Tissue tonometry: a useful tool for assessing filarial lymphedema

A tissue tonometer was used to assess peripheral lymphedema in patients with filariasis in a Bancroftian endemic community. Matched populations of 34 patients with Grade II and 29 patients with Grade III unilateral lower limb edema and 26 healthy subjects were assessed for leg tissue compressibility and circumference. Tonometry was performed at three fixed points on the leg using three weight levels (70, 140, and 210 gms). The mean value of compressibility for each weight level and points measured in the edematous leg were significantly less compared with the contralateral non-edematous leg in the filarial patients and the legs of healthy subjects. Patients with Grade III lymphedema were more resistant to compression than Grade II patients throughout the leg but especially at the foot. The least mean square analyses of circumference and compressibility differential values of edematous compared with non-edematous legs revealed a positive correlation at the foot in Grade II and the proximal and distal parts of Grade III lymphedema; moreover, the slopes were significantly different from zero. These findings support progressive tissue changes of edema and fibrosis first in the foot and later in the more proximal portions of the leg which correspond to progressive volume expansion with protein-rich fluid. Tissue tonometry appears to be a sensitive measure for assessing progression of both edema and fibroplasia in patients with peripheral lymphedema associated with filariasis, and, therefore, may be a useful tool to measure the efficacy of drugs commonly used to treat this condition.