Screening of ragdoll cats for kidney ‐disease: a retrospective evaluation

Abstract

Objectives To assess the prevalence of renal abnormalities in ragdoll cats. Ragdoll breeders often warn clients to watch for future renal problems, mainly due to chronic interstitial nephritis and polycystic kidney disease. Therefore, ragdoll screening by abdominal ultrasonography, measurement of serum creatinine and urea concentrations and genetic testing is often performed without documented scientific evidence of increased risk of renal disease. Methods Retrospective evaluation of ragdoll screening for renal disease at one institution over an eight‐year period. Results Renal ultrasonography was performed in 244 healthy ragdoll cats. Seven cats were positive for polycystic kidney disease, 21 were suspected to have chronic kidney disease, 8 had abnormalities of unknown significance and 2 cats had only one visible kidney. Cats suspected to have chronic kidney disease were significantly older and had significantly higher serum urea and creatinine concentrations than cats with normal renal ultrasonography. All 125 genetically tested cats were negative for polycystic kidney disease. However, only one of the seven ultrasonographically positive cats underwent genetic testing for polycystic kidney disease. Clinical Significance Ultrasonographic findings compatible with chronic kidney disease were observed in almost 10% of cats, and polycystic kidney disease occurred at a low prevalence (<3%) in this ragdoll population. Further studies are required to elucidate if ragdoll cats are predisposed to chronic kidney disease.

Ultrasonography does not consistently detect parathyroid glands in healthy cats

“…What we can conclude is that nodules internal to the thyroid gland in cat cadavers closely resembled those identified on ultrasound in our clinically healthy population of cats, and represented a number of different entities histologically, including normal internal parathyroid glands, thyroid follicular cysts, multifocal follicular dilation, or thyroid adenomatous hyperplasia. While not seen in the cadavers evaluated in this study, review of the literature indicates that other lesions such as thyroid lobules, follicular adenomas, or lymphoid tissue occur in the thyroid glands of cats and might also appear as hypoechoic nodules . Our data supports that hypoechoic nodules are more common in healthy older cats compared to a younger population, even with normal parathyroid and thyroid testing.…”

“…using an 8–5 MHz curvilinear transducer and a commercially available ultrasound unit (Philips iE33, Philips Healthcare, Andover, MA). Kidneys were assessed for the following features: renal length <2.9 cm, irregular or undulating kidney shape or surface, reduced corticomedullary distinction, heterogenous renal parenchyma, focal or diffuse cortical hyperechogenicity, focal or diffuse medullary hyperechogenicity, “medullary rim sign”, or evidence of more than one renal infarct, and/or renal parenchymal mineralization . No cat was included if more than one of the listed abnormalities was detected.…”

Current Understanding of the Pathogenesis of Progressive Chronic Kidney Disease in Cats

“…Persian, Abyssinian, Siamese, Ragdoll, Maine coon but the current evidence base for these breed predispositions is low. 5,24,25 Similarly although the study above suggested a predisposition in neutered male cats, overall other studies have not supported a sex predisposition.…”

Prevalence and clinical significance of the medullary rim sign identified on ultrasound of feline kidneys

“…The US examinations were performed using several different ultrasound machines over the study time (Logiq 7, GE Medical Systems; Logiq LS7, GE Medical Systems; Zonare ZS3, Mindray). A multifrequency (8)(9)(10)(11) microconvex or a multifrequency (10-14 MHz) linear transducer was used for ultrasound examination as per institutional protocol. All abdominal ultrasound examinations were completed by board-certified radiologists or radiology residents under direct supervision of a board-certified radiologist.…”