCS, serum SDMA and serum creatinine were analyzed by univariable analysis. Statistical significance p < 0.05. CABA: Cortical anisotropic backscatter artifact; BCS: Body condition score; SDMA: Symmetric dimethylarginine.

Table 3. Comparison of echogenicity differences among spleen, liver and renal cortex at CABA region and non-CABA region.

Echogenicity	CABA region	non-CABA region
Kidney > Spleen > Liver	56.7% (17/30)	16.7% (5/30)
Kidney = Spleen > Liver	33.3% (10/30)	43.3% (13/30)
Spleen > Kidney > Liver	10.0% (3/30)	20.0% (6/30)
Spleen > Liver > Kidney		13.3% (4/30)
Spleen = Liver > Kidney		3.3% (1/30)
Liver > Kidney > Spleen		3.3% (1/30)

CABA: Cortical anisotropic backscatter artifact.