Assessment of the diabetic foot begins with a thorough background and physical examination as well as directed laboratory studies to assess the metabolic status of the patient. The foot exam is directed toward assessing the main pathophysiological mechanisms of disease, namely vascular and neurological compromise, and a search for occult or advanced infection.
Assessment of vascular compromise is crucial, since it defines the degree of ischemic switch to the foot. Evaluation of the femoral, popliteal and pedal pulses may suggest the site of huge vessel arterial compromise if present. Additionally, prolonged capillary refill time, dependent rubor, pallor on elevation and lack of foot hair are all signs and symptoms of arterial compromise. Although sensibility and motor function should be part of any vascular exam, impairment may be due to ischemia as well as neuropathic changes.
When distal pulses are absent or impaired, the ankle-brachial index (ABI) can measure the level of large vessel perfusion towards the extremity. These values can be helpful in determining the opportunity of wound healing. An ABI of 0.4-0.6 correlates with significant claudication along with a 10%-40% possibility of continuing development of disease to amputation or revascularization to avoid amputation. Most diabetics need an ankle pressure of at least 80 to 90 mm Hg to heal a digit or metatarsal amputation.
However, the ABI must be interpreted within the context from the disease. Medial arterial calcinosis, frequently seen in diabetics, especially those with end-stage renal disease results in artificially inflated indices. Although calcification appears to spare the vessels of the toes, disease in this area can often limit the utility of toe pressures.
Segmental Doppler analysis can warn the clinician of arterial compromise in the background of the elevated ABI. An attenuated waveform indicates a proximal occlusion, whereas a normal waveform is suggestive of insignificant proximal disease. Although segmental Doppler waveforms and pulsed Doppler recordings aren't suffering from calcification, they are qualitative, not quantitative, measures.
The caliber of the waveforms is suffering from local edema, and cuff placement might be affected by ulceration. The hindrances the diabetic foot presents to those noninvasive tests can significantly limit the usefulness of these modalities. The clinician is encouraged to evaluate these values in the context of the disease state and physical exam.
When foot pulses are absent and ulceration present, large vessel disease can be assumed to be a significant component of the condition process. Ischemic ulcers are often painful, superficial lesions having a rim of vascularized tissue along with a necrotic center. Arteriography, or magnetic resonance angiography (MRA) from the pelvis and entire lower extremity will give you a road map for a planned bypass procedure.
Since the proximal leg and foot vessels are often spared in diabetics, extreme distal bypass isn't an infrequent procedure. Judicious hydration and renal protective agents prior to infusion of IV contrast are suggested for diabetics with compromised renal function. Although arteriography is the defacto standard in vascular imaging, MRA is really a useful alternative, particularly in patients with compromised renal function.
The foot should be thoroughly inspected for signs and symptoms of neuropathic disease. Claw-foot deformity or other changes representative of motor disease should be noted. High-risk areas like the plantar surface of the metatarsal heads, the dorsal PIP joints and the tips of the toes are inspected for ulceration. The toes are also inspected for ingrown nails; the web spaces and also the plantar surface of the foot are inspected for dry, cracked skin. Sensibility, that is usually impaired in a bilateral, symmetrical pattern is assessed.
Vibratory sensation, typically lost first, might be tested having a 128-cycle tuning fork. Light touch, temperature and pain can be assessed having a cotton swab, warm and cool tubes, and a pinprick, respectively. Neuropathic ulcers, known as mal perforans ulcers, present as nontender ulcers found on the plantar contact areas, like the metatarsal heads or underneath the heel. There is a deep, punched-out appearance with a hypertrophic callous formation in the edges.
A thorough search for ulceration, purulent drainage, crepitus, erythema and sinus formation should be part of the initial evaluation. Heavily calloused areas are unroofed and cultures obtained from the base of all ulcers. All wounds are probed to determine if the lesion exclusively affects the superficial tissue or when the deeper planes are involved. The tissue surrounding the ulcer is compressed to express occult purulence.
Osteomyelitis is a very common complication from the diabetic foot disease and it is seen in up to 70% of diabetic foot ulcers. The existence of exposed bone in an ulcer is assigned to bony infection. This observation can be made visually or having a sterile probe. In addition, plain X-rays, 3-phase bone scans, labeled leukocyte scans, CT and MRI enables you to assess osteomyelitis.
Bone biopsy may be the defacto standard of diagnosis. It should be noted that the hallmarks of infection for example erythema and pain might be absent in the diabetic because of the sequelae of microvascular and neuropathic dysfunction. Even patients with deep abscesses may not present with expected fever, chills and leukocytosis. Uncontrolled hyperglycemia may be the only harbinger of an active infection.
Necrotizing fasciitis, contamination of the subcutaneous tissue and fascia, is really a frequently missed condition affecting diabetics. While not a typical infection, it is a devastating disease that can rapidly result in large tissue loss, sepsis and death. Clinicians may mistake this disease with cellulitis, and the diagnosis of necrotizing fasciitis is not usually considered before patient is floridly septic. Diagnosing is frequently missed because the skin often shows no proof of deep tissue infection. Crepitus, cyanosis or bronzing of the skin should raise suspicion.
Simple and easy , painless introduction of a probing instrument into the necrotic subcutaneous space is extremely suggestive of the diagnosis. A X-ray CT or MRI from the affected limb may show subcutaneous air. Fascial thickening and stranding can also be appreciated on CT. Affected patients should be taken emergently to the operating room for aggressive debridement of all infected tissue. Patients may require repeat debridements, which might ultimately lead to amputation.
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