A Histogram Analysis of the Pixel Grayscale (Luminous Intensity) of B-Mode Ultrasound Images of the Subcutaneous Layer Predicts the Grade of Leg Edema in Pregnant Women.

The technique most widely used to quantitatively measure leg edema is only a pitting edema method. It has recently become possible to digitize B-mode ultrasound images and accurately quantify their brightness using an image-analysis software program. The purpose of this study was to find new indices of the grade of leg skin, to study whether or not analyses of the subcutaneous layer of leg skin on ultrasound images using image-editing software program can be used to evaluate it and to digitize it. Images of 282 subcutaneous layers of leg skin in 141 pregnant women were obtained using a B-scan portable ultrasound device. Rectangular photographs (vertical: skin thickness; horizontal: width of probe) were obtained using an image-editing program, and the luminous intensity (pixel grayscale: 0-255) and thickness of the skin were calculated using a histogram. We investigated the correlation between these parameters and the grade of pitting edema (0-3). There was a significant positive correlation between the grade of pitting edema and the average luminous intensity value, its standard deviation, and the skin thickness (ρ = 0.36, ρ = 0.22, ρ = 0.51, p < 0.0001, respectively). In particular, there was strong positive correlation between the grade of pitting edema and both the total number of pixels in a rectangle × (multiplied by) the average luminous intensity value and the total number of pixels in a rectangle × the standard deviation of the average luminous intensity value (ρ = 0.58 and ρ = 0.59, p < 0.0001, respectively). We could quantitatively evaluate the grade of leg edema by analyzing ultrasound photographs of the subcutaneous layer of the leg skin using an image-editing software program and found new indices to digitize it.

Measurement of Skin Thickness Using Ultrasonography to Test the Usefulness of Elastic Compression Stockings for Leg Edema in Pregnant Women.

Background: One of the most common treatments for leg edema during pregnancy is the use of compression stockings. The purpose of this study was to evaluate the objective effectiveness in pregnant women, by measuring the changes of skin thickness using ultrasonography. Methods: Pregnant women were diagnosed with leg edema using the pitting edema method at 36 weeks of gestation. Twenty-four pregnant women (48 legs) with leg edema spent time without wearing elastic stockings at 36−37 weeks of gestation. Then, they wore elastic stockings for one week at 37−38 weeks of gestation. We measured the grade of edema (from 0 to 3) and the skin thickness of the lower leg by portable ultrasonography at 36, 37, and 38 weeks of gestation (a before-and-after study). Results: In 24 pregnant women, thigh edema was not detected in any of the 48 legs before or after the use of elastic stockings. All 48 legs in 24 pregnant women had physiological lower leg edema, but not thigh edema. The average grade of pitting edema in each lower leg significantly decreased after using the stockings (36 weeks, 1.77 ± 0.85; 37 weeks, 1.79 ± 0.77; 38 weeks, 1.04 ± 0.74, p < 0.0001). In addition, the skin thickness of the lower legs was significantly decreased after the use of elastic stockings (36 weeks, 7.47 ± 2.45 mm; 37 weeks, 7.93 ± 2.83 mm; 38 weeks, 7.15 ± 2.35 mm, p < 0.0001). Conclusions: The wearing of elastic compression stockings on the lower legs is objectively effective for improving leg edema in pregnant women.