Kidney Stones - Diagnosis and Treatment
22 September 2016
I write this with the recent summer days just behind us. The temperature topped 30° Celsius and we often see a tidal bulge of patients with stones a few weeks after this event.
There is good evidence of a tie-in between stones not only from the point of view of ureteric colic, but renal stones as well in the hotter months (1). This may not come as a surprise, as often fluid management is one of the key preventers in stone disease, but nevertheless, new stone formers with their first stone are more likely to present in the summer than the winter.
Stones can of course present to GPs in a number of ways. Relatively few present with ureteric colic, as the pain is so excruciating that most patients will call an ambulance and present to Accident & Emergency. A proportion will appear insidiously, slowly growing within the ureter and others within the kidney where the pain again may be more of an ache. Stones may also present with sepsis, infections and haematuria. Patients these days are usually referred with haematuria to the Haematuria Clinic, and of course I am delighted to see patients with haematuria through the Roding, but in a proportion the cause of the blood will indeed be a stone in the urinary tract.
One of the commonest questions asked is whether urinary tract infections in women can be related to stones. Certainly there is evidence that patients with persistent urinary tract infections, i.e. the same culture, with the same sensitivities over and over again, are usually associated with some type of surface, and stones are a good medium for this. In other women with recurrent infections, stones can still be a cause, and it is not unreasonable in these women to arrange an ultrasound scan to assess the upper tracts. A residual volume estimation is also possible on these scans and can be useful.
Are any groups more prone to stones than others? Stones were used to be thought of as a disease for men and whilst the rate in men now reaches 1 in 8, women are becoming more like men in many of their habits, and whilst oestrogen does generally protect women to an extent whilst menstruation continues, from stones, the overall instance in women is 1 in 13 (2). Indeed, in one study in Germany the amount of money spent on stones in one year in one area was £1,000,000 equivalent (2).
Stones are therefore common and should be thought of. Ultrasound can be very useful in the community to screen patients, but has its limitations. Pfister in 2001 demonstrated that typically, ultrasound has an overall sensitivity in specificity of 75% for stone disease. In a series we presented at the World Congress of Endourology in 2015 (3), we found that generally a negative ultrasound was correct, but a positive one was not necessarily so.
Dedicated, in-house ultrasound provided by the Roding Hospital, can be extremely
useful in delineating the stones further as necessary, although the gold standard remains CT KUB at ultra-low dose, which gives prediction information, such as stone density and the presence of Randall’s Plaques, which are a precursor of stone disease. The Roding Hospital is able to offer a full complement of diagnostic tests, and management of stones in-house.
Patients may also wish to consider Flexible Ureterenoscopy, which involves passing a telescope via natural orifices, to remove the kidney via a basket with or without the use of a laser. Stones can also be removed percutaneously with a PCNL and the modern take on this operation for difficult lower pole stones which are large, is an ultra-mini PCNL through a small track. All of this can be offered locally at the Roding Hospital, including a surveillance pattern. There is evidence that stones of 4mm or above have a 75% chance of some trouble in the future including bleeding, infections, enlargement, pain and ureteric colic (5), nevertheless that does leave 25% which will not change and so a discussion needs to be had with patients about this. Certainly at the Roding the author prefers an MDT type approach with all options being on the table and the pros and cons being discussed with every patient fully so that patients can be empowered to make up their own mind to see fit.
Prevention is a key thing with stone disease for 2 reasons. The first is that there is a lot of erroneous information found on-line including miracle cures and various different homeopathic style medicines which allegedly dissolve stones. The second reason is that prevention of disease is clearly a better option than continued surgery and to prevent even one stone episode in 10 years would be sensible. Classically, patients with a typical 1500ml urine output and a stone, have a 50% risk of a further stone in 10 years (6).
Certainly the most important factor in stone prevention remains fluid intake. Whilst many people believe that water is the best form of fluid and this may be correct, the key thing is to set up a lifestyle change and this means something which lasts lifelong or the stone risk will return. As such for patients who are not Calcium Phosphate stone formers, generally fluids which do not acidify the urine are better, and I often recommend drinks such as sugar-free orange squash, as the citric acid in these drinks is converted as citrate in the urine, which not only alkalinises it, but may help stone formation as it inhibits this. We know that salt increases the risk of stone formation along with many other conditions, and so I suggest to my patients that salt load should be reduced. The evidence for most stones is that Calcium intake is generally preventative, and the key message of this is the idea of a balance between Calcium and Oxalate ingestion. The stores of Calcium are of course extremely high, whereas Oxalate are almost non-existent, and to increase the amount of Calcium in a diet generally binds out Oxalate in the gut, which can be helpful. Certainly supplementation with Calcium and vitamin D may be safer, if taken at mealtimes therefore.
Many foods contain a degree of Oxalate. The key again remains the level of unopposed Oxalate in the diet. Significantly large amounts of Oxalate appear in Beetroot, Rhubarb and Swiss Chard. Moderation is the key here, and with fluid intake, this can be an important message. Vitamin C which is generally seen as a very safe vitamin, is excreted into the urine and almost completely converted into Oxalate, and so more than a 1000% of the RDA, which is a single tablet, is something to be discouraged in stone formers.
I was on television last year on Food Unwrapped on Channel 4 discussing Protein in stone formers. There is good evidence that excessive protein intake is linked with stone formation. This is particularly in the form of animal protein as it is converted into purines. The Urate production from this is a strong promoter for stones and very important in patients who make Urate stones.
Stone disease is not going to go away any time soon. The ability of the Roding to diagnose and treat these patients is without question. Key messages in prevention remain important and fluid intake has to be the number 1 thing to discuss with every patient with stone disease.
Mr Stuart Graham
- Boscolo-Berto R, Dal Moro F, Abate A, Arandjelovic G, Tosato F, Bassi P, Do Weather Conditions Influence the Onset of Renal Colic? A Novel Approach to Analysis. Urol Int 2008;80:19-25
- Romero V, Akpinar H, Assimos DG. Kidney Stones: A Global Picture of Prevalence, Incidence, and Associated Risk Factors. Reviews in Urology. 2010;12(2-3):e86-e96.
- MP27-2 Evaluating and Improving the Diagnostic Accuracy of USS for Urolithiasis in Hospital and in the Community: a 12 month Study JM Withington, M Mercer, SJ Graham World Congress of Endourology 2015, London
- M. Tligui, M.R. El Khadime, K. Tchala, F. Haab, O. Traxer, B. Gattegno, P. Thibault, Emergency Extracorporeal Shock Wave Lithotripsy (ESWL) for Obstructing Ureteral Stones, European Urology, Volume 43, Issue 5, May 2003, Pages 552-555
- Current Opinion in Urology March 2005 - Volume 15 - Issue 2 pp: i-i,65-147
- Goldfarb DS, Coe FL. Prevention of recurrent nephrolithiasis. Am Fam Physician. 1999 Nov 15;60(8):2269-76