3 CE CE Article CREDITS Methods of Urolith Removal Cathy Langston, DVM, DACVIM (Small Animal Internal Medicine) Kelly Gisselman, DVM Douglas Palma, DVM John McCue, DVM Animal Medical Center New York, New York Abstract: Multiple techniques exist to remove uroliths from each section of the urinary tract. Minimally invasive methods for removing lower urinary tract stones include voiding urohydropropulsion, retrograde urohydropropulsion followed by dissolution or removal, catheter retrieval, cystoscopic removal, and cystoscopy-assisted laser lithotripsy and surgery. Laparoscopic cysto- tomy is less invasive than surgical cystotomy. Extracorporeal shock wave lithotripsy can be used for nephroliths and ureteroliths. Nephrotomy, pyelotomy, or urethrotomy may be recommended in certain situations. This article discusses each technique and gives guidance for selecting the most appropriate technique for an individual patient. ew, minimally invasive techniques for removing preventive measures.7 Surgical removal of partial or com- uroliths have been developed or have become more pletely obstructing ureteroliths that do not pass within 24 Nreadily available in veterinary medicine. TABLE hours may be prudent.8 A staged approach to surgery can be 1 summarizes the advantages and disadvantages of each considered if uroliths are found at multiple sites in the upper method, the number and type of uroliths for which each is urinary tract. The reversibility of renal dysfunction depends appropriate, and necessary equipment for each. on completeness and duration of obstruction. Studies in Uroliths can be eliminated by physical removal, and cer- dogs have shown variable and permanent decreases in renal tain types can be dissolved. Indications for physical removal function after 7 days of acute ureteral obstruction, with no include obstruction of the urethra, renal pelvis, or ureters; improvement after 40 days of obstruction,8 although there failure of dissolution therapy; and unacceptable clinical are reports of improvement after 70 days in people,9 and we signs associated with urolithiasis, such as recurrent urinary have observed improvement in cats after 70 days. tract infections or pollakiuria.1–3 The benefits of physical All methods of stone removal should be followed by imag- removal of cystic calculi include rapid resolution, definitive ing to confirm complete urolith removal. Appropriate man- diagnosis of urolith type (via quantitative urolith analysis), agement to prevent regrowth of uroliths is recommended. and reduced risk of urinary obstruction.4 In asymptomatic patients, removal of cystic calculi is not mandatory, particu- Nonsurgical Techniques larly if there are relative contraindications to anesthesia or Voiding urohydropropulsion is used to evacuate small uro- surgery.5 If a urolith is suspected to be composed of struvite, cystoliths by flushing them out through the urethra BOX( urate, or cystine, medical dissolution can be attempted if 1).10–12 A general guideline is that this technique can be used no indication for more immediate removal is present. There to remove uroliths <5 mm in diameter from male and female are no effective medical dissolution protocols for calcium dogs weighing more than 8 kg, uroliths <3 mm from female oxalate uroliths. cats and small dogs, and uroliths ≤1 mm in diameter from The decision to remove nephroliths or ureteroliths is more complicated than the decision to remove cystic or urethral calculi. Nephroliths are commonly detected in cats RELATED ARTICLES with chronic kidney disease, but in most cases, they do not cause progression of renal dysfunction, and nephrotomy is • Diagnosis of Urolithiasis, August 2008 6 generally not recommended. Nephroliths and ureteroliths • Urate Urolithiasis, October 2009 should be physically removed if they are causing obstruc- • Calcium Oxalate Urolithiasis, November 2009 tion to urine flow, progressive deterioration in renal function, • Feline Struvite Urolithiasis, December 2009 or recurrent urinary tract infection or are enlarging despite Vetlearn.com | June 2010 | Compendium: Continuing Education for Veterinarians® E1 ©Copyright 2010 MediMedia Animal Health. This document is for internal purposes only. Reprinting or posting on an external website without written permission from MMAH is a violation of copyright laws. FREE CE Methods of Urolith Removal table 1 Comparison of Various Methods of Urolith Removal Urolith Urolith Size/ Urolith Technique Location Number Type Advantages Disadvantages Anesthesia Equipment Upper Urinary Tract Extracorporeal shock Kidney, Small to All No surgery Limited availability Yes Extracorporeal wave lithotripsy ureter moderate size shock wave lithotripter Percutaneous Kidney, Moderate size All Less invasive than Limited availability Yes Lithotripter; rigid nephrolithotomy proximal to large open surgery cystoscope ureter Pyelotomy Kidney Any All Less renal damage Renal pelvis must be Yes Surgical than nephrotomy distended Ureterotomy Ureter Any size, All Rapid resolution of Risk of urine leakage; Yes Surgical; small number obstruction postoperative swelling magnifying loupes or stricture may cause or operating obstruction; multiple microscope in cats uroliths increase risks Nephrotomy Kidney Any All No special Temporary decrease in Yes Surgical equipment renal function Ureteral stent Ureter Large number All May be only option Stents not readily available, Yes Surgical; difficult to place intraoperative fluoroscopy Lower Urinary Tract Voiding Bladder, Small size, All No surgery Risk of obstruction with Sedation or Catheter urohydropropulsion urethra any number larger uroliths anesthesia Retrograde Urethra Small size All Avoids urethrotomy Does not remove uroliths Sedation or Catheter hydropropulsion anesthesia Cystoscopic Bladder Small size, All No surgery Only small uroliths Yes Rigid cystoscope evacuation any number removed Laser lithotripsy Bladder, Medium All No surgery Limited availability; may Yes Rigid or flexible urethra size; small take longer than cystotomy cystoscope; laser to moderate if large urolith burden lithotripter number Laparoscopic- Bladder Any All Less invasive than Same procedure duration Yes Rigid cystoscope assisted cystotomy standard cystotomy as standard cystotomy with skilled operator Cystotomy Bladder Any All Rapid, readily Bigger incision than Yes Surgical available laparoscopic-assisted cystotomy Urethrotomy Urethra Any All Removes uroliths Risk of stricture Yes Surgical resistant to other techniques Urethrostomy Urethra Any All Decreases risk of Increased long-term risk of Yes Surgical future obstruction infection in dogs with recurrent urolith formation Upper and Lower Urinary Tract Dissolution Bladder, Any Struvite, No anesthesia or Not applicable to all urolith No None kidney urate, surgery types; takes weeks to cystine months for resolution E2 Compendium: Continuing Education for Veterinarians® | June 2010 | Vetlearn.com FREE Methods of Urolith Removal CE Box 1 Box 2 Voiding Urohydropropulsion10–12 Retrograde Urohydropropulsion13 1. Anesthetize the patient if needed (short-acting • Chemical restraint may be necessary in some patients. anesthesia can be used for easily removed, small General anesthesia may be required if uroliths cannot uroliths; consider epidurals to relax the urethra in be dislodged. male dogs). • Decompress the bladder by cystocentesis. 2. Place a urinary catheter. • Pass a urethral catheter to the point of obstruction. 3. Attach a three-way stopcock to the end of the urinary • Mix aqueous lubricant with an equal amount of saline catheter to facilitate control of fluid into and out of and inject via the urethral catheter to lubricate the the bladder. urolith and urethral mucosa. 4. Fill the urinary bladder with sterile saline or lactated • Attempt to retropulse the urolith into the bladder by Ringer’s solution via the catheter until the bladder gentle palpation (vaginally or rectally). is distended (confirmed by palpation to avoid overdistention, approximately 4–6 mL/kg). Males • Two people are needed to perform retrograde 5. Position the patient so that the spine is perpendicular urohydropropulsion in males. to the table or 20° to 25° caudal to perpendicular. • With rectal palpation, occlude the proximal urethra by 6. Agitate the bladder to dislodge uroliths loosely pressing a finger against the ventral pelvic bone. adhered to the bladder mucosa. • Occlude the urethral opening by compressing the tip 7. Remove the urinary catheter. of the penis around the catheter. 8. Express the urinary bladder (apply digital pressure • Inject saline through the catheter until resistance is felt dorsally and cranially to induce micturition; if the by the person performing the injection. This dilates the bladder is pushed toward the pelvic canal, a kink section of urethra between the two sites of occlusion. can form in the distal urethra, preventing passage of • Rapidly release the pressure in the pelvic urethra (but uroliths). not distal urethra) while continuing to inject saline. This flushes the urolith into the bladder. 9. Repeat steps 2 through 8 until uroliths are no longer being expelled. Females 10. Use imaging to evaluate the success of the • With rectal palpation or vaginal palpation (preferred), procedure (consider cystoscopy or double-contrast occlude the distal urethra around the catheter. cystography to evaluate small uroliths that may • Inject saline through the catheter. remain; only a lateral exposure is needed). • Gently manipulate the urolith to move it toward the bladder lumen.