Does a Swollen Limb Make You Weigh More

[brazil84]

Or is the fluid just shifted from some other area in the body? If it's the former, and your leg has swollen about 20% in each direction, roughly what is the range of weight that could add?

[wood95]

I'm not a doctor or a scientist, but it seems likely to be the latter, not the former, unless for some reason you are eating and drinking and not expelling waste.

[Kimstu]

IANA Doctor either, but apparently some kinds of tissue edema (fluid retention) can cause short-term weight gain:

Swelling is the enlargement of organs, skin, or other body parts. It is caused by a buildup of fluid in the tissues. The extra fluid can lead to a rapid increase in weight over a short period of time (days to weeks).

If your leg increases 20% in diameter, then assuming your leg is roughly cylindrical, by my calculation its volume will also increase by 20%. Assuming that the leg on average has a density roughly equivalent to that of water, then its weight will go up by about the same percentage.

If we're just talking the lower leg here, and it weighs about 7 pounds, then the swelling would increase its weight to somewhere between 8 and 8.5 pounds. Roughly.

Could somebody please summarize this information for brazil84 in another post, since he can't see my posts? (Mods, I apologize if it's not etiquette to mention that, but otherwise the OP is never going to know that an answer to the question has been offered.)

[Michael63129]

Originally Posted by Kimstu

If your leg increases 20% in diameter, then assuming your leg is roughly cylindrical, by my calculation its volume will also increase by 20%...

You need to square the increase in diameter to get volume increase (shape doesn't matter as long as it stays the same), so you actually have a 44% increase in volume and weight (again assuming that the average density is that of water), which is more significant and would show up more on a scale.

[Damfino]

You are squaring the radius to get the volume of the cylinder. So a 20% increase in diameter (and radius) does not equal a 20% increase in volume.

Pi x r squared = 3.14 with a radius of 1
Pi x r squared = 4.52 with a radius of 1.2

[Kimstu]

Whoopsie, you're both right and I used the wrong formula: thanks.

[Chief Pedant]

A variety of homeostatic mechanisms keep a reasonably constant intravascular volume.

When something swells up, fluid is transferred from the blood into the intracellular spaces, but that lost intravascular fluid is replaced from fluid you drink (or don't urinate or defecate out).

So, your weight increases overall when something is swollen. Sometimes remarkably so, depending on the underlying condition.

The mathematicians can give you formulas, but of course there's a much easier way: weigh yourself.

As an aside, you can have a fairly marked amount of fluid retention before you start looking like you are retaining fluid, so for some conditions such as kidney problems, weight, rather than girth measurements or the like, is used as a reasonably accurate proxy for how much fluid is being retained.

[WhyNot]

Unintended weight gain or loss of more than 5 pounds per week is to be reported to the doctor, as it indicates water retention beyond "normal", and may indicate impaired kidney or heart function.

[psychobunny]

Just as an anecdote-the most dramatic case I've seen was a woman with heart failure. When she was put on the correct cocktail of medications and diuretics she lost 100 lbs in 3 weeks. (No-I am not exaggerating. She pretty much lived in the bathroom. I saw her initially with the cardiologist and one week later she had lost 50 lbs. I found it hard to believe but when I say she was retaining fluid I mean everything was swollen-arms, legs, abdomen). I have never ever seen anything like it again.* As an answer, though, I say yes. You can retain amazing amounts of fluid in your tissues.

*Actually-I take that back. A diabetic patient of mine became preeclamptic and went into kidney failure and put on 70 lbs in about 2 weeks. Luckily, she lost almost all of it when they delivered her child.