Approach to lower limb edema: Clinical sciences

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Introduction0:00–1:00

Edema is an abnormal accumulation of interstitial fluid in the tissues. This occurs due to an imbalance between the hydrostatic and oncotic forces at the level of the capillaries.
The lower limbs are especially prone to the development of edema because of gravity. Based on location and symmetry, lower limb edema can be classified as unilateral and bilateral.
Unilateral lower limb edema is usually caused by a pathological process in the limb itself, such as DVT or compartment syndrome, while bilateral lower limb edema is usually due to systemic causes like heart, liver, and kidney failure.
A more severe type of edema is anasarca, where the whole body develops generalized edema, and can be caused by things like malnutrition, as well as cirrhosis, nephrotic syndrome, or even burns.When approaching a patient with lower limb edema, you should first perform an ABCDE assessment to determine if your patient is unstable or stable.

Unstable branch1:00–1:31

If your patient is unstable, you should first stabilize their airway, breathing, and circulation before trying to identify the cause.
This means that you might need to intubate the patient and establish IV access before continuing with your assessment.On the other hand, if the patient is stable, the next step is to obtain a focused history and physical examination.

Stable branch1:31–2:11

Your history should explore if one or both lower limbs are affected, time span over which edema developed, associated symptoms such as pain or shortness of breath, known acute or chronic medical conditions, and a list of medications.
Your physical exam should focus on describing the characteristics of the edema, like location, symmetry, and whether it’s pitting or non-pitting, as well as other features like skin discoloration and the quality of the pulse in the affected limbs.

Unilateral edema2:11–2:40

First, let’s start with conditions that cause unilateral edema. Unilateral edema generally affects a single limb and can be acute, that is developing over a period of 72 hours or less, or it might be chronic where it takes longer than 72 hours to develop.
You’ll want to rule out potentially life and limb-threatening conditions associated with unilateral edema first. Let’s take a look at the most important causes of acute-onset unilateral edema.

Acute: DVT2:40–3:37

A very important one is DVT, which is a blood clot that develops in the deep veins. Keep this in mind if your patient reports painful swelling, especially in the presence of DVT risk factors, like smoking or oral contraceptive use.
Exam might reveal edema, erythema, and warmth, perhaps a difference in calf circumference or a positive Homan sign, which means pain behind the calf when passively dorsiflexed.
At this point you should consider DVT, and calculate a Wells score. Additionally, you might need to order a D-dimer and ultrasound.
Wells score above 2, elevated D-dimer, and positive ultrasound findings showing a non-compressible deep vein with obstructed flow can confirm the diagnosis of DVT.

Acute: Cellulitis3:37–4:13

Another important differential is cellulitis. This is a bacterial skin infection involving dermis and subcutaneous tissue.
The patient may develop painful swelling, often associated with fever. If your examination shows erythema, warmth, induration, or abscess formation, then your patient most likely has cellulitis.
While this is a clinical diagnosis, you may want to order a CBC, and to collect any drainage or purulence from the affected area to send for culture.
Elevated WBC and positive cultures support the diagnosis of cellulitis. Next up is compartment syndrome.

Acute: Compartment syndrome4:13–5:01

The edema here is contained within fascial compartments, leading to a limb-threatening rise in intracompartmental pressures.
In this case, there’s usually a history of recent trauma, surgery, or burn; while a physical exam reveals the 6 Ps: pain, pallor, paresthesia, pulselessness, paralysis, and poikilothermia.
These findings are highly-suggestive of compartment syndrome, which is usually a clinical diagnosis. To support the diagnosis, you may measure intracompartmental pressures and order labs, such as serum creatine phosphokinase, or CPK, and urine myoglobin, all of which would be elevated.Finally, there’s Baker cyst rupture.

Acute: Baker cyst rupture5:01–5:44

Baker cyst is a collection of synovial fluid that develops in the popliteal fossa that can rupture and drain into the lower leg, causing edema.
History typically reveals a previous knee injury or osteoarthritis, while physical exam findings usually include redness, warmth, and sometimes a palpable cyst in the popliteal fossa.
At this point, you should consider Baker cyst rupture. You can confirm the diagnosis with an MRI showing an intermuscular fluid collection.
Now, let's discuss causes of chronic unilateral edema. One important cause is venous insufficiency.

Chronic: Venous insufficiency5:44–6:43

Your patient may report an aching discomfort and discoloration associated with swelling that developed gradually. Examination often reveals varicose veins and hemosiderin deposition, and less commonly venous ulceration.
If this is the case, your patient most likely has chronic venous insufficiency, which occurs due to faulty valves in the veins, and is the most common cause of gradual onset unilateral lower limb edema.
An ultrasound showing venous reflux confirms the diagnosis. Occasionally, venous reflux may affect both lower limbs.
Whether unilateral or bilateral, compression stockings are often prescribed to minimize any associated discomfort and decrease the likelihood of venous stasis ulcers.
Another chronic cause is lymphedema. If your patient is affected by chronic unilateral leg edema and has a history of malignancy, lymph node resection, or radiation in the pelvis, and physical exam shows skin thickening and non-pitting edema, consider that they may have lymphatic obstruction causing lymphedema.

Chronic: Lymphedema6:43–7:29

Lymphoscintigraphy is the diagnostic test of choice, which generally demonstrates abnormal lymphatic flow. Lymphedema may also affect both lower limbs if the lymphatic obstruction is near the center of the pelvis.
Manual techniques, such as massage, are often utilized to improve lymphatic edema as well as compression stockings.Finally, there’s complex regional pain syndrome, or CRPS.

Chronic: CRPS7:29–8:05

This is caused by local disruption in autonomic balance. If your patient has a history of lower limb trauma and severe pain long after the expected course of healing, and physical exam reveals atrophic skin changes, discoloration, and coolness to the touch, then you may suspect CRPS.
Keep in mind that this is a diagnosis of exclusion, so you’ll need to order some lab tests and imaging to rule out other conditions before you can confirm the diagnosis.Now, let's turn our focus to bilateral lower limb edema.

Bilateral edema8:05–8:17

Like with unilateral edema, we can also break these down into acute or chronic. First, let’s look at the acute causes of bilateral edema which includes iatrogenic causes or acute exacerbation of chronic disease.

Acute: Iatrogenic8:17–9:14

If your patient has a history of current or recent hospitalization, or has been recently started on a new medication, and has symmetric lower limb edema on exam without other specific findings, one possibility is iatrogenic edema, which, by definition, is caused by medical treatment or medication side effects.
Excessive IV fluid administration is a common cause of edema in hospitalized patients, and can quickly be determined by measuring fluid intake and output, to see if fluid input exceeds fluid output.
Additionally, you need to review your patient’s medication list to look for medications that can cause edema, such as calcium channel blockers, thiazolidinediones, and NSAIDs.Okay, now let’s take a look at the chronic causes like heart, liver, and kidney failure.

Chronic branch: Heart failure9:14–10:10

If your patient reports shortness of breath and chest heaviness associated with symmetrical swelling in the lower limbs, especially in the presence of cardiac risk factors, like diabetes and hypertension, or a known history of heart disease, and a physical exam reveals jugular vein distention, a new heart murmur or gallop, and bibasilar rales, then you should consider heart failure.
You can support diagnosis with labs showing an elevated BNP level; an ECG showing evidence of arrhythmia, ischemic changes, or myocardial hypertrophy; a chest x-ray showing cardiomegaly and pulmonary edema, and an echocardiogram that demonstrates impaired ventricular function.
On the flip side, you should consider liver failure if your patient has bilateral leg edema associated with abdominal fullness and yellowing of the eyes and skin, especially if they have a history of heavy alcohol use or viral hepatitis.

Chronic branch: Liver failure10:10–11:06

On physical exam, you may see ascites, jaundice, and signs of portal hypertension, like caput medusae, which refers to enlarged visible superficial veins on the abdomen radiating from the umbilicus.
Liver failure is a clinical diagnosis, but labs will show the presence of abnormal transaminases, an elevated bilirubin and INR, low platelets, and low albumin.
The definitive diagnosis of the underlying cause may require a liver biopsy, which could show hepatocellular injury in the case of hepatitis, or chronic fibrosis and necrosis in the case of cirrhosis.
Finally, you should consider kidney failure if your patient reports swelling in both lower limbs but is otherwise asymptomatic, or has nonspecific symptoms like fatigue and generalized weakness.

Chronic branch: Kidney failure11:06–12:30

Some patients may even have a history of chronic kidney disease or CKD, as well as CKD risk factors like uncontrolled hypertension or diabetes mellitus.
Physical exam may demonstrate a pericardial friction rub or uremic frost, which is when urea crystallizes on the skin. Typical lab findings in kidney failure include electrolyte imbalances, like hyperkalemia, elevated BUN and creatinine, and albuminuria, that is if the kidneys are still producing urine.
Renal ultrasound may reveal clues to the underlying cause of disease, like obstruction or atrophy, but a biopsy of the kidney is required to pinpoint the cause.Here’s a high yield fact!
Systemic conditions like heart, liver, and kidney failure are also a frequent cause of acute edema due to decompensation or exacerbation.
So, if you see bilateral lower limb edema develop acutely in your patient with known or suspected systemic disease, you’ll want to determine the underlying organ system affected.

Review12:30–13:09

Alright, as a quick recap… When evaluating a patient with lower limb edema, first characterize the edema by location, symmetry, and acuity.
Acute unilateral lower limb edema can be caused by DVT, cellulitis, compartment syndrome, or a baker cyst rupture, while chronic unilateral edema may indicate venous insufficiency, lymphedema, or CRPS.
On the other hand, acute bilateral edema is most often iatrogenic, but can be caused by exacerbation of chronic causes, such as heart, liver, or kidney failure.