Cystoscopy-assisted urolith retrieval via a perineal urethrostomy stoma in male cats

Abstract

Objectives

We sought to characterize cystoscopy-assisted urolith retrieval via a perineal urethrostomy stoma (CUPU) initially in a cadaveric model and then in clinical cases. We hypothesized that a CUPU would provide a reasonable alternative to the traditional approach of performing a cystotomy after perineal urethrostomy in male cats with complex or recurrent urolithiasis-associated urethral obstruction (UO).

Methods

A perineal urethrostomy (PU) was performed in 20 male cat cadavers. A randomly assigned number of synthetic calculi (SynC) was placed retrograde into the urinary bladder, and an endoscopist blinded to the SynC number, performed CUPU using a flexible ureteroscope and basket retrieval device. Procedure characteristics were summarized with descriptive statistics. After completion of the cadaver phase, two male cats with naturally occurring complex or recurrent urolithiasis-associated UO that warranted PU were recruited to undergo CUPU. Clinical features and outcomes of these cases were described.

Results

Four cadavers were excluded because of urethral tearing during SynC placement. A narrow urethral lumen precluded ureteroscope passage in two cadavers. In the 14 remaining cadavers, a median of 7.5 SynC (range 3–9) were placed in the urinary bladder. The CUPU median procedural time was 13.2 mins (range 6.1–24.0) and all 99 (100%) SynC were successfully retrieved from the 14 cadavers. Scope-associated tearing of the urethra or surgical site was not observed in any cadavers. Two client-owned cats with struvite urolithiasis-associated UO underwent a PU followed by CUPU. All uroliths were successfully retrieved, and periprocedural complications were not observed. Both cats had normal stoma sites 4 weeks postoperatively and neither cat had owner-reported dysuria 3 months postoperatively.

Conclusions and relevance

This study highlighted that CUPU is a feasible procedure with the potential to obviate the need for abdominal surgery in some cats with cystolithiasis and urolithiasis-associated UO that warrant PU.

Plain language summary

Urinary bladder stone removal with minimally invasive scope technique after an indicated urethral obstruction relieving urinary surgery in male cats.

Cats are prone to the development of bladder stones, which can cause various complications, including urinary blockages. Life-threatening blockages most often occur in male cats when small stones become lodged in the small urethra. In some affected male cats with recurrent or refractory disease, a penile amputation is performed thus enabling urination through the wider remaining urinary tract opening (stoma) and decreasing the likelihood of future blockages. This surgery is termed perineal urethrostomy. However, most cats that undergo perineal urethrostomy surgery still require simultaneous full abdominal surgery to remove the stones that are remaining in the bladder. We sought to use a minimally invasive technique to remove bladder stones in male cats undergoing perineal urethrostomy so that a full abdominal surgery could be avoided. After an indicated perineal urethrostomy was performed in selected cadavers and clinical cases, the research team used a small fiberoptic camera, an endoscope, to evaluate the urinary tract and remove urinary bladder stones. When indicated, a perineal urethrostomy stoma was capable of accommodating successful endoscopic removal of urinary bladder stones in most patients. No evidence of complications was reported among clinical patients 4 weeks after the procedure. The authors hope the newly described technique offers an alternative approach for stone removal in some cases.

Introduction

Feline lower urinary tract disease (FLUTD) is one of the most common reasons cat owners seek non-wellness veterinary care in the USA. ¹ After idiopathic cystitis, urolithiasis is the second most common etiology and is estimated to account for over 20% of FLUTD cases. ² The Minnesota Urolith Center reported 23,806 feline urolith submissions in 2023 alone, with 71% of those being submitted from North American veterinary practices. ³ Unfortunately, recurrence of urolithiasis is common despite advancements in dietary and medical management. In fact, recurrence rates for struvite and calcium oxalate urolithiasis are estimated to be 25% and 70%, respectively.^{4 –6}

Urethral obstruction (UO) is a potentially life-threatening sequela of urolithiasis. This complication most commonly occurs in castrated male cats because of their narrow urethras, which have a distal luminal diameter of approximately 1.1–1.4 mm. ⁷ Cats that develop UO are often prone to recurrence, making this either a costly or fatal process. Indeed, owner-elected euthanasia was reported in over 25% of cats with recurrent UO. ⁸ Surgical intervention in the form of perineal urethrostomy (PU) widens the urethra and lessens the likelihood of future UO in male cats. ⁹ Cats undergoing PU typically experience long-term survival, and most of these cats are reported to have a good quality of life.^10,11 However, cystolith retrieval is still often warranted at the time of PU surgery. Most veterinary surgeons will perform either a cystotomy or, less commonly, a laparoscopic-assisted cystotomy (LAC) at the time of PU to address the underlying urolithiasis.^{12 –15} Both of these procedures require incisions through the abdominal body wall and into the urinary bladder, which increase anesthetic and surgical times, cost, patient discomfort and postoperative morbidity.^{16 –18}

Options for minimally invasive urolith retrieval in dogs and cats have garnered considerable attention in recent years and include voiding urohydropulpulsion, cystoscopic-assisted basket retrieval, intracorporeal lithotripsy, LAC and antegrade urethral catheterization.^{17 –24} True minimally invasive urolith retrieval would offset some limitations associated with the current approach of combining a PU with a traditional cystotomy or LAC, but most characterizations of these procedures are in dogs and, to a lesser extent, female cats because of the narrow male cat urethra.^15,17,22,24 Given that a PU substantially increases the urethral lumen diameter, investigation of alternative approaches seems warranted. The primary aim of this study was to describe a new technique of a cystoscopy-assisted urolith retrieval via a perineal urethrostomy stoma (CUPU) in male cats. We also sought to apply this procedure clinically in cats with naturally occurring urolith-associated UO.

Materials and methods

Cadaver study

This was a two-part investigation consisting of an initial cadaveric study of 20 cats with a subsequent clinical study of two cats. Cadavers were castrated male cats that had been euthanized for reasons unrelated to the current study and had no known previous urogenital surgeries other than castration. All cats were aged ⩾6 months and weighed 2–8 kg. Cadavers were stored frozen at −4°C and thawed for 48–72 h before use. A single veterinarian (MS) board-certified by the American College of Veterinary Surgeons performed each PU with slight modifications from the original procedure described by Wilson and Harrison in 1971. ⁹

These modifications included the use of electrocautery, placement of tom cat catheters for urethral catheterization and the use of a no. 15 Bard-Parker scalpel blade rather than Iris scissors to perform the urethrostomy incision. In addition, the mucosa-to-skin apposition was achieved with absorbable monofilament suture placed in a simple interrupted pattern. After completion of the dorsal longitudinal urethral incision, the tom cat catheter was then removed and an 8 F red rubber catheter was placed in all stomas to facilitate mucocutaneous apposition and to document a minimally acceptable urethral diameter.^7,9 Then, three, six or nine synthetic calculi (SynC) were placed retrograde into the urinary bladder via the PU stoma. Randomization software (Randomized.org) was used to select the number of calculi placed in each cat. The SynC were small, non-buoyant, off-white-colored circular hallowed beads (Seed Beads; Hildie & Jo). All SynC were measured with digital calipers before placement to ensure a maximal diameter ⩽3 mm. This diameter was selected based on the known dimensions of the 1.9 mm internal diameter, 2.8 mm outer tip diameter flexible ureteroscope (FLEX-XC; Karl Storz), although the investigators recognize that slightly larger uroliths would likely be able to be retrieved in clinical practice if there was minimal resistance to scope passage.

All cadavers were then transported to a separate operating room for endoscopic examination by a single veterinarian board-certified by the American College of Veterinary Internal Medicine. The endoscopist was blinded to the size and number of SynC. The examinations were performed using the lubricated flexible ureteroscope (FLEX-XC; Karl Storz). The urethroscopic and cystoscopic examinations were performed through the PU stoma with each cat positioned in right lateral recumbency. The endoscopist noted if any difficulty passing the ureteroscope through the urethra was observed. Irrigation was performed using sterile isotonic saline and the urinary bladder was repeatedly irrigated as needed to improve visual assessment. The urinary mucosa was carefully inspected for any defects or perforations. Visualized SynC were retrieved using a 3 F, 115 cm long, closed-end basket with a diameter of 1 cm (NCircle Nitinol Tipless Stone Extractor; Cook Medical). Once SynC had been secured in the basket, the entire ureteroscope and basket were slowly and carefully removed. This process was repeated until all visualized SynC had been removed and final inspection of the urinary mucosa was evaluated for evidence of iatrogenic tears or perforations. After the procedure, the perineal region and stoma were inspected for any evidence of fluid extravasation, characterized by postoperative perineal swelling or incisional breakdown. ²⁵

Data collected for analyses included the size and number of SynC placed into each urinary bladder, pre- and postoperative body weights, the total duration of the CUPU procedure, the number of scope passages through the PU stoma, the total number of SynC retrieved, the number of SynC retrieved during each passage and whether there was evidence of urethral tearing or trauma. Data for the 14 cadaveric cats included in the analyses were summarized using descriptive statistics and medians (ranges) were reported. Wilcoxon signed-rank testing was used to compare pre- and postoperative body weights. Spearman’s correlation coefficients (ρ) were calculated to explore the relationships between procedural times and the number of SynC. All analyses were performed with commercially available software (GraphPad Prism Version 6.0; GraphPad Software) and P values ⩽0.05 were considered statistically significant.

Clinical study

After completion of the cadaver study, two cats identified with naturally occurring urolithiasis-associated UO were recruited for participation in a pilot study of PU followed by CUPU. Only cats that were deemed appropriate candidates for PU and cystoscopy based on the attending clinicians’ observations were considered for inclusion. The specific inclusion criteria were as follows: male cats with cystolithiasis and urolithiasis-associated UO on presentation; no evidence of urethral tearing to the authors’ preoperative knowledge; non-azotemic before surgery; and radiographic measurement of cystoliths ⩽4 mm in diameter. The PU surgery and CUPU were performed by the same investigators using the same techniques as described above. Pre- and postoperative radiographs were obtained and follow-up evaluations were performed at 2 and 4 weeks postoperatively. The clinical portion of the study was approved by the Institutional Animal Care and Use Committee (PROTO202400085) and informed consent was obtained from the owners.

Results

Cadaver study

A total of 20 cadaveric male castrated cats underwent PU. The median body weight of the 20 cadavers was 3.66 kg (range 2.11–7.72). It was possible to perform cystoscopic evaluation of the lower urinary tract in 18/20 (90%) cats. The attempted passage of the ureteroscope was met with urethral narrowing and resistance approximately 1 cm proximal to the PU stoma in two cats, precluding further evaluation. The weights of these two cats were 3.38 and 5.71 kg, which were 0.28 kg less than and 2.05 kg greater than the median weight of 3.66 kg.

Of the 18 cats in which cystoscopic evaluation was possible, four cats were found to have SynC outside of the lower urinary tract. During endoscopic examination, 3/4 cats had visible full thickness linear defects in the distal urethra that were near the PU mucocutaneous anastomosis. These defects were approximately 3 mm in length, and SynC were visible within the subcutaneous tissues. These defects were presumably created during retrograde placement of the SynC. In the fourth cat, 2/9 SynC were not visualized in the urethra or the urinary bladder. No obvious defects in the urethral or bladder mucosa were apparent during cystoscopic evaluation, but a postprocedural dissection recovered these SynC within the subcutaneous tissues near the PU mucocutaneous anastomosis. These four cats were excluded from further descriptions and analysis because of the likely iatrogenic urethral defects created during retrograde SynC placement.

The remaining 14 cadavers, which excluded the two cats in which ureteroscope passage was not possible and the four cats with presumed iatrogenic urethral tears, were included for characterization of the CUPU procedure. These 14 cats had a median body weight of 3.83 kg (range 2.11–7.72) and had retrograde placement of a median of 7.5 SynC per cat placed. There was a total of three, six or nine SynC placed in two, five and seven cadavers, respectively. Most of the urinary bladders contained a large amount of amorphous cellular and crystalline debris; however, SynC were able to be identified in the gravity-dependent portions of the urinary bladder in all cats (Figure 1). The overall successful retrieval rate of the 99 SynC placed in these 14 cadavers was 100%. The median time for retrieval was 13.2 mins (range 6.1–24.0). The median number of retrieval attempts in each cat was seven (range 3–10). The median postoperative weight of 3.85 kg (range 2.13–7.75) was significantly greater than the preoperative weight of 3.83 kg (range 2.11–7.72; P <0.001). Of the 99 SynC placed in the 14 cats, 65 (65.6%) were retrieved one at a time. However, the removal of two SynC in one retrieval attempt was accomplished for 35/99 (35.3%) SynC. The procedural time was not significantly correlated with the number of SynC (ρ 0.38; P = 0.23).

Figure 1

Image taken during cystoscopic evaluation of a cadaveric urinary bladder depicting the closed-end basket retrieval instrument and multiple synthetic calculi in the gravity-dependent region of the urinary bladder

Clinical study

Cat 1

A 3-year-old male castrated domestic shorthair cat, weighing 7.56 kg, was evaluated for a several-day history of pollakiuria and stranguria. Physical examination revealed UO based on a large, firm urinary bladder that was unable to be expressed. Initial biochemical evaluation did not reveal azotemia or hyperkalemia. The patient was anesthetized with midazolam (0.2 mg/kg IV), buprenorphine (0.02 mg/kg IV), ketamine (1.3 mg/kg IV) and alfaxalone (2 mg/kg IV) and deobstructed using a 3.5 F red rubber urinary catheter. The urinary catheter was maintained and connected to a collection system to monitor urine production. A sterile urine sample was collected and submitted for analysis, revealing no evidence of bacteriuria. Abdominal radiographs at the time of deobstruction revealed a properly placed urinary catheter and evidence of several small mineral opaque uroliths (Figure 2a). The cat was initiated on intravenous (IV) fluid therapy (lactated Ringer’s) and the rate was tailored to urine production. The cat was also treated with buprenorphine (0.015 mg/kg IV q8h) and gabapentin (13 mg/kg PO q8h). This was the cat’s second episode of UO in the past 2.5 weeks. The initial obstructive event was treated by the primary veterinarian and the cat was prescribed gabapentin and prazosin (dosage unknown). The cat had been fed a prescription urinary diet (c/d MultiCare Urinary Care; Hills) since its initial UO, although the cause of the initial UO was not definitively identified. The owner expressed both clinical and financial concerns over the possibility of recurrent UO and elected to pursue PU to decrease the likelihood of UO recurrence.

The cat was transferred to the surgical service. All procedures were performed under general anesthesia, which was achieved using methadone (0.28 mg/kg IV), midazolam (0.35 mg/kg IV), alfaxalone (1.07 mg/kg IV) and sevoflurane inhalant anesthetic. Both the PU and CUPU were performed using an aseptic technique in a dedicated operating room. The PU was routinely performed, followed by CUPU. The lubricated ureteroscope was passed retrograde into the urinary bladder six times with successful removal of seven uroliths. Three retrievals recovered single uroliths while two retrievals recovered two uroliths each (Figure 2b). The final passage was to ensure no further stones remained. There was minimal to no resistance to scope passage. The urinary bladder was mildly hemorrhagic with moderate crystalline debris and was lavaged via the ureteroscope working channel four times for improved visualization. The CUPU procedural time was 29.2 mins. No urethral tearing was noted, but mild hemorrhage was appreciated at the stoma site. Post-CUPU abdominal radiographs revealed no uroliths (Figure 2c). Samples of the uroliths were submitted for aerobic and anaerobic microbial cultures and determination of mineral composition. No bacterial growth was identified and the uroliths were 100% struvite composition.

Figure 2

Right lateral abdominal radiograph and cystoscopic images of a 3-year-old male castrated cat (case 1). (a) Preoperative image utilizing a wooden paddle for improved visualization of the catheterized urinary bladder with evidence of mineral opaque uroliths measuring 1–3 mm in diameter. The uroliths are marked with a white circle. (b) Image during cystoscopy-assisted urolith retrieval via a perineal urethrostomy stoma depicting urolith retrieval via a closed-end basket retrieval instrument. (c) Postoperative image utilizing a wooden paddle for improved visualization of the urinary bladder depicting absence of uroliths in the urinary bladder

The patient was maintained in hospital on fluid therapy (1.3 ml/kg/h IV lactated Ringer’s), buprenorphine (0.012 mg/kg IV q8h), gabapentin (14 mg/kg PO q8h) and robenacoxib (2 mg/kg SC q24h), with frequent monitoring of vital parameters and the incision. No signs of fluid extravasation were appreciated postoperatively. The cat was discharged 24 h postoperatively and robenacoxib (6 mg PO q24h for 2 days) and buprenorphine (0.012 mg/kg sublingual q8h for 3 days) were dispensed for short-term management of pain and inflammation. Owners were instructed to utilize an Elizabethan collar and non-clumping litter for 4 weeks and to continue feeding a prescription urinary diet indefinitely (c/d MultiCare Urinary Care; Hills).

The cat was evaluated 18 and 35 days postoperatively. The PU stoma was intact with no evidence of stricture formation. The cat was reportedly normal with no stranguria or pollakiuria at 3 months postoperatively.

Cat 2

A 5-year-old male castrated domestic shorthair cat, weighing 3.68 kg, was evaluated for a 3-day history of periuria, lethargy, vocalizing and stranguria. The cat was dull and laterally recumbent on presentation and was diagnosed with UO. Deobstruction was performed under general anesthesia using methadone (0.26 mg/kg IV) and midazolam (0.18 mg/kg IV), and an indwelling 3.5 F open-end polytetrafluroethylene urinary catheter (Slippery Sam; Patterson Veterinary) was placed and connected to a collection system to monitor urine production. A sterile urine sample was collected and submitted for analysis; the urine pH was 6.5 and no crystalluria was observed. There was also no evidence of bacteriuria although urine culture revealed moderate Pasteurella multocida and moderate Streptococcus canis species sensitive to amoxicillin/clavulanate. Abdominal radiographs revealed an appropriately placed urinary catheter and many small mineral opaque uroliths. Biochemical analysis revealed azotemia and electrolyte derangements (see Table 1 in the supplementary material). The cat was initiated on IV fluid therapy (lactated Ringer’s) and the rate was tailored to urine production, buprenorphine (0.014 mg/kg IV q8h) and gabapentin (12 mg/kg PO q8h). The cat had a >2-year history of intermittent lower urinary tract signs and was previously fed a prescription urinary diet (c/d MultiCare Urinary Care; Hills) for 3 months without resolution of clinical signs. The owner elected for PU given the chronicity of clinical signs, apparent failed response to dietary management, severity of current UO and financial concerns over potential future UO.

Transfer to the surgery service occurred 48 h after deobstruction to allow time for the resolution of azotemia and correction of electrolyte derangements. All procedures were performed under general anesthesia with methadone (0.29 mg/kg IV), midazolam (0.21 mg/kg IV), alfaxalone (1.05 mg/kg IV) and isoflurane inhalant anesthetic, using an aseptic technique in a dedicated operating room. PU was routinely performed, followed by CUPU. The lubricated ureteroscope was passed retrograde into the urinary bladder and abundant amounts of amorphous debris were observed. Several large blood clots were noted in the gravity-dependent areas of the bladder. There was multifocal bladder wall thickening, increased vascularity and numerous pinpoint hemorrhages. Because of the large amount of crystalline material identified within the urinary bladder, the ureteroscope was removed, an 8 F red rubber catheter was passed and the urinary bladder was lavaged with sterile saline several times to improve subsequent visualization. A red rubber urinary catheter was utilized to take advantage of the increased luminal diameter in comparison with the ureteroscope’s working channel diameter. In total, the ureteroscope was passed 16 times with removal of large amounts of amorphous crystalline debris and small uroliths at each retrieval. The CUPU procedural time was 51.2 mins. No urethral tearing was noted. The PU stoma was mildly erythematous immediately postoperatively, but the mucocutaneous apposition was intact. Post-CUPU abdominal radiographs revealed no uroliths. Samples of the uroliths were submitted for microbial cultures and determination of mineral composition. Moderate growth of P multocida and S canis was reported, and the uroliths were 100% struvite composition.

The patient was maintained in hospital on fluid therapy (2 ml/kg/h IV lactated Ringer’s), methadone (0.2 mg/kg IV q4h), gabapentin (7.14 mg/kg PO q8h), amoxicillin and clavulanate (14.9 mg/kg PO q12h), with frequent monitoring of vital parameters and the incision. No signs of fluid extravasation were appreciated. The cat was discharged 48 h postoperatively on buprenorphine (0.02 mg/kg PO q8h for 3 days), gabapentin (8.3 mg/kg PO q8h for 14 days), prazosin (0.24 mg/kg PO q24h for 12 days) and amoxicillin and clavulanate (14.9 mg/kg PO q12h for 14 days), which was supported by results of culture and susceptibility testing. Owners were instructed to utilize an Elizabethan collar and non-clumping litter for 4 weeks and to indefinitely continue feeding a prescription urinary diet (c/d MultiCare Urinary Care, Hills).

The patient was evaluated 16 and 28 days postoperatively and the PU stoma was intact with no evidence of stricture formation. The cat was reportedly normal with no stranguria or pollakiuria at 3 months postoperatively.

Discussion

We evaluated a novel technique of cystoscopy-assisted urolith retrieval through a PU stoma in selected cadaveric and client-owned male cats. Successful ureteroscope passage was possible in all but two cadavers. In the 14 cadavers in which cystoscope retrieval was possible, CUPU was highly successful, with all SynC successfully retrieved (median of 7.5 SynC per cat). The median procedural time was <14 mins. Most SyncC were removed individually, although the retrieval of two SynC in one scope passage was possible for approximately 33% of SynC. Two client-owned cats were successfully treated with CUPU, had no evidence of urethral tearing or fluid extravasation, and remained normal 3 months postoperatively.

The purpose of the PU intervention is to make the narrow distal male cat penile urethra redundant by creating a stoma between the wider, more proximal, pelvic urethra and perineal skin. This alteration aims to improve the cat’s ability to successfully void crystalline material and small uroliths, as well as reducing urethral spasm, thereby reducing the risk of UO recurrence. This alteration aims to improve the cat’s ability to successfully void crystalline material and small uroliths, thereby reducing the risk of UO recurrence.^10,23 Historically, small uroliths were treated with voiding urohydropropulsion after PU surgery. Unfortunately, this resulted in incomplete removal in 6/21 cases and visible hematuria in all animals. ²¹ Because of this, cystotomy or LAC are typically pursued. Both cystotomy and LAC utilize an open abdominal approach and have reported complications, including incomplete urolith removal, infection and seroma formation, which may be associated with increased body mass index.^{13 –15,24,26 –30} In the veterinary literature, the risk of incomplete urolith removal after open cystotomy approaches 20% and the rate of surgical site infections is approximately 5.5%.^{14,16,26,27,30} These complications appear less frequent with LAC, but this technique is not available to most general practitioners.^{13 –16,24,26,29,30} In addition, a recent study suggested that the procedural time for a traditional cystotomy performed by experienced surgeons was 48 mins and the average duration of hospitalization for cats was >2 days. ²⁶

Our proposed technique might offset some of the limitations of traditional cystotomy and LAC. This could eliminate the need for an open abdominal incision and shorten anesthetic and hospitalization times. ²³ However, CUPU necessitates important considerations. Two cadavers were found to have urethral diameters unable to accommodate the ureteroscope. This represented only 10% of our population and did not appear to be directly associated with patient body weight. This should be considered when therapeutic options are discussed as surgical conversion may be required. Another important consideration is that repeated scope passage through the newly created PU stoma could predispose the site to mucosal edema and subsequent obstruction, dehiscence or future stricture formation. This complication was not observed in the two clinical cases we evaluated. Still, the use of a peel-away introducer sheath might be of value in decreasing trauma to the urethral mucosa and anastomosis site owing to decreased direct contact with these surfaces during repeated scope passage. ³¹ The size, number and shape of uroliths must also be considered on a case-by-case basis. Smaller and fewer uroliths are likely amenable to CUPU. Although speculative, larger and more numerous uroliths would seemingly increase the likelihood of procedural complications or failure. The potential use of lithotripsy in combination with CUPU is intriguing for larger uroliths. Finally, the procedural time observed in the cadaveric study was only 14 mins; however, one of the clinical cases required 51.2 mins. This was anticipated because of the substantial amount of inflammatory and crystalline material within the urinary bladder, but the procedural time was not substantially different from the reported average cystotomy time of 48 mins. ²⁶

The main limitations of this study include the primarily cadaveric nature and limited number of clinical cases. The cadaveric population does not enable assessment of tissue healing or long-term complication evaluation. Furthermore, tissue friability is presumably different in previously frozen cadavers compared with live cats. The iatrogenic urethral tearing in the three cadaver cats supports this speculation. All SynC were ⩽3 mm in diameter, and the maximal urolith diameter that can safely be retrieved by CUPU is unknown. These limitations, in conjunction with the aforementioned, further underscore the need for continued evaluations before CUPU can be routinely recommended in clinical settings. Still, the results of this initial investigation yielded encouraging results.

Conclusions

Our study demonstrated that CUPU can be an effective method for small urolith removal in male cats undergoing PU for urolithiasis-associated UO although appropriate patient selection is critical. Future studies including larger numbers of clinical cases are warranted to better define the ideal patient population, potential procedural and postoperative complications, and comparative aspects with traditional interventions.

Supplemental Material

Table S1

Venous blood gas at presentation to referral hospital for cat 2.