Causes of limb swelling
Limb swelling is a common and important symptom for medics to be able to interpret when taking a history, examining, and choosing investigations. It can be helpful to look at causes of single-sided (unilateral) or both-sided (bilateral) limb swelling separately. Most unilateral causes result from a problem at the site of swelling, and bilateral from a systemic problem.
Figure 1: Causes of unilateral limb swelling: lymphoedema, post operative swelling, trauma (e.g. sprain, fracture, inflammation, and bleeding), compartment syndrome, soft tissue swelling/mass (e.g. abscess), deep vein thrombosis (DVT), cellulitis, Baker’s cyst, varicose eczema, thrombophlebitis, joint swelling (e.g. infection of gout), anaphylaxis, filiriasis. Medical illustration by Dr Ciléin Kearns (Artibiotics). PDF posters here.
Unilateral causes of limb swelling
I’d like to draw some extra attention to deep vein thrombosis (DVT), a blood clot in the venous circulation. These arise from blood stasis (e.g. during a long journey while seated, or when the limb is immobilised in a cast), or anything that makes blood more likely to clot ie prothrombotic (e.g. infection, cancer, surgery, contraceptive pills, clotting disorders). People present with a painful, red, swollen, limb, and there will often be the risk factors mentioned in their story.
Figure 2: DVT and its mimics (Baker’s cyst, cellulitis, varicose eczema, thrombophlebitis), and Pulmonary Embolism (PE). Medical Illustration by Dr Ciléin Kearns (Artibiotics). PDF posters here!
Medics care about these clots because fragments can embolise (break off) into the circulation. The path they travel narrows at the lung (pulmonary) arteries, where these clots get stuck and reduce or stop blood flow beyond the blockage (pulmonary embolism). This affects the lungs function and can kill. People feel breathless, and sharp chest pain when breathing in (pleuritic pain). If a patient with a swollen leg has chest pain or breathlessness - consider PE.
Note the mimics of DVT:
A few diagnosis can look similar to DVT’s, including a Bakers cyst, varicose eczema, thrombophlebitis, and cellulitis. The treatments are different so being able to distinguish between them is important. History, examination, and investigations can exclude or confirm these causes. A DVT can often be caught on an ultrasound scan.
Figure 3. Causes of bilateral limb swelling: drug side effects and misuse, heart failure, inferior vena cava (IVC) obstruction, liver failure, kidney failure, nephrotic syndrome, weight gain, varicose veins, polyarthritis e.g. rheumatoid arthritis, podoconiosis (nonfilarial lymphoedema). Medical illustration by Dr Ciléin Kearns (Artibiotics). PDF Posters here!
Bilateral causes of limb swelling
Remember that weight gain and obesity are more complex issues than simply food intake vs activity. This can be a side effect of medication (e.g. steroids, antipsychotics, and contraceptive medicines), disease and disability affecting how active a person can be (e.g. painful joint inflammation in rheumatoid arthritis, heart pain in angina), mental health (e.g. depression affecting motivation, energy, etc), and social deprivation (healthy foods tend to be more expensive and time-consuming to prepare). This can be an emotionally charged issue and is something I’d love to explore further in another article. A little empathy goes a long way.
Anyway that’s my illustrated overview for ‘causes of limb swelling’. I hope it was helpful! My goal is to create an illustrated book from this series, which also expands on each differential diagnosis. It’s a cray amount of work beyond the scope of publishers, so I’m building it independently. You can support me opening medicine with art by a coffee membership to the Scrub Club on Patreon. In return, you get to see new work early, behind-the-scenes how I make my art, and bonus resources like PDF posters.
‘Til next time!