Use of high-frequency ultrasonography for evaluation of skin thickness in relation to hydration status and fluid distribution at various cutaneous sites in dogs

Objective—To assess the usefulness of high-frequency diagnostic ultrasonography for evaluation of changes of skin thickness in relation to hydration status and fluid distribution at various cutaneous sites in dogs. Animals—10 clinically normal adult dogs (6 males and 4 females) of various breeds. Procedures—Ultrasonographic examination of the skin was performed before and after hydration via IV administration of an isotonic crystalloid solution (30 mL/kg/h for 30 minutes). A 13-MHz linear-array transducer was used to obtain series of ultrasonographic images at 4 different cutaneous sites (the frontal, sacral, flank, and metatarsal regions). Weight and various clinicopathologic variables (PCV; serum osmolality; and serum total protein, albumin, and sodium concentrations) were determined before and after the infusion. These variables and ultrasonographic measurements of skin thickness before and after hydration were compared. Results—Among the 10 dogs, mean preinfusion skin thickness ranged from 2,211 μm (metatarsal region) to 3,249 μm (sacral region). Compared with preinfusion values, weight was significantly increased, whereas PCV; serum osmolality; and serum total protein, albumin, and sodium concentrations were significantly decreased after infusion. After infusion, dermal echogenicity decreased and skin thickness increased significantly by 21%, 14%, 15%, and 13% in the frontal, sacral, flank, and metatarsal regions, respectively. Conclusions and Clinical Relevance—Cutaneous site and hydration were correlated with cutaneous characteristics and skin thickness determined by use of high-frequency ultrasonography in dogs. Thus, diagnostic ultrasonography may be a useful tool for the noninvasive evaluation of skin hydration in healthy dogs and in dogs with skin edema.