(临床诊断学) 仁济临床医学院诊断学教研室 An Introduction to Clinical Diagnostics



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Skin


The skin has been called the “mirror” of an individual’s health, since diseases of any organ system is often reflected from it. Inspection is the most important part of the examination of the skin. Color, shape, skin eruption, muculae, roseolae papulaes wheals, maculopqpulaes wheals, maculopapulaes spider angioma, petechia, purpura, ecchymosis, hematoma are noted.

Obviously, skin color varies greatly from person to person and even from area to area on the same person. If possible by use of photographs or findings from earlier examinations, the previous skin pigmentation should be ascertained so that the present coloring can be evaluated more precisely. Usually, an area of increased or decreased pigmentation in skin that is otherwise normally pigmented signifies some abnormality-for example, postinflammatory hyperpigmentation or vitiligo.

The normally occurring skin pigments are melanin, hemoglobin, and carotenoids. Diffuse or localized melanin hyperpigmentation can be seen in such conditions as Addison’s hypoadrenocorticism, hyperthyroidism, pregnancy, hemochromatosis, and, most commonly, after exposure to sunlight. Melanin pigment is lacking in albinism (diffuse) and vitiligo (patchy). Erythema of the skin results from increased amounts of oxygenated blood in the dermal vasculature, such as might occur with fever or sunburn. Increases in deoxygenated blood hemoglobin result in a bluish tint to the skin (cyanosis) in such conditions as congestive heart failure, pneumonia, and congenital heart disease with right-to-left shunts. Localized red or purple changes result from vascular neoplasms, birthmarks, and hemorrhage into the skin (petechiae and ecchymoses). Pallor results if the hemoglobin content of the skin is decreased, as in anemia or shock.

Changes in the color of the skin may result from the deposition of pigments normally not found in significant quantities in the skin. Thus, the yellow or even greenish hue of jaundice results from increases in tissue bilirubin in the skin and sclerae. Carotenemia also results in yellowing or the skin but, unlike jaundice, the sclerae are not involved. This pigment change is caused by increased amounts of carotenoids in the skin and results from myxedema, diabetes, or ingestion of excess amounts of foods containing these pigments, principally carrots. Carotenemia is occasionally present during pregnancy. Certain metal salts, such as silver, gold, and bismuth, when administered over prolonged periods as mediacations, may be deposited in the skin and cause a greyish discoloration. Foreign bodies such as carbon-containing particles can also cause localized pigmentation of the skin-for example, tattoos.

Generally, palpation of the skin is used to confirm and amplify the findings observed on inspection. Inspection and palpation are inseparable interrelated and the examiner often uses them synchronously. Such findings as temperature, moisture, texture, elasticity, and presence of edema in the skin are detected by palpation.

Although the skin temperature is a poor gauge of the temperature of the inner body care, it may reflect a maladjustment in the thermoregulatory mechanism of the body. Thus, if a febrile person’s skin is warm and dry, one knows that sweat evaporation is not cooling the body and that the patient’s temperature is probably rising. On the other hand, if the skin is warm and wet, then the sweating is probably acting to reduce the temperature. Skin temperature depends on the amount of blood circulating through the dermis. Thus, localized hyperthermia indicates localized increased blood flow, as noted in localized burn or furuncle. Generalized skin hyperthermia suggests increased blood flow in the entire integument-for example, generalized sunburn and hyperthyroidism. Localized reduced blood flow results in coolness of that area-for example, peripheral arteriosclerosis and Raynaud’s phenomenon. Generalized cutaneous hypothermia signifies a generalized reduction of skin blood flow-for example, shock.

Sweating results from autonomic discharge arising from stimulation of either the central nervous system or the peripheral nervous system. Various combinations of skin moisture and temperature findings can be evaluated on the basis of the previously described physiologic principles. Thus, cool wet hands in indicate vasoconstriction and adrenergic sweating-a combination often resulting from autonomic nervous system stimulation caused by anxiety.

“Skin texture” refers to the quality and character of its surface. Is it rough and dry as it may become in hypothyroidism, the postmenopausal state, or “winter itch?” Is it velvety smooth, as seen in hyperthyroidism?

Loss of elasticity of the skin refers to its inability to return promptly to its normal position when stretched or pulled. This occurs most commonly in such areas of chronic actinic damage as the backs of the hands and the face. Increased elasticity of the skin and joints occurs in the Ehler-Danlos syndrome (cutis hyperelastica). Laxness or laxity of the skin refers to sagging or looseness of the integument and is seen following rapid weight loss and in the aged as the result of a lifetime of gravitational pull on the loose tissues of the face, buttocks, and other areas of the body.

Since the skin is a large depot for body water and electrolytes, much can be learned about the state of total body hydration by careful palpation. Thus, if the skin is loose, wrinkled, and lax in areas not previously subjected to chronic sun-damage, this suggests dehydration of the entire body. On the other hand, excess body water may also be stored in the skin and may be manifested by pitting edema, wherein firm pressure against the fluid-filled area results in an indentation in the skin.


Edema


Generalized edema is easily detected during inspection and usually results from nephrotic syndrome and sepsis and rarely from severe heart failure. Dependent edema involving the inferior extremities, on the other hand, is a consequence of systemic venous hypertension associated with right heart failure and can be detected by inspection.


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