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Chemical Dipsticks: Glucose & Ketones

by Carlo Raj, MD
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    00:00 let's talk about glucose in order for you to understand your glucose, we had previous lectures in which we spent a lot of time with understanding as to how the kidney handles this glucose, right? first and foremost, normally should you be urinating your glucose? No. almost all of it gets reabsorbed.

    00:19 it should, normally through your glucose transporters that we've talked about in great detail when dealing with proximal convoluted tubule now, if by chance your patient has hyperglycemia, then at some point, you may then hit what are you gonna hit first? what's that term called medically, where you detect glucose early on in the urine? Good, that's called renal threshold, right? Not TM - that's transport maximum; renal threshold so if you start finding glucose within the urine, be careful.

    00:53 we'll not detect fructose or other sugars.

    00:56 so when you use these dipsticks, be careful glucose could be detected but if your patient is suffering from fructosuria, and so forth it won't detect it so you have to be smart your patient is exhibiting issues as cataracts and such, and then glucose comes out to be negative, you're still detecting symptoms like fructosuria, you need to use something else to find it detects glucose in the urine as low as 30 mg/dL do you understand how low this is? point is, are you supposed to have any glucose in the urine? basically, No.

    01:30 so you need to find or you need to have effective dipstick that finds glucose even at really low levels serum glucose plus glucosuria, obviously we're referring to diabetes mellitus now normal serum glucose plus glucosuria normal pregnancy you understand the difference? so if you find serum glucose to be elevated what's normal glucose? give it to me approximately 100, right? normally, approximately 100 keep it simple right now so you'd understand the significance if your serum glucose is elevated, take a look at the arrow and you have glucosuria, what's your diagnosis? diabetes mellitus Stop.

    02:13 if your serum glucose is normal but your patient has glucosuria how about a pregnant lady? we talked about pregnancy in great detail when your pregnant, a female then her plasma volume increases up to perhaps even 50 percent in increase that's a lot of plasma volume that could be increased potentially Number two, do you remember her renal threshold? before we move there, well tell me about a female and what about her ability to take in glucose into her tissue is it impaired? or is it taking up the glucose in great abundance? Think before you speak.

    02:53 the fetus, she's pregnant, that fetus wants food, "Mama, feed me" now you have glucose in that mother in her plasma don't you want to feed that fetus? so therefore her ability to take up glucose in her skeletal muscles are impaired on purpose, physiologically. so that she can then deliver the glucose passing through the placental barrier to the fetus are we clear? we'll talk more about this when we talk about gestational diabetes mellitus won't we? so normal serum glucose, glucosuria perhaps you'll be thinking about pregnancy low threshold don't memorize it, understand it low threshold for glucose in a pregnant lady benign glucosuria, low renal threshold for glucose let's say genetically speaking, a patient is just born with a low renal threshold you understand how important it was for us to walk through the physiology so that you'd understand the concept of renal threshold what does that mean to you? the early, early, early signs of finding glucose in the urine let's continue..

    04:05 so what about microalbuminuria as being a dipstick? well if you find microalbuminuria along with glucosuria you know that this is diabetic nephropathy more sensitive than standard dipstick Remember, if you use the standard dipstick, you may not find albumin in your urine at lower levels but there's a microalbuminuria dipstick, sensitive at very low levels microalbuminuria plus glucosuria, they'll give you information in which you can then arrive at the proper diagnosis, here diabetic nephropathy what if that's ketones that you find? now before we begin, tell me simple biochemistry for ketones breakdown product of which one of these? is it protein? No.

    04:46 is it carbohydrates? No.

    04:48 is it lipid? Yes Are we clear? your best example would be symptom like diabetic acidosis what happens? more likely in which type of diabetic mellitus patient? Type 1. Why? No insulin to begin with you tell me insulin responsible for breaking down what? carbohydrate, protein or is it lipid? obviously carbohydrates. really? yes of course you know this.

    05:16 insulin responsible for breaking down carbohydrates so that you can have glucose and company, correct? Now my point is this, you got through glycolysis say that you don't have insulin. Wow, I still need energy.

    05:29 So if you can't get them from carbohydrates, who are you turning to? you're turning to me? No you turn to lipids.

    05:35 so you're gonna break down your lipids and that lipid is gonna do what? breakdown into ketones.

    05:40 you've heard of beta-oxidation, have you not? of course you have from biochemistry.

    05:45 so if you're weak in beta-oxidation, i'll quickly take a look at your topic on ketones so you're breaking down your lipid, what are some important ketones that you wanna know? take a look, now pay attention so now that you've understood, or recapped DKA (diabetic ketoacidosis) worst case scenario: where you're breaking down ketones in great excess you have to, cause you're left with no other choice and some of these ketones include acetone, acetoacetic acid, and betahydroxybutyric acid here it detects acetone, acetoacetic acid but not betahydroxybutyric acid why is that so important? well, betahydroxybutyric acid is one of those ketones that you produce as alcohol metabolism Is that clear? so now i'm giving you two differentials for ketones appearing pathologically number one: diabetic ketoacidosis, what's the other one? alcohol now in alcohol, you produce mass amounts of betahydroxybutyric acid but this ketone dipstick is not going to measure, so you're gonna come back negative for ketones But for Pete's sakes, if your patient is telling you that I'm drinking one bottle of Jack Daniels per day, are you kidding me? of course that's alcohol of course there's alcoholic type of metabolic acidosis taking place Nitroprusside in the test system only reacts with acetoacetic acid and acetone but not the betahydroxybutyric acid so look for your ketone dipstick being negative even in a patient who's an alcoholic who you know is producing ketone such as betahydroxybutyric acid


    About the Lecture

    The lecture Chemical Dipsticks: Glucose & Ketones by Carlo Raj, MD is from the course Urinalysis.


    Included Quiz Questions

    1. 30 mg/dL
    2. 50 mg/dL
    3. 200 mg/dL
    4. 150 mg/dL
    5. 100 mg/dL
    1. Renal threshold for glucose is lowered.
    2. It is always pathologic.
    3. Glucosuria is not common in pregnant patients.
    4. Renal threshold for glucose is higher.
    5. None of these are correct.
    1. Essential fructosuria
    2. Pregnancy
    3. Paroxysmal nocturnal hemoglobinuria
    4. Acute intermittent porphyria
    5. Diabetes mellitus type 1
    1. Beta hydroxybutyric acid
    2. Acetone
    3. All of the answers are detected.
    4. Two of the answers are not detected.
    5. Acetoacetate
    1. Microalbuminuria dipstick
    2. Nitroprusside dipstick
    3. pH dipstick
    4. SSA dipstick
    5. Glucose dipstick

    Author of lecture Chemical Dipsticks: Glucose & Ketones

     Carlo Raj, MD

    Carlo Raj, MD


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