Clinically accurate diagnosis can be made in light of the symptoms and signs as well as the regions covered in cyclical flowing and the viscera connected with. In the Chapter of Tendons of the Meridians in Lingshu (Spiritual Pivot), the syndromes of the twelve meridians, fifteen collaterals and twelve tendons were recorded. The twelve meridians, the core of the meridian system, were summarized in terms of the disorders of the regions covered in their cyclical flowing and the diseases of the viscera associated with them.
Such a record is known as "diseases caused by morbid changes of the meridians" and "the diseases included in the indication of the meridians", which can be used as the principle for syndrome differentiation. Besides, the distribution of the meridians is also helpful for syndrome differentiation of the viscera. Examples are  stomachache and vomiting due to disharmony between the liver and stomach; cough due to invasion of liver fire into the lung; hernia due to cold retention in the liver meridian; red eyes due to hyperactivity of liver fire; and dizziness and headache due to hyperactivity of liver yang.
These symptoms are all caused through the meridians and may appear simultaneously or one after another. Syndrome differentiation with the eight principles, syndrome differentiation with the six meridians as well as syndrome differentiation of defensive qi, qi nutrient qi, and blood are all related to the doctrine of meridians in terms of their origin.