The CSI approach to pruritic pets: interviewing the witnesses (owners) before assessing a crime scene (skin) (Proceedings)

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The CSI approach to pruritic pets: interviewing the witnesses (owners) before assessing a crime scene (skin) (Proceedings)

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Aug 01, 2011

Overview of the issue

The skin is the largest organ of the body and, in the view of many practitioners, it often accounts for the largest number of headaches. One would expect that since the skin is so easy to visualize, a diagnosis should be an easy task when compared with other, more hidden body organs. The problem is that many skin conditions have the same clinical presentation.

Studies have shown that dermatological disease is the second most common reason for presentation at a small animal practice (preventive health care is number one) and that pruritus is the most common presenting complaint in these patients (Hill et al 2006). Educated owners are becoming more knowledgeable these days of the diagnostic capabilities of the practitioner. They are more concerned about adverse and long-term reactions to symptomatic therapy and want to be sure that the therapy is the most appropriate for the condition. In short, they are in search of a diagnosis.

Veterinary dermatology is largely about detective work. This is, of course, most important in the "repeat offenders". It is important to interview the "witnesses" (caregivers) thoroughly before examining the "crime scene" (patient). Then collect appropriate samples (evidence) for evaluation, and finally follow a logical course of action to come to the right conclusion.

Objectives of the presentation

This presentation is designed as a "back to basics" presentation that is divided into 4 parts through the morning. The goal is to present a logical approach to the pruritic pet and to review diagnostic tests available to us. Some of the "tricks" that dermatologists use to increase the sensitivity of these tests will be presented. Discussion will include recommendations as to the correct timing in performing these tests. If time allows, the hope is to end with an audience participation session in working up these cases. Treatments available for these patients were presented in a previous lecture at this conference; this information is available elsewhere in these proceedings. Space limitations for the proceedings did not allow for inclusion of references. However, they are available upon request. Please feel free to email me at

The threshold theory of pruritus

The threshold theory suggests that an individual may tolerate a certain level of a stimulus without exhibiting clinical signs of pruritus (Reedy et al 1989). Put another way, as long as a patient remains below the critical threshold, it isn't pruritic. For example, a patient with a low-level sensitivity to both house dust mites and fleas may tolerate low levels of exposure to each individually, but may become pruritic when exposed to them concurrently. Allergen specific immunotherapy (ASIT) would not be needed as long as the flea burden is controlled. Therefore, our goal should be to determine the causes of pruritus that keep the pet below the "threshold".