When you have kidney disease, your kidneys are no longer able to remove waste effectively from your body or to balance your fluids. The build up of wastes can change the chemistry of your body causing some symptoms that you can feel, and others that you don't.
Reference to a range of cells is typically of the form (A1:A6), which specifies all the cells in the range A1 through to A6. A formula such as =SUM(A1:A6) would add all the cells specified and put the result in the cell containing the formula itself.
The SUM() function does what its name suggests - finds the sum of a series of numbers. Used in its simplest form, you can enter the following into a cell in Excel: =SUM(10,20,30) When you do this, the cell will display 60, which is the result of the formula.