Case 17 Cellulitis in a man’s foot
Reg was an overweight 76-year-old retired shopkeeper who consulted Dr Berg in an emergency appointment with a three-day history of a painful left foot. He was taking bendroflumethiazide for hypertension, had a previous history of gout and was an ex-smoker. On examination the left forefoot was red and swollen. Dr Berg diagnosed cellulitis and treated Reg with flucloxacillin.
Would you have done anything differently?
Three days later Reg returned to see a different doctor because of continuing pain. Dr Haynes recorded that the foot was numb as well as painful. The foot was still red. Dr Haynes diagnosed gout, checked a uric acid level and treated Reg with diclofenac. When the blood result returned the urate level was just above normal. Dr Haynes felt that this confirmed her diagnosis and she did not contact the patient.
Would this result have reassured you?
Reg requested a visit four days later when the pain in his foot was so bad that he could not get out of bed. His left foot was a dusky blue and became pale when elevated. It did not feel particularly cold. However Dr Haynes could not feel any pedal pulses. The dorsalis pedis pulse was palpable on the right foot. Dr Haynes admitted Reg urgently to hospital.
In hospital Reg was found to have a popliteal aneurysm with an embolism in the left foot. Thrombolysis was unsuccessful and the patient had a below the knee amputation. He sued Dr Berg and Dr Haynes for an allegedly negligent delay in diagnosis of an acutely ischaemic foot.
Expert opinion
A painful red foot may be caused by a number of conditions including infection (cellulitis, infective arthritis and osteomyelitis), inflammation (gout and other arthropathies) and ischaemia.
Asymptomatic peripheral arterial disease is very common in older patients. In one US screening study 14% of asymptomatic men and women aged 55 and over who were screened had chronic peripheral arterial disease manifested as reduced pulse pressure in the pedal arteries (McGrae et al., 2001).
General practitioners see chronic incomplete ischaemia quite commonly (Cassar, 2006) but only rarely see the acute or acute on chronic severely or ‘completely’ ischaemic leg (Humphreys, 1999).
Limb ischaemia is usually classified in terms of the time of its onset and its severity. The classification is reproduced in Case Table 17.1 from Callum and Bradbury (2000).
Table 17.1 Classification of limb ischaemia.
| Classification of limb ischaemia Terminology | Definition or comment |
| Onset: | |
| Acute | Ischaemia < 14 days |
| Acute on chronic | Worsening symptoms and signs (< 14 days) |
| Chronic | Ischaemia stable for > 14 days |
| Severity (acute, acute on chronic): | |
| Incomplete | Limb not threatened |
| Complete | Limb threatened |
| Irreversible | Limb non-viable |
Generations of medical students have been taught the ‘6 P’s’ of the acutely ischaemic foot;
- pain
- pallor
- pulseless
- perishing cold
- paraesthesia
- paralysis.
Paraesthesia and paralysis are discriminatory for complete ischaemia but are rare unless the ischaemia is very severe.
If chronic peripheral arterial disease causes symptoms the patient sometimes complains of a cold or discoloured foot but usually complains of intermittent claudication. Rest pain, occurring in the foot at night when the leg is elevated and relieved by dropping the foot over the side of the bed, signifies critical ischaemia. Presumably the residual arterial pressure overcoming the resistance of narrowed vessels is so low that it is augmented by gravity when the foot is in the dependent position.
On examination the acutely ischaemic foot is classically pale and cold. However, it may also be red, and warm and this can cause errors (Humphreys, 1999). The temperature of the limb is not always a reliable sign of the severity of ischaemia because it will depend on the ambient temperature, whether the foot was clothed in a sock and so on. Nevertheless, it is unusual to find asymmetric coolness on palpating a lower limb. Such a finding should put a general practitioner on notice that critical or acute arterial ischaemia needs to be excluded.
Dr Berg ‘prematurely anchored’ on an incorrect diagnosis that was based on an inadequate history and examination. He should have sought a history of intermittent claudication and rest pain. The patient had risk factors of cardiovascular disease. Dr Berg should have noted signs of chronic ischaemia and examined and recorded:
- the relative temperature of the foot;
- the capillary return time by squeezing the under surface of the big toe for 5 seconds and then releasing the pressure; the time in seconds it takes for the normal skin colour to return is the CRT; more than 5 seconds is abnormal; the test is relatively insensitive (it is absent in many cases of peripheral arterial disease) (McGee, 1998);
- whether the foot became pale on elevation;
- the presence or absence of pedal pulses.
Usually the most useful sign for the general practitioner is the presence or absence of palpable peripheral pulses. The acutely ischaemic foot will, for the purposes of a general practitioner, almost always be pulseless.
However, there are two caveats to this assertion:
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