#298 Urinary Stone Disease Will Rock Your World

October 4, 2021 | By Paul Williams

Do kidney stones have you saying “this too shall pass?” Our guest Dr. David S. Goldfarb, MD, FASN, FNKF, FACP can help! In this episode he takes us through risk factors as well as treatment and prevention for urinary stone disease.

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Credits

• Producer: Paul Williams MD
• Hosts: Matthew Watto MD, FACP; Paul Williams MD, FACP, Beth Garbitelli 
• Show Notes by: Shelagh Browne, Kate GrantMBChB MRCGP DipGUMed, 
• Cover Art and Infographic: Kate Grant MBChB MRCGP DipGUMed 
• Reviewer: Molly Heublein, MD
• Editor: Matthew Watto MD (written materials); Clair Morgan of nodderly.com
• Guest: David Goldfarb MD, FSN, FNKF, FACP

Sponsor: ACP acponline.org/telemedicine201

Sponsor: Ten Thousand tenthousand.cc code = CURB

CME Partner: VCU Health CE

The Curbsiders are partnering with VCU Health Continuing Education to offer FREE continuing education credits for physicians and other healthcare professionals. Visit curbsiders.vcuhealth.org .

Show Segments

• Guest book recommendation and advice  
• Common risk factors for urinary stone disease
• Differential diagnosis of kidney stones
• Symptomatology of kidney stones
• Types of stones 
• Urine pH
• Role of physical exam
• Role of imaging 
• STONE score
• Labs to order 
• Management of urinary stone disease
• Prevention of urinary stones and approach to lifestyle/diet changes 
• Outro

Urinary Stone Disease Pearls

1. The best story for a patient presenting with a kidney stone is a patient that previously had one and is telling you they have another one. 
2. Risk factors for urinary stones include gout, diabetes, obesity, warmer climate, and occupational factors where patients drink less or have reduced access to toilet facilities. 
3. CT scan (low dose non contrast when possible) is the gold standard for diagnosing kidney stones.
4. Relaxation is very important for patients passing a kidney stone. NSAIDs (e.g. naproxen) provide similar pain control to opioids for acute pain relief with additional benefits as well (less nausea, less need for additional analgesia, ?anti-inflammatory, ?smooth muscle relaxation) –(Holdgate, 2004; Pathan, 2018; Ashfar, 2015). 
5. For dietary prevention of calcium oxalate stones, accompany oxalate rich foods with dietary calcium to bind oxalate in the intestinal lumen.  

Risk Factors for Urinary Stone Disease

• For the majority of individuals, nephrolithiasis has a multifactorial etiology involving genetic and environmental factors.
• Prevalence of urinary stone disease in developed countries is 10% worldwide, with a recurrence rate of 50% at 5-10 years in the absence of preventative measures (Ferraro et al,  2013)
• Bladder stones are more common in underdeveloped countries. Upper renal tract stone disease is more common in developed countries. (Aggarwal et al, 2017)
• In the USA, 11-12% of American males and 7-8% of American females will get a kidney stone in their lifetime. Twenty years ago the ratio of stone disease of male:female was 2:1, but now it has narrowed to 1.3:1
• Listen to your patients: The best history is if the patient reports previous kidney stones and they tell you they have another (expert opinion). 
• Risk factors for stone disease include a history of diabetes, gout and obesity.
• Stone disease often presents in warmer seasons and globally it is more prevalent in hotter climates. This is due to more extrarenal fluid loss and urine being super-saturated with salts that predispose to stones. However, it is important to remember that not everyone who gets dehydrated gets stones.(Geraghty et al, 2017) and (Tasian et al, 2014)
• Dr Goldfarb says there are anecdotal occupational risk factors linked to those who drink less when there is limited access to toilet facilities, e.g. truck/cab drivers.
• Genetics factors: 15% of those attending clinics with recurrent nephrolithiasis have single gene disorders including renal tubular acidosis with deafness, Bartter syndrome, primary hyperoxaluria and cystinuria. For those with idiopathic recurrent stone disease, twin studies estimate genetic factors of >45% for nephrolithiasis and >50% for hypercalciuria (Howles et al, 2020). 

Differential Diagnosis of Urinary Tract Stones 

• The location of the stone may cause different presentations of pain. Back/flank pain can indicate a stone at the uretero-pelvic junction, as the stone passes to the ureter pain radiates to the abdomen, and once reaching the uretero-vesico junction pain can radiate to low abdomen and genitals (Goldfarb, 2009)
• Differential diagnosis includes peritonitis, appendicitis, ovarian cysts, ectopic pregnancies, UTI, diverticular disease.
• Patients with recurrent stone disease may present to primary care requesting more conservative management, and decline further imaging.

Imaging

• First presentation with renal colic should be imaged (expert opinion).
• Gold standard is low dose non contrast CT renal tract, however this is not available in all areas.
• Note: Some experts recommend against the indiscriminate use of CT renal tract for female patients with flank pain because of a considerably lower positive rate for stone disease.  Instead, these experts suggest an initial evaluation with ultrasound to detect the presence of hydronephrosis –this was not discussed in the episode with Dr. Goldfarb. (Patatas K et al,  2012) (Patatas K, 2010) (Leo et al, 2017)
• A KUB (X-ray) is inexpensive, low radiation, and available in most settings. X-ray will detect calcium but not urate stones. Stool and gas may obscure small stones, but it can be used to track change in size of stones over time.
• Renal tract ultrasound can also demonstrate hydronephrosis. However, it is operator dependent. The STONE score may have some utility in increasing the index of suspicion for a urinary stone; high STONE scores reduce the possibility of an alternative diagnosis to less than 2%, potentially meaning that some of these patients could be managed without an immediate CT Scan.  Hydronephrosis on ultrasound would increase the likelihood of urinary stones. 

Blood tests

• Helpful blood tests include urea, creatinine, eGFR, sodium, potassium, chloride, urate, calcium (for sarcoidosis, Primary hyperparathyroidism), and bicarbonate (renal tubular acidosis)

Urinalysis

• Check urine dipstick: pH, erythrocytes, leukocyte esterase, citrate, nitrites, urine culture
• Urinalysis – frank or microscopic hematuria is common, but is not always present.
• Urine pH: Dr. Goldfarb notes this varies throughout the day, typically being pH 5 in the morning, and 6.5 in the evening. Lack of variation in urinary pH predisposes to specific stone types.
  • Patients with uric acid stones typically have persistent urine pH 5-5.5 all day
  • Patients with RTA usually have a urine pH of 6.5
  • Patients with struvite stones have urine pH of 8.5

Types of Stones

Below are some pearls from Dr. Goldfarb

• You can only confirm the composition of stones by sending the stone to the lab.  They can be caught by the patient by urinating on a gauze or toilet paper. Dr. Goldfarb notes that hounsfield Units (HU) –used to describe radiodensity on CT scan– can hint at the type of stone (expert opinion).
• Checking composition of stones can lead to discussions around future prevention, dietary changes etc.
• Calcium oxalate: Most common type. Usually found in patients with obesity and diabetes. Radiodensity usually high value HU.
• Uric acid stones: Patients with obesity and diabetes, urine pH 5,  Low value HU 
• Struvite: Typically not an acute presentation, often taking months to years to form. Often seen in women who are more prone to recurrent UTI and urines with  high pH 8.5
• Cystine

How likely is a stone to pass?

• 5 mm stones: 50% pass with conservative management, analgesia, and rest. Patients with recurrent stones often prefer this approach and typically request analgesia but no imaging. Dr Goldfarb says this is a reasonable approach for primary care.
• 7mm stones: only 20% pass without intervention
• Always check mid-stream urine for infection (dipstick for leukocyte esterase or send for culture).  An obstructed urinary tract with infection is an emergency and risks urosepsis!
• NSAIDs (e.g. naproxen) are similar to opioids for acute pain control, but with less nausea, and less need for additional short term analgesia (Holdgate, 2004; Pathan, 2018; Ashfar, 2015). Dr. Goldfarb also recommends other measures to help the patient relax, such as a warm bath.  Alpha blockers have not been successful in aiding passage of stones (Pickard et al, 2015).  Dr Goldfarb states that many urologists still use them in urinary stone patients because they are relatively safe and inexpensive. 
• While it is important to hydrate the vomiting patient, do not routinely advise the patient to ‘drink plenty’ as they have missed the boat during an acute renal colic episode. A kidney passing a stone is already functioning with a lowered GFR, thus any fluid consumed by the patient will be filtered by the contralateral kidney. Springhart et al (Pickard et al, 2006) in a randomized trial of  forced or minimal IV fluids showed that fluids do not aid stone passage, nor provide pain relief in  management of acute renal colic.
• Consider re-imaging the patient to ensure a stone has passed (expert opinion).

Urological Intervention

• Reserved for larger stones or those that cannot pass independently 
• ESWL (Extracorporeal Shockwave Lithotripsy) typically just treats one stone, which breaks into fragments. Multiple stone fragments must be passed! It is used less frequently now. 
• Ureteroscopy with laser lithotripsy is a preferred method now. Dr. Goldfarb notes younger urologists are trained this way. It can be used to treat all the stones and remove fragments from one or both kidneys; flexible scopes can reach more calyces.

Prevention of future urinary tract stone disease

• Without prevention, 50% of patients will have another stone at 10 years and 80%  will have recurrence at 20 years. Counseling about prevention is essential to minimize recurrence, pain, and complications from urinary stones. 
• Remember that patients with recurrent stone disease often have obesity, diabetes, hypertension, and coronary artery disease, indicating a metabolic syndrome, so the following interventions benefit them overall.
• Fluids: aim for 96oz /2.5-3 litres of water per day (expert opinion)
• Some patients may find increasing fluid intake difficult due to physical constraints such as limitations in ambulation, benign prostatic hypertrophy, or due to occupational considerations that limit access to water or bathrooms (e.g. cab driver)
• Weight loss & exercise.
• Specific dietary interventions can be recommended if stone composition is known. 
• Dr. Goldfarb recommends the Borghi diet, as this is the only study showing that a diet can reduce urinary tract stones.  This study compared the typically recommended low calcium, low oxalate diet to the Borghi diet which has decreased sodium, low animal protein (source of uric acid), and low oxalate (beets, chocolate, berries, rhubarb, nuts and leafy greens) with non-restricted calcium (Dietary sources preferred, not supplements!). During a meal, combine calcium rich food with oxalates, since calcium will bind to oxalate in intestinal lumen and excreted in stool. (Borghi et al, 2002) 
• Adding citrus fruits to the diet may increase citrate and reduce stone formation.

Kashlak Pearl: General tips for urinary stone prevention include: increased water intake, weight loss, exercise, low sodium intake, low animal protein intake, and high dietary calcium intake. High oxalate foods are delicious and nutritious. Don’t avoid them altogether. Instead, combine them with dietary calcium. 

Pharmacological considerations  

• Thiazide diuretics (indapamide, hydrochlorothiazide, chlorthalidone) prevent kidney stones by reducing calcium excreted in urine and by extension improve bone density. Dr. Goldfarb endorses giving thiazides empirically for kidney stone prevention. 
• Citrate supplementation also helps to prevent stones either as citrus fruit or medication.  Potassium citrate is recommended over sodium citrate because the latter can  increase urinary calcium.
• Bisphosphonates increase bone density and lower urinary calcium, which may reduce kidney stones.  (Prochaska, 2021)
• Calcium supplements vs dietary calcium? The Women’s Health Initiative (Wallace et al, 2011) showed that post menopausal women taking calcium/Vit D supplements had more kidney stones. Dr. Golfarb says it is preferable to take dietary calcium rather than supplements when possible, e.g., a dairy source at the same time as oxalate rich foods. Alternatively, take calcium supplements with meals.

Tertiary Urology Centers

• Patients referred there are more likely to have cystinuria, primary hyperoxaluria, or recurrent/frequent/larger stones 
• 24h urine collections may be requested more at these centers when investigating stone composition and tailoring more specific dietary interventions

Links

1. Dr Goldfarb’s pick of the week From Fish to Philosopher by Homer Smith 
2. STONE score MD Calc.  accessed 9/2021.
3. Picard R et al. Medical expulsive therapy in adults with ureteric colic: a multicentre, randomised, placebo-controlled trial. Lancet 2015; 386(9991): 341-9. PMID: 25998582
4. Springhart WP, Marguet CG, Sur RL, Norris RD, Delvecchio FC, Young MD, Sprague P, Gerardo CA, Albala DM, Preminger GM. Forced versus minimal intravenous hydration in the management of acute renal colic: a randomized trial. J Endourol. 2006 Oct;20(10):713-6. doi: 10.1089/end.2006.20.713. PMID: 17094744.
5. Borghi L, Schianchi T, Meschi T, Guerra A, Allegri F, Maggiore U, Novarini A. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002 Jan 10;346(2):77-84. doi: 10.1056/NEJMoa010369. PMID: 11784873.
6. Howles, S.A., Thakker, R.V. Genetics of kidney stone disease. Nat Rev Urol 17, 407–421 (2020). https://doi.org/10.1038/s41585-020-0332-x
7. Ferraro P et al. When to suspect a genetic disorder in a patient with renal stones, and why Nephrology Dialysis Transplantation, Volume 28, Issue 4, April 2013, Pages 811–820,
8. Aggarwal R, et al. RENAL STONES: A CLINICAL REVIEW EMJ Urol. 2017;5[1]:98-103
9. Geraghty R et al  Worldwide Impact of Warmer Seasons on the Incidence of Renal Colic and Kidney Stone Disease: Evidence from a Systematic Review of Literature  Journal of Endourology.Aug 2017.729-735.http://doi.org/10.1089/end.2017.0123
10. Tasian G et al,  Daily mean temperature and clinical kidney stone presentation in five US metropolitan areas: a time-series analysis  Environ Health Perspect. 2014 Oct;122(10):1081-7. doi: 10.1289/ehp.1307703. Epub 2014 Jul 10. PMID: 25009122; PMCID: PMC4181925.
11. Patatas K et al   Emergency department imaging protocol for suspected acute renal colic: re-evaluating our service  Br J Radiol. 2012;85(1016):1118-1122. doi:10.1259/bjr/62994625
12. Patatas K. Does the protocol for suspected renal colic lead to unnecessary radiation exposure of young female patients? Emerg Med J. 2010 May;27(5):389-90. doi: 10.1136/emj.2009.084780. PMID: 20442172. 
13. Leo, et al. Ultrasound vs. Computed Tomography for Severity of Hydronephrosis and Its Importance in Renal Colic West J Emerg Med. 2017;18(4):559-568. doi:10.5811/westjem.2017.04.33119
14. Wallace RB, et al.  Urinary tract stone occurrence in the Women’s Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements Am J Clin Nutr. 2011;94(1):270-277. doi:10.3945/ajcn.110.003350
15. Borghi L, Schianchi T, Meschi T, Guerra A, Allegri F, Maggiore U, Novarini A. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002 Jan 10;346(2):77-84. doi: 10.1056/NEJMoa010369. PMID: 11784873.
16. Prochaska M. Bisphosphonates and management of kidney stones and bone disease. Curr Opin Nephrol Hypertens. 2021 Mar 1;30(2):184-189. doi: 10.1097/MNH.0000000000000682. PMID: 33394731.

Goal

Listeners will describe the risk factors, pathophysiology, workup, and prevention of urinary stone disease. 

Learning objectives

After listening to this episode listeners will…  

1. Describe the risk factors for urinary stone disease

2. Discuss the underlying pathophysiology of kidney stone formation

3. Perform a targeted laboratory work-up for suspected urinary stone disease

4. Contrast the imaging modalities used to diagnose urinary stone disease

5. Manage straightforward urinary stone disease in the outpatient setting

6. Counsel patients on prevention of urinary stone disease

7. Discuss the work-up behind stone composition and recurrent urinary stone disease

8. Understand the therapies used to prevent recurrence in urinary stone disease

Disclosures

Dr.  Goldfarb is a co-founder of Moonstone, which makes nutritional supplements and drink mixes for kidney health and hydration. The Curbsiders report no relevant financial disclosures. 

Citation

Shelagh B, Goldfarb D, Garbitelli E, Grant K, Watto MF, Williams PN.  “#298 Urinary Stone Disease Will Rock Your World”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list Final air date October 4, 2021.