Thursday, 09 December 2021

When it comes to dropsy, doctors often have to think like detective

ALTHOUGH the word “dropsy” sounds like something you might name a pet rabbit, in reality it was the name previously given to the condition we now know as oedema.

Both words have their origins in Greek (hydrops meaning “water” and oidein “swelling”) and both refer to the excess accumulation of fluid in body tissue or a body cavity.

Although fluid can accumulate anywhere in the body, I am focusing here on the legs.

Leg swelling is a very common symptom that we as medical professionals see most days.

In a simpler life, there would be one cause and one treatment for such a symptom but, alas, there are many causes.

This means that, if someone presents with leg swelling, it becomes a bit of a detective game for us doctors.

To know how something goes wrong, it is normally useful to know how things go when they are working perfectly.

In the case of leg swelling, it all has to do with the drainage of the leg. There are two key systems that we need to discuss: the veins and the lymphatics.

The lymphatic system consists of a network of tubules and drainage channels throughout the soft tissue which intersect at checkpoints otherwise known as lymph nodes.

These are the things that often get swollen and tender when we have an infection.

The lymphatic system contains lymph, a thin watery fluid that carries white blood cells around the body to fight infection.

It also drains excess fluid from soft tissues along with waste from cells and transfers it all back into the bloodstream.

If the lymphatic system becomes blocked, that gives rise to swelling downstream. We refer to this as lymphoedema.

The most common cause for this, at least in the developed world, is probably from the removal of lymph nodes during operations to remove cancers. Lymphoedema affects more than 200,000 people in the UK.

Unchecked, it can result in some really quite spectacular swelling. The term elephantiasis refers to severe lymphoedema.

There are many other causes for such swelling, of course, though less common. In developing parts of South America, central Africa and Asia, one particularly gross cause is something called lymphatic filiariasis.

This is damage to the lymphatic system caused by a group of nematode worms, introduced to the body in larval form through an infected mosquito bite.

The other system responsible for fluid throughout the body is, of course, the blood. Oxygen required by the tissues of the legs arrives attached to red blood cells via arteries.

These arteries then branch off into smaller arterioles and then eventually capillaries, which are so narrow that red blood cells have to squeeze through in single file.

Once offloaded of their oxygen, the blood cells emerge into veins.

These are the vessels responsible not only for taking the red blood cells back to the heart for replenishment, but also for draining all the fluid back to the body.

Veins have a battle against gravity and, considering they have lost the pressure of which arteries have the luxury, they need help.

To prevent backflow, veins have a series of valves on their inner walls.

Critically, in our legs they rely heavily on the contraction of surrounding muscles, the ones we use to walk, to force the blood back into the body.

If this system is not working well, it can result in accumulation of blood in the legs, resulting in pressure in the veins that pushes fluid out of the vessels and into the tissues. Simple age and wear and tear can often be the culprit. If the valves in the veins are not working well and if someone is living a sedentary lifestyle, both of the key mechanisms on which veins rely are absent. This is sometimes called dependent oedema.

Being overweight certainly does not help with this either and in pregnancy women sometimes experience leg swelling due to pressure on the veins upstream.

There are some medications that can cause ankle swelling but there are other causes that need more attention.

It is always worth considering how well the heart is working if someone presents with leg swelling, particularly if it is associated with becoming easily breathless on minimal exertion.

Congestive heart failure refers to the condition in which the heart muscle has been compromised in some way, thereby pumping less blood and, by extension, less oxygen with each beat of the heart.

This means two things. Firstly, one might become tired and fatigued due to reduced efficiency of the heart.

Secondly, the heart itself acts as the bottleneck, thereby creating swelling downstream.

People with congestive heart failure therefore might find they have fluid pooling not only in their legs but also in their lungs, depending on what side of the heart is lacking in function.

If this is suspected, your GP might suggest a blood test to check something called a BNP (brain natriuretic peptide) blood test.

If raised, it might suggest the heart is straining and this might result in a referral for an echocardiogram (an ultrasound of the heart). The GP may also request a chest X-ray.

The heart is not the only possible culprit, however.

There are too many possibilities to list in full here, with the kidneys and the liver being two other notable potential organs at fault.

Whatever the underlying cause, clearly having a swollen leg is not fun. The skin stretches and becomes more vulnerable under the pressure.

The term “pitting” is used to describe the dent that forms when the skin is pressed and this can range from very mild and subtle to really quite severe.

With oedema comes the increased risk of infection. Brown pigmentation can occur in chronic swelling related to the deposition of something called haemosiderin.

In other cases, the skin can become flaky, dry and itchy in what is known as venous eczema.

Apart from anything else, a swollen leg can be sore too.

In the past, treatment of swollen legs often consisted of the classic seemingly catch-all practice of blood-letting, sometimes with leeches.

Small calibre cannulae known as Southey tubes were also used to drain fluid but these are now obsolete.

Today, we advocate first and foremost a healthy diet, low in salt, and an active lifestyle to get the leg muscles pumping.

Keeping the legs raised above hip height when sitting is important and appropriate skin care is also key to avoiding damage.

For those with lymphoedema, specialist massage can be helpful and compression garments are useful in providing pressure to help boost the fluid flow up and out of the legs.

In really severe cases of oedema, regular bandaging can be really useful.

Before any form of compression is embarked upon, however, your GP might send you for something called an ABPI (ankle-brachial pressure index), which can be done by the nurse and checks that the arteries in the leg are working properly.

If not, you wouldn’t want to compress the leg and cut off the blood supply.

If all else fails, water tablets (diuretics) can be used to promote fluid loss by way of making you pee more, often necessary in those with heart failure.

So far, all the above causes would likely affect both legs (unless lymph nodes have been removed on one side only, for example).

If you suddenly develop a swollen calf that is red, hot and tender, one must consider whether a deep vein thrombosis has occurred. This is potentially serious as, if this dislodges, further clots can develop in the lungs (pulmonary embolism).

If such a symptom occurs, contact your GP straight away and they may arrange for an ultrasound and for some blood-thinning medication to be started.

Of course, an injury to the leg might also cause swelling so a one-sided swelling isn’t always due to a DVT.

Remember, whatever the underlying issue, prevention is better than cure so a healthy and active lifestyle will stand you in good stead when it comes to your legs and the veins within upon which they rely so much.

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