Background: Diabetic polyneuropathy of the feet and legs obscures the diagnosis of critical limb ischaemia (CLI) because of lack of pain sensation. Hence, the Fontaine classification does not apply to these patients. Furthermore, many of them will exhibit medial arterial calcification, which invalidates the application of sphygmomanometry. This study was done to evaluate the pulsatility index (P1) assessed at the ankle arteries by colour Doppler ultrasonography as a non-invasive method to diagnose CLI in diabetic polyneuropathy.
Patients and methods: 140 legs of 106 diabetic patients were studied who presented with polyneuropathy and painlessness of the feet; of these, 117 feet displayed an ulcer or gangrene. CLI was defined as the need for arterial revascularisation, as indicated by the physicians in charge on the basis of a) a foot lesion Wagner grade 1-5, and b) a positive arteriography. All patients were subjected to 4 vascular assessment techniques: digital subtraction arteriography, ankle-brachial Doppler index, systolic ankle blood pressure, and PI.
Results: Of the 140 legs, 61 (44%) were affected by CLI, and 76 (54%) by medial arterial calcification. A PI < 1.2 indicated CLI with a sensitivity of 0.87 and a specificity of 0.62. The sensitivity and specificity of ankle-brachial index < 0.9, and of systolic ankle pressure < 70 mm Hg to predict CLI was 0.71 and 0.42, and 0.30 and 0.89, respectively.
Conclusions: The pulsatility index is a better noninvasive technique than the ankle-brachial Doppler index or the systolic ankle pressure to assess critical limb ischaemia in diabetic polyneuropathy. A pulsatility index < 1.2 at the ankle arteries is a reliable criterion for diagnosis of CLI in diabetic patients with polyneuropathy.