There are a bunch of things in medicine that I never really understood the gravity of until I got into clinical practice. I didn’t quite understand how big a deal Mallory-Weiss tear was, which is not a big deal. I didn’t really understand ileus. When a radiologist reported back an ileus on a CAT scan or a plain film radiograph, what did that mean? I never really understood how big a deal a Wenchebach is. The cardiologist wanted to be woken up at three in the morning with a Wenchebach. Now that takes some experience.
I felt the same way about nephrolithiasis, when someone presented with a kidney stone. How big of a deal was it? How important was it when the radiologist said there’s hydronephrosis or hydroureter? I’m like, oh my gosh, that means the kidney’s swollen. That’s got to be a big deal. So, today’s talk is going to be on nephrolithiasis.
Oftentimes they have a history of this. It’s like DKA. If someone’s in diabetic ketoacidosis, I’ll say to them, “Is this DKA? Have you been in it before?” A lot of times they know, “Yeah, I’ve been here before.” The same is true with nephrolithiasis. If you get a kidney stone, you have a fifty/fifty shot of getting another one. If you get a second one, then you’re probably going to be a stone former for the rest of your life. That’s kind of the deal. But fifty percent of the time you get one kidney stone and you never get another one.
Now, the onset of pain is normally very acute, because once that stone drops into the ureter, the pain comes on very quickly. That’s a key part of the history. If you have right lower quadrant pain, you have to ask, did it come on gradually or acutely? Appendicitis would come on gradually, because it’s an infectious process. Ectopic pregnancy would be a growing fetus in a fallopian tube, where somewhere outside it would be a slow grower until it perfs.
But when a stone drops into a ureter, the pain comes on very quickly. That’s a key part of the history. Is the stone pain colicky, did it come on very quickly? The pain in renal colic is from the peristalsis of the ureter. So, that peristalsis is what causes this horrible pain and that peristalsis is driven by prostaglandins. What does that mean?
If someone has kidney stone pain, you give them 30 IV of ketorolac. That can immediately take their pain from 10 out of 10 to zero out of 10. It’s not the most potent analgesic, but for kidney stones, it’s super sensitive. If I have someone who’s writhing in pain and vomiting, and ketorolac completely takes their pain away, that makes me pretty sure it’s probably nephrolithiasis. Symptoms are acute onset hematuria, dysuria frequency, and typically there are nausea and vomiting.
Can you have someone who does not have hematuria and a kidney stone? You can, but proceed with caution. Take your tongue and rub it over your cheek, on the inside of your cheek, you’ll feel the soft tissue, the buccal membrane. That’s kind of like what happens within the kidney. If you ever had a hard piece of cereal and it scratched your mouth, and you spit, microscopically you’d have blood in your spit. So, if I have someone who I think had a kidney stone but they have a negative urine for blood, I’m suspicious.
The pain the patient has, at least the location, is really going to be dependent on where the kidney stone got hung up. If it’s in the upper ureter, it’s typically anterior abdominal pain. If it’s lower ureter, a lot of times it’ll radiate to the groin. And if it’s the ureterovesical junction, they’ll often have urinary symptoms like frequency, urgency, and lower pelvic pain.
The pain comes on so acutely that, if they have a lower ureter kidney stone, that can go right to the groin. Why is that concerning? Because if you have acute onset of testicular pain, you have to think, is it torsion versus nephrolithiasis? Why is that important to understand? Well, if it’s testicular torsion, they’ve got a four- to six-hour window before they’re going to lose that testicle. It becomes so ischemic it can’t be saved. Nephrolithiasis doesn’t really cause that kind of long-term sequelae. So, that’s really important to differentiate nephrolithiasis versus testicular torsion. So what would be my advice there? Always rule out the torsion. Always go to the ultrasound first. I mean, clearly, the kidney stone will be much more common, but the sequelae of missing testicular torsion are pretty significant.
Say Can You See
So, what I teach is, if I was back in the Marine Corps… I’m getting patriotic on you… I’d go, “Oh-oh, say can you see.” If you think about the letters that start off “Say can you see,” SCUC, you’ll be able to remember the four kinds of kidney stones. You have struvite, calcium, uric acid, and cystine. You have four different kinds of kidney stones.
Struvite is typically made up of a bunch of different chemicals, like calcium ammonia magnesium and it’s normally because of infection. That’s why, when we work up someone with kidney stones, we’ve got to make sure we culture the urine at the same time. Often, it’s from frequent catheterizations.
The C stands for calcium; 85% of kidney stones are calcium. That’s the opposite of gallstones, where 85% of gallstones are cholesterol. Cool thing about struvite and calcium is, you can see them on a plain film radiograph.
Uric acid and cystine are radiolucent, which means I can’t see them.
So, there are four different kinds of kidney stones. That’s why we send people home with a strainer. We want them to collect that stone so we can analyze it to see which one of the categories they’re in, because it may change how urology follows them up.
With calcium stones, there is some literature that shows that lemon water decreases the incidence of getting kidney stones. The concentration they use in the study is eight to one. So, if you have a patient that has a kidney stone, you may want to recommend they fill a glass with one shot glass of lemon juice and seven additional shot glasses of water. That may decrease the incidence of kidney stones.
Hydrochlorothiazide also is helpful. If a patient has uric acid stones, allopurinol is an option. If they have struvite stones, remember that’s an infectious process and you want to look for the reason why they got a struvite stone, also known as a staghorn stone.
When there’s hematuria, always order urine cultures. Spiral CT is the image of choice. It’s a non-contrasted image. You don’t need contrast on it. They suggest ultrasound for children and pregnancy, but it really depends on where you work. And, in a radiograph is normally used to track a stone, so you don’t want to do a whole bunch of CAT scans to track a stone. If you found it, then the CAT scan can be used to monitor it.
Now, a urology provider that I worked with said this, he said, “If the stone is greater than 10 mm, a hundred percent of the time they’re not going to pass it. If it’s a 9 mm stone, they only have a ten percent chance of passing it. If they have an 8 mm stone, they have a 20% chance of passing it. A 7 mm stone, 30%.” I thought it was helpful to communicate that to patients, because if you have a really big stone, you’re going to need either a ureteral stent or shock waves. You’re going to need extracorporeal shock wave lithotripsy and we would refer that on to urology.
What is the indication for admission? Well, they do really pretty well. The question is, if someone’s got hydroureter and hydronephrosis, how long can the stone stay there before there’s permanent damage to the kidneys? As long as the other kidney is working well, it can stay there two weeks. That’s what we know.
Now, if a person only has one kidney and a kidney stone, that’s really a big deal. You really want to look at BUN and creatinine levels and make sure that those are normal. They should be normal. If you have one side ureter that’s blocked with a kidney stone and the other side is fine, BUN and creatinine should not take a hit. If they only have one kidney and they have a kidney stone, and they have a pyelonephritis on that side, that’s an absolute emergency.
They will get as sick as someone with Reynold’s Pentad. Remember, Reynold’s Pentad is right upper quadrant pain, fever, jaundice, hypotension, and altered mental status. It’s like a septic Charcot’s Triad. That needs to be decompressed emergently, either with a ureteral stent or a percutaneous nephrostomy tube by intervention radiology.