Best prep for KUB X-ray for kidney stone?

January 4, 2009 6:45 AM

How can I maximize the odds of a KUB X-ray seeing my kidney stone? Do I drink lots of water? Fast? Avoid foods that lead to gas?

I have a kidney stone in my upper ureter (verified by CT scan). It did not show up on a KUB X-ray. I'm going for a followup KUB X-ray in a few weeks. I would like to maxmize the chances that the stone will show up in the KUB so that I do not have to follow up with a CT.

Now, I know the stone may be transparent to X-rays (radiolucent). What I'm trying to minimize is that my bowels will obstruct the X-ray and hide the stone. I've read that stools and gas can block the stone from view. Should I do anything about this? Are there other things that can occlude the X-Ray that I should know about?

I know that you are not my doctor, etc. However, if you have advice on how to maximize the odds that a stone will show up, fire away. Bonus points if you can point me to a radiology text or similar that explains what a patient should do to prep for the exam.

In case it makes a difference, based on the CT the stone is approx 4.5mm. As far as I know no assessment has been performed for the kind of stone.

Thank you.

PS. I want to maximize the odds of the KUB finding the bugger because it will increase the odds that my doc will be able to use the external shock-wave thing to fragment it, assuming it's moved a bit lower in my ureter, and also it will let me avoid the higher dose of radiation I'd get from a CT.

PPS. I know you are not my doc. I would ask my doc, but he's got poor communication skills and so I'd rather find pointers to authoritative material, or advice that will lead me there.

posted by anonymous to Health & Fitness (2 answers total)

I've passed probably a dozen or more kidney stones over the last ten years. I've had probably twice that many KUBs and maybe 6 or 7 CT scans. Each CT scan has been when I presented in the ER over night for pain relief in the middle of an attack. The preferred ER protocol is to through a whole CT at it, which must make sense in that context. My urologist, however, always uses the KUB for inter-attack assessments, and when he does follow up between the time a present in the ER and when I eventually pass the stone.

Your 4.5mm stone is plenty big enough to show up on a KUB. My doc has been able to identify stones both in my kidney and in the ureter from 2mm, and occasionally smaller. In the years I had the most attacks my BMI was around 30, so it's not because I'm peculiarly see-through. I never had to do any special prep, but I do understand your concerns about bowel obstruction hiding the image, but I was never given any special prep instructions. Not once. The thing is, most stones light up the x-ray like crazy, because they're the same consistency as bone. In some cases they're made of the same stuff bone is. I have been able to pick out a 4.5mm stone on a KUB. If yours is in the radiolucent category- which I wasn't aware existed (uric acid based stones, maybe?) - you're just sunk on being able to see it.

I have passed every stone that has entered my ureter except one. In October a passed a 7mm stone without help other than Vicodin. In my experience the first attack from each kidney stone is the worst. I haven't been shy about getting even morphine at that point. When that same stone has gotten caught up again though, I've been able to get by with oral pain-killers and waiting the thing out. Not once has any doctor mentioned the shock-wave fragmentation of a stone. I wondered about that so one time I asked about it, and was told by my urologist that he didn't consider it necessary and that the same result could be achieved by waiting.

The one time the stone wouldn't come out on its own they fished it out without making an incision. My stones in the 4.5mm range hurt like hell in the first attack, a couple made me take percocet once between attack 1 and passing, but they all came out without much trouble, and they all lit up the KUB like a Christmas light. I'd skip the CT and wait it out.
posted by putzface_dickman at 9:00 AM on January 4, 2009

Please note that anything you plan to do (bowel prep, drink lots of water, etc) could just as easily make it harder to see to the stone. I think you're over-thinking this. If it shows up, it shows up. If it doesn't, it doesn't.
posted by gramcracker at 12:51 PM on January 4, 2009 [1 favorite]