Relationship Between Age, Plasma Renin Activity, and Renal Resistive Index in Dogs

Abstract

The renal resistive index (RI) value of 0.73 has been proposed as the upper limit in normal adult dogs. In humans, changes in RI with age are associated with plasma renin activity. There are relatively few equivalent reference data for dogs. We obtained reference RI data from 22 clinically healthy dogs <4 months of age and 33 healthy dogs between 4 months and 7 years of age. An association between the RI and plasma renin activity was investigated. The mean RI in the older dogs was 0.65 +/- 0.05 vs. 0.75 +/- 0.05 in dogs <4 months of age. The mean plasma renin activity in the older dogs was 1.18 +/- 1.03 vs. 4.23 +/- 3.09 ng/ml/h in dogs <4 months of age. There was a weak linear relationship between the RI and plasma renin activity (r2 = 0.280, P < 0.01) in dogs <4 months of age. Also in these younger dogs, RI was negatively correlated with age (r2 = 0.682, P < 0.01). The RI was higher in dogs <4 months of age than in older dogs. Therefore, the mean renal RI is slightly higher in young dogs than reported for an older population and interpretation of the RI must include an assessment of patient age.

The Evaluation of Renal Hemodynamics with Doppler Ultrasonography

“…Mechanism by renin-angiotension-aldosterone system plays a role has not been clearly established in dogs and its effect in clinic application is not yet completely understood. In a study by Chang et al (2010), the intrarenal RI in dogs younger than 4 months was higher than in older dogs. Therefore, the use of 0.73 as the upper limit for intrarenal RI in normal dogs is not appropriate for dogs younger than 4 months.…”

Effect of Breed on Plasma Endothelin‐1 Concentration, Plasma Renin Activity, and Serum Cortisol Concentration in Healthy Dogs

“…This was not surprising, as the study only included young adult to middle‐aged dogs and was not designed to evaluate age differences. Age and sex differences have been shown for cortisol and components of RAAS in dogs 37, 38, 39. Age and sex differences have been shown for ET‐1 in people,40, 41 whereas scarce information is available for dogs.…”

B-Mode and pulsed Doppler sonography of kidney in healthy sheep according to age

“…The same animal also presented 1.01cm of dilation of the kidney pelvis, which was not observed in this animal study because they were healthy. The measurements of the length of the right kidney (8.66cm) and left (8.49cm) of this sheep were higher than the average of the Hoffmann et al (1997) Horses (n=7) 0.512±0.004 (renal artery) Koma et al (2006) Dogs (n=10) 0.66±0.07 (renal artery) 0.64±0.09 (interlobar artery) Chang et al (2010) Dogs < 4 months (n=22) 0.75±0.05 (renal artery) Dogs > 5 months (n=33) 0.65±0.05 (renal artery) Carvalho & Chammas (2011) Cats (n=25) 0.54±0.07 (renal artery) 0.52±0.06 (interlobar artery) Chetboul et al (2012) Dogs (n=39) 0.62±0.05 (interlobar artery) Novellas et al (2012) Dogs (n=27) and Cats (n=10) 0.62±0.04 (renal artery) adults cited in this paper. This ram also showed post-renal azotemia, with 11.48mg/dL of creatinine and 203.57mg/ dL of urea.…”

“…However, it was not possible to obtain the vascularization satisfactorily in lambs (n=20) and in rams (n=8). The impossibility of obtaining renal vascularization in lambs may be related to high renal vascular resistance, cited by some authors (Chang et al 2010), or even by technical failures. As for the rams, there was no success in the exam, either, probably due to increased abdominal muscle layer and large amount of intra-abdominal fat of this group, in addition to frequency limitation of the equipment.…”

“…The RI values obtained in this study were similar to the values reported in the literature. Chang et al (2010) evaluated the RI of the renal artery of 22 healthy dogs of up to four months old and 33 dogs of five months to seven years old. These authors found a negative correlation between the RI and age.…”