What is trench foot?

Trench foot (also known as immersion foot syndrome) is a condition that results from feet being both cold and wet for a long period of time.¹ The cold and wet conditions result in skin and tissue breakdown, which increases the risk of infection and associated mortality.² Trench foot is a type of non-freezing cold injury- it occurs in cold conditions that are above freezing. Other examples of non-freezing cold injuries include: chilblains, frostnip and Raynaud’s phenomenon.¹ Trench foot was first described in 1812 by a French army surgeon, and was a common issue referred to during World War I, where soldiers were found standing in wet, muddy trenches over long periods of time.³ Trench foot became a cause of concern for the Allies, resulting in 75000 casualties in the British and 2000 in the American forces.⁴ 

This article will focus on exploring the causes, diagnosis and treatment of trench foot in addition to the specific stages of progression of trench foot.

Symptoms and causes

Symptoms

Trench foot is a progressive disease with a total of 4 defined stages; thus, symptoms vary depending on the progression/stage of trench foot. The initial symptoms begin with a tingling, itching sensation that can progress to numbness. Due to the cold conditions present with trench foot, this results in narrowing of the blood vessels (known as vasoconstriction), which can lead to feet becoming erythematous or cyanotic and can result in feet going from a bright red to pale.^{1, 2} 

Once an individual experiencing trench foot has left the previous cold and wet conditions, their feet will change colour.¹ A lighter-skinned person may develop a blue/purple colour.¹ However, discolouration in a darker-skinned person may not be as noticeable.¹ Significant swelling can occur with concurrent widening of blood vessels and result in the feet doubling in size (oedema). ²  

Prolonged exposure to cold and wet conditions can lead to a decaying smell and necrosis.²  

Causes 

Trench foot is a result of standing in wet, cold conditions over a prolonged period of time (one to three days on average).⁵ Conditions are generally above freezing, with cases of trench foot being reported in temperatures as high as 15°C.⁵ The combination of cold temperatures and moisture results in the capillaries (small blood vessels) of the feet weakening, restricting blood flow and damaging surrounding tissue.¹ To appreciate the nature of trench foot, we will discuss the four associated stages seen with trench foot. 

Stages of trench foot

Patients with trench foot may pass through the four stages of trench foot, whereby the lengths of each stage may vary significantly between individuals. As a result, some stages may be rather short and easy to miss.

Stage 1: cold exposure

Cold exposure is the initial stage of trench foot, associated with feelings of numbness or having feet or hands feel like blocks of wood.⁵ The key finding of stage one is a loss of sensation, resulting in patients becoming clumsy and having difficulty walking.⁶ Feet and hands may initially look bright red, but become pale or completely white due to narrowing of the blood vessels (vasoconstriction).⁶ This stage is considered generally painless.⁶     

Stage 2: after cold exposure

The second stage (the pre-hyperaemic stage) begins when the patient is removed from the cold, wet environment and makes continual attempts to rewarm themself.⁶ The hands and feet now become mottled and pale blue in light-skinned individuals.⁵ The discolouration present is hard to identify in darker-skinned individuals. The discolouration present indicates the slow return of circulation and blood to patients after cold exposure, with the duration of this stage varying between a few hours to several days.⁵ With the return of blood flow, pulses can gradually strengthen from their prior weakened state; however, the hands and feet will still remain cold. Swelling of the hands and feet may also be present in this stage.     

Stage 3: hyperaemia 

The third stage is referred to as the hyperaemic stage. This is defined as more blood than normal flowing to your body’s tissues or organs.⁷ As a result of increased blood flow to the hands and feet, they may present as bright red and swollen with strong pulses.5 The increased blood flow can cause the patient to feel extreme pain (hyperalgesia).⁵ This stage starts abruptly and can last from a few days to 6 to 10 weeks (in extreme cases).⁶ At this stage, tissue damage may not be present; however, blisters may develop in areas with tissue damage.^5,6 Areas of tissue that are severely damaged and cannot be repaired are rare, and if present, can lead to necrosis, seen in stage four.⁶       

Stage 4: post-hyperaemia

The final stage following hyperaemia can last for weeks to years, or may be permanent. This is where the hands and feet remain cool and become sensitive to the cold.^5,6 The appearance of the hands and feet remains normal (unless there was tissue loss). The majority of patients will develop chronic pain in response to the cold. Other symptoms commonly reported in patients include: hyperhidrosis (excessive sweating) and complex regional pain syndrome.^5,6 Only in severe cases will tissue necrosis occur, which requires amputation as treatment.  

What can be done about trench foot?

Diagnosis

Diagnosis of trench foot is made by a doctor through a physical exam. They are able to assess your foot for any injuries and can determine whether you have trench foot based on your recent history.¹ A key indicator for trench foot diagnosis is whether you have had prolonged exposure to a cold, wet environment.¹ To ensure your condition is not a result of an infection or other conditions (such as frostbite), your doctor may have you undergo a series of tests, including the likes of a white blood cell count, a sed rate test or an X-ray/bone scan if you are suspected of having a bone infection.¹

Treatment

If caught early, trench foot is entirely treatable. Treatments include: 

• Gentle rewarming of the foot
• Keeping feet dry and warm
• Resting and elevating your foot above your heart¹

Gently rewarming your foot is important as rapid rewarming can cause severe pain and swelling.¹

Prevention 

Trench foot is entirely preventable by:

• Avoiding cold/wet conditions
• Keeping feet dry 
• Keeping feet elevated
• Changing into a new pair of socks at least once a day
• Wearing non-constricting thermal clothing
• Avoiding malnutrition, dehydration and fatigue^1,6 

Complications

Trench foot that is left untreated can cause a variety of complications, including:

• Cellulitis
• Gangrene
• Sepsis
• Death ¹ 

Therefore, it is ever so important to contact a medical professional, such as a GP, if you suspect having trench foot, to prevent further complications and death. 

Summary

Trench foot is an uncommon condition caused by prolonged exposure to cold and wet conditions.³ Trench foot is entirely preventable by taking precautions to prevent exposure to cold and wet conditions, including removing wet socks, keeping feet dry and so forth.^1,6 This article discusses the different stages of trench foot, varying from mild to severe forms. Severe outcomes of trench foot, such as amputation and necrosis of tissue, are considered uncommon and rare; however, precautions should still be made to prevent the onset of trench foot.