# Ultrasonography of the Tympanic Bulla in Llamas and Alpacas: Techniques and Physiological Findings

## TL;DR

This study shows that ultrasonography can be used to examine the tympanic bulla in llamas and alpacas without sedation, offering a non-invasive diagnostic alternative.

## Contribution

The study is the first to describe ultrasonographic techniques and findings for the tympanic bulla in healthy camelids.

## Key findings

- Ultrasonography successfully visualized the tympanic bulla and surrounding structures in live camelids.
- Llamas have a significantly longer visible lateral bulla wall compared to alpacas.
- Ultrasonography measurements showed high intra- and inter-observer reliability.

## Abstract

Computed tomography and radiography are considered the “gold standard” for visualizing the tympanic bulla and the diagnosis of otitis media in camelids. Both methods must be performed in a sedated or anesthetized animal. Ultrasonography, a non-invasive technique, requires no sedation or anesthesia of the animal. This study aimed to evaluate the ultrasonographic examination of the tympanic bulla and describe the sonographic approach and appearance of the visualized structures in healthy camelids for the first time. A 10 MHz linear probe was positioned caudal to the mandibular ramus and ventrally to the base of the ear using a lateral approach, both in the rostrocaudal and dorsoventral directions. The equipment used proved to be appropriate to visualize the tympanic bulla and surrounding structures in cadaver specimens and healthy live camelids. Measuring the visible lateral part of the bulla wall revealed that llamas have a significantly longer bulla wall than alpacas. The intra- and inter-observer reliability between two ultrasonographers measuring the bulla length yielded a significant consistency. The results of this study demonstrate the feasibility of ultrasonographic imaging to visualize the tympanic bulla in healthy camelids. Further studies evaluating the diagnostic potential of ultrasonography in llamas and alpacas suffering from otitis media are required.

This study aimed to perform ultrasonography of the tympanic bulla in healthy, non-sedated camelids for the first time. In the first step, dissection and sonography in cadaver specimens allowed the essential identification of the anatomical structures of the region of interest. Ultrasonography of the tympanic bulla was then performed on 71 healthy llamas and alpacas, and the length of the visible lateral bulla wall was measured sonographically. The reproducibility of measuring was determined between two examiners. Differences in length and the influences of gender, age, and body condition scores were monitored. A 10 MHz linear probe was positioned in the rostrocaudal and dorsoventral directions caudal to the mandibular ramus and ventral to the base of the ear using a lateral approach. The equipment used proved to be appropriate to visualize the tympanic bulla, the zygomatic bone, the paracondylar process, the external ear canal, and the parotid gland in the cadaver specimens and all live animals. Llamas revealed a significantly longer visible lateral bulla wall than alpacas, but its length was not influenced by gender, body condition score, or age. In alpacas, older females showed a significantly shorter tympanic bulla wall. The intra- and inter-observer reliability yielded a significant agreement. Based on this study’s results, ultrasonography may serve as a non-invasive diagnostic tool for detecting osseous and soft-tissue changes in camelids with otitis media.