The distribution of oedema in the lower limb of patients with chronic critical limb ischaemia: a study with computed tomography

Background: A substantial number of patients with chronic critical limb isc haemia (CLI) have considerable oedema at the distal leg and foot of non dee p venous thrombosis origin. The primary aim of the present study was to qua ntify the distribution of oedema in the different tissues of the leg and fo ot bit applying computed tomography and planimetry. The interstitial fluid hydrostatic pressure (P-if) in the subcutaneous tissue was measured to eval uate the effect of oedema on local tissue pressure. Patients and methods: Six men and 12 women with unilateral CLI and peripher al pitting oedema were in eluded. Cross sectional areas (CSA) of subcutaneo us tissue, muscle and bone were measured by computer tomography combined wi th planimetry to assess the distribution of oedema oedema within the soft t issues. Pif was measured by "wick-in-needle" technique. Results: The median total CSA of soft tissue, subcutaneous and muscle tissu es at the foot level were respectively 17%, 34% and 9% greater in the limbs with CLI compared to the contralateral limb (p < 0.001). At ankle level th ese differences were 13%, 30% and 4%, respectively (p < 0.001). At the leve l of the calf these differences were not significant. Mean P-if in the limb s with CLI was 0.3 mmHg, significantly higher than in limbs without CLI (-1 .8 mmHg), (p < 0.003). Conclusion: The study verified oedema of considerable magnitude at the ankl e and foot. The great part of the oedema was located within the subcutaneou s tissue, which was associated with a relatively moderate, but significant increase in P-if confirming the high compliance of the subcutaneous tissue. The combination of the excessive fluid and increased P-if in the interstit ial tissue might aggravate the microcirculation. The aetiology of oedema fo rmation is probably multifactorial.