Correlation between age and ultrasonographic B-mode appearance of cecum in 29 healthy cats

Background: The sonographic appearance of the cecum has been described previously in young cats. We believe that there may be different aspects of the cecum in healthy subjects of different ages. Purpose: The present study aims to describe the B-mode ultrasonographic appearance of cecum in healthy cats and its correlation with age. Methods: Twenty-nine clinically healthy cats underwent ultrasonographic evaluation (two-dimensional ultrasound with a 7.5\u201313 MHz linear transducer). The cecum was identified in transverse and longitudinal section. Two different patterns of ultrasonographic appearance were identified: hypoechoic homogenous and heterogeneous with a nonuniform hyperechoic band parallel to the lumen. Cecal content was recorded and wall measured (in longitudinal section) in the thin portion (S1, next to the colic junction) and in the thicker portion (S2, cul-the-sac). Medium values and standard deviations were recorded. Correlation between age and wall thickness (age/S1 and age/S2) was evaluated with Pearson correlation test. Friedman test was performed to examine the relationship between S1 and S2. Correlation between age and ultrasonographic appearance was evaluated with a logistic regression (using age as a continuous variable and binary output). Findings: Cats ranged from 1 to 14 years old (SD = 0.6). The cecal wall appeared hypoechoic homogenous in 19 cats while heterogeneous in 10. Logistic regression showed a correlation between age and ultrasonographic appearance (older cats tend to have an heterogeneous cecal wall, P = 0.016). Cecum content was gassy (15 cats) or mucous (14 cats). Medium thickness value was 0.20 cm (ranging 0.13\u20130.34 cm, SD = 0.04) in S1 and 0.27 cm (ranging 0.16\u20130.38 cm, SD = 0.05) in S2. Values of S1 and S2 were statistically different (P = 0). No significant statistical correlations were found between age/S1, age/S2, and age/luminal content (P > 0.05). Conclusion: Normal ultrasonographic appearances of feline cecum and their correlation with age are described. The cecal wall tends to be hypoechoic and homogenous in young cats, while heterogeneous in older individuals. We hypothesize that heterogeneous appearance of ce- cal wall could be explained by \u201ccecal tonsil\u201d theory: with aging, the immunostimulation of the lymphatic structures that are plenty in the cecal wall could lead to echostructural modifica- tions. However, our hypothesis should be confirmed by histopathological examination even if all cats in our study were healthy and remained asymptomatic for 6 months after the initial evaluation