Is a “Mottled” Kitten Spleen Normal? New Evidence from High-Frequency Ultrasound

A Sonographic Reticulonodular Pattern Is Likely a Normal Finding in Kitten Spleens Using a High-Frequency Linear Transducer

Catana M. Capps, Alison M. Lee, Marc A. Seitz

Background

A reticulonodular (mottled or “Swiss-cheese”) splenic pattern on ultrasound is commonly associated with neoplastic or infectious disease in veterinary patients, often prompting concern and further diagnostics. However, this appearance has been established as a normal, age-related finding in children and in puppies up to approximately one year of age. Anecdotal observations suggested a similar phenomenon in kittens, but this had not been systematically studied. The purpose of this study was to determine whether a reticulonodular splenic pattern is a common and likely normal ultrasonographic finding in apparently healthy kittens and young cats.

Methods

This prospective, descriptive study enrolled apparently healthy, client-owned kittens and young cats up to 1.5 years of age presenting for routine care. A total of 67 spleens from 50 kittens were evaluated, including serial examinations in 13 kittens. Ultrasound examinations were performed using high-frequency linear transducers (≥11 MHz). Splenic echotexture was graded on a four-point scale ranging from homogeneous (grade 1) to extensive, well-defined reticulonodular involvement (>25% of parenchyma, grade 4). Images were independently reviewed by blinded evaluators, with consensus grading applied. Statistical analyses assessed associations between age and splenic grade while accounting for repeated measurements.

Results

A reticulonodular splenic pattern was identified in 92% (62/67) of spleens examined. Grade 2 changes were most common overall, while grades 3 and 4 were most frequently observed in kittens between 0 and 4 months of age. The highest average splenic grades occurred between 2.25 and 4 months of age, followed by a general trend toward decreasing grade with increasing age. Despite this trend, statistical analyses did not identify a significant association between age and splenic grade. Notably, many cats older than 12 months continued to demonstrate a reticulonodular pattern. Serially evaluated kittens most often showed stable or decreasing grades over time.

Limitations

Limitations included the absence of confirmatory diagnostics such as splenic cytology, histopathology, or retroviral testing to definitively exclude subclinical disease. The sample size within individual age categories—particularly cats older than one year—was small, increasing the likelihood of Type II error. Variability in patient restraint, lack of universal hair clipping, and heterogeneous environmental and antigenic exposure may also have influenced image quality and splenic appearance.

Conclusions

The findings support that a sonographic reticulonodular splenic pattern is common in apparently healthy kittens and young cats and is likely a normal age-related variant when detected using high-frequency linear transducers. This pattern is most pronounced in early life and generally becomes less conspicuous with age, though it may persist beyond one year. In kittens and cats under 1.5 years of age, this splenic appearance should not automatically be interpreted as pathologic, and clinical context and signalment should guide further investigation.

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