The normal metabolism of body fluids (津液, jīnyè) is a fundamental condition for maintaining the relative balance between the generation, distribution, and excretion of body fluids.
Abnormal metabolism of body fluids refers to the disruption in the distribution of body fluids, leading to insufficient generation or impaired excretion, resulting in slow circulation of body fluids within the body, which can cause pathological changes such as fluid retention, obstruction, and overflow.
The metabolism of body fluids is a complex physiological process that relies on the coordination of various physiological functions of multiple organs to maintain normal metabolic balance, particularly closely related to the lungs (肺, fèi), spleen (脾, pí), and kidneys (肾, shèn). Therefore, any abnormality in any organ or physiological function can lead to metabolic disorders of body fluids, resulting in insufficient body fluids or retention of body fluids, which can lead to the internal generation of dampness (水湿, shuǐshī) or phlegm (痰饮, tándrǐn).
(1) Insufficient Body Fluids
Insufficient body fluids refer to a deficiency in the quantity of body fluids, leading to a loss of nourishment and moisture for internal organs, orifices, and skin, resulting in a series of pathological changes characterized by dryness. Insufficient body fluids are often caused by heat (热邪, rèxié) or fire from the five emotions (五志之火, wǔzhì zhī huǒ), high fever, excessive sweating, vomiting, diarrhea, frequent urination, blood loss, or overuse of pungent and drying agents.
The pathological changes due to insufficient body fluids vary depending on the degree of fluid loss, distinguishing between damage to body fluids and damage to yin (阴, yīn). Body fluids (津, jīn) and liquid (液, yè) differ in properties, distribution, and physiological functions, leading to differences in the pathogenesis and clinical manifestations of insufficient body fluids. Body fluids are relatively clear and fluid, filling the blood vessels and moistening the organs, while liquid is thicker and less mobile, nourishing the marrow and joints. Damage to body fluids is more easily lost and replenished, while damage to liquid is more difficult to recover once depleted.
For example, excessive sweating in hot summer or thirst due to high fever; dry mouth, nose, and skin in dry seasons; and symptoms such as sunken eyes, thin skin, and even cramps during severe vomiting, diarrhea, or frequent urination are primarily manifestations of body fluid damage. In contrast, during the late stages of heat illness or chronic illness damaging yin, one may observe a red, glossy tongue with little or no coating, dry lips and tongue, emaciation, and dry skin and hair, indicating depletion of yin fluids and the potential for wind (风, fēng) movement.
Although damage to body fluids and liquid depletion differ in pathogenesis and clinical manifestations, they are interrelated and influence each other. Generally, mild cases are classified as body fluid damage, while severe cases are classified as yin damage. Body fluid damage does not necessarily imply yin damage, but yin damage will always involve body fluid damage, hence body fluid damage is a gradual process leading to yin damage, while severe yin damage results in significant body fluid depletion.
Since body fluids and blood (血, xuè) share a common source, a deficiency or depletion of body fluids inevitably leads to a deficiency of blood, resulting in pathological changes such as internal heat (内生虚热, nèi shēng xū rè) or wind generated from dry blood (血燥生风, xuè zào shēng fēng). If body fluids are depleted, blood volume decreases, leading to stagnation and obstruction of blood flow, ultimately resulting in both body fluid deficiency and blood stasis (血瘀, xuè yū).
Qi (气, qì) and body fluids are mutually dependent and interrelated. The metabolism of body fluids relies on the ascending and descending movements of qi; qi has the functions of consolidation and transformation, which can control and regulate the generation and excretion of body fluids. Qi also depends on body fluids for its existence; if a significant loss of body fluids occurs, qi loses its support, leading to a critical state of qi and body fluid loss.
(2) Accumulation of Dampness
The distribution and excretion of body fluids are two important aspects of body fluid metabolism. Dysfunction in either distribution or excretion can lead to abnormal stagnation of body fluids within the body, becoming the fundamental cause of internal dampness and phlegm.
Obstruction in the distribution of body fluids refers to the inability to distribute body fluids normally, leading to slow circulation or local retention, resulting in the internal generation of dampness and phlegm. Many factors can cause obstruction in the distribution of body fluids, involving the lung’s (肺, fèi) dispersing and descending functions, the spleen’s (脾, pí) transformation and transportation, the liver’s (肝, gān) regulation, and the patency of the San Jiao (三焦, sān jiāo) water pathways, but the primary cause is often dysfunction of the spleen’s transformation and transportation.
Obstruction in the excretion of body fluids primarily refers to the reduced ability to transform body fluids into sweat and urine, leading to fluid retention and edema (水肿, shuǐzhǒng). The transformation of body fluids into sweat is mainly governed by the lung’s dispersing function, while the transformation into urine is primarily governed by the kidney’s (肾, shèn) vaporization function. Weakness in lung and kidney functions can lead to fluid retention and edema, but the kidney’s vaporization function plays a dominant role in excretion.
Although obstruction in the distribution and excretion of body fluids are distinct, they often influence each other and are causally related, resulting in the internal generation of dampness and phlegm, leading to various pathological changes.
In summary, the accumulation of dampness primarily leads to pathological changes such as damp turbidity obstruction, phlegm condensation, and fluid retention.
1. Damp Turbidity Obstruction: Damp turbidity obstruction primarily involves the spleen’s inability to transport dampness. Dampness as a disease is often insidious and difficult to detect. Common manifestations include swelling and coldness, back pain, a heavy head, or limb heaviness, sores, and ulcers. Dampness is persistent and can cause various diseases, leading to stagnation of qi and symptoms such as distension and fullness, or various forms of damp phlegm diarrhea.
2. Phlegm Condensation: Phlegm and fluid are pathological products formed due to dysfunction of the organs and metabolic disorders of body fluids, which can lead to complex pathological changes. For details, refer to Chapter Seven on etiology.
3. Fluid Retention: Fluid retention is often caused by dysfunction of the lung, spleen, and kidney, leading to metabolic disorders of body fluids and resulting in edema. If fluid overflows into the skin, it can cause swelling of the face, eyelids, and limbs, and in severe cases, generalized edema. If dampness accumulates in the abdominal cavity, it can lead to abdominal swelling and ascites.
Qi can transform water; if water stagnates, qi is obstructed. Disorders in body fluid metabolism, dampness, and phlegm retention can lead to pathological changes in qi stagnation: for example, if phlegm obstructs the lungs, it can cause lung qi stagnation, leading to symptoms such as chest fullness, cough, and difficulty lying flat; if phlegm obstructs the heart, it can impede heart qi, leading to palpitations and chest pain; if phlegm stagnates in the middle jiao, it can obstruct the spleen and stomach qi, causing symptoms such as dizziness, fatigue, abdominal distension, and nausea; if phlegm stagnates in the limbs, it can obstruct the flow of qi and blood, leading to heaviness and pain in the limbs.
(3) Imbalance in the Relationship Between Body Fluids, Qi, and Blood
Imbalances in the relationship between body fluids, qi, and blood are commonly observed clinically, primarily manifesting as water stagnation and qi obstruction, qi loss with fluid loss, dryness of body fluids and blood, and blood stasis due to body fluid deficiency.
1. Water Stagnation and Qi Obstruction: Water stagnation and qi obstruction refer to the pathological changes caused by the retention of body fluids, leading to qi stagnation. The generation, distribution, and excretion of body fluids depend on the ascending and descending movements of the organ qi; when qi moves, water moves. If the qi transformation is abnormal, it can lead to the accumulation of dampness and phlegm, which obstructs the movement of qi. For instance, if phlegm obstructs the lungs, it can cause lung qi stagnation, leading to symptoms such as chest fullness, cough, and difficulty lying flat; if phlegm obstructs the heart, it can impede heart qi, leading to palpitations and chest pain; if phlegm stagnates in the middle jiao, it can obstruct the spleen and stomach qi, causing symptoms such as dizziness, fatigue, abdominal distension, and nausea; if phlegm stagnates in the limbs, it can obstruct the flow of qi and blood, leading to heaviness and pain in the limbs.
2. Qi Loss with Fluid Loss: Qi loss with fluid loss occurs when a significant loss of body fluids leads to the loss of qi, resulting in a critical state of both qi and body fluid deficiency. This is often caused by excessive sweating or severe vomiting and diarrhea.
3. Dryness of Body Fluids and Blood: Dryness of body fluids and blood refers to a deficiency or depletion of body fluids, leading to the internal generation of heat and dryness, or the generation of wind from dry blood. Body fluids are an important component of blood, and both share a common source from the refined essence of food and water. If body fluids are severely depleted due to high fever or burns, or if yin deficiency leads to the consumption of body fluids, it can result in dryness of body fluids and blood, leading to symptoms such as irritability, dryness of the nasal passages and throat, thirst, muscle wasting, scanty urination, a red tongue with little moisture, and a thin, rapid pulse.
4. Blood Stasis Due to Body Fluid Deficiency: Blood stasis due to body fluid deficiency refers to the pathological changes resulting from insufficient body fluids, leading to poor blood circulation. Adequate body fluids are essential for maintaining the fullness of blood vessels and smooth blood flow. If body fluids are significantly consumed due to high fever, burns, vomiting, or excessive sweating, it can lead to both body fluid and blood deficiency, resulting in blood stasis. Clinical manifestations may include a purplish tongue or the appearance of petechiae.
