四诊

Chinese medical diagnosis depends on four basic methods: looking, listening and smelling, asking, and touching — together known as the Four Examinations (四诊, sì zhěn). The framework descends from the Yellow Emperor's Inner Classic and was elaborated through the Classic of Difficulties and Zhang Zhongjing's Treatise on Cold Damage. Each of the four collects a distinct kind of information, and each must be interpreted in light of the others. Relying on any single one in isolation tends to mislead; only the four examinations "considered together" (四诊合参, sì zhěn hé cān) yield a sound diagnosis.

Looking (望, wàng) gathers visible signs: the patient's overall vitality, complexion, body shape, posture, the tongue, the skin, and the appearance of any secretions or excretions. Two specific applications are paramount. "Inspecting the spirit" (望神, wàng shén) — the brightness of the eyes, the responsiveness of expression, the alertness of speech — yields a quick reading of how strong the upright qi remains and gives a strong prognostic indicator. Tongue inspection (see the dedicated article on Tongue Diagnosis) is one of the most distinctive diagnostic techniques in Chinese medicine, in which the body, color, shape, and coating of the tongue all serve as windows onto the state of the internal organs and the qi and blood.

The single Chinese verb wén (闻) covers both hearing and smelling. The clinician listens to the patient's voice (loud and forceful versus weak and faint), the quality of the breathing (coarse or fine), the character of any cough (dry or moist, productive or barking), and the presence of bowel sounds. The clinician also smells — the breath, the sweat, the stools and urine — for clues to the nature of the disorder. Loud, forceful sounds and rancid odors generally indicate excess and heat; quiet, faint sounds and bland odors generally indicate vacuity and cold.

Asking is the systematic interrogation of the patient — and, where necessary, the family — about the history and current state of the illness. The Ming dynasty physician Zhang Jingyue (張景嶽) condensed the key questions into a famous mnemonic, the "Ten Questions Verse," which is still taught today: ask about cold and heat, about sweating, about head and body, about urination and defecation, about appetite and thirst, about chest and abdomen, about hearing, about old diseases and current medications. For women, ask about the menstrual cycle and any obstetric history. In actual clinical practice asking is the backbone of the four examinations, the most extensive and the most consequential.

Touching (切, qiè) comprises two parts: pulse-taking and palpation. Pulse-taking is performed at the radial artery just behind the wrist, using three fingers to feel three sequential positions (cun, guan, chi) and to discriminate the depth, rate, force, and quality of the pulse — floating or sinking, slow or rapid, vacuous or replete, wiry, slippery, choppy, and so on. The system has its own dedicated article in the Pulse Diagnosis page. Palpation extends touching to the skin, limbs, chest, and abdomen, judging warmth and coolness, softness and hardness, tenderness, and the location of any masses or accumulations.