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Urinary Disease
Judith Hudson

Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA

27.1 The Feline Kidneys echogenicity, reduced corticomedullary definition, or a
medullary rim sign (Figure 27.4). Focal lesions included
Radiographic and sonographic abnormalities can be dystrophic mineralization, cysts, solid nodules, and focal
described in terms of size, shape, location, margination, mineralization in the pelvis or proximal ureter. Decreased
and opacity (for radiographs) or echogenicity (for ultra- renal size or increased size differential between kidneys,
sonography). The presence of sonographic artifacts, such increased echogenicity of the urine, and bladder uroliths
as acoustic shadowing and acoustic enhancement, can fur- were other findings. The incidence of most abnormalities
ther help determine the cause of disease. in Ragdoll cats was similar to that in cats of other breeds,
with the exception of capsular abnormalities, cortical
segmental lesions, and increased echogenicity of the
27.1.1 Chronic Renal Disease urine. The cortical segmental lesions were only seen in
In chronic renal disease (Figure 27.1), one or both kidneys Ragdoll cats and may represent infarcts or scarring from
are frequently smaller than normal and may be misshapen other causes. Based on the severity of sonographic find-
with parenchymal mineralization or calculi [1]. If disease is ings, 5.3% of the Ragdoll cats were suspected to have
unilateral, the unaffected kidney may undergo compensa- chronic kidney disease but none were suspected to have
tory hypertrophy and become enlarged (Figure 27.2). On polycystic kidney disease. Additionally, although abnor-
ultrasonography (Figure 27.3), corticomedullary definition malities were common in both groups, most of the cats
is often reduced and may be poor. There may be focal or dif- did not appear to have significant disease. Echogenic
fuse changes in echogenicity. Cats with chronic renal dis- urine was common in both groups although more com-
ease are often middle‐aged or older. In very young animals, mon in the Ragdoll cats (25.8% in controls compared to
small misshapen kidneys can be a sign of renal dysplasia, 51.9% in Ragdoll cats).
where the kidneys fail to develop normally. In these kittens,
blood creatinine and urea nitrogen levels are often surpris- 27.1.2 Acute Kidney Disease
ingly high although the patient may initially only show a
failure to thrive. Diagnosis is made on the basis of histopa- Acute kidney disease or injury (AKD or AKI) has been
thology that reveals disorganized renal parenchyma [2]. proposed as a term to replace acute renal failure. Causes
It is important to recognize that renal abnormalities of AKD are numerous but include toxins (such as lilies,
are common in cats that are not considered to have clini- ethylene glycol, and nonsteroidal antiinflammatory
cal renal disease. In a study comparing Ragdoll cats with drugs [NSAIDS]), obstruction, neoplasia (lymphoma,
normal control cats from other breeds [1], ultrasono- adenocarcinoma, hemangiosarcoma, nephroblastoma),
graphic renal abnormalities were common in both infection, sepsis, and ischemia [3, 4]. Acute disease often
groups. Abnormalities included irregularity or undula- occurs in the presence of chronic renal disease.
tion of the capsular margin, irregular or bumpy shape, Radiography is helpful for determination of the size,
segmental cortical lesions or other changes in cortical margination, and opacity of the kidneys and ureters.
echogenicity (primarily hyperechoic but occasionally Increased opacity could be associated with parenchymal
hypoechoic). Some cats had diffusely increased medullar mineralization or calculi. Ultrasonography is useful to

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.