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Specific Gravity of Urine – Visual and Chemical Exam (Nursing)

by Rhonda Lawes

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    00:01 Alright, we've looked at the physical appearance of the urine.

    00:04 We look at the pH of the urine.

    00:06 Now let's spend some time in specific gravity.

    00:09 Now, I can learn about the patient's hydration status and their kidneys ability to concentrate urine from this number.

    00:16 The specific gravity of pure water is 1, and I know that urine is water with other things dissolved in it.

    00:24 So it makes logical sense that the urine specific gravity should be greater than 1.

    00:28 In fact normal is 1.010-1.030, still with me? Good deal, okay now, I'm not trying to confuse you but I'm going to show another value on the screen.

    00:41 But before I do, I want you to keep in mind that's the value I recommend for you to memorize for NCLEX.

    00:47 Okay, that's a good reference range.

    00:50 I'm putting this one up here just to let you know that some labs might consider 1.002 to 1.030 as normal.

    00:59 I put it up there just as a caveat for you to be aware of but if I was memorizing for the NCLEX, it's 1.010 to 1.030, that's the value I would go with.

    01:11 Now have you ever wondered why there aren't units with specific gravity.

    01:15 It's kind of weird, isn't it? It's because specific gravity of urine is just a ratio.

    01:21 We're looking comparing one substance to another substance.

    01:25 In the case of urine specific gravity, we're comparing urine to water, so that's why we don't need any type of units.

    01:33 Now a specific gravity and hydration.

    01:37 The greater a number is past 0.10 you're moving towards relative dehydration.

    01:45 Okay. So at 0.1010, no, I'm not dehydrated.

    01:50 But I want you to have the concept put your finger on 1.010, now move it towards 1.020, move it towards to 1.030, as you're going that direction in the numbers are going up.

    02:05 It's moving you towards dehydration because the higher the specific gravity number is that indicates the severity of dehydration.

    02:15 Now again, it's not that 1.24 is dehydrated and 1.22 isn't it's all on a spectrum and what your patient can tolerate.

    02:25 But know that urine in the 1.010 range is going to be be lighter much lighter than urine at 1.030.

    02:36 So the higher the specific gravity number is it indicates the severity of the dehydration.

    02:41 Now what are underlying causes of higher specific gravity? Dehydration.

    02:46 We just talked about it.

    02:47 What is glycolysuria? Will uria means urine, glyco means sugar.

    02:54 So if I have extra glucose in the urine, that means I've got more things dissolved in that water in the urine, and that's why my urine specific gravity would be higher.

    03:06 Remember pure water is 1, the more things I have dissolved in my urine the higher the number of urine specific gravity.

    03:14 Now glucose in urine or diabetes mellitus, you're going to end up with extra things in your urine and a higher specific gravity.

    03:23 Same principle applies to proteinuria.

    03:25 Someone might have nephrotic syndrome their kidneys are struggling they end up with protein in their urine that's going to be more things dissolved in the urine and a higher specific gravity number.

    03:38 Remember protein is supposed to stay in your blood not in your pee.

    03:43 So if we have protein being dumped into your urine, that's a sign that the kidneys are struggling.

    03:49 Shock we've got issues with your kidneys being perfused.

    03:53 And so they're not able to really release a lot of water because they're trying to hang on to everything as a compensatory mechanism to raise your blood pressure.

    04:02 Last one is SIADH.

    04:04 That's an endocrine imbalance, where you have excess of this hormone, anti diuretic hormone.

    04:12 If I have excess ADH, then on a hanging on to everything and I'm not putting out very much water at all with my urine and that's why my urine specific gravity will be higher.

    04:24 Okay now what if it's lower, everything's just the opposite right? So the closer I am to 1.010, that's means I'm relatively hydrated because the lower the specific gravity number is that means the concentration of urine is not as intense as it is moving towards 1.030.

    04:46 Okay, so give me your finger again if I was at 1.030 put your finger there where that would be and as you're moving along the continuum, you should be at about 1.020 now know that your urine is becoming more dilute.

    05:03 This patient is probably becoming more hydrated if they were dehydrated.

    05:07 So 1.020 keep on moving to 1.010.

    05:13 I'm still within a lot normal range, normal range, but I want you to have in mind the lower that number is, there's less things dissolved in that urine so it's becoming closer and closer and closer to pure water with nothing dissolved in it.

    05:31 Now what am I thinking about if I get a urine analysis back on a patient and I see a low urine specific gravity.

    05:37 I want to look at the following things.

    05:39 First of all, are they on any diuretics? Okay, because that's going to cause them to dump off all kinds of excess fluid.

    05:46 Is it possible? They could have diabetes insipidus.

    05:50 Do they have adrenal insufficiency.

    05:53 Okay now we are really messing with the endocrine system.

    05:57 Diabetes insipidus remember that is not enough ADH or I can't respond to the ADH I have.

    06:04 Adrenal insufficiency.

    06:06 Okay so you adrenal glands sit on top my kidneys, right? Those are those little endocrine organs.

    06:11 I have an Adrenal medulla and I have an adrenal cortex.

    06:15 Now, the cortex comes all those corticosteroids but out of the medulla I've got like epinephrine pen all those things, all those hormones that come out of my adrenal gland.

    06:27 But it also has aldosterone.

    06:30 Now aldosterone is a hormone that tells my body to hang onto sodium and wherever sodium goes what follows? You got it, water! Okay so, whoa, that's a lot of stuff about the endocrine system.

    06:45 We got diabetes insipidus because we've talked about that before.

    06:48 Adrenal insufficiency.

    06:50 One of the things my adrenal glands, squirts out is aldosterone.

    06:55 So that's that same thing from the RAAS.

    06:59 So when my body recognizes, hello I do not have enough volume.

    07:04 It responds by squirting out, aldosterone.

    07:08 When the aldosterone cames out my kidney say, whoa, hang on to sodium when my kidneys hang onto sodium then it naturally they hang on the water.

    07:19 If my adrenal gland is insufficient, I don't have the ability to do that.

    07:24 So what do I do? I'm not getting the message to hang onto sodium and I saw water just keeps leaving my body instead of being reabsorbed like I need it to be the floodgates have opened.

    07:37 So that's why specific gravity of urine in adrenal insufficiency will be low.

    07:44 What will their urine look like? Pale, very pale.

    07:48 It's going to look like water.

    07:50 Because instead of hanging under water, your body is just letting it leave your body because it doesn't have the hormone messenger to tell it to hang on to it.

    07:59 Okay, that's a lot of stuff.

    08:00 So let's back up a little bit, diuretic Yeah, that's working in the parts of my kidney tell my body to put out extra water.

    08:08 Diabetes insipidus, I don't have the chemical messenger that tells me hang onto water.

    08:13 Adrenal insufficiency that's going to be another endocrine problem because I don't get the message to hang on to sodium and water, so it's all leaving my body.

    08:24 Now let's look at the other side.

    08:26 If you have aldosterone and impaired renal function.

    08:28 We've got that same issue with aldosterone and you could have early stages of chronic kidney disease.

    08:36 Okay catching a clue here.

    08:38 Yeah, all of this either impacts the kidney on some way or as a direct problem with the kidney.

    08:46 So I'm either giving you a medication.

    08:48 You have an endocrine disorder or your starting to see the early signs of chronic kidney disease.

    08:54 Those are all possible reasons of a low urine specific gravity.

    08:59 Now, how do I know which one it is? Well, you can't tell from the urine specific gravity.

    09:04 Remember that's your job.

    09:05 Anytime a lab value is abnormal, that's a warning shot to you to know, hey, I got to dig deeper into the patient's assessments and their history and their meds and figure out why this is low.

    09:18 Now, this is the saddest one of all fixed urine specific gravity means it doesn't change.

    09:24 So that urine specific gravity will stay the same right around 1.010, which is normal, but it doesn't matter how much fluid the patient takes in or doesn't take in.

    09:36 It's essentially unchanged.

    09:38 I like to say that means your kidney is the equivalent of a pet rock, fluid is going through it, but it's not changing it in any way shape or form.

    09:47 This can often happen after chronic glomerular nephritis, remember that's inflammation in the glomerulus.

    09:54 So this is a really really bad sign.

    09:57 If you have fixed urine specific gravity, you need multiple urine analysis to identify that and you clearly do other testing, but if you have a patient who has an intrinsic renal insufficiency, they've had chronic glomerular nephritis, you would expect that as it progresses and gets worse, you'll see fixed urine specific gravity.

    10:18 So it'll hang out right there about 1.010, no matter what you do as far as fluid volume.


    About the Lecture

    The lecture Specific Gravity of Urine – Visual and Chemical Exam (Nursing) by Rhonda Lawes is from the course Introduction to Urinalysis – Renal Assessment (Nursing).


    Author of lecture Specific Gravity of Urine – Visual and Chemical Exam (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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