Start with the part that cannot wait. If a diabetic foot has spreading redness up the foot or leg, fever or chills, black or dark tissue anywhere on the foot, a foul smell, or discharge of pus, go to an emergency department now. That combination points to infection that can spread within hours, and it is treated the same day, not at an appointment next week. The other four signs below are serious but less immediate, and they mean the foot should be assessed by a team that deals with limb salvage rather than being managed with dressings alone at home.
Sign one: spreading infection, black tissue or a bad smell
This is the emergency sign. Warning features include redness that is climbing above the ankle, swelling that is increasing by the hour, fever, shivering, feeling generally unwell, sugar readings that suddenly become hard to control, pus, an area of skin turning dusky, blue or black, and a smell from the wound. Any one of these in a person with diabetes needs same day hospital assessment.
The reason for the urgency is simple. Nerve damage means the foot may not hurt much even when infection is deep. High blood glucose weakens the response to infection. Reduced circulation limits how well antibiotics reach the tissue. So an infection can be far more advanced than it looks from outside, and delay is what most often turns a treatable foot into an untreatable one. Do not wait to see if it settles overnight, and do not start leftover antibiotics at home.
Sign two: an ulcer that has not healed after several weeks
A superficial break in the skin on a diabetic foot should be improving steadily with proper dressing and pressure relief. If an ulcer has been there for weeks and is the same size or larger, something is preventing healing. The usual reasons are ongoing pressure on the area, inadequate blood supply, hidden infection, bone involvement underneath, or all of these together.
Continuing the same dressing while the wound stands still is the commonest pattern seen in the clinic. If a wound has not shown clear progress in a few weeks, that is the point to ask for a specialist opinion rather than another month of the same treatment.
Sign three: you can see bone, tendon or a deep track in the wound
An ulcer that looks small on the surface can extend deeply. If the base of the wound shows glistening white tendon, exposed bone, or a probe passes easily into a deep space, the problem is no longer a skin wound. Bone infection, called osteomyelitis, changes both the treatment and the timeline, usually requiring imaging, samples for culture and often surgery to remove infected bone.
A related sign is a toe that has become swollen, red and sausage shaped, particularly with an ulcer over it. Deep infection under a callus, where there is a small opening but a large cavity underneath, is another. None of these are managed by dressings alone.
Sign four: pain at rest, night pain, or a cold pale foot
Poor arterial supply has its own signals, and they are different from infection. Look for pain in the foot or toes when you are lying down, especially at night, that eases when you hang the leg over the edge of the bed. Look for skin that is pale on elevation and dusky when the foot is down, a foot that feels cold compared with the other, thin shiny skin, loss of hair on the toes, thickened nails and weak or absent pulses at the ankle.
Circulation matters more than any other single factor in whether a wound can heal. A wound in a foot with inadequate blood flow will not close no matter how good the dressing is. This is why assessment includes examination of pulses and studies of circulation such as Doppler ultrasound, ankle and toe pressures, and where indicated an angiogram. If the arteries can be reopened, healing becomes possible in situations that otherwise look hopeless.
Sign five: repeated ulcers in the same place, or a suddenly hot swollen foot
An ulcer that keeps coming back at the same spot under the ball of the foot, the tip of a toe or the heel is telling you that pressure at that point is not being relieved. Deformity, clawed toes, a collapsed arch, thick callus or unsuitable footwear are the usual causes, and the ulcer will keep returning until the mechanics are addressed with offloading, appropriate footwear and sometimes corrective surgery.
Separately, a foot that becomes hot, red and swollen without an obvious wound, in a person with long standing diabetes and numbness, may be a Charcot foot, in which bones and joints weaken and collapse. It is frequently mistaken for infection or gout. It needs prompt assessment, because continuing to walk on it can destroy the shape of the foot and create the deformity that later causes ulcers.
What happens at a limb salvage assessment
The assessment looks at the wound, the circulation, the bone, the infection and you as a whole. Expect examination of both feet, testing of sensation, feeling for pulses, gentle probing of the wound, swabs or deep tissue samples for culture, blood tests including glucose control and markers of infection, an X ray of the foot, and vascular studies. Sometimes an MRI is used to assess bone. Kidney function, heart disease, nutrition and smoking all form part of the picture, because they affect healing.
Only after this is a plan made. It may involve removing dead and infected tissue, treating the infection with the right antibiotics, restoring blood flow through angioplasty or bypass with vascular colleagues, taking pressure off the area, and then closing the wound with dressings, a skin graft or a flap. Dr. Ashutosh Shah is a Plastic, Reconstructive and Cosmetic Surgeon in Surat with more than 22 years of surgical experience, M.Ch. Plastic Surgery from The Maharaja Sayajirao University of Baroda and DNB from the National Board of Examinations, New Delhi, and diabetic foot work here is done with physicians and vascular colleagues rather than in isolation.
An honest word about what salvage can and cannot do
Limb salvage means doing everything reasonable to keep a functional foot or leg. It succeeds in many people, and feet that look frightening at first do sometimes heal. It does not always succeed. When infection has destroyed the deep structures, when the arteries cannot be reopened, when bone is extensively involved, or when the person is too unwell for repeated surgery, amputation of a toe, part of the foot or the leg may be the safer choice, and sometimes it is the choice that saves a life or restores walking sooner.
No honest surgeon can promise a foot will be saved before examining it and studying the circulation. What you should expect is a clear explanation of what has been found, what is being attempted, what the alternative is and how the decision will be reviewed as treatment progresses. The single thing that most improves the odds is being seen early.
