Special Senses System

Ear, Canal - Dilation

Narrative
Comment:
Dilation of the external ear canal (Figure 1, Figure 2, and Figure 3) is usually secondary occlusion of the ear canal by plugs of sloughed keratin lamellae, cerumen, and necrotic debris that distends the canal. The lining epithelium may be hyperplastic. These findings usually occur in aged animals.
Recommendations:
Dilation of the ear canal should be diagnosed with an appropriate topography modifier (external ear canal, etc.). Dilation should be diagnosed as present (without assignment of a severity grade). Associated lesions such as inflammation or epithelial hyperplasia should not be diagnosed separately unless warranted by severity, though they can be described in the pathology narrative.
References:

National Toxicology Program. 1990. NTP TR-378. Toxicology and Carcinogenesis Studies of Benzaldehyde (CAS No. 100-52-7) in F344/N Rats and B6C3F1 Mice (Gavage Studies). NTP, Research Triangle Park, NC.

Abstract: https://ntp.niehs.nih.gov/go/11295

National Toxicology Program. 1996. NTP TR-455. Toxicology and Carcinogenesis Studies of Codeine (CAS No. 76-57-3) in F344 Rats and B6C3F1 Mice (Feed Studies). NTP, Research Triangle Park, NC.

Abstract: https://ntp.niehs.nih.gov/go/6054

Yoshitomi K, Brown. 1990. HR. Ear and pinna. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, CA, 227-238.

Abstract: https://www.ncbi.nlm.nih.gov/nlmcatalog/9002563
  • Image of canal dilation in the ear from a male F344/N rat in a chronic study

    Ear, Canal - Dilation in a male Fischer 344/N rat from a chronic study. Dilation of the external ear canal (arrow), characterized by plugs of sloughed keratin lamellae, cerumen, and necrotic debris that occludes and distends the canal.

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Ear, Canal - Dilation in a male Fischer 344/N rat from a chronic study. Dilation of the external ear canal (arrow), characterized by plugs of sloughed keratin lamellae, cerumen, and necrotic debris that occludes and distends the canal.
Ear, Canal - Dilation in a male Fischer 344/N rat from a chronic study. Dilation of the external ear canal (arrow), characterized by plugs of sloughed keratin lamellae, cerumen, and necrotic debris that occludes and distends the canal.
Ear, Canal - Dilation in a male B6C3F1 mouse from a chronic study. The dilated external ear canal (arrow), is distended by sloughed keratin lamellae, cerumen, and necrotic debris that occludes the canal.
Ear, Canal - Dilation in a male B6C3F1 mouse from a chronic study. The dilated external ear canal (arrow), is distended by sloughed keratin lamellae, cerumen, and necrotic debris that occludes the canal.
Ear, Canal - Dilation in a male B6C3F1 mouse from a chronic study. This higher magnification image of Figure 2 shows the dilated external ear canal (arrow) plugged with sloughed keratin lamellae, cerumen, and necrotic debris in greater detail.
Ear, Canal - Dilation in a male B6C3F1 mouse from a chronic study. This higher magnification image of Figure 2 shows the dilated external ear canal (arrow) plugged with sloughed keratin lamellae, cerumen, and necrotic debris in greater detail.

Author

Margarita M. Gruebbel, DVM, PhD, DACVP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Reviewers

Ruth E. Hurley, DVM, PHD, DACVP
Senior Veterinary Pathologist
Huntingdon Life Sciences
North Brunswick, NJ

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC