ROCKS THAT ROLL NEVER FORGET: UROLITHIASIS CALCIUM OXALATE AND NEW TREATMENTS

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Linda Gaines
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1 ROCKS THAT ROLL NEVER FORGET: UROLITHIASIS CALCIUM OXALATE AND NEW TREATMENTS Je Bartges, DVM, PhD, DACVIM, DACVN Prfessr f Medicine and Nutritin The University f Gergia jbartges@uga.edu Calcium xalate accunts fr 40-50% f all urliths and > 85% f nephrureterliths Risk factrs fr calcium xalate frmatin Increased urinary calcium excretin (hypercalciuria) May result frm hypercalcemia, GI hyperabsrptin (excessive absrptin f calcium frm the GI tract), resrptive (excessive calcium resrptin frm bne), r renal leak (decreased calcium reabsrptin frm the distal tubule) Increased urinary xalate excretin (hyperxaluria) May result frm excessive absrptin frm the GI tract, excessive absrptin frm the GI tract due t deficiency f Oxalbacter frmigenes (an enteric bacterial rganism that metablizes xalate in the GI tract), and pssibly frm vitamin B6 deficiency (vitamin B6 is invlved with xalate metablism) In a small study f Miniature schnauzers, GI hyperabsrptin appears t be the mst likely cause as urinary calcium excretin decreased with fasting Net result f risk factrs is urinary versaturatin with calcium xalate Signalment Cats Middle-aged r lder Males = females Lng-haired cats; Siamese and Ragdlls tend t frm at yung age Overweight t bese bdy cnditin Dgs Middle-aged r lder Males > females Small breed dgs (e.g. Miniature schnauzers, Lhasa apss, Yrkshire terriers, Bichns). Bichns tend t frm at yung age Overweight t bese bdy cnditin Labratry evaluatin Aciduria Hypercalcemia 20-35% f cats usually idipathic hypercalcemia 4% f dgs usually primary hyperparathyridism Crystalluria nt present in > 50% f cases with active stne disease Renal aztemia assciated with nephrureterliths Management Medical prtcls that will prmte disslutin f calcium xalate urliths are currently unavailable; therefre, urliths must be remved physically If urethral bstructin is present, urliths shuld be retrpulsed int bladder and remved If necessary urethrtmy r urethrstmy may be perfrmed If n clinical signs, then minimize grwth in size and number and mnitr fr urethral bstructin and clinical signs Remval f calcium xalate urliths Surgery cysttmy and / r urethrtmy / urethrstmy Catheter-assisted retrieval Technique can be used t retrieve sand r small urliths

2 Urliths must be small enugh t pass thrugh the internal diameter f the lumen f the urethral catheter It is imprtant t jiggle the urinary bladder t get the sand/urliths in mtin in rder t facilitate retrieval thrugh the catheter Descriptin f technique 1. Urinary bladder must be distended 2. As cleanly as pssible, pass a urethral catheter. The runded end f the catheter may be cut ff t facilitate retrieval f larger urliths. 3. Infuse sterile fluid if urinary bladder is nt distended. 4. In lateral recumbency r in vertical psitin, agitate the urinary bladder t put the urliths in mtin. 5. Aspirate fluid frm urinary bladder thrugh urethral catheter. 6. Repeat if necessary. 7. Radigraph if an attempt was made t retrieve all urcystliths. Cmplicatins Occur very rarely Iatrgenic bacterial urinary tract infectin is mst likely cmplicatin that might ccur Irritatin frm catheterizatin resulting in urethral spasm and lwer urinary tract signs may als ccur, but they ccur rarely Viding urhydrprpulsin Viding urhydrprpulsin is a nn-surgical technique fr remving bladder stnes frm dgs and cats The technique is based n the idea f using gravity t assist an animal in viding ut stnes Indicatins The largest diameter stne must be able t pass thrugh the urethra at its narrwest luminal diameter We have retrieved stnes with the fllwing sizes: 10 mm kg F / S K9 5 mm - 9 kg M / C K9 5 mm kg F / S Fel 1 mm kg M / C Fel It will nt wrk in animals that present with urethral bstructin Descriptin f technique 1. Sedate r anesthetize the patient 2. If the urinary bladder is distended, prceed t #4. If the bladder is nt distended, distend the bladder with a sterile physilgical slutin injected thrugh a urethral catheter that is placed as cleanly as pssible. 3. Remve the catheter; if the fluid is expelled prematurely, the vulva r penile urethra can be gently clsed. 4. Psitin the patient s that the vertebral clumn is apprximately vertical t the grund by supprting the animal under the axillae In large dgs, place in drsal recumbency n a table that can be tilted s that ne end f the table is lwer than the ther Supprt the dg under the axillae 5. Gently agitate the urinary bladder by palpatin t prmte gravitatinal mvement f all urcystliths int the trigne. 6. Apply steady digital pressure t the urinary bladder t induce micturitin; nce viding begins, the bladder is mre vigrusly cmpressed; the bject is t sustain maximum urine flw thrugh the urethral lumen t keep it dilated as lng as pssible. The idea is t induce a micturitin reflex, nt t squeeze ut the stnes. Place a cllectin cntainer under the urethral rifice r vulva t cllect vided stnes 7. Repeat steps 2 thrugh 6 if the number f urliths that are vided is less than that previusly detected by radigraphy; if urliths detected by radigraphy were t numerus t cunt, repeat viding urhydrprpulsin until urliths are n lnger detected in the expelled fluid.

3 8. If the number f urliths retrieved equals the number bserved by radigraphy, recver the patient. If there is a questin cncerning whether all f the urliths were retrieved, repeat radigraphy. 9. Animals shuld be treated fr 3 t 7 days with antibitics due t catheterizatin. It is als a gd idea t recheck a urinalysis and if necessary a urine culture 5 t 10 days after discntinuatin f antibitic therapy. Cntraindicatins Animals that present with urethral bstructin due t stnes Animals that have urethral utflw bstructin such as strictures, tumrs D nt perfrm in animals that have had a cysttmy in the previus 14 days the bladder incisin may nt be strng Use cautin when applying pressure n the bladder in animals with a bacterial cystitis as this may cause reflux f infected urine up the ureters int the kidneys Animals with ther mre serius disease shuld be stabilized r treated Cmplicatins Hematuria ccurs cmmnly In dgs, this usually subsides in a cuple f hurs In cats, this may persist fr hurs Urethral bstructin may ccur if ne r mre stnes are larger than the smallest diameter f the urethra Bacterial urinary tract infectin ccurs uncmmnly, but may ccur secndary t pr technique and urethral catheterizatin Bladder and/r urethral rupture culd ccur, but is very rare Viding urhydrprpulsin can be used in cmbinatin with ther treatment mdalities fr bladder stne disease Stnes amenable t medical disslutin can be disslved t a size where they can be retrieved using viding urhydrprpulsin Stnes that are accidentally left behind at surgery may be retrieved with this technique if they are small enugh This technique can be dne at time f inductin fr a cysttmy. If all stnes are retrieved then the animal can be recvered. If nt, then prceed with cysttmy. Cystscpy and retrieval and laser lithtripsy Cystscpy can be perfrmed using rigid cystscpe (in female dgs and cats) r flexible cystscpe (in male dgs) A small semi-rigid cystscpe is available fr use in male cats; hwever, due t its size (1 mm) there is n perating channel This permits visualizatin f the lwer urgenital tract Prcedures such as bipsy, urlith retrieval, injectins, and use f laser can be perfrmed thrugh the perating channel I perfrm cystscpy usually with the patient in drsal recumbency Requires general anesthesia Fluid fr instillatin thrugh the scpe fr distentin f the lwer urgenital tract and fr visualizatin Cystscpic retrieval f urliths Baskets and graspers can be inserted thrugh the perating channel f the cystscpe fr remval f urliths They must be small enugh t be extracted thrugh the mst narrw prtin f the urethra Laser lithtripsy Laser lithtripsy can be used t manage bladder stnes Cystscpy is perfrmed and a laser fiber usually a H:YAG laser is inserted thrugh the perating channel The laser energy is used t fragment the stne int small fragments that can be retrieved Cystscpic-assisted cysttmy

4 A cystscpic-assisted cysttmy is similar t laparscpic remval A small incisin is made n ventral midline In male dgs, the incisin is made just cranial t the preputial reflectin The urinary bladder is grasped and brught t the incisin edge f the linea It is sutured t the edges f the linea A stab incisin is made and a rigid cystscpe is inserted int the urinary bladder Stnes are retrieved using instruments passed thrugh the cystscpe Preventin Calcium xalate urliths are recurrent; therefre, preventative measures are 8% recurrence at 6 35% recurrence at 1 year Recurrence increases with subsequent years Pseudrecurrence refers t leaving urliths behind after a prcedure is perfrmed Occurs in 15-20% f cysttmies With hypercalcemia, ptential causes shuld be investigated. 4% f dgs with calcium xalate urliths have hypercalcemia usually due t primary hyperparathyridism 20-35% f cats with calcium xalate urliths have hypercalcemia usually idipathic in nature Management The gal f preventin is lwer the urinary saturatin fr calcium xalate by decreasing urinary levels f calcium and xalate and by increasing urine vlume in rder t dilute the minerals Cats with hypercalcemia Feed a high fiber, mineral restricted diet Administer an alkalinizing agent (Ptassium citrate) Citrate is an inhibitr f calcium xalate crystallizatin and frmatin In cats with idipathic hypercalcemia, we have had success feeding a higher fiber diet (Hill s Prescriptin Diet Feline w/d) and administering ptassium citrate (see belw) Cats withut hypercalcemia Feed a diet that induces a diuresis, is mineral restricted, and induces a neutral t alkaline urine ph There are several multiple use feline diets frmulated t prevent struvite and calcium xalate Prescriptin Diet c/d Multicare Ryal Canin S/O Purina CNM UR st/x S/O and UR are higher in sdium than c/d In a study cmparing these 3 diets, they each induced a similar degree f urine undersaturatin with calcium xalate albeit by different mechanisms Data frm clinical studies is lacking, althugh in ne clinical study f 10 cats with naturally-ccurring calcium xalate bladder stnes, cnsumptin f Prescriptin Diet Feline c/d xl decreased urinary saturatin level t the lw end f the metastable range Data frm healthy, nn-urlith-frming cats have demnstrated decreased urinary saturatin with calcium xalate when cats cnsumed c/d xl r S/O Dgs Feed a diet that is mineral restricted, diuresing, and alkalinizing Prescriptin Diet U/d This is an ultra-lw prtein diet riginally frmulated fr uremic dgs It is als lw in minerals, has increased vitamin D, has increased B vitamins, and is very alkalinizing Ryal Canin S/O Ryal Canin s/ has been shwn t decrease urine saturatin with calcium xalate but n clinical studies have been dne

5 These diets are higher in fat than maintenance fds. Can feed a higher fiber diet and administer the alkalinizing agent, ptassium citrate Pharmaclgic management Ptassium citrate Citrate is an inhibitr f calcium xalate crystal frmatin because it frms a sluble salt with calcium Oral ptassium citrate may be beneficial in managing calcium xalate urliths because it is a calcium xalate inhibitr and because it is alkalinizing in nature Dsage is titrated t achieve a urine ph f apprximately 7.5 Calcium xalate preventative diets cntain ptassium citrate Vitamin B6 Vitamin B6 increases metablism f glyxylate, a precursr f xalic acid, t glycine Whether vitamin B6 deficiency ccurs in adult animals, especially cats, with calcium xalate urliths is unknwn, but unlikely One study in adult calcium xalate frming dgs shwed lwer plasma B6 levels when cmpared with nn-urlith frming dgs Vitamin B6 supplementatin is inexpensive and safe and shuld be cnsidered in pets that have difficult t cntrl urliths Thiazide diuretics By inducing a diuresis and decreasing urinary calcium excretin, thiazide diuretic administratin may be beneficial in pets with difficult t cntrl calcium xalate urliths Thiazide diuretics decrease urinary calcium excretin in human beings, dgs, and cats In cats, thiazide diuretics have been shwn t decrease urinary saturatin fr calcium xalate in healthy cats nly and they appear safe. One 2-week study in calcium xalate urlith frming dgs demnstrated decreased urinary calcium excretin Diuretic administratin may als be assciated with dehydratin and electrlyte imbalances and shuld be used cautiusly in animals with renal failure Other agents Gluccrticids have been recmmended t decrease bld calcium cncentratins in cats with idipathic hypercalcemia; hwever, they d s by increasing urinary excretin Bisphsphnates have been recmmended fr cats with idipathic hypercalcemia; hwever, n studies have been published

JUST TAKE A PEBBLE: NEPHROURETEROLITHIASIS

JUST TAKE A PEBBLE: NEPHROURETEROLITHIASIS Je Bartges, DVM, PhD, DACVIM, DACVN Prfessr f Medicine and Nutritin The University f Gergia jbartges@uga.edu Mst (>70%, and prbably > 90%) upper urinary urliths