Ultrasound morphology of cecal appendix in pet rabbits

Cecal appendix is the terminal part of cecum and is characteristic of rabbit, among domestic animals. The purpose of this work is to evaluate its morphology upon ultrasound.

A prospective study was planned for the duration of approximately 1 year. Rabbits presented in the study period for abdominal ultrasound with no clinically evident alterations of the gastrointestinal tract were eligible for inclusion in the study. Abdominal ultrasound was performed under manual restrain with a high frequency linear probe (8-18 MHz).

Cecal appendix was visualized in 40/42 rabbits (95.2%) with median or left paramedian views. The wall appeared multilayered in accordance with normal bowel anatomy, and the luminal content showed in all cases an alimentary pattern. Measurement of appendix wall thickness (AWT) was possible in all 40 rabbits in which the appendix was visualized while measurement of the appendix diameter (AD) was possible in 39 rabbits. Reference intervals for AWT were 1.1-2.1 mm, and for AD were 3.9-8.8 mm. There was a negative correlation between age and AWT (r = - 0.35, P = 0.027) and a moderate positive correlation between AWT and AD (r = 0.71, P < 0.001).

Cecal appendix is recognizable via ultrasound in the vast majority of rabbits. We describe the normal morphological aspect of the appendix and we provide reference intervals for wall thickness and diameter of the appendix, in order to aid in the diagnosis of disorders of the appendix. The negative correlation between age and AWT indicates lower values of AWT associated with increasing age that could represent the physiological decrease in the immunitary function of the appendix in aged rabbits.