[김남엽 칼럼] ‘Leg swelling’ may indicate kidney function problem

Kim Nam-yeop, Director of Junkyung Oriental Medical Clinic

Patients frequently visit hospitals for lower extremity edema. Depending on the symptoms, swelling may be limited to the top of the foot, or in severe cases, the entire area below the knee may exhibit swelling. In instances of localized edema, the swelling occurs around the foot due to gravity, and it is often pitting edema, which indents when pressed with a hand and does not recover quickly. So, what causes edema?

When making kimchi, if you soak cabbage in salt water, moisture from the cabbage escapes into the salt water, causing the cabbage to lose water and wilt. This process of osmosis—where moisture moves from an area of low concentration to an area of high concentration—is similar to the mechanism of edema. If we think of cabbage as a blood vessel, then the salt water represents the interstitium (the space between cells). When the concentration of blood in the blood vessels becomes diluted and lower than that in the interstitium, water from the blood vessels escapes, leading to edema.

Edema is classified into two types: exudate and transudate. Exudate primarily occurs in response to inflammation. During inflammation, the gaps between vascular endothelial cells widen, which increases vascular permeability. This allows larger substances, such as blood cells or proteins in plasma, to leak into the interstitium (the space between cells), resulting in exudate that is relatively cloudy and has a high specific gravity (greater than 1.015), often mixed with blood or pus.

On the other hand, transudate refers to the leakage of clear fluid with a low specific gravity (less than 1.015) from the blood vessels due to changes in osmotic or hydrostatic pressure without altering vascular permeability. In cases of lower extremity edema, treatments that directly remove fluid, such as bloodletting, typically result in the release of clear, non-inflammatory fluids; thus, edema due to leakage is more common.

In the case of leakage (non-inflammatory edema), the underlying cause is often an imbalance between osmotic pressure (which encourages fluid to enter the blood vessels) and hydrostatic pressure (the outward water pressure). A decrease in osmotic pressure within the blood vessels or an increase in hydrostatic pressure can lead to fluid leakage from the vessels. When excessive fluid accumulates in the interstitial tissues, the adjacent lymphatic vessels may help remove this surplus; however, if this mechanism is impaired, edema will occur.

Under normal conditions, the concentration of fluids within blood vessels is higher than that in the interstitial tissues, largely because blood vessels contain more non-permeable proteins. These proteins do not diffuse into the interstitial tissues, thereby maintaining a certain level of osmotic pressure.

However, if a pathological condition leads to a low concentration of proteins in the blood, osmotic pressure weakens, which can contribute to edema. Conditions such as proteinuria due to impaired renal function or inadequate protein intake can result in such situations. Consequently, the resulting edema may gravitate downwards to the legs due to gravity, producing lower extremity edema.

An increase in hydrostatic pressure can occur when there is inadequate venous return. This means that blood cannot return smoothly to the heart through the veins, resulting in blood pooling and elevated pressure within the blood vessels. Congestive heart failure is a typical example of this phenomenon, leading to generalized edema.

In Oriental medicine, kidney function is critical in controlling water and fluids. The kidneys manage fluid metabolism by excreting unnecessary water or excess minerals (such as sodium and potassium) through urine, regulating osmotic pressure within the blood vessels to maintain homeostasis. A decline in kidney function may lead to frequent urination or difficulty in urination.

Even when urine or blood tests from a nephrologist yield normal results, edema may still occur due to functional issues within the kidneys. In such situations, medicinal herbs like aloe, poria, and rehmannia glutinosa may be utilized to enhance kidney function and alleviate edema.

For those experiencing leg edema, it is essential to evaluate your lifestyle habits. When sitting, avoid crossing your legs and keep your legs elevated above heart level. Refrain from wearing tight clothing and high heels, and engage in exercises that benefit your toes. Additionally, minimizing salt intake and regularly massaging your legs is crucial.

Particularly, individuals with diabetes should take extra care of their feet to prevent diabetic foot complications. If swelling occurs in the feet, or if the toes become cold or change color to blue or black, seeking treatment from a specialist promptly is vital. The health of your feet is interconnected with the health of your entire body, so maintaining proper foot health is crucial when you are well.

Understanding Lower Extremity Edema: Causes, Treatments, and Prevention

Patients with lower extremity edema often visit the hospital. Depending on the symptoms, only the top of the foot may swell, and in severe cases, the entire area below the knee may swell. Local edema typically occurs around the foot due to gravitational effects; most notably, it manifests as pitting edema, which sinks when pressed and is slow to recover. So why does edema occur?

The Science Behind Edema

When making kimchi, if you soak cabbage in salt water, the moisture inside the cabbage escapes, causing it to shrivel. This osmosis mirrors the principle of edema. If the cabbage represents a blood vessel, the salt water corresponds to the interstitium (the space between cells). When the blood concentration inside the vessels becomes diluted compared to the interstitium, fluid escapes, leading to edema.

Types of Edema

Edema can be categorized into two main types: exudate and transudate.

• Exudate: This occurs primarily due to inflammation, which increases vascular permeability. This allows larger substances, such as blood cells and proteins, to leak into the interstitium, resulting in a turbid fluid mixed with blood or pus.
• Transudate: This involves a clear fluid leaking out of the blood vessels due to changes in osmotic or hydrostatic pressure, typically without inflammation. In lower extremity edema, non-inflammatory fluid is commonly released.

Causes of Lower Extremity Edema

The causes of leakage (non-inflammatory edema) stem from an imbalance between osmotic pressure and hydrostatic pressure in the blood vessels.

Key Factors Affecting Edema

• **Osmotic Pressure Reduction:** A decrease in blood protein concentration can weaken osmotic pressure, leading to edema. Conditions such as proteinuria or insufficient protein intake contribute to fluid accumulation in the legs.
• **Hydrostatic Pressure Increase:** When the return of blood through the veins is compromised, it can cause pooling and increased pressure in veins. A common example is congestive heart failure, leading to generalized edema.

Oriental Medicine Perspective

In Oriental medicine, kidney function plays a pivotal role in controlling fluid metabolism. The kidneys excrete unnecessary water and minerals, regulating osmotic pressure to maintain homeostasis. Impaired kidney function can lead to frequent urination or difficulties in voiding.

Even with normal urine or blood test results, functional kidney issues may still cause edema. In such cases, medicinal herbs like aloe, poria, and rehmannia glutinosa can help enhance kidney function and alleviate edema.

Practical Tips to Manage Edema

If you experience leg edema, check your lifestyle habits. Here are some practical tips:

• Keep your legs elevated above your heart when sitting.
• Avoid crossing your legs.
• Wear loose clothing that doesn’t restrict blood flow.
• Limit high heel usage and incorporate toe exercises regularly.
• Steer clear of excessive salt intake and consider leg massages.

Special Considerations for Diabetics

Diabetic patients should pay special attention to foot health to prevent diabetic foot disease. If swelling occurs, or if there are changes in toe coloration or temperature, it’s essential to consult a healthcare professional promptly. Maintaining the health of your feet is foundational for overall well-being.

Case Studies and Experiences

Many patients have successfully managed their edema by implementing lifestyle changes and herbal treatments tailored to their conditions. For instance, one diabetic patient noted significant improvement in foot swelling after adhering to a strict sodium-reduced diet combined with regular toe exercises. Their proactive measures not only alleviated their edema but also boosted their overall health.

Conclusion

Understanding lower extremity edema, its causes, and effective management strategies is essential for improving quality of life. Patients experiencing swelling in legs should consult healthcare providers for personalized treatment options and guidance.