MRI features of presumed normal palatine tonsils in dogs

Objective: To describe the MRI characteristics of normal palatine tonsils in dogs.

Materials and methods: Retrospective study of 95 dogs with presumed normal tonsils. Tonsillar margination, shape and signal intensity in pre- and postcontrast studies were assessed and the cross-sectional area was measured at the point of maximal size on transverse images.

Results: In all cases the tonsils were located with their largest transverse cross-section at the level of the temporomandibular joints. Their margins were well-defined in all dogs; in 57 (60%) the borders were smooth and in 38 (40%) slightly irregular. The majority (96%) of the tonsils were rounded to oval in cross-section and the remainder were elongated. All tonsils were hyperintense to the medial pterygoid muscles in T1-weighted, T2-weighted, FLAIR and T2* gradient echo images and they showed either homogeneous (53%) or heterogeneous (47%) signal intensity. Contrast enhancement was marked (65%) or moderate (33%) in the majority of animals. Median tonsillar cross-sectional area was approximately 29 mm² (90% confidence interval: 10.0 to 64.4 mm² ). There was significant positive correlation between bodyweight and tonsillar cross-sectional area and a weak negative correlation between age and tonsillar cross-sectional area.

Clinical significance: MRI is of value in assessing normal palatine tonsils in dogs. This study could be used as a baseline for the investigation of the value of MRI in assessment of tonsillar disease in dogs.