Introduction

Trench foot is a medical condition caused by prolonged exposure to cold, wet conditions, typically affecting the feet. It results in tissue damage due to impaired circulation and is characterised by symptoms such as numbness, swelling, and, in severe cases, necrosis.

Trench foot is caused by prolonged immersion of the feet in cold water, usually at temperatures between 0°C and 10°C (32°F to 50°F), which disrupts blood flow and damages tissues. Historically, it became widespread during World War I when soldiers were stationed in damp, cold trenches. Today, it can occur in various situations involving extended exposure to cold, wet environments, such as hiking, military operations, or natural disasters.

Understanding the pathophysiology of trench foot is crucial for effective prevention, early diagnosis, and treatment. Knowledge of how cold and moisture affect blood flow and tissues helps in minimising long-term damage and guiding proper medical interventions to prevent complications like gangrene or permanent disability.¹

The role of prolonged moisture and cold

Moisture exposure

Impact of wet environments on skin and tissues

Prolonged exposure to wet environments softens the skin, making it more vulnerable to damage. The skin becomes macerated, which leads to increased permeability and a higher risk of infection, as bacteria and fungi can more easily penetrate the skin. Swelling and fluid buildup in the tissues can also occur, leading to discomfort and further damage.²

Impaired skin barrier function and water absorption

The skin’s protective barrier is weakened in wet conditions, impairing its ability to regulate water balance. As a result, the skin can absorb excess moisture, leading to further swelling, maceration, and a higher risk of infection.²

Cold exposure

Vasoconstriction in response to cold

In cold environments, the body’s natural response is to constrict blood vessels (vasoconstriction) to conserve heat. However, this reduces blood flow to the extremities, including the feet, leading to oxygen deprivation and nutrient supply issues, which can damage tissues over time.²

Decreased tissue metabolism and oxygen supply

The cold also reduces metabolic activity in the tissues, further slowing the rate of cellular processes such as repair and waste removal. Reduced blood flow decreases oxygen and nutrient delivery to tissues, impairing their ability to function and heal. This combination of low oxygen levels and nutrient deficiency contributes to tissue damage and increases the risk of necrosis in severe cases.²

Mechanisms of damage to blood flow

Vasoconstriction

Initial response to cold temperatures

When exposed to cold, the body initially responds by constricting blood vessels (vasoconstriction) to preserve heat and maintain core body temperature. This reduces blood flow to the extremities, including the feet, in an attempt to prevent heat loss.³

Effect on peripheral blood vessels

Vasoconstriction primarily affects the smaller peripheral blood vessels, such as the arteries and veins in the feet, leading to restricted circulation. This limits oxygen and nutrient delivery to tissues, impairing their function and increasing the risk of injury.³

Capillary damage

Reduced blood flow and oxygen delivery

As blood flow to the capillaries diminishes due to vasoconstriction, tissues receive less oxygen and fewer nutrients. This leads to tissue hypoxia (lack of oxygen) and reduces the ability of cells to repair and regenerate.³

Formation of microvascular clots

Reduced blood flow increases the likelihood of blood clots forming in the tiny capillaries. These microvascular clots further impede circulation, exacerbating tissue damage by limiting blood flow and the delivery of oxygen and nutrients.³

Swelling and oedema in tissues

The lack of proper blood flow can lead to increased permeability of blood vessel walls, causing fluid to leak into surrounding tissues. This results in swelling (oedema), which can further damage cells and increase pressure on tissues, thereby exacerbating discomfort and potentially leading to injury.³

Disrupted circulation

Impaired rewarming process

Once the body is exposed to cold for extended periods, the normal process of rewarming is impaired. Without proper circulation, tissues have a reduced ability to regain heat and restore normal blood flow, prolonging the state of cold-induced injury and preventing effective recovery.³

Reduced venous return and poor tissue perfusion

The reduction in blood flow due to vasoconstriction and capillary damage also decreases the ability of veins to return blood to the heart (venous return). This leads to poor delivery of oxygen and nutrients to tissues (perfusion), worsening the effects of cold exposure and increasing the risk of tissue damage and necrosis.³

Tissue changes and cellular injury

Cell metabolism and oxygen deficiency

Impact of hypoxia on tissues

When blood flow is reduced due to cold exposure, tissues experience hypoxia, which means they receive insufficient oxygen. This leads to impaired cellular function, as cells rely on oxygen for energy production. Hypoxia can cause cellular damage, dysfunction, and even cell death if the oxygen deficit continues for too long.⁴

Reduced nutrient supply and waste removal

As blood flow decreases, the delivery of essential nutrients (like glucose and amino acids) to tissues is also limited, which impairs cellular processes such as energy production and repair. Additionally, waste products like carbon dioxide and lactic acid accumulate in tissues, leading to a toxic environment that further damages cells.⁴

Mitochondrial dysfunction

Mitochondria are the powerhouses of cells, responsible for producing energy (ATP) through a process called oxidative phosphorylation. In cold conditions, mitochondrial activity slows down, reducing energy production. This impairs the cell's ability to carry out normal functions, such as repair and maintenance, leading to cellular stress and damage.

When mitochondria function abnormally in cold temperatures, they can generate an excess of reactive oxygen species (ROS). ROS are highly reactive molecules that can damage cellular components, such as proteins, lipids, and DNA. This oxidative stress further contributes to cellular injury and tissue damage.⁴

Inflammatory response

The cold-induced injury activates the body’s inflammatory response. Cells release pro-inflammatory cytokines, which are signalling molecules that promote inflammation. These cytokines can lead to tissue swelling, increased blood vessel permeability, and more damage to surrounding tissues.

In response to the release of cytokines, immune cells like neutrophils and macrophages are recruited to the affected areas. While these cells attempt to repair damaged tissue, they also release more ROS and enzymes that can exacerbate oxidative stress and tissue injury. This creates a cycle of inflammation and further tissue damage.⁴

Clinical signs

Early signs

The skin becomes cold to the touch, pale in colour, and swollen due to reduced blood flow and fluid accumulation in tissues. Numbness may also occur due to impaired nerve function.

A sensation of "pins and needles" (paresthesia) may develop as nerves react to the reduced blood flow and cold exposure, signalling early nerve damage or irritation.⁴

Progressive symptoms

Blisters and ulcers

As the condition worsens, blisters may form on the skin, often filled with fluid. These blisters can break open, leading to open sores (ulcers) that are prone to infection.⁴

Tissue necrosis and gangrene

In extreme cases, when blood flow is severely compromised, the affected tissues begin to die (necrosis). Gangrene, the death of body tissue, can occur, and amputation may be required to prevent infection from spreading.⁴

Long-term effects

Chronic cold sensitivity

Individuals who have experienced trench foot may develop an increased sensitivity to cold in the affected areas, making it difficult to tolerate even mildly cold environments in the future.⁴

Persistent pain and movement limitations

After recovery, individuals may experience ongoing pain, stiffness, and limitations in movement due to long-term damage to tissues and nerves. This can result in reduced functionality and discomfort.⁴

Risk factors and vulnerable populations

Prolonged immersion in water or damp environments

Extended exposure to wet conditions, such as walking in cold, waterlogged environments, increases the risk of trench foot by preventing the feet from drying and causing prolonged cold exposure.⁶

Insufficient protective clothing and footwear

Wearing inadequate footwear or clothing that doesn't provide warmth or moisture protection makes individuals more susceptible to trench foot, especially in cold, wet conditions.⁶

Pre-existing health conditions

Conditions like diabetes and peripheral vascular disease compromise blood flow and reduce the body's ability to regulate temperature, making individuals more vulnerable to trench foot.⁶

Environmental factors

Harsh environmental conditions, particularly freezing temperatures or prolonged exposure to cold and damp areas, increase the likelihood of developing trench foot, especially without proper insulation and care.⁶

Prevention and treatment

Prevention strategies

• Keep the feet dry and warm, regularly changing wet socks and drying feet when exposed to damp conditions
• Wear waterproof, insulated footwear and moisture-wicking socks to help protect feet from cold and wet conditions⁷

Treatment approaches

• Gently rewarm the affected feet using warm (not hot) water or warm blankets, avoiding rapid rewarming to prevent further tissue damage
• Pain relief, such as anti-inflammatory medications, and the use of antibiotics to prevent or treat infection, are important for managing trench foot
• In severe cases, where tissue necrosis or gangrene occurs, surgical interventions like debridement (removal of dead tissue) or amputation may be necessary to prevent the spread of infection⁷

Conclusion

Trench foot is a serious condition resulting from prolonged exposure to cold and wet environments, which leads to impaired blood flow, tissue damage, and cellular dysfunction. Understanding how moisture and cold affect blood circulation, tissues, and cellular metabolism is crucial for both prevention and effective treatment. Early intervention, such as keeping feet dry, warm, and protected, can significantly reduce the risk of long-term damage. In severe cases, proper rewarming, pain management, and surgical intervention are essential to prevent complications like infection or gangrene. Raising awareness in high-risk environments can help reduce the incidence and severity of trench foot, improving outcomes for affected individuals.