The Urinary Tract and Different Types of Urolith

What are Kidney Stones?










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Home > Key Issues > Kidney Stones



  • Kidney stones are stones formed from minerals which lodge in the kidneys.

  • They may cause CKD, and they also increase the risk of kidney infections.

  • If the cat's body attempts to pass them, they may get stuck in the ureter and cause a medical crisis.

  • They can be difficult to treat, but there are a number of newer treatments available at a few centres which look promising.

The Urinary Tract and Different Types of Urolith


I sometimes hear from people whose cats have another type of problem to kidney stones, so I shall start by trying to explain a bit more about the urinary tract and what sort of problems may arise.


The urinary tract consists of:

  • two kidneys

  • two ureters (thin tubes, each of which leads from a kidney to the bladder)

  • the bladder

  • the urethra, a tube which carries urine from the bladder to outside the body

The kidneys and ureters are considered to be the upper urinary tract and the bladder and urethra are considered to be the lower urinary tract.


One of the kidneys' functions is to filter waste products. Unfortunately sometimes this process doesn't work as well as it should and calculi or uroliths (stones) form somewhere in the urinary tract. The medical term for this is urolithiasis.


There are two main types of uroliths commonly seen in cats. The cat's urine pH may give you a clue as to which type of stone you are dealing with. A normal urine pH level is in the range of 6.0 - 6.5.



A cat with a urine pH higher than normal (i.e. more alkaline urine) can be at risk of developing struvite crystals. These may be found in the bladder (when they may be referred to as bladder stones) or the urethra, i.e. in the lower urinary tract. Therefore struvite crystals belong to the category of conditions known as feline lower urinary tract disease (FLUTD).


In some cases, struvite crystals can be dissolved with a change of diet which may also prevent them from reappearing. Therapeutic diets are available which are acidified to change the balance of the urine so struvite crystals are less likely to develop. Many non-therapeutic diets are also acidified these days to help prevent struvite but this may be one factor in the increased incidence of calcium oxalate stones in cats (see below).


In more severe cases, where the urethra is blocked, the cat will need surgery to unblock him (cats with this type of blockage are usually male). During the period of the blockage, the cat may suffer from acute kidney injury, but with luck this will resolve once the blockage has been removed.


It is rare for CKD cats to develop problems with struvite because CKD cats tend towards acidity.


This page does not discuss struvite any further but there are some links here and Harpsie's Website has some information about this problem.


Calcium Oxalate

A cat with a lower urine pH than normal (i.e. more acidic urine) can be at risk of developing calcium oxalate stones. These may also be found in the bladder, but are also often found in the kidneys so may be referred to as renal calculi or nephroliths, or kidney stones.


The rest of this page focuses on calcium oxalate stones found in the kidneys and ureters.


Cornell University College of Veterinary Medicine has a good overview of both struvite and calcium oxalate uroliths.

Cornell University College of Veterinary Medicine also has photos of the different types of stones and crystals that may be seen.

The Merck Veterinary Manual discusses the different types of stones seen in dogs and cats.


What are Kidney Stones?


In over 90% of cases, stones that form in the kidneys are calcium oxalate stones, i.e. formed from a combination of calcium and oxalate. Other, rarer stones are occasionally found, but struvite is not found in the kidneys. The stones may calcify, though some cats may develop calcified blood clots rather than actual stones.


The presence of kidney stones increases the risk of kidney infections (pyelonephritis), and may cause CKD.


Many kidney stones are inactive (static) so they do not cause any problems and you may not even know your cat has them. However, problems may arise if the cat's body attempts to pass the stones (active) through the ureter (the tube that connects the kidney to the bladder) and down into the bladder.


Smaller stones, although painful, may be successfully passed, though it may take some time (one cat on Tanya's Support Group took fifteen months to pass a stone).


Some stones may move into the ureter, then back into the kidney. This is less serious but may still cause kidney damage.


The main problem arises when large kidney stones start actively moving into the ureter. Since the ureter is very narrow (around 0.3mm in a cat, less than a quarter of an inch), larger stones may lodge in the ureter (i.e. get stuck). This is called obstructive nephropathy or a blockage. This is very serious because it prevents waste products that would normally be excreted via the bladder from being excreted, so they build up in the kidneys. This can cause acute kidney injury.


Stones in the kidneys are called nephrolithiasis. Stones in the ureter are called ureterolithiasis.


Royal Canin has a picture of a calcium oxalate stone. Ouch!


Mar Vista Vet has a helpful overview of kidney stones.


Calcium oxalate crystalluria (2008) Haak CE & Cohn LA NAVC Clinician's Brief Sept 2008 pp27-28 has an overview of calcium oxalate stones.


The University of Minnesota College of Veterinary Medicine Urolith Center will analyse feline stones free of charge.




Kidney stones may form if there is reduced urination for some reason, or if the urine contains more of the substances contained in the stones (in over 90% of cases, calcium and oxalate) than usual.


Urine that is more acidic (pH below 6) increases the risk of developing calcium oxalate stones. The recent trend for acidifying cat food (which is done to prevent the opposite problem of struvite crystals, which develop in urine that is too alkaline) is thought to be a factor in some cases. Magnesium levels are often reduced in cat foods in order to reduce the risk of struvite crystals and The Merck Veterinary Manual states "Common management schemes that involve feeding urine-acidifying diets with reduced magnesium have reduced the incidence of feline struvite urolithiasis. Magnesium has been reported to be an inhibitor of calcium oxalate formation in rats and people; thus, the reduced magnesium concentration in feline urine may partially explain the increase in calcium oxalate stones in cats."


Many cats with calcium oxalate stones also have idiopathic hypercalcaemia (elevated calcium levels in the blood with no obvious cause). It is not yet known which comes first, the hypercalcaemia or the kidney stones.


Occasionally, calcium oxalate stones may be caused by a Vitamin B6 deficiency.


Calcium in food does not contribute to the development of kidney stones. In fact, calcium in foods can bind with oxalate and therefore help prevent the formation of kidney stones. However, calcium supplements may contribute to the problem.


Studies indicate that certain breeds appear to be more likely to develop calcium oxalate stones, including Persian, British Shorthair, Ragdolls and Scottish Fold cats.




Kidney stones can be very painful but in some cases, there may be no obvious signs, since cats instinctively try to hide pain. In other cases the cat may be subdued and lethargic and not want to eat. Some cats will have blood in the urine (haematuria) or frequent kidney infections.


Some cats urinate more, but others exhibit reduced urination. If your cat is unable to urinate, this is a medical emergency and you need to get to a vet as quickly as possible.




Blood Tests

Your vet will probably run blood tests. If a cat's kidney values suddenly becomes extremely high, a kidney stone blocking the ureter may be the cause.


A cat with active kidney stones may also have elevated phosphorus and potassium levels.


Around 48% of cats with kidney stones will be anaemic, perhaps because of concurrent kidney disease, infection or inflammation.


A cat with big kidney little kidney (see ultrasound below) may have kidney values that wax and wane.


Palpation and X-Rays

Your vet will also palpate (feel) your cat's kidneys, which may be tender to the touch. The vet may also be able to feel a difference in size, in which case an ultrasound will usually be performed. X-rays should be performed, and may help the vet assess the number and size of the stones.



An ultrasound may show dilation of the ureter and renal pelvis (the upper end of the ureter). Dilation of the renal pelvis is called pyelectasia. Stones may also be visible on the ultrasound, though this is not always the case (bloodstones are often not visible on ultrasound).


Kidney stones may also cause hydronephrosis or fluid build up in the kidney, which the ultrasound will show. Pet MD has some information about hydronephrosis.


One thing that may be seen is one small kidney and one enlarged kidney, known as big kidney little kidney syndrome. What this usually indicates is that a stone previously moved into one ureter, blocking it, but the cat did not exhibit any symptoms. This kidney gradually ceased to function and shrank (i.e. became the little kidney). The remaining kidney had to take over some of its work, so it grew in size (i.e. became the big kidney). If a stone eventually also moves from the big kidney into the ureter, the cat is then in crisis, because the one working kidney is no longer able to function.


Some cats with big kidney little kidney syndrome will be unable to urinate, which is a medical emergency and you need to get to a vet as quickly as possible. See below for treatment options.




There are a number of different treatments, and which one to use depends upon how severe your cat's case is, including whether there is a blockage and, if so, whether both kidneys are affected.


Inactive kidney stones are not normally treated in cats, not even in CKD cats. Don't worry if your vet suggests this because ACVIM small animal consensus recommendations on the treatment and prevention of uroliths in dogs and cats (2016) Lulich JP, Berent AC, Adams LG, Westropp JL, Bartges JW & Osborne CA Journal of Veterinary Internal Medicine 30(5) pp1564–1574 states that "The presence of nephroliths in cats with chronic kidney disease did not significantly affect the progression of renal disease." The cat should be monitored via urinalysis (to make sure the cat has not developed pyelonephritis) and x-rays every few months (to see if the stones have moved).


If treatment is required, the treatment options fall into these categories:

ACVIM small animal consensus recommendations on the treatment and prevention of uroliths in dogs and cats (2016) Lulich JP, Berent AC, Adams LG, Westropp JL, Bartges JW & Osborne CA Journal of Veterinary Internal Medicine 30(5) pp1564–1574 lists the various treatment options available in order of preference. These recommendations assume that every possible treatment is freely available where you live, which of course is not always the case.


How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 has an overview of the various treatment options.


Medical Management


Your vet may offer a number of medical treatments. How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 says that medical management is "effective in some feline cases (8-17%)" and recommends that it should be considered for 24-48 hours before any more invasive treatment is instigated. Dr Berent adds "During these few days of stabilization, there is a possibility that the ureterolith may pass spontaneously, making an intervention unnecessary."


Intravenous Fluids (Diuresis)

This means that the vet uses intravenous fluids to try to flush out the stones. The cat will be hospitalised for 2-3 days and other treatments may also be offered, such as those listed immediately below.


How successful this is depends upon a variety of factors, including the size of the stone and how long it has been in the ureter. Calcified blood clots can often be dislodged, but fewer than 10% of kidney stones are passed.



Sometimes diuretics such as Lasix or mannitol are used to increase the flushing effect and help force the stone out. ACVIM small animal consensus recommendations on the treatment and prevention of uroliths in dogs and cats (2016) Lulich JP, Berent AC, Adams LG, Westropp JL, Bartges JW & Osborne CA Journal of Veterinary Internal Medicine 30(5) pp1564–1574 recommends that mannitol should be used in conjunction with IV fluids.



Medications may also be given to relax the ureter in the hope that this will help the stone to pass through. Commonly used medications for this purpose are amitriptyline and prazosin, a muscle relaxant.


One cat on Tanya's Support Group who was given prazosin for six weeks managed to pass the stones and lived for a further 20 months, see Success Stories.


Amitriptyline eliminates calculi through urinary tract smooth muscle relaxation (2003) Achar E, Achar RAN, Paiva TB, Campos AH & Schor N Kidney International 64 pp1356–1364 discusses the use of amitriptyline in this manner in cats.


Mar Vista Vet has some information about amitriptyline.



It is wise to give antibiotics to a cat in an acute situation with kidney stones. How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 says "Note that many patients with ureteral obstructions have concurrent UTI, and broad-spectrum antimicrobial therapy is recommended for all patients, with urine culture and sensitivity testing part of the work-up."



Active kidney stones can be very painful, so discuss the use of painkillers with your vet.


Dietary Changes

If your cat is not in crisis, your vet may initially suggest dietary changes. Unlike struvite crystals (see above), calcium oxalate stones cannot be dissolved through a change in diet but there are a few things you can try that may help maintain your cat.


As it happens, most therapeutic kidney diets are also suitable for cats with calcium oxalate stones, whether or not they have CKD. There is a list of therapeutic kidney diets here but check with your vet that the one you wish to use is suitable.


If, on the other hand, you are feeding an acidified food (these foods are often labelled "for urinary tract health"), stop immediately. These foods are intended to treat the opposite problem to calcium oxalate stones, and can therefore make the problem worse by making the urine even more acidic. You should not give your cat anything containing cranberries for the same reason. Acidified foods are not normally appropriate for CKD cats in any event.


Pet food safety: sodium in pet foods (2008) Chandler ML Topics in Companion Animal Medicine 23(3) pp148-53 states that "Increased dietary sodium increases urine output and may decrease the risk of forming calcium oxalate uroliths due to the decrease in relative supersaturation of solutes. However, caution should be used in increasing the sodium intake of patients with renal disease as increased dietary sodium may have a negative effect on the kidneys independent of any effect on blood pressure." Do not increase your cat's sodium intake without your vet's approval.


Oxalate degradation by intestinal lactic acid bacteria in dogs and cats (2004) Weese JS, Weese HE, Yuricek L & Rousseau J Veterinary Microbiology 101(3) pp161-6 mentions that the use of prebiotics, including fructooligosaccharide products (FOS), a type of fermentable fibre, may help reduce the formation of calcium oxalate stones. However, fermentable fibre may lead to elevated calcium levels in the blood (hypercalcaemia).


University of California at Davis College of Veterinary Medicine has some information on the dietary management of stones.


Surgical Management



A number of possible invasive surgeries are available, such as opening up the kidney and removing the stones, or removing a kidney or a ureter. This is very expensive (it costs several thousand dollars) and invasive. It has a relatively high mortality rate, and the stones often recur. The use of nephroscopy and ureteral tertograde hydropulsion for urolith removal from the upper urinary tract in 11 patients (2014) Buttin P, Collard F, Cachon T, Fau D, Goy-Thollot I, Carozzo C & Viguier E Revue de Médecine Vétérinaire, 165 pp1-2, 2-11 reviewed the cases of nine cats and two dogs treated between 2008 and 2011 and found the mortality rate was 18.8% even before discharge. How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 says about ureterotomy (cutting into a ureter) "In cats, the procedure-associated complication and mortality rates are reported to be over 30% and 18%, respectively."


In almost all cases, a stent or a subcutaneous ureteral bypass would be a better choice. 



I am sometimes asked about this as a possible treatment. Extracorporeal shock wave lithotripsy (ESWL) uses shock waves to smash the stones so they can be passed. This non-invasive treatment works well in humans, and a small number of facilities in the USA do now offer this treatment for dogs, for whom it can also work well.


ESWL is only suitable if the stones are large enough to be seen on ultrasound, which unfortunately is not usually the case with cats: How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 says "This procedure can be safely performed for nephroliths <10 mm and ureteroliths <5 mm; however, because the fragments are rarely less than 1 mm, and the feline ureter is 0.3 mm in diameter, this is not an effective treatment for cats."


Ohio State University College of Veterinary Surgery has a FAQ sheet about lithotripsy and says "All male cats and most female cats will not be large enough to have the surgery performed."


Percutaneous Nephrolithotomy (PNLE)

This is an endoscopic (keyhole) treatment for stones which are too large for lithotripsy. ACVIM small animal consensus recommendations on the treatment and prevention of uroliths in dogs and cats (2016) Lulich JP, Berent AC, Adams LG, Westropp JL, Bartges JW & Osborne CA Journal of Veterinary Internal Medicine 30(5) pp1564–1574 states "In human medicine, endoscopic nephrolithotomy is the most effective minimally invasive treatment option for large stone burdens and has the highest stone-free rate when compared to alternative therapies. Endoscopic nephrolithotomy has been successfully performed in dogs and cats." Although a cat's size is not an issue here as it is with ESWL (How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 says "we have performed this technique on a dog weighing 3.1 kg"), I don't know anyone who has had this performed on a cat, like ESWL I think this is probably offered more to dogs.


The Animal Medical Center in NYC has some information about this procedure.


Interventional Management


Interventional treatment methods still require surgery but are much less invasive and more likely to be successful with fewer complications. Unfortunately these treatments are very expensive.

The Animal Medical Center has some information on these devices.



A stent is a mesh-like tube, ideally with double pigtails at the ends to hold it firmly in place, which is placed inside the ureter. The stent causes passive dilation of the ureter. A cat's ureter is around 0.3mm in diameter, but an Animal Medical Center case study states that once a stent is in place for up to two weeks, the diameter can increase to up to 1.5mm. This means that the urine can flow around the stones, and in some cases (depending upon the size of the stones), it may be possible for the stones to be passed.


The cat will usually be in hospital for several days after stent placement and will usually be fitted with a feeding tube at the same time, which will remain in place for 6-12 weeks.


The success rate is approximately 96%, and the stent can remain in place for years. In about 5% of cases, the stent moves, but it can usually be repositioned. Other possible problems include infections and a biofilm forming on the stents, which may necessitate replacement.


Possible side effects include blood in the urine, and I have heard from a couple of people whose cats have stents that their cats seem to pee more.


The main problem I see with stents is their cost. One member of my support group paid US$15000 back in 2012 for a stent on one side and a SUB (see below) on the other. The stent was replaced eighteen months later at a not inconsiderable additional cost. Another member paid US$8000 for two stents in 2014. Eleven months later both stents had to be replaced at a cost of US$4700. I have heard from a couple of people that the estimates they received were a lot lower than the actual cost, so bear this in mind if you decide to go ahead. You can read below about a research study at UC Davis where some of the costs are covered for participants.


Ureteral obstructions in dogs and cats: a review of traditional and new interventional diagnostic and therapeutic options (2011) Berent AC Journal of Veterinary Emergency and Critical Care 21(2) pp 86–103 has detailed information on the use of stents.


How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 is a more up to date report on Dr Berent's use of stents.


Technical and clinical outcomes of ureteral stenting in cats with benign ureteral obstruction: 69 cases  (2006-2010) (2014) Berent AC, Weisse CW, Todd K & Bagley DHJ American Veterinary Medical Association 244(5) pp559-76 reports on 79 stents placed in 69 cats. 95% of the cats had elevated kidney values (azotaemia) before treatment and 71% of them continued to be azotaemic, though in most cases the numbers improved. 27% of the cats needed a stent exchange at some point.


Subcutaneous Ureteral Bypass

A subcutaneous ureteral bypass (SUB) is a form of microsurgery which was pioneered at the Animal Medical Center in New York City. It does not aim to remove the stones unless it is easy to do so; instead, it aims to bypass the stones by providing an alternative route between the kidneys and the bladder (an artificial ureter, if you like).


A SUB consists of a tube within a tube surrounded by mesh which runs outside the ureter (unlike a stent, which is placed inside the ureter). Because the SUB is outside the ureter, it can be bigger than a ureter or a stent and is around 5-6mm in diameter (for comparison, a feline ureter is around 0.3mm in diameter). Therefore, although the cat may still develop kidney stones, the urine should in principle still be able to flow through because of the extra width of the device compared to a ureter.


In order for a cat to receive a SUB, the renal pelvis (the upper end of the ureter) must be dilated, so essentially your cat must have an active blockage at the time the SUB is fitted. If your cat's renal pelvis is not dilated, you may be offered a stent instead (see above).


The success rate is good, with SUBs remaining effective in around 94% of cats over a median of two years. One of the main post-operative risks is pancreatitis.


The cat will usually be in hospital for several days after SUB placement and will usually be fitted with a feeding tube at the same time, which will remain in place for 6-12 weeks.


An advantage of a SUB is that it also incorporates an access port in the abdomen which can be easily accessed later if necessary in order to flush out any stones that are accumulating. Initially these flushes are performed four times a year, but this may be gradually reduced to every six months. Your cat should not need to be an inpatient for this to be done (I am told it only takes about ten minutes). Other tests (bloodwork, blood pressure measurement and urinalysis with urine culture) should also be performed, though if your cat has CKD, you are probably having these tests run this frequently anyway.


Like a stent, sometimes a SUB has to be redone. I understand that in around 20% of cases the tubing needs to be replaced. One member of my support group's cat needed to have the SUB tubing replaced and then had to take her cat to the vet for t-PA (tissue plasminogen activator) flushes 2-3 times a week for about a month to break up a blood clot that was presumed to be in the kidney itself. Although this was expensive (costs range from US$150-360 per flush), her cat's kidney function did eventually return to normal.


Previously a stent was the first line of treatment but as SUB techniques have improved, so SUBs have become more reliable and are probably a better choice if your cat is a suitable candidate (and your vet has extensive experience with them) because of the option to flush through the port, which you cannot do with a stent.


The surgery is now available at a small number of centres in the USA, Canada, UK, France, Switzerland, Italy and France. As with stents, one major concern is the cost:

  • One member of Tanya's CKD Support Group had this surgery performed on her cat in the USA in early 2012. She paid US$2000 for the tube. Surgery costs were an additional US$4000 - 6000.

  • Another member paid US$15000 that same year for a stent on one side and a SUB on the other. The stent was replaced eighteen months later at a not inconsiderable additional cost.

  • Another member was quoted US$5000 in 2015 for one SUB.

  • A fourth member was quoted US$6000-8000 but her cat had some post-surgery complications so in the end she paid around US$10000.

  • One member in Germany paid 2400 in 2015 for a SUB, but her cat had complications and infections, so in total over 11 months she paid around 17000 (this cost included SUB flushes).

  • I have heard from a couple of people that the estimates they received were a lot lower than the actual cost, so bear this in mind if you decide to go ahead.

Subcutaneous ureteral bypass device for treatment of iatrogenic ureteral ligation in a kitten (2015) Johnson CM, Culp WTN, Palm CA & Zacuto AC Journal of the American Veterinary Medical Association 247(8) pp924-931 reports on a 17 week old kitten who successfully received a SUB.


Ureteral obstructions in dogs and cats: a review of traditional and new interventional diagnostic and therapeutic options (2011) Berent AC Journal of Veterinary Emergency and Critical Care 21(2) pp 86–103 has detailed information on the use of SUBs.


How I approach... ureteral obstruction in dogs and cats (2013) Berent A Veterinary Focus 23(3) pp17-25 is a more up to date report on Dr Berent's use of SUBs.


Other Treatments


These are more holistic treatments but as far as I know, there has been no research into these treatments in cats to date.


Chanca Piedra

Chanca piedra is a tropical plant which is sometimes used for liver problems. It has been used in Brazil to treat calcium oxalate stones. There are a number of varieties but the two varieties commonly found in chanca piedra commercial products are Phyllanthus amarus, which is from the Amazon region, and Phyllanthus niruri, which is from the Andes. Web MD has an overview of chanca piedra.


I am not aware of any studies in cats and do not know of anybody who has used chanca piedra, but there are some studies into its use in rats and humans.


In one study in rats, Effects of Orthosiphon grandiflorus, Hibiscus sabdariffa and Phyllanthus amarus extracts on risk factors for urinary calcium oxalate stones in rats (2011) Woottisin S, Hossain RZ, Yachantha C, Sriboonlue P, Ogawa Y & Saito S Journal of Urology 185(1) pp323-328, the rats were fed a diet designed to increase the presence of calcium oxalate in the kidneys. The rats in one group were then given 3.5mg of chanca piedra daily. The study found "The Hibiscus sabdariffa group showed significantly decreased serum oxalate and glycolate, and higher oxalate urinary excretion. The Phyllanthus amarus group showed significantly increased urinary citrate vs the untreated group. Histological examination revealed less CaOx crystal deposition in the kidneys of Hibiscus sabdariffa and Phyllanthus amarus treated rats than in untreated rats. Those rats also had significantly lower renal tissue calcium content than untreated rats.'


Can Phyllanthus niruri affect the efficacy of extracorporeal shock wave lithotripsy for renal stones? A randomized prospective long-term study (2006) Micali S, Sighinolfi MC, Celia A, De Stefani S, Grande M, Cicero AF & Bianchi G Journal of Urology 176(3) pp1020-1022 looked at the use of chanca piedra in 150 human patients for three months following treatment with lithotripsy (ESWL). The study found that 93.5% of patients given the chanca piedra were stone-free after six months, compared to 83.3% who did not receive chanca piedra. For lower stone patients, " the stone-free rate was 93.7% in the treatment group and 70.8% in the control group." The study concludes "Its efficacy and the absolute lack of side effects make this therapy suitable to improve overall outcomes after extracorporeal shock wave lithotripsy for lower pole stones."


The effect of Phyllanthus niruri on urinary inhibitors of calcium oxalate crystallization and other factors associated with renal stone formation (2002) Freitas AM, Schor N & Boim MA BJU International 89(9) pp829-834 examined the use of chanca piedra in rats. It concludes "Treatment with Pn strongly inhibited the growth of the matrix calculus and reduced the number of stone satellites compared with the group receiving water. The calculi were eliminated or dissolved in some treated animals (three of 22)."


Phyllanthus niruri normalizes elevated urinary calcium levels in calcium stone forming (CSF) patients (2004) Nishiura JL, Campos AH, Boim MA, Heilberg IP & Schor N Urological Research 32(5) pp362-366 gave chanca piedra or a placebo to human patients for three months. The study concludes "we observed that P. niruri induced a significant reduction in the mean urinary calcium in hypercalciuric patients. In this short-term follow-up, no significant differences in calculi voiding and/or pain relief between the groups taking P. niruri or the placebo were detected. Our data suggest that P. niruri intake reduces urinary calcium based on the analysis of a subset of patients presenting with hypercalciuria.'


Kidney Atlas assessed a number of commercial variants of chanca piedra and found many of them were contaminated or devoid of any active ingredient. It mentions two brands which it considered to be pure.


As always, do not use any product without your vet's approval.



Renalof is a dietary supplement for humans made from activated couch grass (Agropyron repens). It is said to help dissolve calcium oxalate stones. It has apparently undergone trials in humans in Romania, Indonesia and Cuba.


The effectiveness of Renalof compared to Kalkurenal and placebo (2012) Kristyantoro B, Alif S, Djojodimedjo T & Budiono B Indonesian Journal of Urology 19(2) found there was a significant decrease in stone size in patients treated with Renalof.


Randomized double-blind study with Renalof in patients with calcium oxalate renal lithiasis (2012) Sánchez MCA, Villanueva VE & Vázquez RA Revista Cubana de Investigaciones Biomédicas 31(1) reports on the Cuban trial and states that "Stone size reduction was 7.7% for the Renalof group and 0% for the placebo group by the third month, whereas the stone disappearance response was 86.5% by the third month for the Renalof group... It was concluded that Renalof is an efficient product for the destruction or reduction of calcium renoureteral calculi, with no adverse effects."


Renalof is not approved for cats, though I did hear from one lady whose vet decided to use it as a last ditch attempt to help her cat (I don't know how she got on). As always, do not use this product without your vet's approval.


Vet Medic sells Renalof for £23.30 for 150ml.




Much depends upon whether the stones are static or active, how severe your cat's case is, which treatment is used and how successful it is. Unfortunately it is difficult to stop the development of kidney stones and some of the available treatments are very expensive, but I do know of cats who have survived for years.


Management and outcome of cats with ureteral calculi: 153 cases (1984 - 2002) (2005) Kyles AE, Hardie EM, Wooden BG, Adin CA, Stone EA, Gregory CR, Mathews KG, Cowgill LD, Vaden S, Nyland TG, Ling GV. Journal of the American Veterinary Medical Association 226(6) pp937-44 discusses a large number of cases over a period of eighteen years, and states that even after successful treatment, many cats will have impaired kidney function.


That study refers to cases that occurred before some of the more modern treatments were available. Rate and frequency of recurrence of uroliths after an initial ammonium urate, calcium oxalate, or struvite urolith in cats (2009) Albasan A, Osborne CA, Lulich JP, Lekcharoensuk C, Koehler LA, Ulrich LK & Swanson LL Journal of the American Veterinary Medical Association 236(12) pp1450-55 found that only 7% of cats developed calcium oxatale stones again following treatment, and the average grace period before this happened was over two years. The authors believe the actual recurrence rate may be higher than this, but it does appear that following successful treatment, the chance of recurrence may be relatively low for some cats, and this is particularly true for cats who receive newer treatments such as a stent or a SUB.


There are several members of Tanya's CKD Support Group who have dealt with kidney stones in their cats. I will be adding some of their stories to the Success Stories page in due course, but in the meantime feel free to join the group for information and support on the treatments available.




Prevention is not easy, but you can take a few steps to reduce the risks. Ideally you want your cat to have a urine specific gravity below 1.30.

  • Follow the dietary changes outlined above.

  • Try to keep protein intake around 35% on a dry matter analysis basis. This is a suitable level for a CKD cat anyway.

  • If your cat has hypercalcaemia (elevated calcium levels in the blood), try to get it under control, though this is not always easy.

  • For some cats, calcium oxalate stones may be caused by a Vitamin B6 deficiency, in which case a Vitamin B supplement may help (be guided by your vet as to an appropriate brand).

  • Do not give your cat supplements containing calcium.

  • Have monthly x-rays or ultrasounds performed to ensure existing stones have not moved.



Ureteral Obstructions and Stent Placement: UC Davis

Evaluation of post-operative outcome in cats undergoing ureteral stent placement to relieve ureteral obstruction


This study is to assess the complications that may arise during and after the placement of a stent to relieve blockages. Bloodwork and urine output will be monitored, with visits required two weeks and three months after stent placement. Some of the blood tests and ultrasound tests will be paid for by the study.


Dr. Culp

Phone (530) 752-1393



SDMA and Creatinine Levels in Cats with Blockages: Animal Medical Center, NYC

Assessment of symmetric dimethylarginine SDMA and creatinine concentrations in cats with post-renal obstructions before and after decompression of the obstruction


This study investigates the usefulness of SDMA, a new measure of kidney function, in cats with animals with post-renal azotemia (increased kidney values caused by obstructions of the ureters or urethra).


Dr. Kendall Wilson






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This page last updated: 30 March 2017

Links on this page last checked: 29 March 2017







I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who has lived through CKD with three cats. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.


If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.



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