How Dry Weight and Fluid Gain Affect Dialysis Patients

A person with healthy kidneys may urinate up to seven times a day. Most people on dialysis; however, make little to no urine, because their kidneys are no longer properly removing wastes and extra fluid from the body. Without urination, fluid builds up in the body and can cause swelling, shortness of breath and/or weight gain. Hemodialysis filters the blood to remove excess fluid from your blood to get you down to your dry weight.
What is dry weight?
Dry weight is your weight without the excess fluid that builds up between dialysis treatments. This weight is similar to what a person with normal kidney function would weigh after urinating. It is the lowest weight you can safely reach after dialysis without developing symptoms of low blood pressure such as cramping, which can occur when too much fluid is removed.
Dialysis cannot rid the body of fluid as effectively as healthy kidneys that work around the clock. Most hemodialysis patients go to dialysis treatment three times a week for about four hours, so the body holds onto extra fluid and waste in the days between treatments.
Fluid is removed during dialysis to return the patient to his or her dry weight by the end of the treatment. Ideally, the goal is to target a weight where the patient will be normally hydrated (not feel thirsty) and feel comfortable.
How is dry weight determined?
In most cases, dry weight is an estimate determined by your doctor, based on his or her experience and your input. Your doctor will prescribe your dry weight based on your weight when you have:
normal blood pressure
the absence of edema or swelling
neck veins that are not distended
the absence of lung sounds (rales and crackles) related to fluid overload
no shortness of breath or congestive heart failure
a normal size heart shadow on X-ray
It is generally a clinical estimate since there are no reliable scientific ways of measuring dry weight. Many patients can be above their dry weight and have extra fluid without it being noticeable or causing clinical symptoms.

Dry weight should be assessed every three to six weeks and adjusted when a patient gains or loses actual weight. Other factors, such as urine output and swelling between treatments, also should be considered when adjusting the dry weight. (Urine output often stops completely after six months of being on hemodialysis.) Your doctor will determine dry weight gain, as opposed to fluid weight gain.