Urolithiasis - Veterinary PDF

Urolithiasis Please open Echo360 to participate in polls Jennifer M. Reinhart, DVM, PhD, DACVIM (SAIM), DACVCP Assistant Professor, SA Internal Medicine [email protected] Learning Objectives Uroliths • For each stone type, know: • Polycrystalline concretions that contain >95% inorganic mat...

Urolithiasis Please open Echo360 to participate in polls Jennifer M. Reinhart, DVM, PhD, DACVIM (SAIM), DACVCP Assistant Professor, SA Internal Medicine [email protected] Learning Objectives Uroliths • For each stone type, know: • Polycrystalline concretions that contain >95% inorganic matrix and <5% organic material • Classified by • • • • • • • Common signalment Predisposing factors Urine pH at which it forms Radioopaque vs. radiolucent Whether dissolution is possible Recommendations for dissolution Recommendations for prevention • Mineral composition: struvite, calcium oxalate, urate, cystine, xanthine, calcium phosphate, silica • Location: Cystic, urethral, renal, ureteral • Size • Shape MOST COMMON Crystalluria vs. Urolithiasis Urolithiasis – Clinical Signs • Crystalluria, by itself, is not a disease • Bladder and urethral stones cause lower urinary tract signs: • • • • Normal finding in many animals Most animals with crystals will not get stones Does not cause bladder irritation Does not require dietary therapy • If an animal has urolithiasis and crystalluria • The crystal type MAY or MAY NOT match the stone type • Preventing crystalluria with dietary therapy is a goal for stone treatment and preventing recurrence • Pollackiuria • Stranguria • Hematuria • If obstructive, • Failure to void urine • Severe pain • Large distended bladder • Bladder stones can also by asymptomatic Urolithiasis – Physical Exam Findings Urolithiasis – Diagnostics • May or may not have discomfort around bladder • Thorough rectal palpation • Goals • Urethral stones sometimes palpable • In male dogs • Examination of prepuce and penis • Palpate perineum to examine the turn of the urethra • • • • Locate the stone(s) Determine whether or not it is obstructive Make a best guess as to the type Identify predisposing or complicating factors Urolithiasis – Diagnostics Urolithiasis – Diagnostics Survey abdominal radiographs • First line diagnostic • Determine site, number, shape and density of stones • Density of stone can help predict type: If suspect radiolucent stones, need • Contrast cystourethrogram • Radiopaque: struvite, calcium oxalate, calcium phosphate, silicate • Radiolucent: urate, cystine, xanthine • Highlights the bladder and urethra • Requires catheterization and sedation • Abdominal ultrasound • Will identify any stone type in bladder • Insensitive for urethra Urolithiasis – Diagnostics Urolithiasis – Diagnostics Urinalysis • Urine specific gravity Urinalysis • Crystalluria • Stones are more likely to form in concentrated urine • Therapeutic target • Urine pH • Alkaline urine: struvite, calcium phosphate • Acidic urine: Calcium oxalate, urate, cystine • Therapeutic target • May or may not be helpful in identifying stone type • Hematuria/Pyuria • Common if animal is clinical for stones • Bacteriuria • Struvite stones in dogs are associated with UTIs Urolithiasis – Diagnostics Urolithiasis – Treatment • Urine culture General principles • Use least invasive method possible • If non-obstructive and medical dissolution is possible, try it first • Obstructive urolithiasis is an emergency situation • Struvite stones are associated with UTIs in dogs • Other stone types may serve as a nidus for infection • CBC/Chemistry Panel • Screen for predisposing factors for stone formation • Hypercalcemia – calcium oxalate • Hepatic dysfunction – urates • Includes ureteroliths and nephroliths causing azotemia • Urinary Stone Analysis • Definitively determines type • Perform on all stones removed Urolithiasis – Treatment Urolithiasis – Treatment Benign Neglect • Only for asymptomatic animals • Very small stones (<2-3 mm) that can easily pass through urethra on their own Medical Dissolution • Possible for struvite, urate, xanthine, and cystine • Not possible for calcium oxalate, calcium phosphate, or silica • Treatment generally includes diet +/- medication • Monitoring every 4 weeks • Females more likely to pass than males • Larger dogs more likely to pass than smaller dogs or cats • Very large stones in the bladder that are unlikely to become obstructive • • • • Urine specific gravity (< 1.015-1.020 in dogs, < 1.035 in cats) pH – stone dependent Radiographic appearance If consistent decrease in size is not seen, stones should be removed Urolithiasis – Treatment Urolithiasis – Treatment Voiding Urohydropulsion • Appropriate for small stones that can pass through the urethra • Procedure: Intracorporeal lithotripsy and basket retrieval • Standard of care for urethral obstruction • Ideal for patients with a small number of stones • Endoscopic procedure • • • • • • • Patient is anesthetized Urinary catheter is placed Bladder is emptied and then distended with saline Catheter is removed Patient is positioned vertically Bladder is agitated and expressed Radiographs to confirm stone removal • Break down of stones with laser • Stone fragments retrieved with endoscopic tools Urolithiasis – Treatment Urolithiasis – Treatment Cystotomy • Surgical retrieval of bladder stones • For dogs that have had previous stones, prevention is the best medicine • Preventative measures are highly dependent on stone type • Usually include • Can be performed laparoscopy-assisted • Antegrade and retrograde urohydropulsion to remove urethral stones • Urethrotomies should be avoided • Diluting urine by increasing water consumption • Dietary recommendations • +/- medications to alter pH/urine content Urolith Types – Distributions Stone Type Struvite (MAP) Calcium oxalate Urate Cystine Xanthine Calcium phosphate Silica Mixed/Compound Dogs 36.8% 42.8% 4.0% 2.1% 0.1% 0.5% 0.4% 13.1% Urolith Types – Struvite Cats 46% 41% 5% rare rare <1% rare ~4% • Magnesium ammonium phosphate • Form in alkaline urine (pH > 7.0) • In dogs, usually associated with ureaseproducing bacterial cystitis • F>M • Always culture • In cats, usually sterile • F~M • Culture is still useful to r/o infection Urolith Types – Struvite Urolith Types – Struvite Dissolution recommended as first line treatment • Antibiotics Dissolution recommended as first line treatment • Struvite/CaOx Prevention Diet • Culture and treat with appropriate antibiotic • Maintain abx therapy 1-month past dissolution • Diet • • • • Encourage water drinking, high moisture diets Avoid excess magnesium and phosphorus and maintain acidic pH Treat for 1 month past radiographic resolution NO other foods, treats • • • • • pH neutral Decrease urine concentration à prevent supersaturation Struvite dissolution Struvite and Calcium Oxalate prevention Examples • Hill’s c/d Multicare • Purina UR St/Ox Urinary • Royal Canine Urinary SO • Struvite Dissolution Diet – Hill’s s/d • Not nutritionally balanced for long term feeding (> 6 months) Urolith Types – Struvite Urolith Types – Struvite Dissolution recommended as first line treatment • Monitor radiographs every 4 weeks Prevention • Urinary diet • Routine monitoring for UTIs • Monitor USG, pH, and presence of crystalluria • If no improvement, consider minimally invasive or surgical removal • Monitor urinalysis • USG < 1.020 in dogs, < 1.035 in cats • If not, add in other water sources, switch to moist food • pH < 6.5 • If not, consider poor dietary compliance, consider adding methionine (urinary acidifier) • Struvite crystalluria should be absent Urolith Types – Calcium Oxalate Urolith Types – Calcium Oxalate • Form in acidic urine (pH < 6.5) • In dogs, M > F; in cats, M ~ F • Common breeds: Shih Tzu, Yorkie, Mini Schnauzer, Bichon, Chihuahua, mixed breed • Hypercalcemia may predispose (e.g., hyperparathyroidism) • CANNOT BE MEDICALLY DISSOLVED! Prevention • Increase water consumption, high moisture diets • Struvite/CaOx Preventation Diet • Hill’s c/d Multicare, Metabolic + Urinary, Multicare Stress Purina UR St/Ox Urinary • Royal Canine Urinary SO, Moderate Calorie • Monitor USG, pH, crystalluria Urolith Types – Calcium Oxalate Urolith Types – Urates Prevention • Drugs • Ammonium biurate, uric acid • Form in acidic urine • Two distinct patient populations • Potassium citrate – if urine pH is not > 7.0 on diet alone • Hydrochlorothiazide – reduces urine Ca excretion (resistant cases only) • Vitamin B6 – minimizes oxalate production (only when diet is deficient) • Hepatic dysfunction (e.g., portosystemic shunt) • Yorkie, Shih Tzu, Mini Schnauzer • Dogs with genetic defect of uric acid transporter (SLC2A9) • Dalmatians, English Bulldogs Urolith Types – Urates Urolith Types – Urates Purines somewhat soluble Treatment • Animals with portovascular anomalies should be treated appropriately Hypoxanthine xanthine oxidase somewhat soluble Xanthine xanthine oxidase insoluble Uric acid uricase (in the liver) soluble Allantoin • Medical vs. surgical management (consider cystotomy during shunt attenuation) • Medical dissolution can be attempted in other dogs prior to minimally-invasive/surgical management • Ultra-low protein diet - Hill’s l/d, u/d, Royal Canin UC • +/- Allopurinol Urolith Types – Urates Urolith Types – Urates Purines somewhat soluble Treatment • Animals with portovascular anomalies should be treated appropriately Hypoxanthine xanthine oxidase somewhat soluble ALLOPURINOL Xanthine xanthine oxidase insoluble Uric acid uricase (in the liver) soluble Allantoin • Medical vs. surgical management (consider cystotomy during shunt attenuation) • Medical dissolution can be attempted in other dogs prior to minimally-invasive/surgical management • Ultra-low protein diet - Hill’s l/d, u/d, Royal Canin UC • +/- Allopurinol • Monitoring – USG, pH (> 7.0), crystalluria, imaging (radiolucent) Urolith Types – Urates Urolith Types – Cystine Prevention • Diet alone • Diet + allopurinol • Form at acidic pH • Caused by a rare inherited disorder • Renal tubules fail to resorb cystine • Cystine is poorly soluble • Common breeds: Bulldogs, Chihuahua, Dachshund • Sometimes may be androgen responsive • Recommend neutering for intact males Urolith Types – Cystine Urolith Types – Xanthine Treatment • Medical dissolution is possible • Encourage water consumption, moist foods • Low protein diet - Hill’s l/d, u/d, Royal Canin UC • Xanthine, hypoxanthine • Form at acidic pH • Most commonly occur secondary to allopurinol use • Occasionally in dogs with genetic defects in purine metabolism • Avoid animal origin proteins • Potassium citrate, if needed to maintain alkaline pH • Monitor USG, pH (> 7.5), crystalluria, imaging (radiolucent) • Removal if lack of response somewhat soluble Hypoxanthine ALLOPURINOL xanthine oxidase somewhat soluble Xanthine xanthine oxidase insoluble Prevention • Continue low protein diet Uric acid uricase (in the liver) soluble Urolith Types – Xanthine Urolith Types – Others Treatment/Prevention • Medical dissolution can be tried • Increased water consumption, moist food • Low protein diet - Hill’s l/d, u/d, Royal Canin UC • REDUCE or DISCONTINUE allopurinol • Monitor USG, pH (> 7.5), crystalluria, imaging (radiolucent) • Calcium phosphate • Potassium citrate to further alkalinize • Removal if lack of response Purines Allantoin • Many different types • Management similar to calcium oxalates • Silica • Associated with consumption of silicon dioxide • Inert ingredient in some tablets, high silica foods (rice, beet pulp, soybeans), food and water from volcanic areas • Mixed – multiple mineral types • Compound – one mineral type in the core, another in the shell • E.g., a CaOx former with a secondary UTI causing struvites Nephroliths and Ureteroliths Nephroliths and Ureteroliths • Most approaches for removal are invasive and can cause further damage • If stones are non-obstructive and not infected, benign neglect is best • Dissolution can be tried in dogs Nephrolith treatment options • Shock-wave lithotripsy • Endoscopic nephrolithotomy • Percutaneous nephrolithotomy • Nephrotomy • Canine upper uroliths 20-30% struvites • Feline upper uroliths > 90% CaOx • If obstructive, aggressive therapy is needed to preserve renal function Nephroliths and Ureteroliths Urolith Knowledge Check #1 Ureterolith treatment options • Ureterotomy In a dog with lower urinary tract signs and urolithiasis, for which stone type should you perform a urine culture? A) Struvite B) Calcium oxalate C) Urate D) All of the above • Healing complications • Subcutaneous ureteral bypass system Urolith Knowledge Check #2 References A 5 yo MC Yorkie presents for lower urinary tract signs. Abdominal radiographs are unremarkable, but three cystoliths are seen on ultrasound. What should your next step be? A) Biochemistry profile B) Contrast cystourethrogram C) Cystotomy D) Benign neglect • Lulich JP, Osborne CA. Chapter 331: Lower Urinary Tract Urolithiasis in Dogs. Textbook of Veterinary Internal Medicine. Ettinger SJ, Feldman EC, Cote E, editors. 8th ed. 2017. • Labato MA. Chapter 332: Lower Urinary Tract Urolithiasis-Feline. Textbook of Veterinary Internal Medicine. Ettinger SJ, Feldman EC, Cote E, editors. 8th ed. 2017. • Adams LG. Chapter 329: Ureteral Disorders. Textbook of Veterinary Internal Medicine. Ettinger SJ, Feldman EC, Cote E, editors. 8th ed. 2017. • Lulich JP, Berent AC, Adams LG, Westropp JL, Bartges JW, Osborne, CA. (2016). ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats. J Vet Intern Med. 2016;30(5);1564–1574. • University of Minnesota Urolith Center. https://www.vetmed.umn.edu/centers-programs/minnesota-urolith-center QUEST ONS?