This this episode of PodMD, Melbourne trained Urologist Dr Kapil Sethi will be discussing the topic of when to treat kidney stones, including what kidney stones are, the natural history of kidney stones, when to treat and the treatment options, when to refer and more.
Please note this is a machine generated transcription and may contain some errors.
*As always, all in this PODMD podcast is intended for health professionals and the comments are of a general nature. Information given is not intended as specific medical advice pertaining to any given patient. If you have a clinical issue with one of your patients please seek appropriate advice from a colleague with expertise in the area.
Today I’d like to welcome to the PodMD studio Dr Kapil Sethi.
Dr Kapil Sethi is a Melbourne trained Urologist with special interest in minimally invasive surgical techniques for benign and malignant conditions of the kidney, prostate and bladder. He completed international fellowships in advanced laparoscopy and robotics in Hamburg and Manchester and has public appointments at St Vincent’s and Austin Health, with a private practice in East Melbourne.
Today, we’ll be discussing the topic of when to treat kidney stones.
*We do hope you enjoy this podcast but please remember that the advice here is of a general nature and is not intended as specific advice about a given patient. The views and opinions expressed in this podcast are those of the doctor, not PodMD.
If you do have a patient on whom you require specific advice, then please seek advice from a colleague with appropriate expertise in that area.
Kapil, thanks for talking with us on Pod MD today.
Kapil: Thank you for having me.
The topic of today’s discussion is when to treat kidney stones. Kapil, can you give us a brief overview about how kidney stones usually present?
Kapil: Sure, kidney stones are usually either incidentally found during routine imaging, or may present with symptoms when they move around and, in particular, drop into the ureter.
Kidney stones are common, with 10% of Australians likely to have a kidney stone in their lifetime. When stones remain within the kidney, they are often in a fixed position and don’t cause much pain. If the stone moves around or causes any obstruction, this may cause discomfort or even haematuria.
Renal colic is the result of the kidney stone migrating to the ureter, causing an acute severe flank pain caused by ureteric spasm and obstruction. The distribution of this pain is from the flank under the ribs and radiating down into the groin and genitals.
What Investigations are useful when we suspect kidney stones ?
Kapil: The primary investigations that aid us would be good quality imaging. The gold standard here is to get a CT scan, as a CT KUB. This is a non-contrast scan that gives us great information. It tells me whether there are 2 healthy kidneys, along with accurate size and location of the stone. We are able to use density measurements to predict possible composition of the stone and what treatment might work best.
It is hard to rely on a renal US or XR KUB alone. With an ultrasound, the size is sometimes overestimated, and it is hard to visualise the ureter. With XR KUB, up to 20% of renal calculi are radiolucent so we cannot see them, and we cannot get an idea of internal anatomy and drainage either.
Many people may be worried about the radiation exposure with a CTKUB. For that reason, using renal US and XR KUB is routine in pregnant women and in children. For everyone else, a CT KUB would be the best. Because no contrast is used, radiation exposure becomes minimal. A CT KUB ends up having the same radiation exposure as 1-year background radiation or a single flight to Europe.
Once we have good quality imaging, there are some extra simple tests which may aid management. The first is getting a urine dipstick or MSU if we suspect there is a concurrent UTI. A serum renal function would tell us that there is no renal impairment and getting a baseline serum calcium and uric acid would look for any obvious underlying causes for stone formation.
Are there any red flags to look out for ?
Kapil: So yes there are some red flags to watch out for.
The first is if we suspected an infected obstructed kidney. This is in someone who would be septic with a kidney stone that may have led to obstruction and is a medical emergency. The differentiating feature here is that the patient would have a fever, sweats or rigors and be really quite unwell from sepsis. They need to go into the emergency department for prompt specialist review and decompression.
The second red flag is in someone who is anuric. We would see an anuric patient if they had bilateral obstructing calculi or an obstructing calculus in a solitary kidney.
The third red flag to look out for would be renal failure.
These three are absolute indications for urgent treatment. There are some relative indications that we would see, which are less time-critical but may also prompt specialist review.
They would be a rising creatinine, they may have pain not controlled by analgesia or persistent nausea and vomiting with an inability to keep down any oral fluid down. If there is any doubt about any of these, refer urgently to your urologist.
What is the natural history of kidney stones?
Kapil: So it’s fair to say that the majority of ureteric calculi that are less than 4mm in diameter pass spontaneously. There’s quite a famous study that included stones up to 4 mm in size, with 95% of them passing in a little over 4 weeks. And this is really quite size-dependent in the ureter, so if you had a small stone of 1 or 2 mm, this is more likely to pass quicker than a larger stone, makes sense really.
If a stone is 5 mm or larger within the ureter then the chances of passage are less than even. We therefore use a size of 5 or 6mm as a rough cut off for intervention.
Asymptomatic stones in the kidney do one of 3 things.
– Number 1, they do absolutely nothing and cause no issue to the patient lifelong.
– Number 2, they may grow in size and cause local symptoms such as discomfort and haematuria.
– Number 3, they may go on the move and drop down to the ureter causing renal colic.
When should you treat kidney stones and what are the treatment options?
Kapil: So when answering this question the two things I would look carefully out at our patient factors and also stone factors.
For the same reasons outlined earlier, we use a size cut-off of 5 mm in an asymptomatic kidney stone to recommend treatment. We tend to be more aggressive with certain types of patients and the patient factors I mentioned earlier may be related to occupations such as Pilots or public transport drivers who need to be stone-free in order to be cleared to work. If someone is quite isolated such as living in a remote area, working in mining or is an itinerant worker, we would try and get these patients completely stone free. The last group that we tend to be aggressive with stone clearance are those who have a solitary kidney because, as you can imagine, an obstructing calculus would put them into renal failure instantly.
Treatment options are dependent upon a number of variables that I mentioned.
If somebody has an infected obstructed kidney comma, anuria or renal failure they would require urgent decompression with either a ureteric stent or a nephrostomy which is a tube placed directly through the back into the collecting system of the kidney.
In a stable patient, we’ll see what the stone is likely made of and whether we can dissolve it in the first instance if we suspected something like a uric acid stone.
If you can’t dissolve it, the surgical options we can offer would be either shock wave lithotripsy, which is a non-invasive approach to delivering high-frequency sound waves to break larger stones into small passable fragments. We’re also able to go internally within the entire collecting system by an endoscopic approach where we can laser the stone under direct vision or extract it with a basket. For someone with a very large stone over about 2 cm or a complete staghorn, we would do keyhole surgery as percutaneous nephrolithotomy where through a small incision we access the kidney directly through the flank and fragment the stone that way. All modalities have a very high clearance rate.
When should a patient be referred to a urologist ?
Kapil: The answer to that question is really just anyone that you are concerned about. For a urologist, this is a very common condition to treat. Of course, if there are any red flags they would get an immediate referral.
Other reasons to refer would be
– If there was any complicating anatomy and especially in a solitary kidney,
– If the size was greater than 5 mm in diameter,
– If they were symptomatic
– If they had a specialist occupation or social circumstances that I discussed earlier
And finally, if they just not progressing despite appropriate conservative management and they’re being watched carefully they may have ongoing pain or renal impairment and these guys should be referred on.
How should patients with kidney stones be followed up ?
Kapil: I will answer that in two parts. The first is if we have kidney stones. If these are causing no symptoms in less than 5 mm in diameter they can be conservatively managed with no follow-up imaging required unless they became symptomatic. The stone may not grow for a number of years and so routine imaging is not indicated unless there were multiple small stones.
If it’s a ureteric stone that we’re dealing with, we just need to have a really good plan in place. The first objective is to confirm the passage of the stone. For a small uncomplicated stone, observation for 2 to 4 weeks would be very reasonable with repeat imaging at that stage. The patient should be informed to present to a hospital if they have a fever or ongoing pain. A referral to a urologist would be appropriate if the stone has not progressed or there is ongoing hydronephrosis in a ureteric calculus.
Are there any prevention strategies available?
Kapil: Sure I get asked this question all the time by my patients especially those who experience renal colic, and never want to go through it again ! Once you’ve had a stone you’ve got a 40 to 50% chance of having another stone in your lifetime. The number one prevention strategy is Hydration. It doesn’t matter what you drink but if you can drink 2-3 L a day, that would reduce stone formation. It’s very hard to do that volume daily and so what I usually tell a patient is to just drink so that their urine is clear and not that dark yellow concentrated colour.
Other dietary measures that have been proven to work are reducing the amount of salt and meat in your diet as animal protein can increase stone formation. 1 dietary supplement may reduce stone formation and that’s citric acid found in lemon juice. Squeeze 1 lemon into your water today and that will be enough.
If someone’s a recurrent stone former then we would consider a more invasive metabolic evaluation such as a 24-hour urine collection to look for high levels of excreted salts.
Thank you for your time here today in the PodMD studio. To sum up for us, could you please identify the three key take home messages from today’s podcast on when to treat kidney stones.
Kapil: My key takeaway points
1. Many stones less than 5 mm in diameter can be conservatively managed with analgesia and monitoring
2. Watch out for red flags of annual, fever, persistent pain or persistent nausea and vomiting
3. Small ureteric calculi can be conservatively managed if there is appropriate follow-up imaging to confirm passage
Thanks for your time and the insights you’ve provided.
Kapil: Thanks you.