JUST TAKE A PEBBLE: NEPHROURETEROLITHIASIS

Transcription

1 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 are cmpsed with calcium xalate. Struvite, particularly infectin-induced, and ther mineral types d ccur. Struvite urliths ccur either due t a bacterial infectin with a urease-prducing micrbial r withut an infectin Occasinally, ther minerals frm urliths in the upper urinary tract. Urate urliths ccur in the upper urinary tract in apprximately 10% f cases, and ccur secndary t liver disease, particularly prtvascular anmalies, r in breeds predispsed t frming urate urliths, such as Dalmatians and English bulldgs. Upper urinary tract urlithiasis is being recgnized mre frequently; hwever, accunt fr < 2% f urliths that are retrieved and submitted fr analysis. 50 fld éin upper urinary tract stnes between Nephrliths nt assciated with higher mrtality in Feline CKD Ureterliths assciated with higher mrtality in Feline CKD In 19 cats treated with renal transplantatin fr ureterlithiasis 5/18 develped new calculi 23% f cats presented fr peritneal dialysis, 60% survival 50% f hemdialysis patients Small, multiple urliths are cmmn and usually fund in bth kidneys and/r ureters. Small ureterliths appear t migrate ver time and can mve retrgrade in the ureter. Apprximately 15% f cats with upper urinary tract urliths had lwer urinary tract urliths. When lwer tract urliths ccur in assciatin with upper tract urliths, it is unknwn whether they frmed in the lwer urinary tract r whether they passed thrugh the ureter and int the urinary bladder. A cmmn scenari is t find upper tract urliths in a cat with chrnic renal failure. When there is unilateral nephrlithiasis, ften they ccur in the larger and mre functinal kidney. Clinical signs Upper urinary tract urliths (nephrliths and ureterliths) can lead t bstructin t urine flw, deteriratin f renal functin, serve as a nidus fr bacterial urinary tract infectin, hematuria, r pain. Clinical signs, when present, include systemic signs assciated with renal failure r pyelnephritis, vague signs (abdminal pain, arched back, vmiting, r anrexia) r hematuria. Smetimes animals present fr an abrupt change in behavir r an acute nset f abdminal pain r vmiting when an acute ureteral bstructin ccurs; this may be mistaken fr intervertebral disk disease. Clinicpathlgic finding Mst cmmn clinicpathlgic findings include aztemia, hyperphsphatemia, hyperkalemia, hypercalcemia, anemia, and hypcalcemia. Many f these may be related t the assciated CKD. Diagnsis Survey abdminal radigraphy Abdminal ultrasngraphy With & withut fursemide Excretry urgraphy Antegrade cntrast pyelgraphy Abdminal CT GFR (DTPA) With & withut fursemide Cmbinatin f survey radigraphy and abdminal ultrasngraphy has 90% sensitivity

2 Treatment General principles Nt all upper tract urliths require treatment especially by surgery. In ne study, presence f nephrliths withut ureteral bstructin, was nt assciated with prgressin f chrnic kidney disease Treat ureteral bstructin is present Treat secndary issues Manage CKD 80% f feline nephrliths ccur in cats with CKD Cllect baseline data CBC, Bichemical panel, UA, U C/S, BP, imaging Up t 80% f cats with ureterliths have CKD Supprtive therapy Treat hyperkalemia previusly discussed Fluid therapy previusly discussed Increase urine utput Analgesia Patients may experience renal clic Cautin with NSAIDs and CKD Manage nausea / vmiting, if present previusly discussed Anti-hypertensives treat systemic arterial hypertensin, if present previusly discussed Nutritinal supprt Antimicrbials (if infected) Manage bstructin N therapy Interventin Urinary diversin Lng term management Manage CKD Manage urliths If urliths are cmpsed f struvite r urate, medical disslutin can be attempted (see belw). Indicatins fr treatment f upper urinary tract urliths include bstructin t urine flw, increase in urlith size and/r number despite apprpriate therapy, if urliths are cmpsed f a mineral amenable t medical disslutin therapy, recurrent r persistent urinary tract infectins, cmprmise f renal functin due t urliths, recurrent r persistent clinical signs assciated with renal pain (e.g. vmiting r abdminal pain), r severe hematuria. Many cats with upper tract urliths already have renal cmprmise. Remval f upper tract urliths in cats with chrnic renal failure, especially if ureterliths, imprves survival; hwever, there is an assciated mrbidity and mrtality assciated with surgery fr upper tract urliths. Medical management Review medical disslutin prtcls fr thse minerals that are amenable t medical disslutin Cnsider dialysis fr stabilizatin Dialysis is the prcess f remving slutes and/r water frm ne slutin (plasma) t anther slutin (dialysate) by an smtic gradient thrugh a semi-permeable membrane. The 2 types f dialysis are peritneal dialysis and hemdialysis. There is little infrmatin n utilizatin f dialysis in veterinary medicine cmpared with human medicine. Dialysis invlves the use f ne type f semi-permeable membrane that allws the passage f small mlecules while preventing the transfer and lss f large mlecules. In peritneal dialysis, the peritneal membrane, interstitial tissue, and capillary endthelium act as the membrane. In hemdialysis, bld is circulated utside f the bdy thrugh a dialyzer. Peritneal Dialysis - The fundatin f peritneal dialysis is the dynamics f fluid and slute exchange acrss a semi-permeable membrane. Large mlecules such as prteins pass slwly thrugh such a

3 membrane. Smaller mlecules (urea and glucse) and ins (sdium and ptassium) mve easily acrss the membrane dwn a cncentratin gradient until equilibrium is reached n either side f the membrane. Water mves acrss the membrane frm the slutin f lwer smlality t that f higher smlality until equilibrium is reached. Hemdialysis - Hemdialysis is a renal replacement therapy that prvides a bridge f metablic stability t patients wh wuld therwise die frm the systemic effects f severe uremia. The principles f hemdialysis are similar t thse f peritneal dialysis except that bld is shunted utside f the bdy, passed thrugh a dialyzer ( purified ), and returned t the bdy. The cmpsitin f uremic bld is nrmalized by expsure t a cntrived slutin, the dialysate, acrss a semi-permeable membrane in a device called a hemdialyzer. During hemdialysis, water and small mlecular weight slutes and uremic txins pass readily thrugh the membrane pres (diffusin channels), alng diffusive and hydrstatic gradients, but the mvement f larger slutes (such as plasma prteins and cells), are limited by the size f the pres. Excessive bdy water and additinal slute can be frced thrugh the membrane by ultrafiltratin prduced by hydrstatic r smtic frces impsed acrss the dialysis membrane. Net remval f uremic slutes is influence by: (a) the cncentratin gradient fr diffusin, (b) the diffusivity f the slute, (c) permeability characteristics and surface area f the membrane, (d) bld and dialysate flw within the dialyzer, (e) duratin f dialysis, (f) distributin vlume f the slutes, and (g) amunt f ultrafiltratin (cnvective transfer). Nephrstmy tubes A nephrstmy tube may be placed fr urinary diversin in rder t relieve pressure n bstructed kidney One end is curled (pig-tailed) that has a lcking mechanism t maintain it in the dilated renal pelvis Tubing exits the bdy wall and is cnnected t external urine cllectin bag Medical expulsin therapy (MET) Increase urine utput IV fluids Diuretics Mannitl D nt use if under- r ver-hydrated Others? Relax ureteral smth muscle Alpha blckers In humans, these are a mainstay f treatment Amitriptyline Has been shwn t relax urethral smth muscle in cats May relax ureteral smth muscle as well Calcium channel blckers Cntract ureteral smth muscle Glucagn Used t cntract ureteral smth muscle Nt shwn effective in cats Assciated with side effects Decrease edema and inflammatin Sterids NSAIDs Interventin Surgical remval is nt necessary fr all upper urinary tract urliths. Surgery is nt indicated fr relatively small, nn-bstructive upper urinary tract urliths. Small upper urinary urliths may pass int the urinary bladder. It is unknwn what a safe time perid t allw fr ureterliths passing withut resulting in irreversible renal damage. Renal functin des nt recver n dgs with unilateral ureteral ligatin fr 40 days.

4 If a dg r cat is ill due t ureteral bstructin, it is nt prbably apprpriate t wait fr the ureterliths t pass r t medically manage them fr a prlnged perid f time if renal functin is t be preserved. If a urinary tract infectin is present, remval f the upper urinary tract urlith may be necessary t cntrl the infectin; hwever, it is nt pssible t determine prir t surgery if the urliths are the surce f infectin. If bilateral upper urinary tract surgery is required, the prcedures shuld be staged with an apprximate separatin f 4 weeks in rder t re-evaluate renal functin and t allw recvery frm the first prcedure. In general, the side with the mst renal functin shuld be perated first in rder t preserve as much renal functin as pssible. S when t intervene? BIG questin Nn-respnsive t medical management, and increasingly aztemic Ureterlith Evidence f pyelnephritis +/- stne size/number increasing Relieving bstructin may nt return renal functin; hwever, it may prevent further deteriratin Nephrtmy Surgical lngitudinal incisin thrugh renal parenchyma D nt cut arcuate arteries Allws access t renal pelvis fr nephrlith remval Nt assciated with decreased renal functin in healthy cats But these are nt healthy cats Pyellithtmy / prximal uretertmy Pyellithtmy is preferred because renal parenchymal tissue is nt incised and s lss f renal functin is less likely t ccur when cmpared with nephrtmy; hwever, pyellithtmy cannt be perfrmed unless the renal pelvis is dilated. Often it requires micrsurgical technique In cats, the renal pelvis is buried within the renal medullary parenchyma; therefre, technically, a prximal uretertmy is perfrmed Uretertmy A uretertmy can be perfrmed in dgs Ureteral stricture ften ccurs A 5cm defect will heal ver days if a ureteral stent is placed and the abdmen is kept evacuated f urine Neuretercyststmy If enugh ureter is present prximal t the ureterlith, the ureter is transected and distal part remved. The kidney and ureteral remnant is mved t the urinary bladder The dilated ureter is sutured t the urinary bladder Nephrectmy With r withut ureterectmy Remval f the bstructed kidney Indicated with cancer, pus-filled kidney, r n functinal tissue Try t avid as many cats with nephrureterliths have CKD Lithtripsy Extracrpreal shck wave lithtripsy (ESWL) is a standard f care fr many human patients with upper urinary tract urliths, and has been perfrmed successfully in dgs and cats. Acceptable canine candidates are thse with nephrliths smaller than 2-3 cm in their greatest dimensin r ureterliths. With bilateral nephrliths, bth kidneys are treated at the same time, unless there is cncern abut cmprmising renal functin further.

5 Mre than 100 dgs with nephrliths r ureterliths have been treated at 3 institutins. Mst f the urliths were cmpsed f calcium xalate. Mst canine upper urinary tract urliths fragment with 1 r 2 treatments. Feline upper urinary tract urliths appear t be mre difficult t fragment with ESWL than in dgs, and renal functin is mre likely t be cmprmised. Successful fragmentatin has been reprted t ccur in < 20-25% f feline cases. Althugh renal functin was nrmal in 4 healthy cats underging lithtripsy13 lithtripsy f clinical cases f upper urinary tract urlithiasis in cats suggests that many cats, particularly thse with pre-existing renal disease, experience renal functin cmprmise r wrsening f their renal failure. While lithtripsy is cnsidered safer and less invasive than surgical remval f upper urinary tract urliths, there are risks. Abdminal pain, hemrrhage, and bruising f the kidneys ccurs, and hematuria may be bserved immediately after the prcedure. Mre significant hemrrhage within r arund the kidney may ccur in sme cases. Residual stne fragments ften take several weeks t mve frm the kidney int the urinary bladder. Transient r permanent ureteral bstructin can ccur. If permanent and prgressive ureteral bstructin ccurs, it requires re-treatment by lithtripsy r surgical interventin. Uncmmn cmplicatins include pancreatitis, bwel irritatin, hemlysis, and systemic hypertensin. Percutaneus nephrlithtmy A rigid scpe can be inserted thrugh the renal parenchyma int the dilated renal pelvis. The nephrlith is visualized and either retrieved r fragmented using laser lithtripsy and fragments retrieved Ureteral stent In patients where nephrureterliths cannt be managed surgically, urinary diversin may be accmplished by placing a ureteral stent. Usually a duble pig-tailed stent is placed surgically, flurscpically, r via cystscpy. One f the pig-tails is placed s that it is within the dilated renal pelvis and the ther pig-tail is placed s that it is within the urinary bladder. The bdy f the stent cnnects the 2 pigtails and prvides diversin f urine flw arund the bstructive ureterliths Stents are ften used with neplastic ureteral bstructin Subcutaneus urinary bypass device (SUB) Used t divert urine frm renal pelvis t urinary bladder bypassing the ureter Similar t a nephrstmy tube; hwever, used lng term and implanted subcutaneusly A lcking pig-tail catheter is inserted int the renal pelvis and the kidney is pexied t the bdy wall (nephrpexy) Tube is tunneled subcutaneusly t a metallic prt that is implanted subcutaneusly just ff f ventral midline The metallic prt is used fr cllecting a urine sample using a special needle (Huber needle) A tube exits the ther side f the prt and re-enters the abdmen and is inserted near the apex f the urinary bladder, which is pexided t the ventral abdminal wall (cystpexy) These are ften used with neplastic ureteral bstructin Cmparisn f medical vs surgical management In a retrspective analysis f medically versus surgically managed patients with ureterliths, surgically managed patients tended t d better ver a lnger time. Surgery, thugh, was assciated with mre cmplicatins primarily in the periperative perid. There was a recurrence rate f 40%. Renal transplantatin

6 A retrspective study f 19 cats with renal failure assciated with calcium xalate urlithiasis has been published There were 13 females and 7 males All cats were aztemic and 17 were anemic Hypercalcemia was present in 7 cats Mean duratin f survival in all cats was 605 days 8 cats were alive 282-1,005 days (median = 1,305 days) 11 cats died 2-1,197 days (median = 300 days) 5 cats frmed urliths in their allgraft kidney 2 were hypercalcemic 4 died fllwing cmplicatins assciated with urlith frmatin Pst-bstructin relief Fluid therapy VITAL Pst-bstructive diuresis Electrlytes Hypkalemia Acid-base Metablic acidsis Clinical signs f uremia Anemia Analgesia Nutritin Manage CKD see previus lectures