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Radiolucent vs. Radiopaque

Discussion in 'Step I' started by Pox in a box, Jun 4, 2005.

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  1. Pox in a box

    Pox in a box 1K Member

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    1. Does "radiolucent" mean it appears white on radiographs?

    2. Does "radiopaque" mean it appears black on radiographs?

    3. If something is radiolucent, is it also white (or yellowish in the case of cholesterol stones) in the body?

    4. If something is radiopaque (like pigment stones), is it black (or dark green) in the body?

    I've been stumped by this concept for several months now and keep confusing it. I asked last year's step 1 MVP at my school and he even seemed a bit confused. I used to have a mnemonic but I can't remember what it was...

    BOWL, WOBL, BLOW???? Thanks in advance.
  2. H0mersimps0n

    H0mersimps0n HMO CRUSHER

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    r u serious?

    air is radiolucent (black) on film, bone is radioopaque (white) on film...

    dictionary.com

    1 entry found for radiolucent.

    Main Entry: ra·dio·lu·cent
    Pronunciation: -'lüs-&nt
    Function: adjective
    : partly or wholly permeable to radiation and especially X rays


    1 entry found for radioopaque.

    radioopaque

    radio-opaque adj : not transparent to X-rays or other forms of radiation; "barium sulfate is radiopaque" [syn: radiopaque] [ant: radiolucent]

    IF x-rays make it through a material then they make it to the film where they develop that part of the film thereby "developing" that part of the film (black) and leaving the radioopaque parts undeveloped (and white)
  3. Pox in a box

    Pox in a box 1K Member

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    Yeah, I'm serious. Your explanation doesn't make a lot of sense though in terms of stones (gallstones/kidney stones). I knew the air/bone relationships on chest x-rays but I don't understand what it means for these stones.
  4. H0mersimps0n

    H0mersimps0n HMO CRUSHER

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    x-rays (that I've ever seen) come in two "colors" - black and white, WHETHER something is radioopaque or radiolucent or not depends on the DENSITY of the object the rays are going through- That is what I should've stated sooner...

    color of the stone doesn't affect anything on the radiograph, it's all about density- clearly you DON'T understand the difference between bone and air...
  5. guarana

    guarana like a bird on the wire..

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    yeah, i always get the stones mixed up too. it's like, you have to do an order of operations to remember what it will look like.
  6. Pox in a box

    Pox in a box 1K Member

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    Clearly you don't understand that you don't do an x-ray to detect gallstones or kidney stones. I didn't ask how you can tell if there's air in the chest cavity due to a tension pneumothorax (like if someone stabs me in the back) or how to count ribs. I understand that concept fine. I was just wanting to see if there's a way to figure out if a gallstone, for example, is mainly cholesterol, pigment, or something else. I have my answer now so don't reply.
  7. HiddenTruth

    HiddenTruth Senior Member

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    Well, actually, usually they end up doing an abdominal KUB (which is an abdominal XRAY), since it's the cheapest and quickest way. In terms of kidney stones, there are a couple of things you should know, I think.

    1. Calcium Oxolate and Uric acid (rhomboid shaped) stones form in ACIDIC urine (vowels)
    2. Clacium phosphate (coffin lid shaped) and MAP (mag ammon phosp/struvite) stones form in alk urine.
    3. Only PURE uric acid stones are radiolucent (which means they do not show up on regular KUB's--meaning they are BLACK on xray), and for sake of being complete, some cysteine stones are also radiolucent. But, the big one is uric acid.
    4. So, the 3 other stones are radiopaque (which means they DO show up on KUB very nicely, and they appear WHITE). But, keep in mind, that sometimes you get uric acid stones which are partially composed of calcium oxolate as well, and thoe can show up on KUB.
    5. So, KUB will usually detect number and size of stones; however, smaller stones (<2mm) are still not seen, and usually you can do US, which will detect anything larger than 3mm. And, it will detect ALL types of stones.

    Ok, for gall stones.
    1. Pure cholesterol stones are usually solitary, round to oval, radially aranged crystals: they are are radiolucent (black; won't show up on KUB).
    2. Mixed stones- faceted shape, most common, but only 20% are radiopaque
    3. Pigment stones- these are the ones that are most likely to be observed on xray (about 70% radiopaque), and these are usually caused by cases of hemolysis (calcium bilirubinate stones). These can be black (sterile), or brown (usually as a result of infection).
    Distant likes this.
  8. Pox in a box

    Pox in a box 1K Member

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    I'm pretty sure ultrasound is the way to go for gallstones.
  9. HiddenTruth

    HiddenTruth Senior Member

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    Yea, for gallstones, it's US (first line study); however, I think for kidney stones, esp. in the ER setting, a KUB may be done. But, we've ordered US straight up too--
  10. alhkim

    alhkim

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    in surgery you will learn the 90/10 rule...90% of kidney stones are radiopaque (i.e. visible on x-ray), 10% are radiolucent (i.e. not visible); for gallstones, 10% are radiopaque, 90% are radiolucent (therefore, US is study of choice)
  11. Pox in a box

    Pox in a box 1K Member

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    KUB?
  12. Mumpu

    Mumpu Burninator, MD

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    Kidneys, ureter, bladder, aka flat plate, an AP abdominal xray.
  13. HiddenTruth

    HiddenTruth Senior Member

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    It's an abdominal xray (stands for kidney ureter bladder, but no one says that)
  14. a_ditchdoc

    a_ditchdoc

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    Most often I have seen IVP done in the ER to rule out kidney stones. Perhaps they ordered KUB first without my knowledge...

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