Introduction

Have you ever seen a child or an image of a child with a swollen belly, puffy face, dry, brittle hair and dry skin? The swelling you are seeing is called edema and is defined as fluid retention in the tissues.¹ Edema is a hallmark feature of kwashiorkor, which is one of two main types of severe protein-deficient undernutrition, meaning a person is severely lacking protein in their diet.¹ It occurs commonly in children, particularly in underdeveloped countries where there are high levels of food security and poverty.¹ But why does swelling (edema) happen in kwashiorkor? This article will explore what kwashiorkor is in detail, what edema is, and why swelling occurs specifically in kwashiorkor. It is vital to understand this process, as early detection of kwashiorkor can improve its outcomes.¹

What are malnutrition and kwashiorkor?

Kwashiorkor is a form of malnutrition, defined as an imbalance between the nutrients your body needs to survive and the nutrients it actually receives.² A person can be malnourished either from an overall excess of calories or from not consuming enough calories and nutrients.² Your body needs a variety of nutrients to maintain its normal functioning, and having a lack or excess of these nutrients can harm your body.² Undernutrition, the lack of sufficient nutrients, can be divided into two categories: macro- and micronutrition.² Macronutrient deficiency is a deficiency of proteins, carbohydrates and fats.² Micronutrient deficiency, on the other hand, is a deficiency of vitamins and minerals.²  Overnutrition, which is an equally significant problem, will not be discussed as it falls outside the scope of this article.

Kwashiorkor is one of the two main types of severe protein-energy (macronutrient) undernutrition.² Marasmus, the second type of macronutrient deficiency, is a deficiency of all macronutrients- protein, carbohydrates and fats, while people affected by kwashiorkor only lack protein in their diet.² People with marasmus generally lack calories, while people with kwashiorkor may not be deprived of calories but are lacking in protein-rich foods.² As a result, children with marasmus do not have signs such as swelling of their limbs, face and belly, such as in kwashiorkor.

Kwashiorkor is rare in middle- to upper-income countries and is typically found in conjunction with high rates of poverty and limited access to food.² Countries with high rates of infectious diseases, war, and natural disasters also have higher incidences of kwashiorkor, as these factors contribute to a lack of access to protein-rich diets.² Kwashiorkor can occur at all ages, but it most commonly occurs in children who have recently transitioned from breastfeeding to a diet with too many carbohydrates and not enough protein.² This makes children aged 1 to 5 most vulnerable to getting kwashiorkor.² In contrast, infants less than 1 year old are more prone to marasmus.⁴

What is edema?

Edema is the buildup of fluid in your tissues, often in the feet, legs and ankles. Edema can affect anyone and has various underlying causes, including kwashiorkor.³ In kwashiorkor, the face is commonly affected by edema too.³ Other signs associated with edema are the skin over the swollen area appearing shiny and stretched, and difficulty walking if the lower limbs are swollen.³ 

In other conditions, edema can be caused by spending a lot of time standing, causing bodily fluid to accumulate in the legs. If one's vein valves are weakened, it is also harder for blood to be pushed back up to the heart, causing of fluid in the legs. However, the cause of edema in kwashiorkor is due to the protein deficiency itself and will be discussed later.

It is important to note that in kwashiorkor, this swelling may be misleading and is not fat, but rather a sign of fluid imbalance and undernutrition.² This swelling can often hide the actual severity and extent of malnutrition.

How the body normally regulates fluids

Typically, fluids flow between the blood vessels and the surrounding tissues, supplying them with essential nutrients. The four ways the body maintains fluid regulation are through normal blood vessel pressure, oncotic pressure (the “pulling force” inside blood vessels), permeability( “leakiness”) of capillary walls and normal lymphatic drainage system.⁵ 

If blood vessel pressure builds up excessively, as in heart failure, consider it akin to water in a hose that is turned up too high: fluid is pushed out into the surrounding tissue, causing swelling. 

In kwashiorkor, the main problem is that the oncotic pressure is low. The main protein inside the blood is called albumin, and the protein hangs on to water molecules like a sponge. If there is not enough protein, the pulling force is too weak and fluid leaks out, causing swollen legs, arms and face in children with kwashiorkor.⁵ When blood vessels become leaky, such as during infections or inflammation, they allow fluid and proteins to escape into the surrounding tissues. This often exacerbates kwashiorkor, as infections that cause capillary leakiness are more prevalent in the same regions where protein malnutrition is widespread.⁵ 

Lastly, the lymphatic system is like a drain for excess fluid from tissues. If it is blocked, such as after surgery or in certain infections, fluid cannot be adequately drained, causing edema.⁵

What goes wrong in kwashiorkor?

A lack of protein in the diet leads to low levels of protein in the blood; as mentioned earlier, this protein is primarily known as albumin.⁵ In kwashiorkor, the body also produces fewer proteins, worsening the already low protein levels in the body. Proteins act as a sponge for keeping water inside the blood vessels, as they are too large to exit the blood vessels, so they hold water inside.⁵ Therefore, when there is not enough protein in the body, such as in kwashiorkor, excess fluid escapes into the surrounding tissues, leading to swelling of the legs, arms and face.⁵

A common misconception of kwashiorkor is that the belly also swells by the exact mechanism; however, it is not directly related to protein deficiency.⁶ A swollen belly is caused by liver disease due to malnutrition. The liver becomes extremely enlarged, which is what causes the protruding belly. This is also made worse by weakened abdominal muscles.⁷ However, the cause of a swollen belly in kwashiorkor is not due to oedema itself. 

Other signs and symptoms of kwashiorkor

As mentioned previously, edema (swelling) of the legs, arms and face is the key sign of kwashiorkor, also helping to differentiate from marasmus. The swollen belly is also a key feature of kwashiorkor, which is not present in marasmus. Additional signs include thin, dry skin, which may appear darker.⁷ The hair of a child with kwashiorkor is typically lighter than usual and falls out very easily. These children are also behind on their growth and are often dehydrated, irritable and fatigued.⁷ These children are also predisposed to having low blood sugar.⁷

Treatment and prevention of kwashiorkor

The treatment of the edema associated with kwashiorkor is linked to the treatment of the protein deficiency itself. The most essential part of both treating and preventing this disease is maintaining a diet rich in protein (preferably animal protein) with a sufficient intake of vitamin B12.⁸ It is crucial to note that reintroducing protein and nutrients must be done slowly. Treating any underlying infection also improves kwashiorkor.

In terms of prevention, educating families and promoting nutrition is key. Breastfeeding support should be provided to mothers, as well as routine dietary screening once a baby is weaned off breast milk. Long-term food and security programs are also key in preventing kwashiorkor on a global scale. 

Conclusion

In light of the points above, kwashiorkor is a life-threatening condition that can often go masked due to swelling of the arms and legs, which may lead to a “healthy” appearance of the child.¹ It occurs most commonly in low-income countries due to diets lacking sufficient protein.¹ The swelling of the arms and legs comes from the lack of protein in the diet itself, while the protruding belly is due to liver enlargement.⁶ It is essential to recognise the early signs of kwashiorkor as it is a preventable disease; however, public health interventions need to be implemented to educate communities about kwashiorkor as well as to introduce affordable protein and nutrient-rich foods into these communities.⁸ With early intervention, kwashiorkor can be treated and is a preventable disease with proper nutrition and education.