Specific varieties of gangrene

Specific varieties of gangrene

Diabetic gangrene Diabetic gangrene is usually caused by a combination of three factors: ischaemia secondary to macrovascular disease and microvascular dysfunction; peripheral sensorimotor neuropathy (PSN), which leads to trophic skin changes; and immunosuppression caused by an excess of sugar in the tissues, which predisposes to infection ( Figure 61.26 ). Macrovascular

Figure Figure 61.26 Diabetic gangrene.

with relative sparing of the pedal vessels, whereas increased microcirculatory shunting causes microvascular dysfunction. The PSN is usually sensory in the early phase – classically in a stocking distribution – and renders the patients at high risk of soft-tissue injury and its subsequent neglect. The PSN may extend to the joints of the foot and ankle, resulting in loss of nociceptive and proprioceptive protective reflexes and a repeated cycle of joint injury and bony destruction. Motor involvement causes an imbalance between flexors and extensor muscle groups of the foot, promoting altered foot biomechanics and abnormal pressure loading, which result in thick callosities developing on the sole of the foot. Ischaemia and PSN act synergistically to increase the risk of diabetic foot ulceration and reduce its subsequent healing potential. Superadded infection due to poor wound care can spread rapidly and proximally in subfascial planes, leading to fulminant foot sepsis, gangrene and death. T reatment depends on the degree of arterial involvement, which should be investigated and treated rapidly with angio - plasty or surgery . The gangrene is trea ted by drainage of pus, liberal debridement of dead tissue and antibiotics. Unfortu - nately , a number of patients present with life-threatening sys - temic upset and should be considered for primary amputation.

(b) Figure 61.27 Bedsores typically appear over areas exposed to pres sure, such as the sacrum and (as in this case) the heel. They can quickly deteriorate from an area of discoloration (a) to gross ulceration extending to the calcaneum (b) . (a) (b)