Lower Urinary Tract Uroliths

3 CE Credits

New Alternatives for Minimally Invasive Management of Uroliths: Lower Urinary Tract Uroliths

Alice Defarges, DVM, DACVIM University of Guelph

Marilyn Dunn, DMV, DACVIM Université de Montreal

Allyson Berent, DVM, DACVIM The Animal Medical Center New York, New York

Abstract: In small animals, removal is indicated for lower urinary tract calculi that are not amenable to medical dissolution and are causing, or may cause, urinary tract obstruction, inflammation, or recurrent infection. Surgical removal of lower urinary tract uroliths by cystotomy or urethrotomy has been the traditional method. The current standard of care for human urinary tract stones involves the use of lithotripsy and is minimally invasive. This article reviews the current literature on the various minimally invasive options available for managing lower urinary tract stones in small animal veterinary patients. Options for managing nephroliths and ureteroliths will be presented in forthcoming companion articles.

ower urinary tract calculi should be removed if they are not can lead to suture-induced stones, strictures, adhesions, bleeding, amenable to medical dissolution and if they are causing, or may uroabdomen, pain, and other, life-threatening complications.5,6 cause, urinary tract obstruction, inflammation, or recurrent In 2002, open surgical removal of uroliths was described in only L 7 infection. In small animals, surgical removal of uroliths by cystotomy 0.3% to 4% of human patients. The current standard of care for or urethrotomy has been the traditional method of choice. In a 1992 human urinary tract stones that cannot be passed or medically study, calculi remained in the bladder after cystotomy in 10% of dogs dissolved typically involves the use of lithotripsy. and 20% of cats.1 In a larger, more recent study, removal of uroliths In small animals, minimally invasive treatment options for lower was incomplete in 20% of dogs after cystotomy.2 Postoperative urinary tract stones consist of voiding urohydropropulsion (VUH), radiography of the entire urethra is indicated to ensure that all intracorporeal lithotripsy, extracorporeal shock-wave lithotripsy calculi have been removed.1 A 2008 study reported that 9.4% of (ESWL), cystoscopic stone basket retrieval, percutaneous cysto- recurrent stones in dogs were suture induced, indicating that cys- lithotomy (PCCL), and laparoscopic-assisted cystotomy. Ideally, all totomy could increase the risk of stone formation.3 More recently, minimally invasive stone retrieval procedures should be performed complications associated with traditional surgical cystotomy, regard- after a negative urine culture has been documented or the patient less of closure method, were reported in 37% to 50% of cases, with has been receiving an appropriate antibiotic for at least 24 hours. a mean duration of hospitalization of 4 days.4 Ideally, less-invasive alternatives with fewer complications, fewer long-term stone recur- Voiding Urohydropulsion rences, more effective stone removal, and shorter hospitalization VUH consists of removing small bladder calculi by inducing voiding times should be sought. while the dog or cat is positioned vertically or laterally. This pro- In humans, minimally invasive treatment options have mostly cedure was described by Lulich et al.8 It can be successfully performed replaced traditional surgical stone removal, which is associated in male or female dogs and female cats. It is not recommended in with a high recurrence rate of calculi, the need for serial surgeries that male cats, in which the narrow urethra may become obstructed Dr. Dunn discloses that she has received financial benefits from Infiniti Medical and Vétoquinol. by the stones.

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Stone size is the most important criterion in de- ciding if VUH is an appropriate treatment option. Stones <3 mm and <4 mm can typically be voided by tiny (≤2 kg [≤4.4 lb]) and small to medium-sized (2 to 5 kg [4.4 to 11 lb]) female dogs, respectively. Female cats may be able to void stones <3 mm.9 Male dogs weighing 5 to 10 kg (11 to 22 lb) may be able to void stones <2 to 3 mm, and male dogs of 10 to 25 kg Figure 1. Holmium laser lithotripter. (22 to 55 lb) can typically void stones <3 mm. Before attempting VUH, clinicians should try to catheterize the urethra Figure 2. Bladder cystoscopy in a dog with calcium oxalate stones. The laser fiber first to evaluate its size. If a 9-Fr urinary catheter can be passed (A) is being advanced until it contacts the stone (B). through the urethra, 3-mm stones should be able to be voided. For VUH, the patient is placed under general anesthesia. The urethra is catheterized and the bladder distended with saline. Box 1. General Guidelines for Intracorporeal Lithotripsy The urinary catheter is then removed and the patient positioned in the Lower Urinary Tract vertically. The bladder is agitated so that gravity causes the stones to fall into the trigone. Bladder palpation increases intravesicular • Follow laser safety guidelines pressure and helps maintain a strong urine stream as small stone • Maintain a distance of ≥0.5 mm between the probe and the bladder mucosa fragments are voided. General anesthesia is mandatory for this procedure, and the bladder can rupture if the patient does not • Flush abundantly with saline during the procedure have a relaxed, unobstructed urethra. The procedure is repeated • Use lowest power settings until no calculi or stone fragments are passed. Radiography, with or without positive or negative contrast, or cystoscopy can be • Palpate the bladder during the procedure and VUH performed after the procedure to confirm complete urolith removal. • Administer prophylactic antibiotic therapy for 3 days after the procedure VUH can also be used to obtain a few small stones for analysis to determine whether medical dissolution is an option. In our expe- • Administer antiinflammatory drugs (NSAIDs often used) rience, using cystoscopy rather than digital urethral catheterization for bladder filling in female dogs and cats can be very helpful. Empiric antibiotics should be given during the procedure and for intracorporeal lithotripsy in veterinary and human medicine14–18 3 to 5 days afterward. Broad-spectrum antibiotics such as ampicillin (FIGURE 1). It uses an active-medium crystal made of yttrium, alu- or cephalexin are usually prescribed. To minimize discomfort minum, and garnet (YAG) mixed with holmium (chromium and during urination, NSAIDs or opioids are administered for 1 to 4 thulium). The Ho:YAG laser emits light at an infrared wavelength days as needed and based on clinical signs.10 of 2100 nm.25 For lithotripsy using a Ho:YAG laser, the patient is placed under Intracorporeal Lithotripsy general anesthesia for routine cystoscopy. Once the urolith is visual- Methods ized with the cystoscope, a small-diameter, flexible quartz laser Electrohydraulic lithotripsy (EHL) and laser lithotripsy were devel- fiber (200, 365, or 550 µm) is guided through the working channel oped in the 1970s to fragment bladder uroliths in humans,11 and of a small-diameter flexible or rigid cystoscope/ureteroscope(FIGURE the overall success rate in humans is reported to exceed 90%.11–14 2). The tip of the fiber is placed in direct contact with the surface Intracorporeal lithotripsy has been reported for the treatment of the urolith at a 90° angle, and pulsed laser energy is transmitted of bladder and urethral stones in dogs,15–18 goats,19 horses,20–23 from the energized crystal to the urolith via the fiber. The stone and rabbits.24 Two types of intracorporeal lithotripsy have been is fragmented by a thermal drilling process, in which the pulse of described in veterinary patients: laser lithotripsy16–19 and EHL.15 energy traveling through the fiber creates a microscopic vapor To date, the recommended laser for intracorporeal lithotripsy bubble on the surface of the calculus. This microscopic “parting” is the Ho:YAG laser. This laser is the most commonly used device for of the fluid medium by an air bubble (known as theMoses effect)

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allows more of the laser’s energy to be transmitted directly into the stone, creating a shock wave that induces stone fragmentation.10 If the fiber tip is 1 mm or more away from the stone, the vapor bubble collapses, the water or saline absorbs the energy, and no energy is transmitted to the urolith.10 As the fiber tip is advanced to within 0.5 mm of the calculus, the vapor bubble comes in contact with the stone. The closer the fiber tip is to the target, the larger the effect, with the greatest effect achieved when the fiber is in contact with the stone. The energy is absorbed in <0.5 mm of fluid, making it safe to fragment uroliths in tight locations, such as within the urethra, ureter, renal pelvis, or urinary bladder, with limited risk of adjacent urothelial damage.26 The choice of power setting is based on the application. For stone fragmentation, the initial energy setting should be approximately 0.6 to 0.8 J at 6 to 8 Hz. Energy settings can be increased as desired, but levels higher than 1 J and 12 Hz are rarely required to fragment stones in dogs and cats.10 Stones are typically fragmented until the pieces are small enough to be voided using VUH or manually extracted from the bladder using a stone retrieval basket. Figure 3. Bladder cystoscopy in a dog with calcium oxalate stones. The electrohydraulic lithotripsy probe ( ) is being advanced until it contacts the stone ( ) while maintaining This technology is considered the standard of care in human A B a safe distance between the probe and the mucosa (C). medicine and is currently being utilized for lower urinary tract stones in many veterinary hospitals in North America (BOX 1). EHL is slightly different. This technology causes an electric 83% to 96% of female dogs with cystoliths, and 68% to 81% of spark to be generated in a fluid medium, creating a cavitation bubble male dogs with cystoliths.10,16,17 that generates a hydraulic shock wave.27,28 This shock wave disrupts The median procedure time has been reported to be shorter the crystal lattice structure of the urolith via shearing forces.27 Since for dogs in which intracorporeal lithotripsy was performed only in the bladder is constantly irrigated with saline during the procedure, the urethra compared with dogs in which uroliths were fragmented EHL can be done during cystoscopy. The probe is directed toward in the bladder.15 In the abovementioned study in 73 dogs,17 Adams the urolith, and the stone absorbs most of the energy. Calculi are et al reported that the median procedure time was shorter for dogs fragmented into pieces that are smaller than the urethral diameter with urethral stones only (median: 70 min; range: 35 to 180 min) for endoscopic retrieval (FIGURE 3), typically using a stone-retrieval than for dogs with bladder stones (median: 105 min; range: 35 to basket. 382 min). Grant et al reported that the procedure time was longer for males (median: 143 min) than for females (median: 42 min).16 Effectiveness In the Adams et al study, the complication rate reported with The Ho:YAG laser has been reported to be effective on all stone laser lithotripsy was 17.9% in female dogs and 13.3% in male types.29 One in vitro study30 demonstrated that the Ho:YAG laser dogs.17 These rates are lower than those reported for traditional consistently fragmented canine stones of all types (calcium oxalate, surgical cystotomy (37% to 50%).4 Complications reported by Adams cystine, struvite, silica, and urate) into extractable fragments et al were typically minor and short term, including urethral (<3.5 mm in diameter) in <30 seconds. Davidson et al18 first swelling, edema, and mild hematuria, which were medically described using the Ho:YAG laser to fragment uroliths that were managed. Short-term complications were most commonly related surgically implanted at the base of the os penis in healthy dogs, to urethral mucosal swelling from serial passage of the cystoscope showing that laser lithotripsy could successfully fragment obstructive in female dogs and resolved with the placement of an indwelling uroliths in male dogs. More recently, Adams et al17 reported that urinary catheter for 12 to 24 hours.10,16,17 One major complication laser lithotripsy was effective in the fragmentation of bladder and was bladder perforation by the laser fiber, which healed within 24 urethral stones in 73 dogs in a clinical setting. In this study, a hours of urinary catheterization. This complication was reported basket was used to move smaller bladder stones to the urethra in only one study.17 No long-term complications were reported in before fragmentation to minimize their movement during litho- this study.17 tripsy. This technique resulted in complete fragmentation of all In one canine study in which laser lithotripsy was retrospectively uroliths in 100% of females (28 of 28 dogs) and 86.7% of males compared with traditional cystotomy,31 major (i.e., wound dehis- (39 of 45 dogs).17 Grant et al16 performed a prospective clinical cence, urethral obstruction, bladder rupture, and urethral perfo- study in which 25 dogs were treated by laser lithotripsy for bladder ration) and minor complications (i.e., hypothermia and hypo- and/or urethral stones. Twenty dogs (80%) were considered tension) were recorded for each dog. There were no significant stone free after the procedure. In the literature, complete urolith differences between the groups with regard to any of the evaluated removal is typically achieved in 100% of dogs with urethroliths, complications. Both methods were considered equally effective;

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treatment failure was defined as Table 1. Ideal Candidates for Intracorporeal Lithotripsy of the Lower Urinary Tracta incomplete removal of uroliths >3 mm in diameter. The complete EHL Ho:YAG lithotripsy urolith removal rate was not sig- Female dog or any size cat nificantly different between dogs Size Patient Male dog ≥7 kg (≥15.4 lb) in the cystotomy group (86%) and characteristicsb those in the lithotripsy group Sex Females easier than males (89%). On average, it took 23 minutes longer to manage urinary <2 cm in females Size stones using lithotripsy than using <1 cm in males cystotomy.31 Patients undergoing lithotripsy were discharged from Stone characteristics Type Struvite more difficult to break All types of stones easy to break the hospital 12 hours earlier than related to ease Shape Irregular easier to break than smooth All shapes of stones easy to break those having a cystotomy.31 In of fragmentation the Grant et al study of 25 dogs,16 Location Urethral stones easier than bladder stones 84% (21/25) of dogs receiving lithotripsy were discharged the Number <5 stones for males day of the procedure. Adams et EHL = electrohydraulic lithotripsy, Ho:YAG = holmium: yttrium, aluminum, and garnet. al17 reported that of 73 dogs with aBased on author experience. uroliths treated by laser lithotripsy, bEndoscopy done with a 1.9-mm rigid cystoscope or 7.5-Fr flexible ureteroscope. only 19% (14/73) had stone recurrence after approximately 12 to 24 months of follow-up, which is sig- EHL15–17; however, no study has compared the two techniques. The nificantly less than that previously reported with cystotomy (42%).32 greatest challenge of both laser and EHL lithotripsy is the removal A prospective clinical study of 28 dogs undergoing EHL demon- of small stone fragments from the bladder after fragmentation. strated that intracorporeal lithotripsy using EHL was also effective This challenge is accentuated in male dogs due to the length and for treating lower urinary tract calculi in dogs.15 EHL was most smaller diameter of the urethra. Grant et al16 identified female effective in female dogs with bladder stones and male dogs with sex as a positive predictor of success. They reported that smaller urethral stones. EHL appeared to be as safe as laser lithotripsy and body weight, large urolith burden, and increasing urolith size was associated with no major complications. Dogs treated for significantly increased the time required to perform laser litho- urethral stones did not typically show any signs of stranguria after tripsy. This has made the use of other procedures, like PCCL, the procedure.15 appealing for dogs with a large bladder stone burden. Patient and Laser lithotripsy appears to be more efficient, particularly for urolith characteristics that affect EHL and Ho:YAG laser litho- male dogs, than EHL. Although laser lithotripsy is considered to tripsy are summarized in TABLE 1; guidelines for improving the be safer than EHL in confined spaces, such as the ureter and urethra, effectiveness of intracorporeal lithotripsy are listed in BOX 2. repeated pulses on the urothelium can cause perforation.33 Laser lithotripsy may also break stones into smaller fragments than Extracorporeal Shock-Wave Lithotripsy ESWL is a minimally invasive procedure that uses an external unit to Box 2. Guidelines to Improve Effectiveness of Intracorporeal create shock waves that pass through the soft tissue of the patient. Lithotripsy It is typically used for the removal of upper urinary tract calculi from a renal pelvis or ureter. It has also been used to fragment bladder To improve visibility: stones in some dogs.27 However, the movement of stones inside • Use a large cystoscopic working channel for better irrigation the bladder during treatment limits the repeated shock-wave effect and may result in larger-than-desired fragments.10,27,34 After • Use a 30° angled scope for better visualization ESWL for bladder stones, VUH or use of a cystoscopic stone basket • If possible, flush with cold saline to minimize bleeding (monitor patient’s is still required for stone fragment removal. Typically, intracorporeal body temperature) methods are preferred for optimal fragmentation and immediate 10 To improve fragmentation: removal of cystoliths. ESWL is offered at a few veterinary facilities BOX 3 • Use a stone retrieval basket to remove stones from the bladder and bring in the United States ( ). This technique will be described in them into the urethra for fragmentation in male dogs more detail in a forthcoming companion article. To improve expulsion of stone fragments: Cystoscopy-Guided Basket Retrieval • Use a stone retrieval basket to remove stone fragments Another option for stones that are too large for VUH but small • Place patient in dorsal recumbency at a 45° angle for stones to settle in trigone enough to fit down the urethra with gentle traction is stone basket retrieval.35 A variety of stone baskets are available from several

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Box 3. Hospitals Equipped for Extracorporeal Shock-Wave Laparoscopic-Assisted Cystoscopy Lithotripsy Laparoscopic-assisted cystoscopy is performed via a minilaparotomy, the location of which is guided by visualization of the The Animal Medical Center Purdue University School of bladder through a laparoscopic abdominal portal placed just New York, NY 10065 Veterinary Medicine caudal to the umbilicus. In this technique, after the bladder is Contact: Dr. Allyson Berent West Lafayette, IN 47906 catheterized or aspirated to drain urine and the abdominal portal E-mail: [email protected] Contact: Dr. Larry Adams is placed, the abdomen is insufflated with carbon dioxide and the Phone: 212-838-8100 E-mail (Referral desk): bladder is isolated. Another trocar is inserted into the abdomen at [email protected] the level of the bladder apex, and the bladder is partially exteriorized at this access point, using a laparoscopic Babcock forceps.38 The incision is then enlarged creating a minilaparotomy. A small cys- manufacturers. Basket retrieval is typically performed under cysto- totomy is performed, and the bladder wall is sutured to the skin scopic guidance, although fluoroscopy can also be used. Typically, of the abdominal incision. A rigid cystoscope is then inserted into the size of the stone is the limiting factor. Basket retrieval can be the bladder for calculus retrieval. The use of a basket passed through considered in female dogs with stones <5 mm, male dogs with the working channel or a grasping forceps next to the cystoscope stones <4 mm, and female cats with stones <3 mm. aids in stone removal. The cystotomy incision is closed routinely. We recommend using quickly absorbable suture (i.e., Monocryl, Percutaneous Cystolithotomy Ethicon, Somerville, NJ) because these patients are typically prone Use of a newer minimally invasive approach, PCCL, has been to recurrence of uroliths and the development of suture-induced reported in 27 dogs and cats, with excellent complete stone removal stones. If the suture material penetrates the bladder mucosa, fast rates (96%) and dramatically shorter procedure times (total pro- absorption is considered ideal. If concurrent infection is a concern, cedure time: 40 to 75 min) than those seen with transurethral then longer-lasting suture (polydioxanone) is recommended. 36,37 lithotripsy, regardless of patient sex, size, stone number, or species. Rawlings et al39 recommend retracting a portion of omentum PCCL can be an alternative in animals in which transurethral to be sutured over the bladder incision with the traction sutures. lithotripsy is a challenge (small male dogs, male dogs with a large Abdominal incisions should be closed with separate layers of sutures stone burden, and male and female cats) or if lithotripsy is un- placed into the linea alba, abdominal musculature, subcutaneous available. tissue, and skin.39 For this procedure, a single small incision (approximately 1 to Laparoscopic-assisted cystoscopy39 can circumvent some of the 1.5 cm) is made in the abdominal cavity just over the apex of the limitations associated with laser lithotripsy, but it does require bladder. Once the bladder is palpated digitally, a stay suture is creating a pneumoperitoneum. In humans, this procedure has been used to hold the bladder up to the incision while a laparoscopic associated with postoperative discomfort,40 respiratory compro- screw-tip cannula or port is inserted into the bladder at the apex. mise,41,42 and decreased renal43 and splanchnic perfusion.44,45 A small, rigid cystoscope is inserted through this port into the bladder, and stones are identified and removed with a stone-retrieval Conclusion basket through the working channel of the cystoscope. The best Intracorporeal lithotripsy appears to be an effective and safe mini- visualization is achieved with a full bladder; therefore, we usually mally invasive method of treating spontaneously occurring lower use surgical aspiration while flushing fluid into the bladder via a urinary tract stones in dogs and cats. Small male dogs and male urinary catheter in the urethra. The bladder is typically not exte- cats are more difficult to treat; therefore, newer minimally invasive riorized. If the stones are very small, a suction device can be procedures, like PCCL or laparoscopic-assisted cystoscopy, are placed into the port and the stones can be flushed/suctioned out attractive options, especially in patients with large stone burdens. of the port in a retrograde manner. If the stones are larger than Minimally invasive management of urolithiasis in veterinary the port, they can either be fragmented by lithotripsy or manipulated medicine is following the trend seen in human medicine. Over through the small incision with the stone basket.37 Concurrent the past 10 years, the veterinary community has made great lithotripsy is rarely needed. After all calculi are removed from the strides in adapting the technology used for humans to be more bladder, the entire urethra is examined with a rigid cystoscope applicable to small animal veterinary patients. Conditions that (female dogs) or a flexible ureteroscope (male dogs) to ensure were traditionally considered major therapeutic dilemmas, such as that all fragments have been removed. A basket retrieval device ureteral obstructions, stone recurrence, and urethral obstructions, can be used to remove any remaining urethral calculi through the working channel of the endoscope. In patients with embedded now have new, effective, and safe options. urethral stones, laser lithotripsy can be performed. PCCL can References also be used to aid in gaining access to the ureters for diagnostic 1. Lulich JP, Perrine L, Osborne CA, et al. Postsurgical recurrence of calcium oxalate or therapeutic purposes and for resection of bladder polyps or uroliths in dogs [abstract]. J Am Vet Res 1992;6:119. diagnostic evaluation of the bladder and proximal urethra in 2. Grant DC, Harper TA, Werre SR. 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Vetlearn.com | January 2013 | Compendium: Continuing Education for Veterinarians® E6 New Alternatives for Minimally Invasive Management of Uroliths: Lower Urinary Tract Uroliths

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1. Intracorporeal lithotripsy involves which of the following 6. A male, neutered 3.5-kg (7.7 lb) Yorkshire terrier presents mechanisms? with five cystoliths ranging in size from 2 to 8 mm. Which a. delivering shock waves percutaneously to target a stone technique is preferable for treatment? b. delivering laser energy directly to a stone a. percutaneous cystolithotomy c. using laparoscopic scissors to cut a stone in situ b. extracorporeal shock-wave lithotripsy d. using ultrasonography to guide treatment c. cystotomy d. voiding urohydropulsion 2. Which statement is false with regard to the use of extracorporeal shock-wave lithotripsy to treat urinary tract 7. With regard to Ho:YAG laser lithotripsy, which statement is stones in dogs? false? a. It may be used to decrease the size of the stone and a. It does not damage the urothelium as long as the tip of extract a fragment for analysis. the probe is maintained ≥0.5 mm away from the mucosa. b. It may be indicated for upper and lower urinary tract stones. b. It is efficient in fragmenting all types of stones. c. It is the treatment of choice to fragment bladder stones c. It is efficient and safe for fragmenting bladder and urethral in dogs. stones. d. It is not as efficient as intracorporeal lithotripsy in d. It is contraindicated for urethral stones. fragmenting lower urinary tract stones that are more 8. A 8-kg (17.6-lb) male dog presents with one 3-mm bladder mobile than upper urinary tract stones. urolith and several urethral stones. Which statement regarding treatment is true? 3. Postoperative care for intracorporeal lithotripsy for bladder stones consists of which of the following therapies? a. Laser lithotripsy is contraindicated because the patient is male. a. placing an indwelling catheter for 2 days b. Urethrotomy is indicated to remove the urethral stones. b. promoting diuresis for 48 hours c. A rigid cystoscope can be used through a urethrotomy to fragment the stones. c. administering analgesics and antibiotics d. The use of a basket to bring the bladder urolith in the urethra d. placing a cystotomy tube can make the procedure easier because laser lithotripsy is 4. Which statement is true with regard to the use of lithotripsy easier in the urethra than in the bladder in male dogs. in small animals? 9. Which statement is true with regard to intracorporeal a. Intracorporeal methods are preferred for optimal lithotripsy for lower urinary tract stones? fragmentation and immediate removal of cystoliths. a. Removal of fragments is more difficult in females than in b. Extracorporeal methods are preferred for optimal males. fragmentation and immediate removal of cystoliths. b. In males, bladder stones are easier to fragment and c. Extracorporeal methods are contraindicated in treating remove than urethral stones. lower urinary tract stones. c. In males, urethral stones are easier to fragment and d. Sedation is sufficient to permit stone fragmentation. remove than bladder stones. d. It is impossible to fragment calcium oxalate stones in dogs. 5. Voiding urohydropulsion consists of a. flushing urethral stones back into the bladder with fluids 10. Which statement is true with regard to intracorporeal injected through a urinary catheter. lithotripsy for cystoliths? b. flushing bladder stones in the urethra with intravenous a. Canine calcium oxalate uroliths are resistant to fragmentation fluid boluses. by laser lithotripsy. c. removing small bladder calculi by inducing voiding while b. The procedure takes more time in female dogs than in the dog or cat is positioned vertically or laterally. male dogs. d. flushing bladder stones through a cystotomy tube into c. The procedure requires general anesthesia. the urethra. d. The procedure is contraindicated in male dogs.

Vetlearn.com | January 2013 | Compendium: Continuing Education for Veterinarians® E7