Kidney Stones An Overview Gerald Da Roza MD

Kidney Stones: An Overview Gerald Da Roza MD, MHSc, FRCPC March 15, 2010

Overview Case n Diagnosis of kidney stones n Acute management n Epidemiology n Risk factors n Work up and treatment n Diet and kidney stones n

Case – A Few Years Ago 30 year old nephrology fellow n Bright, hardworking, driven n Atrocious diet (hospital cafeteria and vending machines, no fruit and vegetables, ++ salt) n Drinks very little during daytime n Presents with acute onset of R costovertebral pain, radiating around to anterior abdomen, 10/10 in severity, nauseau and vomiting n

Case – A Few Years Ago n Physical Exam Tachycardia, normotensive, afebrile n ++ CVA and RUQ tenderness n Nil else n n Investigations U/A shows hematuria, n CBC, lytes urea, Cr normal n

Diagnosis? ? ? Kidney Stone - Why? n DDx n Renal Cell Ca w/ blood clot n Renal Cyst w/ clot n Pyelonephritis n AAA/dissection n Ectopic Pregnancy (if female) n Intestinal Obstruction n Appendicitis n

How do we make the diagnosis? n Investigative Options: CT Scan n US n Abdominal Plain Film n MRI n IVP n

Non-contrast Helical CT Scan n Gold standard n n Dual energy CT (DECT) is new imaging modality may be able to predict stone composition (future tx) Helps determine if obstruction present Provides alternate diagnosis in many cases n n Sensitivity 95 %, Specificity 98% 33 percent had an alternate diagnosis not suspected on clinical grounds, one-half of whom had significant disease Only misses stones due to protease inhibitors

CT KUB

Ultrasound n Procedure of choice for pts who should avoid radiation n pregnant women and possibly women of childbearing age Sensitive for the diagnosis of obstruction n Can detect radiolucent stones missed on x-ray n May miss small stones and ureteral stones n

Ultrasound

Abdominal X-ray n will identify sufficiently large radiopaque stones n calcium, struvite, and cystine stones will miss radiolucent uric acid stones n may miss small stones or stones overlying bony structures n will not detect obstruction n

Other n Intravenous Pyelogram (IVP) n n higher sensitivity and specificity than plain film for the provides data about the degree of obstruction previously the diagnostic procedure of choice, no longer because of potential contrast rxn, lower sens, higher radiation Magnetic resonance imaging n rarely used during the management of stone disease, except in the evaluation of pregnant patients, because this modality is not optimal for identifying stones.

Acute Management Many pts with acute renal colic can be managed conservatively with pain medication (NSAIDs & Opiods) and hydration until the stone passes n If able to take oral medications and fluids can manage at home n Hospitalization required for those who cannot tolerate oral intake or who have uncontrollable pain or fever n

Acute Management n Pts instructed to strain their urine for several days and bring in any stone that passes for analysis n n Data suggests faster stone passage tamsulosin n n will enable clinician to better plan preventive therapy CCB is other option Pts are re-imaged if spontaneous passage has not occurred.

Acute Management n Urgent urologic consultation warranted in: Urosepsis n Acute renal failure n Anuria n Unyielding pain, nausea, or vomiting n

Acute Management n Stone size major determinant of the likelihood of spontaneous stone passage, although stone location is also important Most stones ≤ 4 mm in diameter pass spontaneously. For stones larger than 4 mm in diameter, there is a progressive decrease in the spontaneous passage rate, which is unlikely with stones ≥ 10 mm in diameter n Proximal ureteral stones are also less likely to pass spontaneously. n

Acute Management n Referral to urology for potential intervention stones larger than 10 mm in diameter n significant discomfort n significant obstruction or who have not passed the stone after four to six weeks n

Urologic Options n Shock wave lithotripsy (SWL) n n n Ureteroscopic lithotripsy with electrohydraulic or laser probes n n n tx choice in 75% pts works best for stones in renal pelvis and upper ureter higher stone-free rates, but with an increased incidence of complications over shock wave lithotripsy Percutaneous nephrolithotomy Laparoscopic stone removal n Rarely needed

Kidney Stones - Epidemiology Renal stones (nephrolithiasis) are a relatively common problem n In US, up to 12% of men and 5% of women will have at least one symptomatic stone by the age of 70 n

Clinical Presentations n Classic Sx Renal Colic n Hematuria (gross or microscopic in majority if symptoms but not all) n n Atypical Sx n n Vague abdominal pain, nausea, urinary urgency or frequency, difficulty urinating, penile pain, or testicular pain. Asymptomatic

Renal Colic n n Varies from a mild and barely noticeable ache to discomfort that is so intense that requires parenteral analgesics typically waxes and wanes in severity, and develops in waves or paroxysms that are related to movement of the stone in the ureter and associated ureteral spasm. Paroxysms of severe pain usually last 20 to 60 minutes Pain is thought to occur primarily from urinary obstruction with distention of the renal capsule.

Stone Composition n 80% are Calcium Stones Calcium Oxalate (majority) n Calcium Phosphate (Hydroxapetite stones) n

Stone Composition n n Uric acid Struvite (magnesium ammonium phosphate) n n Cystine stones n n n only form in pts with chronic upper UTI d/t ureaseproducing organism: Proteus or Klebsiella only develop in pts with cystinuria (an AR disorder) due to the poor solubility of cystine in the urine Mixed stone (eg, calcium oxalate and uric acid) Other: indinavir, sulfadiazine, triamterene, acyclovir stone

Risk Factors for Stones Historical n Anatomic n Dietary n Urinary n

Historical Risk Factors n Prior History of Kidney Stones n n Family History of kidney stones n n n Twofold increase by Health professionals study Individuals with enhanced enteric oxalate absorption n n 50% recurrence in 10 yrs gastric bypass procedures, bariatric surgery, short bowel syndrome Frequent upper urinary tract infections Excessive physical exertion

Historical RF n Medical conditions assoc w/ stones: Primary Hyperparathyroidism, Sarcoidosis n Gout, Obesity, DM (concentrated acidic urine) n HTN n RTA n n Use of medications that may crystallize urine n Indinavir, acyclovir, sulfadiazine, triamterene

Anatomic RF Medullary sponge kidney n Horseshoe kidney n

Medullary Sponge Kidney

Horseshoe Kidney

Dietary Risk Factors n ? Low or High ? Calcium n Fluids n Oxalate n Protein n Salt n Sucrose n

Dietary Risk Factors n Low Calcium Intake n n increases absorption & excretion of oxalate d/t less complexing with calcium in the intestinal lumen Low fluid intake n Higher concentration of lithogenic factors in urine Low potassium n Low phytate n

Dietary Risk Factors High oxalate intake n High animal protein intake n n leads to hypercalciuria, hyperuricosuria, hypocitraturia, and inc urinary acid excretion High sodium intake n High sucrose intake n n n may increase calcium and/or oxalate excretion High Vitamin C Intake

Urinary Risk Factors n n n Low volume Hypercalcuria Hyperoxaluria Hypocitraturia Extremes of p. H n n p. H greater than 7. 5 is compatible with infection p. H less than 5. 5 favours uric acid lithiasis. Urine culture +ve urease-producing organism (struvite) n Proteus or Klebsiella

Work Up & Treatment n Controversial whether evaluation and therapy warranted or cost effective after the first stone or only in patients with: n Active stone disease n formation of new stones, increase in size of old stones, or the continued passage of gravel Multiple stones at first presentation n Pts with a strong family history of stones n

Approaches Limited Evaluation n Targeted Evaluation n base the extent of evaluation upon an estimation of the risk for new stone formation Complete Evaluation n approach should be followed only in individuals willing to make dietary changes or to take medical therapy if warranted by the work-up.

Complete Evaluation n n CBC, lytes, bicarbonate, urea, creatinine Calcium, phosphorus, PTH, uric acid Urinalysis for p. H and crystals 24 -hr urine: volume, calcium, uric acid, citrate, oxalate, sodium, and creatinine n n At least two 24 -hour urine collections while pt maintains usual diet and physical activities wait at least one to three months after a stone event should not be performed if renal/ureteral obstruction or urinary tract infection from existing calculi.

Treatment of Kidney Stones General treatment strategies for all stone formers n Specific treatment strategy is based on: n stone composition if available (assume calcium if not most of the time) n findings from metabolic evaluation n Patient dietary patterns n

General Treatment n Increase fluid intake to target u/o > 2 L per day At 5 yrs, incidence of new stone formation 12% v 27% n increases urine flow rate and lower urine solute concentration n Avoid high animal protein diet n Avoid high salt diet n

Specific Tx – Calcium Stones n If hyperoxaluria present, low oxalate diet should be tried first primary foods to avoid are spinach and nuts n increasing dietary calcium or adding calcium supplement with meals should be considered in addition to a low oxalate diet if insufficient. n Thiazide diuretic for refractory hypercalciuria n Potassium citrate for refractory hypocitraturia n

Specific Tx – Uric Acid Stones n If hyperuricosuria present, lifestyle modification with the aim of reducing uric acid production decreased purine intake n weight loss should be implemented n Allopurinol for refractory hyperuricosuria n Potassium citrate to alkalinize urine n

Specific Treatment – Cystine Stones urinary alkalinization n drugs such as tiopronin n

Specific Tx – Struvite Stones n typically require complete stone removal with percutaneous nephrolithotomy & aggressive prevention and tx of future UTI’s

Monitoring n Monitoring w/ US or plain film for new stone formation initially at one year n if –ve then every 2 -4 yrs based on risk recurrence n not nearly as sensitive for identifying stones as CT, but CT exposes pt to significant amt of radiation n

Asymptomatic Stone n n Balance risk of stone becoming asymptomatic vs. morbidity assoc with therapy Specific factors will dictate how to manage n n stone size and location Active surveillance reasonable approach in asymptomatic pts with n n n small, non-infected calculi no evidence of obstruction not "at risk" for stone episodes (solitary kidney, urinary tract reconstruction, immunosupression, etc)

What about overall diet? While one can modify diet after one discovers a kidney stone is there any type of diet that prevents kidney stones? n Any data available? n

Dash Diet & Kidney Stones n Dash-style Diet Associates with Reduced Risk for Kidney Stones Eric Taylor, Teresa Fung and Gary Curhan n J am Soc Nephrology 20: 2253 -2259, 2009 n n Dietary Approaches to Stop Hyperstension (DASH)

Dash Diet & Kidney Stones n Examined relationship between DASH-style Diet and incident kidney stones in n n Health Professionals Follow-up study (n-45, 821 men; 18 yr follow up) Nurses’ Health Study (n= 101, 837 women; 14 year follow up) Goal to look at dietary pattern as opposed to individual dietary factors In many cases consuming less of one dietary factor to decrease stone risk may lead to consumption of other factors that increase risk

Dash Diet & Kidney Stones n n DASH score based on eight components High intake of n n n Fruits Vegetables Nuts and legumes Low-fat dairy products Whole grains Low intake of n n n Sodium Sweetened beverages Red and processed meats

Dash Diet & Kidney Stones n Pts with higher DASH scores had n n n higher intakes of calcium, potassium, magnesium, oxalate and vitamin C lower intakes of sodium Participants in highest compared to lowest quintile of DASH score had an adjusted relative risk of 0. 55 in men and 0. 58 -0. 60 in women for kidney stones n Robust despite adjustments & substantial differences in individual dietary factors and risk between men and women

Dash Diet & Kidney Stones Study Conclusion “consumption of DASH style diet is associated with marked decrease in kidney stone risk” (though limited as cohort study) n My conclusion: n I AM IN BIG TROUBLE !

Take Home Points Kidney Stones are fairly common n CT KUB is best test for diagnosis in acute setting n Most acute renal colic tx conservatively n Focus on risk factors in work up to guide investigations n Drink lots of fluids and eat healthy DASH style diet n