Prevalence of Publication No. of peripheral vascular year Author Country patients disease (%)
2003 Moulik et al.
Zambia 185 41 2002 Abbas et al.
Tanzania 92 21 2000 Benotmane et al.
Algeria 132 78.7 2000 Abbas et al.
Tanzania 200 12.5 1997 Wikbald et al.
Tanzania 153 12.5 1997 Levitt et al.
South Africa 300 8.2 1995 Lester Ethiopia 43 11.6 1995 Elbagir et al.
Sudan 128 10 1991 Friend et al.
Malawi 100 15 1991 Elmahdi et al.
Sudan 413 3.4 1990 Akanji et al.
Nigeria 50 54 1989 Elmahdi et al.
Sudan 448 6.2 1988 Rolfe Zambia 600 1.7 1987 McCance et al.
South Africa 118 10.2 1984 Lester Ethiopia 847 0.9 1984 Gill et al.
South Africa 475 2.1 1980 Mhando et al.
Tanzania 139 2.9 1971 Osuntokun et al.
Nigeria 832 4.4 1970 Belcher Ethiopia 94 1.1 1968 Greenwood et al.
Nigeria 240 1.7 1963 Gelfand et al.
Zimbabwe 99 0
Table 34.2 was adapted from Ref. 13. Permission to use Table 34.2 was granted by International Scientific Literature, Inc., publishers of the Medical Science Monitor.
the relevant limb.4 Specific factors contributing to development of diabetic foot ulcers include walking barefoot or delays in seeking medical attention for seemingly innocuous foot lesions.
Poverty and absence of access to health care certainly underscore foot ulceration in African diabetic populations.
For diabetic patients living at or below the poverty level, the purchase of appropriate footwear might not be feasible or of high priority (barefoot walking, a common practice in rural communities in Africa, is commonly associated with low income but may be cultural as well).2 Abbas et al. have recorded some unusual examples of foot ulcerations among attendees at their outpatient clinic in Dar es Salaam , in particular, patients with peripheral neuropathy were found to be at risk of acquiring rodent bites on their feet; diabetic rather than non-diabetic patients appear to be singled out by rodents.12 For diabetic patients with peripheral neuropathy, such trauma or injuries might go unnoticed until the patient finally becomes symptomatic and presents to the diabetes clinic with an ulcer or injury that has progressed to fulminating foot sepsis.
Although patients who neither take the time to take care of themselves and address foot care nor attend the diabetes outpatient clinic for follow-up or education are most at risk of developing infected foot ulcers, lack of sensation in the anaesthetic foot may cause ordinarily conscientious and responsible patients to be unaware of injuries sustained through inappropriate
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FOOT INFECTION 383
Table 34.3 Non-ulcerative pathology leading to foot ulcers among patients attending the diabetes clinic, Muhimbili National Hospital, Dar es Salaam, Tanzania
Complications Frequency ( n = 200 ) %
Dry skin 79 39.5 Callus 68 34.0 Fungal infection 66 33.0 Onycholysis 65 32.5 Cracked skin on sole 31 15.5 Corns 14 7.0 Scabies 4 2.0 Ingrowing toenail 1 0.5
or ill-fitting footwear, to walk barefoot on hot asphalt under the midday sun or to use keratolytic agents or razor blades to treat callosities.2 Any foot lesion, however innocuous it may appear, should never be disregarded.9 Ostensibly minor lesions can progress to an ulcer and provide an entry point for rapidly ascending infection. In a study of patients with symptomatic peripheral neuropathy in Tanzania, non-ulcerative sequelae included dry skin, callosities, fungal infection or onycholysis (Table 34.3).2
FOOT INFECTION Diabetic foot infections usually begin in ulcers that are sequelae of existing neuropathy, macrovascular disease or certain metabolic disturbances.14 Such infections have been shown to be the immediate cause of foot or leg amputation in 25, 50% of diabetic patients and may result in death.9 In Tanzania, Abbas et al. have described a population of diabetic patients with infected ulcers who have neither neuropathy nor vascular disease.3, 4 Typically, these patients are young adults with type 1 diabetes, who were diagnosed during their initial presentation to the outpatient clinic with infected feet.
The pathogenesis of these infections usually starts with a non-specific injury, followed by breakdown of skin and spread of infection to deeper tissue layers.
Patients in African communities often present to hospital only after the onset of gangrene or during a stage of sepsis that might be intractable to conventional supportive treatment.2, 6, 12 Because patients with infected ulcers often feel no pain because of neuropathy, or may have no systemic symptoms until late in the course of the condition, medical providers often presume (incorrectly) a degree of self-neglect among affected patients.
Fungal infection of toenails or in the intertriginous areas may lead to cracked skin or fissures on the soles of the feet.
This type of infection produces relatively slight discomfort, but its real importance lies in the fact that these lesions pave the way for the entry of microorganisms into the foot, leading to secondary bacterial infection.2 It is not surprising, therefore, that foot infections are especially common where there are no available services for follow-up of the diabetic foot, or lesions are ignored or detected relatively late in the course of the infection after unsuccessful home therapy, such as soaking in hot water, or application of unproven herbal remedies prescribed by traditional
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384 RECENT INTERNATIONAL DEVELOPMENTS: AFRICA
healers. Foot infections of this nature culminate in the onset of gangrene or disseminated infection with ensuing amputation of the foot or entire limb, or death from overwhelming sepsis.
MORTALITY Abbas and colleagues ascertained clinical correlates for mortality among diabetic patients with foot ulcers in Tanzania. They found that overall mortality rate among patients with foot ulcers was 27% and was significantly higher among patients who had peripheral vascular disease, neuroischaemia or non-healing ulcers.4 In addition, patients with foot ulcers that had progressed to gangrene (Wagner score ≥4) were significantly more likely to die, compared with patients with ulcers of Wagner score <4. Patients with ulcers of Wagner score ≥4 were more likely to have delayed presentation to hospital from the time of onset of the foot ulcer.4 In the same study, the highest mortality rate (54%) was observed among patients with ulcers of Wagner severity score ≥4, who did not undergo surgery.4
AMPUTATION Gangrene and infection appear to be the most commonly cited indications for foot amputation in diabetic patients.9 However, the true lower limb amputation rate resulting from foot infec- tions in African diabetic patients remains underestimated.3, 4, 9, 14 The non-healing ulcer is not generally considered an indication for amputation except in certain instances where patients have developed chronic osteomyelitis.14, 15 In Tanzania, neither peripheral vascular disease nor microvascular disease appears to be an important factor for surgeons when making the decision to operate.3, 4 The importance of delayed presentation to hospital is underscored by the fact that 10% of patients who needed and had agreed to undergo surgery died from advanced sepsis before the planned surgical procedure was actually carried out.3, 4