Clinical clanger: ‘My ankles are really swollen, doctor – can you give me some of those water tablets?’

Continuing our series on clinical scenarios that can be mishandled in primary care, Dr Peter Bagshaw explains the potential for inappropriate use of diuretics in ankle oedema

You see an 82-year-old widow in surgery. She has had swollen ankles for several months and requests ‘water tablets’ for them, as it is becoming difficult for her to put on shoes. Her mobility is limited by hip osteoarthritis, but she has no breathlessness or other symptoms, and no evidence of local infection, cardiac problems or other disease; you note she is overweight and confirm bilateral pitting oedema.  

The reality
Ankle oedema in this age group is common and is usually due to immobility. Differential diagnosis includes cardiac failure, cirrhosis, renal disease, venous insufficiency, lymphatic system disease and protein deficiency. It can also be iatrogenic; calcium channel blockers commonly give swollen ankles, but so too can steroids, oestrogen, pioglitazone, gabapentin, pramipexole and NSAIDs.¹ In most cases, diuretics will not help.²

The issue
Swollen ankles are often treated empirically in older people, sometimes after excluding heart failure, often without investigation. However, diuretics are not benign drugs. They are the commonest cause of side-effects in older people, including weakness, confusion, postural dizziness, falls and fits.³ Around 20% of people taking them develop hyponatraemia and 5% develop hypokalaemia.³ Weight loss, exercise and elevation of legs, and use of compression stockings in venous insufficiency are much more effective, but harder to achieve.

The evidence
Effective treatment depends on knowing the cause. In chronic venous insufficiency, diuretics are inappropriate, with elevation and compression the effective treatments. In medication-induced swelling, diuretics are not effective and in lymphoedema they are rarely effective long term.² For the former, reducing or stopping the medication is the only answer, while lymphoedema is best addressed by compression bandaging, good skin care, exercises and manual lymphatic drainage.

One study found a fifth of over-65s were on diuretics.³ This is often without a clear indication, and with significant risk of harm.The adverse effects of these drugs are often overlooked, and investigation for other causes is often not done.⁴

Avoiding a clanger
Basic investigations are measurement of BNP, FBC, and renal and liver function. If swelling is unilateral, the differential diagnosis alters: it is important to exclude a DVT, and I have seen it as a presentation of cancer, restricting lymphatic drainage. As Bunden comments, ‘the pathologic process, not the oedema is the diagnosis’.⁵ Drug-induced oedema is often apparent from the history, while lymphoedema is non-pitting, unlike the pitting oedema of venous insufficiency or cardiac failure. 

Caveats
There are occasions when diuretics are indicated – specifically, heart failure, although this should trigger other actions such as an echocardiogram and the addition of an ACE inhibitor and (cautiously) a low-dose ß-blocker.

There are also rare scenarios, such as when a very elderly, immobile patient has horrendously swollen, sometimes leaking legs, where a short course of a diuretic might trigger improvement and the application of other treatments. This requires clear documentation to avoid defaulting to repeat prescriptions.

References

1.  Mayo Clinic. Edema.
2. O’Brien J, Chennubhotla S, Chennubhotla R. Treatment of edema. Am Fam Physician 2005;71:2111-7 Link
3.  MacClennan W. Diuretics in the elderly: how safe? BMJ 1988; 296:1551-2 Link
4.  Thaler H , Wirnsberger G, Pienaar S et al. Bilateral leg edema in the elderly. Clinical considerations and treatment options. Eur Geriatr Med 2010;1:353-7 Link
5.  Bunden W. The chronically swollen leg: finding the cause. In Venous Ulcers. Bergen J, Shortell C (eds). Elsevier Academic Press 2006