A formula to estimate water loss in a malnourished patient with ascites: One inch equals one kilogram

Abstract

Severe ascites accounts for a large percentage of body water, making measurements of lean body mass (LBM) inaccurate. Thereare no bed-side methods to determine the contribution of ascites to LBM. Using the formula for a sphear, a patients volume ofascites was obtained by the standard equation (Volume = 4/3 × Pi × [radius]³). A 54-year-old malnourished Hispanic female withChild’s Class C liver cirrhosis presented to the ER with 2-weeks of increasing abdominal pain, girth, fever, chills and decreasednutritional intake. The admission abdominal girth measured 106 cm at the umbilicus. The radius of the sphere was obtainedmeasuring the abdominal girth divided by two times Pia times radius (radius = 106 cm/[2 × 3.14] = 16.9 cm). Using the abovecalculated radius of 16.9 cm, Volume = 4/3×3.14 × 16.9 cm³; = 20,208 cc = approximate volume of the abdomen at presentation.Using the same formulas, abdominal volume was 8,275 cm cubed seven days after discharge from hospital. The difference inabdominal volume from admission to follow up is 20,208 cc-8,375 cc = 11,833 cc, assuming a specific gravity of 1.0, 11.8-litersof volume or kg of weight. The amount of ascitic abdominal fluid lost was confirmed by comparing change in volume to changein body weights (66.0 kg-55.0 kg, admission and follow-up weights, respectively). The 11.0 kg weight loss was similar to theestimated change in abdominal body water change of 11.8 kg. Conclusion: The simple measurement of waist circumference mayprovide an estimate of ascites volume and changes in volume should be similar to changes in weight. For every 2.4 cm (1 inch)that the waist circumference is reduced, body weight (and ascites) should be reduced by 1-kilogram.