Recent comments in /f/askscience

hatsune_aru t1_j9qmunn wrote

Reply to comment by loki130 in Why can’t you “un-blur” a blurred image? by so-gold

I like to think of that extreme example as "edge effects". Obviously there are limitations to the recovery technique, but "deblurring" is absolutely a thing both in imaging and similarly in non-imaging applications.

https://en.wikipedia.org/wiki/Blind_deconvolution

In a sense, electronic engineering (which I can say I'm a specialist in) concepts like emphasis, equalization, etc are just compensations for channel effects, which one could think as time varying signal equivalents for blurring in imaging.

In that sense, recovery of a "blurred" signal via equalization is absolutely used everywhere that uses high speed digital signals like USB, DDR, PCIe, etc.

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DoctorStrangeMD t1_j9qmqz2 wrote

Reply to How can Doctors tell if one of your kidneys isn't working? by FineLetMeSayIt

Generally doctors avoid invasive procedures (like using an arterial Cather - aka small tube- to inject dye) or using contrast dye in a CT if there is renal dysfunction. Those specific Dye can injure the kidney.

Step 1: blood tests, urine tests. Blood tests for creatinine estimate renal function. If it is abnormally high, this triggers a doctor to investigate more. Urine test, mainly looking for urine protein. If you are losing protein in the urine, the kidney is not functioning right but the creatinine may still be in the normal range. This does not distinguish bilateral or unilateral kidney dysfunction.

Step 2: ultrasound (possibly with Doppler) -ultrasound shows the size of the kidney. This can easily show if 1 kidney is normal and the other is missing or “atrophic.” If a kidney has not been working well for a while; it will start to atrophy. Then you know that kidney is bad. -Doppler with ultrasound can see if the arterial flow is normal and equal. This avoids contrast which can hurt the kidneys.

That’s usually all you need.

But other tests could include MAG3 scan. A nuclear study. This shows how much function is in each kidney. This would definitely show if 1 kidney was failing earlier than another

https://en.m.wikipedia.org/wiki/Radioisotope_renography

Kidney biopsy. Usually though you do not biopsy 2 kidneys. As one reply mentioned it is more common to have kidney damage to both kidneys. Because both kidneys do the same work, they are affected similarly by conditions such as diabetes and high blood pressure that stress the kidney over time.

If 1 kidney was not working well, typically it is congenital, has bad blood flow, or had a blockage that does not allow urine the leave that kidney.

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loki130 t1_j9qm08v wrote

Reply to comment by hatsune_aru in Why can’t you “un-blur” a blurred image? by so-gold

In the extreme case, if you take an entire image and average it to a single color, clearly you can't reconstruct any detail from that no matter how clearly you know the algorithm. I think a similar argument could be made that a large image split into 4 quadrants that are each completely averaged would also be unrecoverable. Perhaps there is some floor of smaller blur radius where the image becomes recoverable, but I don't think it's obvious that knowing the blur process always allows reversal.

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dmmaus t1_j9qji0l wrote

Reply to comment by Krillin113 in Why can’t you “un-blur” a blurred image? by so-gold

No, that's not quite right. If you blur the same picture twice using the same blur filter, then yes, you end up with the same final image. But that's not the same as saying that if you blur two different pictures you end up with two different images. Two different pictures blurred with the same filter can end up being identical blurred images.

You can think of a blur filter as a set of vectors that move pixel information around, but the step you're missing is that the pixel information isn't moved to just one other pixel. It's spread around over several neighbouring pixels, and then added together with the information spread from other pixels that overlaps it. That adding together operation muddies the waters, so to speak - once the blurred pixel info is added together to form the final blurred image, you can't work out how to un-add them to separate them again. There will be multiple possible solutions to the problem of going backwards to an unblurred image, and no way to decide which is the correct solution.

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puahaha t1_j9qgvnh wrote

Reply to comment by FineLetMeSayIt in How can Doctors tell if one of your kidneys isn't working? by FineLetMeSayIt

Kidney failure is also sinister because you can be asymptomatic even while function is declining until it's really bad, like less than 20~30% functionality. So not only is compensatory action like one kidney fulfilling the role of the other at play, both will have to fail to a very significant degree before you even notice.

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medlabunicorn t1_j9qen68 wrote

Reply to How can Doctors tell if one of your kidneys isn't working? by FineLetMeSayIt

Couple of things might happen. In the beginning stages, you might put out lots of very dilute urine as your kidneys lose the ability to concentrate urine (other things can cause this , so it’s not definitive). You might put out less and less urine, with objects called ‘casts’ that we can see on the microscope, that are caused by slow flow inside the kidneys (other things can cause this as well, so it’s also not definitive). As it gets worse, your blood chemistries will start to get out of whack, specifically creatinine and electrolytes. If your doctor is looking for kidney failure, one of the things he or she might order is a a blood chemistry panel with an estimated GFR, or glomerular filtration rate; another is a creatinine clearance test, where you collect all of your urine for 24 hours, measure the average creatinine level of your urine over that time, and compare it to the creatinine level in your blood to see if the kidneys are filtering out as much creatinine as they should be.

One kidney, by itself, can do a fine job for you if it’s fully functioning.

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lascivious_boasts t1_j9qe4vg wrote

Reply to comment by FineLetMeSayIt in How can Doctors tell if one of your kidneys isn't working? by FineLetMeSayIt

It's actually much more common for both kidneys to fail together.

The underlying causes of kidney failure tend to be systemic (that is affecting the whole body) rather than local.

The big one is diabetes, and barring a blockage in blood supply to one kidney, the main damage is in all the tiny blood vessels that feed each nephron. This usually happens equally between both sides (although occasionally the renal artery stenosis is more of a problem, in which case one side can get a stent to try to maintain its function).

Other big causes are inflammatory/autoimmune. This means anywhere there's a kidney cell/structure the damage occurs. Broadly, this affects both sides at the same time.

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