Mucous membranes in dogs and cats

Mucous membrane color and capillary refill time (CRT) are used to estimate the adequacy of peripheral perfusion. Normally the oral membranes are assessed; however, caudal mucous membranes (prepuce or vagina) also can be evaluated. The color of the caudal membranes should be compared with that of the oral membranes in polycythemic cats and dogs regardless of whether a cardiac murmur is detected. If the oral membranes are pigmented, the ocular conjunctiva can be evaluated. The CRT is assessed by applying digital pressure to blanch the membrane; color should return within 2 seconds. Slower refill times occur from dehydration and other causes of decreased cardiac output because of high peripheral vasoconstriction.

However, the CRT is normal in anemic animals unless hypoperfusion is also present; the CRT can be difficult to assess in severely anemic animals because of the lack of color contrast. Petechiae in the mucous membranes may be noticed in dogs and cats with platelet disorders. In addition, oral and ocular membranes are often the sites where icterus (jaundice) is first detected. A yellowish cast to these membranes should prompt further evaluation for hemolysis or hepatobiliary disease.