A 62-year-old man presents to the emergency department with an open wound on his left foot. The patient has a history of non–insulin-dependent diabetes mellitus, which is treated with an oral agent. He states that he has not had prior foot infections, foot problems, and denies any recent trauma to the foot. His wound has not been particularly painful, and he only noticed the wound when yellow drainage appeared on his socks over the past several days. The patient’s temperature is 37.9°C (100.2°F), and his vital signs are normal. His peripheral vascular examination reveals palpable pulses in both femoral regions and normal pulses in both feet. The left foot is swollen over the plantar region and has a 1.5-cm open wound over the plantar surface of the foot overlying the fourth and fifth metatarsal heads. There is some yellow drainage from the area, and the surrounding skin is erythematous and warm. There is no exposed bone appreciated at the base of the ulcer. His white blood cell count is 12,000 cells/m3 and the serum glucose is 230 mEq/dL.
What is the diagnosis?
What are the next steps in this patient’s management?
What are the complications associated with this process?
ANSWERS TO CASE 56: Diabetic Foot Complications
Summary: A 62-year-old diabetic man presents with a swollen foot, low-grade fever, and a plantar ulcer.
• Diagnosis: Diabetic foot infection associated with a neuropathic ulcer, although Charcot neuroarthropathy cannot be ruled out based on the initial evaluation.
• Next Steps: Assess the wound and patient for signs of infection. Biopsy the wound for culture and send blood for cultures. Obtain x-rays of the foot to look for Charcot neuroarthropathy and/or osteomyelitis. The patient should be placed on initial bed rest, IV antibiotics therapy, and strict glycemic control.
• Complications: Nonhealing wound and progression of infections may lead to limb loss.
1. Learn to monitor and recognize diabetic foot complications.
2. Learn the principles and strategies applied for the treatment of diabetic foot complications.
A 62-year-old diabetic man presents with a new plantar ulcer associated with foot swelling, erythema, and warmth. The initial presentation is highly suspicious for a neuropathic ulcer and diabetic foot infection. The presence of palpable pulses in the foot and location of the ulcer suggest that ischemia is not a contributing factor in this case. The initial ulcer evaluation could be quantified by the PEDISclassification that takes into account Perfusion, Extent (area size), Depth, Infection, and Sensation. Because all open wounds are colonized and not necessarily infected, the diagnosis of infection should be based on the combination of culture results and clinical assessment, rather than wound cultures alone. In this case, the patient has local signs of infection (redness, drainage, and swelling), and systemic signs of infection (hyperglycemia). Documentation of tissue infections should be based on tissue biopsy and not wound swab. Given the most common pathogens involved in diabetic foot infections are Staphylococcus aureus and β-hemolytic Streptococcus, amoxicillin–clavulanic acid, ciprofloxacin, cephazolin, and vancomycin are all considered appropriate initial empiric therapy. The possibility of polymicrobial infections with aerobic gram-positive cocci, gram-negative bacilli, and anaerobic organisms is unlikely in this patient, given that he has not received prior treatment for diabetic foot infections and does not have evidence of arterial insufficiency. The optimal duration of antibiotic treatment for diabetic foot infections has not been determined on the basis of randomized controlled trials, and treatment courses often ranged between 7 and 14 days. Glycemic control in patients with diabetic foot infection is an important adjunct to the treatment, as hyperglycemia contributes to leukocyte dysfunction and compromised host response to infections. Given the open wound in this patient, if bony destruction is identified during radiography, it would be very difficult to differentiate osteomyelitis from Charcot neuroarthropathy, and long-term (4-6 weeks) course of IV antibiotic treatment may become necessary. In addition to antibiotics, local wound care is essential to promote healing. Local wound care includes a variety of techniques, including sharp debridement, larval therapy with medicinal maggots, and topical agent applications, and in some cases the local infections associated with abscesses would require surgical drainage and minor amputations. For many patients with neuropathic ulcers, contact casting to offload pressure from the wound site is an important adjunct in promoting healing. Once healing of the ulcer is completed, the patient should be thoroughly evaluated for contributory conditions (limited joint mobility of the foot and ankle, calluses, bunions, hammer toes, claw toes) and undergo treatment to prevent the development of future neuropathic ulcers.
APPROACH TO: Diabetic Foot Complications
DIABETIC NEUROPATHIES: These include motor neuropathy leading to muscle atrophy, altered biomechanics, and foot deformities; sensory neuropathy that increases susceptibility to injuries; and autonomic neuropathy leading to decreased sweating, skin dryness, cracks, and increased susceptibility to infections.
CHARCOT NEUROARTHROPATHY: This is a noninfective bone and joint destruction that occurs in a well-perfused and insensate foot. The exact mechanism producing Charcot foot is unknown, and one theory is that the findings are produced by repetitive trauma to an insensate portion of the foot. Radiographically, there is extensive bone and joint destruction, fragmentation, and remodeling. Charcot foot is reported in approximately 16% of patients with diabetes and a history of neuropathic ulceration. The clinical presentation of acute Charcot neuroarthropathy includes soft tissue swelling, soft tissue erythema, and increased local skin temperature. Clinically, this can be difficult to differentiate from diabetic foot infections and osteomyelitis especially when an open wound is present.
FOOT ULCER CLASSIFICATIONS: Neuropathic foot ulcers are located over weight-bearing portions of the foot and are associated with normal arterial examination. Vasculogenic ulcers are generally located at the tips of the toes where perfusion is most limited. Ulcers can also develop initially as neuropathic ulcers and persist as the result of decreased blood flow.
Disease of the foot is common and one of the most feared complications associated with diabetes. “Diabetic foot” refers to a number of pathologic conditions encountered in this patient population, including diabetic neuropathy, ischemic vascular disease, Charcot neuroarthropathy, skin ulceration, soft tissue infections, and osteomyelitis. The lifetime risk of foot ulcer development in a diabetic individual is reported as high as 25%, and infection related to diabetic foot is responsible for 80% of the nontraumatic amputations performed. The prevention of diabetic foot complications is possible through patient education and close patient surveillance so that conditions predisposing to pressure ulceration and trauma could be avoided, identified early, and treated. The National Institute for Clinical Excellence (NICE) has made the following recommendations for diabetic foot surveillance based on patient risk stratification. Low-risk patients with normal sensation and palpable pulses are recommended to have foot examination annually. Moderate-risk patients with neuropathy or absence of pulses are recommended to undergo examinations and maintenance care every 3 to 6 months, and high-risk patients with neuropathy or absence of pulses in addition to foot deformity, skin changes, or prior history of ulcers are evaluated every 1 to 3 months. During these scheduled maintenance evaluations, all patients are thoroughly assessed for neuropathies, structural abnormalities (calluses, bunions, hammer toes, etc), and vascular abnormalities (ankle-brachial index [ABI], skin changes). Patients with active foot ulceration are recommended to undergo aggressive treatment by a multidisciplinary foot care team.
Challenges in the evaluation of diabetic foot disease are the asymptomatic nature of disease and lack of recollection of trauma or injury. Additionally, because of the microvascular disease, even superficial cellulitis can progress to osteomyelitis if not aggressively treated. Hence, the focus of attention should be toward (1) identifying and intervening for deep infection or osteomyelitis due to their associated increased morbidity and mortality, (2) preventing superficial infection from progressing to more significant disease, and (3) educating the patient and family in prevention of foot injury or infection. Diabetic ulcers (Figure 56–1) may be present on pressure points and areas of vascular insufficiency. Pain, induration, and wound drainage of the foot may indicate a deep tissue infection. In general, these infections require prompt surgical drainage and debridement. Osteomyelitis should be considered with deeper ulcers, elevated leukocyte count, and pain. However, fever is an unreliable sign, and adenopathy is inconsistent. Radiographic changes may not be present in acute osteomyelitis but usually will be seen in chronic infection. Radionuclide scans such as with gallium are more helpful in the diagnostic evaluation of acute osteomyelitis.
Figure 56–1. Diabetic, neuropathic ulcers on the soles of the feet due to significant long-standing diabetes-associated neuropathy. (Reproduced, with permission, from Wolff K, Johnson RA, Suurmond D. Fitzpatrick’s Color Atlas & Synopsis of Clinical Dermatology. 5th ed. New York, NY: McGraw-Hill; 2005:436.)
Because atherosclerotic vascular disease occurs commonly in diabetic patients, the contribution of arterial insufficiency to diabetic foot ulcer formation and nonhealing should always be considered. Because the arterial occlusion occurs more commonly in the diabetic population at the level of the tibialperoneal arteries, the patients often do not experience calf claudication. In the diabetic patient, foot claudication is more common because the decreased blood flow occurs at the tibial-peroneal arteries; however, as the result of concurrent sensory neuropathy, foot claudication would often go undetected. Assessment of blood flow can be quantified with measurement of ABIs, measurement of toe-brachial indices, and duplex ultrasonography; however, it is important to bear in mind that ABI in diabetic patients could be falsely elevated from calcification of the tibial vessels. When arterial insufficiency is identified as a possible cause of ulcerations or nonhealing wounds, the patients should undergo additional arterial evaluation by arteriography or magnetic resonance angiography and consideration for revascularization. Because of the increased frequency of multiple level occlusive disease and tibial level occlusive disease, diabetic patients are generally not good candidates for endoluminal arterial interventions and revascularization in this patient population often requires open vascular reconstructions.
56.1 A 56-year-old man presents back in your office with recurrent foul-smelling diabetic foot infection. There does not seem to be ischemia to the region. You noted that the infected area initially improved after a 2-week course of vancomycin treatment. Which of the following is the best antimicrobial therapy for this individual?
D. Higher dose vancomycin
56.2 A 55-year-old man with type 2 diabetes presents complaining of a “foot infection.” He is noted to have foul-smelling and purulent drainage from a 10-cm left plantar ulcer with bone exposure. His temperature is 39.4°C (102.9°F) and blood pressure is 90/60 mm Hg. The serum WBC is 35,000 cells/m3, and x-ray findings indicate extensive osteomyelitis involving several metatarsal bones and gas within the soft tissue in the lower leg. Which of the following is the most appropriate treatment for this patient?
A. Below-the-knee amputation
B. Piperacillin–tazobactam + clindamycin
C. Piperacillin–tazobactam + vancomycin and wound debridement
D. Below-the-knee amputation and piperacillin–tazobactam + metronidazole
E. Transmetatarsal amputation and piperacillin–tazobactam + metronidazole
56.3 A 46-year-old diabetic male is being seen in the office for an ulcer of the right foot and ankle area that appeared approximately 10 days previously. There is some tenderness over the lateral malleolus. An x-ray of the ankle does not show any abnormality. Which of the following would be most likely to help in detecting acute osteomyelitis?
A. Needle aspiration of the region in question
B. MRI of the right ankle
C. Radionuclide scan of the ankle
D. Serum erythrocyte sedimentation rate
E. Bone biopsy
56.1 E. Given the prior history of antibiotic therapy directed toward gram-positive organisms and the current foul-smelling drainage associated with this recurrent ulcer, a polymicrobial infection with a combination of gram-positive and gram-negative organism is highly likely; therefore, piperacillin–tazobactam is a good initial empiric antibiotic choice. Anaerobic organisms are less likely to develop in diabetic foot infections without arterial insufficiency. Fungal infection is uncommon in diabetic foot infection. Increasing the dosage of vancomycin is not likely to improve the infection at this time.
56.2 D. Given the septic presentation of this patient exhibiting advanced diabetic foot infection associated with bone involvement and air-forming organisms in the lower leg soft tissue, the initial management should be directed toward life-saving interventions rather than limb-saving interventions. The most appropriate treatment would include resuscitation, below-the-knee amputation, and broad-spectrum systemic antimicrobial therapy. Transmetatarsal amputation with antibiotics is not appropriate given the presence of gas in the lower leg soft tissue.
56.3 C. With acute osteomyelitis, radiographic changes such as raised periosteum may not be seen until later. Radionuclide scan is often helpful in these circumstances. Biopsy would not reveal specific findings to help establish the diagnosis.
Neuropathic and vasculopathic ulcers may be differentiated based on locations, where neuropathic ulcers occur at pressure and weight-bearing areas of the foot and vasculogenic ulcers occur at the tips of digits.
Acute Charcot foot is associated with acute pain, soft tissue swelling, erythema, and increased warmth in the foot, and these features are often confused with cellulites, deep venous thrombosis, and osteomyelitis.
Apelqvist J, Bakker K, van Houtum WH, et al. Practical guidelines on the management and prevention of the diabetic foot. Diabetes Met Res Rev. 2008;24(suppl 1):S181-S187.
Khanolkar MP, Bain SC, Stephens JW. The diabetic foot. QJM. 2008;101:685-695.
McDermott JE, Fitzgibbons TC. Diabetic foot. In Cameron JL, Cameron AM, eds. Current Surgical therapy. 10th ed. Philadelphia, PA: Elsevier Saunders; 2011:841-844.