Understanding “Channel Transmission,” “Combined Disease,” and “Bad Disease” in the Shanghan Lun from a Modern Medicine Perspective

Because of the great lapse of time, some concepts in the Shanghan Lun are very hard for modern learners to grasp. Without understanding them, it is difficult to accurately judge a condition and decide how to prescribe in clinical practice. Based on my own understanding, I believe some key terms in the Shanghan Lun can be understood through corresponding terms in modern medicine.

The terms “channel transmission” (chuanjing), “combined disease” (bingbing), and “concurrent disease” (hebing), which later physicians used extensively in interpreting the Shanghan Lun, can be understood through the relationship between primary and secondary diseases in modern medicine. And the “bad disease” (huai bing) caused by improper treatment by the physician can be equated with what modern medicine calls iatrogenic disease.

For example, when a Taiyang channel disease transmits inward, it may transmit to the Shaoyang channel, producing a concurrent disease of the Taiyang and Shaoyang channels. This can be understood as the Taiyang disease being the primary disease and the Shaoyang disease the secondary disease. Zhang Zhongjing’s classic formula for treating a concurrent Taiyang-Shaoyang disease is Chaihu Guizhi Tang, a combination of Guizhi Tang (which treats Taiyang disease) and Xiaochaihu Tang (which treats Shaoyang disease)—an approach that treats the primary Taiyang disease and the secondary Shaoyang disease together.

Sometimes, although a primary disease has given rise to some secondary diseases, if the primary disease is radically cured, the secondary diseases can resolve without treatment. Therefore not every concurrent disease requires treating both the primary and secondary diseases simultaneously. For many diseases, as long as one finds the root and radically cures it, even if all kinds of bizarre secondary diseases appear through channel transmission, they can all be cured by the same method. This explains why TCM exhibits the phenomenon of “treating different diseases with the same method.”

There are also diseases that are themselves merely secondary rather than primary. In the Shanghan Lun, these all result from channel transmission. For example, the Shaoyang syndrome triggered by a Taiyang disease has its root not in the Shaoyang channel but in the Taiyang channel. Although this secondary Shaoyang syndrome and a primary Shaoyang syndrome have the same symptoms, the treatment must differ. This is where “different diseases treated by the same method” comes into play.

If we can interpret concepts like “channel transmission,” “combined disease,” and “concurrent disease” from this angle, our thinking in clinical practice will become much clearer. This may perhaps reduce the misdiagnosis rate and avoid mistreatment.

“Bad disease” is also very common. It was not only common in Zhang Zhongjing’s time; bad diseases are also very common in modern society. The Shanghan Lun frequently says things like “Taiyang disease, where the physician erroneously used purgation”—this is a “bad disease” caused by misdiagnosis and mistreatment.

In modern medical terminology, this kind of “bad disease” is an iatrogenic disease. By modern medicine’s definition, an iatrogenic disease is a physical or mental disorder produced in a patient during the process of diagnosis, treatment, or prevention because of improper words, actions, or measures by the physician. So “bad disease” can be equated with iatrogenic disease.

Although my interpretation of these frequently recurring TCM terms in the Shanghan Lun using modern medical terminology may not be entirely correct, I venture to think it has considerable reasonableness and scientific validity. The essence of medicine is no different: whether Chinese or Western, whether traditional or modern, there are still many commonalities in the understanding of human disease. If these commonalities did not exist, medicine would have departed from the principles of science.