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 ischaemia (CLI) have considerable oedema at the distal leg and foot of non deep venous thrombosis origin. The primary aim of the present study was to quantify the distribution of oedema in the different tissues of the leg and foot bit applying computed tomography and planimetry. The interstitial fluid hydrostatic pressure (P-if) in the subcutaneous tissue was measured to evaluate the effect of oedema on local tissue pressure. Patients and methods: Six men and 12 women with unilateral CLI and peripheral pitting oedema were in eluded. Cross sectional areas (CSA) of subcutaneous tissue, muscle and bone were measured by computer tomography combined with planimetry to assess the distribution of oedema oedema within the soft tissues. Pif was measured by "wick-in-needle" technique. Results: The median total CSA of soft tissue, subcutaneous and muscle tissues 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 these differences were 13%, 30% and 4%, respectively (p < 0.001). At the level of the calf these differences were not significant. Mean P-if in the limbs 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 ankle and foot. The great part of the oedema was located within the subcutaneous 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 interstitial tissue might aggravate the microcirculation. The aetiology of oedema formation is probably multifactorial.