Materials and Methods

Case selection—The medical records from the Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania of all client-owned cats and dogs that received a transvesicular PCCL procedure from January 2006 through September 2008 were reviewed. Dogs and cats of any age, sex, and size and with any number of cystic or urethral calculi were included if a transvesicular PCCL procedure had been performed. Most patients were considered poor laser lithotripsy candidates, and the PCCL procedure was elected by the owner. Patients were included if a complete medical record was available for review, and short-term follow-up to suture removal was available. All patients required negative urine culture results prior to the procedure or 48 hours of appropriate antimicrobial administration prior to the procedure to reduce the likelihood of infected urine contaminating the abdomen during the procedure. Available uroliths were submitted to the Minnesota Urolith Center for quantitative urolith analysis. All surgical reports documented that rigid normograde cystoscopy and, in male dogs, flexible urethroscopy were performed during the procedure. Preoperative and postoperative lateral abdominal radiographic views were obtained and available for review to assess urolith location, number, and size as well as postoperative status. Short-term follow-up (2 weeks postoperatively) was obtained in all patients by re-examination. Patients were excluded if postoperative radiographs for confirmation of residual uroliths were not available for review, if cystoscopy or flexible urethroscopy (male dogs) had not been performed, or if a complete medical record was not available for review.

Historical, laboratory, and imaging data—Data regarding signalment, history including previous surgeries or urinary tract interventions, duration of clinical signs, and physical examination findings were recorded. All dogs had a CBC, serum biochemical analysis, urinalysis, and bacteriologic culture of urine and antimicrobial susceptibility testing performed prior to anesthesia. Preoperative radiographs were reviewed, and stone number, urolith location, and ultrasound findings (when available) were recorded.

PCCL procedure—Patients were placed in dorsal recumbency under general anesthesia. The ventral aspect of the abdomen and prepuce or vulva were clipped and aseptically prepared. A red rubber urethral catheter (3.5, 5, or 8F) was placed into the urethra, and sterile saline (0.09% NaCl) solution was infused into the urinary bladder to allow for distention and palpation of the approximate location of the urinary bladder apex. Careful forceful saline solution retropulsion was attempted during the catheterization, which was intended to direct any freely movable urethral calculi into the bladder. An approximately 1.5- to 2.0-cm ventral midline skin incision was made over the anticipated location of the bladder apex. A 1.5- to 2.0-cm incision was subsequently made into the abdominal cavity through the linea alba, large enough to fit 1 finger for digital bladder palpation. Once the bladder was identified, a small Gelpi retractor was placed to maintain the opening of the incision into the abdominal cavity. The bladder apex was then grasped atraumatically with Babcock tissue forceps or digitally manipulated until it was seen in the surgical field at the body wall incision. The bladder was filled and emptied through the urinary catheter to digitally confirm bladder location. Three stay sutures in a triangular pattern were placed immediately caudal to the bladder apex with 3–0 (dog) or 4–0 (cat) polydioxanone sutures^b (1 apical and 2 lateral).

The bladder was then held in traction at the abdominal incision, and the incision was packed with a sterile moistened laparotomy sponge or several sterile gauze sponges to reduce urine contamination of the abdominal cavity. A stab incision with a No. 11 scalpel blade was then made into the bladder lumen between the stay sutures, with suction applied to prevent urine contamination of the surgery site. Immediately, a 6-mm laparoscopic threaded cannula^c with a diaphragm was advanced through the stab incision, screwed in place in the bladder lumen, and directed toward the urethral lumen to maintain a closed system for visibility and irrigation. Keeping a closed system with this trocar allowed for superior visualization, minimal urine leakage during insufflation, and the ability to penetrate in and out of the bladder without damaging the bladder mucosa or incision during stone retrieval. The threads on this cannula allowed for the tissue to be engaged and prevented the movement of this device during stone retrieval and manipulation.

A rigid 30° 1.9- or 2.7-mm cystoscope^d,e with an operating channel was then advanced through the threaded cannula into the urinary bladder by use of irrigation with sterile saline solution to keep the bladder distended and to maintain visibility. The urethral catheter was kept open to allow for saline solution drainage and prevent bladder overdistension. The mucosal surface of the entire urinary bladder and proximal portion of the urethra was carefully inspected with the rigid cystoscope, and the location and number of uroliths were recorded. Evidence of any mucosal lesions including polypoid lesions, masses, and retained suture material from previous surgeries was identified and biopsied or removed if possible. To remove obvious sediment or multiple small calculi > 3 to 4 mm, the trocar diaphragm was removed, a 60-mL syringe filled with saline solution was attached to the red rubber urethral catheter, and a (sheathless) Poole suction tip was applied against the inner portion of the trocar. Sterile saline solution was copiously infused through the urethral catheter in a retrograde manner with suction applied to the exposed inner portion of the trocar, and the flushed saline solution was suctioned while removing small uroliths. Once completed, the trocar diaphragm was replaced and the cystoscope was then reintroduced into the bladder. The larger uroliths were located, and a stone retrieval basket^f,g was advanced through the operating channel of the cystoscope and subsequently deployed to entrap the remaining uroliths (Figure 1). Once entrapped, the basket was closed, retracted, and held firmly against the distal end of the cystoscope while the cystoscope was slowly removed through the trocar. The uroliths were then collected once released from the basket. This was repeated until all visible uroliths were removed from the bladder. For uroliths larger than the 6-mm inner diameter of the trocar, they were entrapped in the stone basket at the end of the endoscope and trocar, and then the trocar was removed from the bladder and the stone was gently removed through the small cystotomy incision. If necessary, the incision was minimally extended to remove all stones en bloc, but this was rarely needed. Once the procedure was complete, the urethra was inspected by use of a 7.5F flexible ureteroscope^h in male dogs and the rigid cystoscope in female dogs or cats. In male dogs < 6 kg (13.2 lb), the flexible urethroscope was advanced as far down as possible, typically to the level of the mid os penis. As the endoscope was directed down the urethral lumen, the red rubber catheter was retracted and irrigation performed with saline solution through the red rubber catheter allowed for retrograde flushing of any remaining urethral stone fragments. If uroliths were identified, they were retrieved by use of a stone retrieval basket. Once the urethra was inspected, the endoscope and cannula were removed. The incision was closed in a simple interrupted suture pattern with 3–0 (dogs) or 4–0 (cats) sutures.ⁱ The bladder was subsequently leak tested through the urethral catheter, and the stay sutures were removed. The abdominal incision was closed routinely in 3 layers.

Photographs taken during PCCL in a dog. The bladder has been elevated to the level of the body wall, 3 stay sutures have been placed in a triangular pattern caudal to the bladder apex, and a 6-mm laparoscopic threaded cannula^c with a diaphragm has been advanced through the stab incision, screwed into the bladder lumen, and directed toward the urethra. A stone retrieval basket^f,g was advanced through the operating channel (left photo) of the cystoscope and subsequently deployed (right photo) to entrap calculi.

Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.344

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Photographs taken during PCCL in a dog. The bladder has been elevated to the level of the body wall, 3 stay sutures have been placed in a triangular pattern caudal to the bladder apex, and a 6-mm laparoscopic threaded cannula^c with a diaphragm has been advanced through the stab incision, screwed into the bladder lumen, and directed toward the urethra. A stone retrieval basket^f,g was advanced through the operating channel (left photo) of the cystoscope and subsequently deployed (right photo) to entrap calculi.

Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.344

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Photographs taken during PCCL in a dog. The bladder has been elevated to the level of the body wall, 3 stay sutures have been placed in a triangular pattern caudal to the bladder apex, and a 6-mm laparoscopic threaded cannula^c with a diaphragm has been advanced through the stab incision, screwed into the bladder lumen, and directed toward the urethra. A stone retrieval basket^f,g was advanced through the operating channel (left photo) of the cystoscope and subsequently deployed (right photo) to entrap calculi.

Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.344

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Postprocedure management—All patients had a lateral radiograph obtained immediately following the procedure to confirm the removal of all uroliths. Analgesia was provided during the recovery with buprenorphine (0.01 mg/kg [0.0045 mg/lb], IV, q 4 to 6 h as needed) and meloxicam (0.1 mg/kg [0.045 mg/lb], PO, q 24 h for 3 days). Available uroliths were submitted for stone analysis at the Minnesota Urolith Center. One crushed stone as well as a sample of the bladder mucosa was submitted for aerobic bacterial culture and susceptibility testing. All animals were discharged with 3 days of prophylactic antimicrobials (amoxicillin and clavulanic acid, 14 to 18 mg/kg [6 to 8 mg/lb], PO, q 12 h).

Short-term follow-up—Patients were initially reevaluated by one of the authors or their local veterinarian at the time of suture removal 14 days postoperatively. The surgical site was evaluated, and any evidence of postoperative complications was noted. After surgery, all patients were discharged with the additional recommendations to the owner to have their pet seen by their veterinarian for cystocentesis and bacterial culture of a urine sample 2 weeks after surgery and a lateral abdominal radiograph 1, 3, 6, 12, 18, and 24 months postoperatively. Reevaluation was then recommended every 3 to 6 months thereafter for life. When the results of urolith analysis were received, appropriate dietary recommendations to reduce recurrence were made (including prescription diets as applicable) on the basis of stone type. Typically, this information was provided at the 14-day postoperative visit.

Long-term follow-up—Although client long-term postoperative follow-up and compliance varied, phone and e-mail communication was attempted for all patients to assess for stone reoccurrence and overall owner satisfaction.

Results

Historical, laboratory, and imaging data—The PCCL procedure for the removal of cystic and urethral calculi was performed in 27 animals. Of the 27 animals, 23 were dogs (22 males and 1 female) and 4 were cats (2 males and 2 females). Results were calculated on the basis of 27 procedures. Median patient age was 8.5 years (range, 3 to 16.5 years), and median patient weight was 8.3 kg (18.3 lb; range, 1.8 to 42.6 kg [4.0 to 93.7 lb]). Preoperative clinical signs included stranguria (n = 4), pollakiuria (2), hematuria (9), and incidental finding with no clinical signs (17). Fifteen (56%) patients had cystotomies (range, 1 to 5 times) prior to this procedure. For all patients, preoperative evidence of cystic or urethral calculi was documented with abdominal radiographs and, in some patients, concurrent abdominal ultrasound (n = 7). The number of uroliths ranged from 1 to > 35 stones on the basis of results of survey radiographs. Stone size ranged from < 1 to 30 mm in largest diameter. Stone locations on preoperative radiographs included urethra only (n = 1), urethra and bladder (8), and bladder only (19).

PCCL procedure—The procedure was successfully performed in all 27 patients. Five of the 27 procedures required the cannula to be removed during retrieval of the largest stone, as it did not fit through the lumen of the cannula. Two of 27 procedures required the cystotomy incision to be minimally extended for removal of 1 or more cystoliths larger than the incision. Two patients had uroliths that preoperatively were known to be larger than the instrument port (2 × 1-cm stone and 6 × 7-mm stone), and in the other 5 patients, the stone measurement on radiographs was < 6 mm but was larger in vivo. Four patients (3 dogs and 1 cat) had large embedded urethroliths that could not be retropulsed into the urinary bladder prior to or during the procedure, requiring retrieval with the stone retrieval basket by use of urethroscopy to dislodge and remove the stone from the urethral mucosa. Percutaneous cystolithotomy eliminated the need for concurrent laser lithotripsy, urethrotomy, or urethrostomy, which would have otherwise been required in these 4 patients. Median procedure time from the start of the skin incision to the last suture placement was 66 minutes (range, 50 to 80 minutes). No procedure-related complications were noted.

One patient had a residual urolith, which was approximately 1.5 to 2 mm in diameter. This occurred in a female cat that was thought preoperatively to have a single 2-cm cystolith on the basis of results of abdominal radiography. During the PCCL, no other uroliths were observed within the bladder.

Postprocedural management—All 27 patients had postoperative radiographs obtained. One cat had a small urolith (1.5 to 2 mm) seen on postoperative radiographs, which was subsequently removed via transurethral approach with a basket under the same anesthetic procedure. This represented 1 of 27 (3.7% incidence) PCCL procedures with residual calculi immediately postoperatively in this study population. The transurethral basket retrieval of the remaining calculus in this patient was not considered an additional PCCL procedure.

All patients were discharged within 24 hours, and most were discharged on the same day as the procedure. No postoperative complications were observed. All patients were discharged with instructions for the owner to administer meloxicam (0.1 mg/kg, PO, q 24 h) and antimicrobial prophylaxis (amoxicillin and clavulanic acid, 14 to 18 mg/kg, PO, q 12 h) for 3 days each.

Short-term follow-up—Short-term postoperative follow-up at suture removal was completed for all animals. Compliance varied with respect to the recommended follow-up after suture removal, although all patients underwent bacterial culture of a urine sample 2 weeks after surgery and the results were negative.

Long-term follow-up—Twenty-two of the 27 owners were successfully contacted by telephone and e-mail for long-term follow-up (> 1 year). Phone and e-mail communication was achieved to assess owner awareness of possible stone reoccurrence and overall owner satisfaction. Three of 22 (13.6%) patients had confirmed recurrence of cystic calculi. One patient underwent a second PCCL procedure 584 days after the initial one. This second PCCL procedure was not considered 1 of the 27 procedures within this study population. One patient underwent voiding urohydropulsion on a subsequent visit after discovery of recurrent cystic calculi 668 days after the PCCL procedure. The third patient had a reoccurrence of urolithiasis approximately 571 days after the initial PCCL procedure, and this owner had elected to treat conservatively with monitoring. All contacted owners expressed satisfaction with the procedure.

Discussion

In the present study, PCCL enabled minimally invasive retrieval of a variable number of uroliths from the bladder and urethra in 27 male (n = 24) and female (3) patients, including 23 dogs (22 males) and 4 cats (2 males) ranging in body weight from 1.8 to 42.6 kg (median, 8.3 kg), over a 20-month period. The procedure was performed via a single small incision, and patients did not experience any perioperative complications. Available follow-up information (22/27 patients; 1 year after surgery) indicated a low incidence of recurrence of stones, and owners were satisfied with the procedure.

The transvesicular PCCL technique used in the present study provided an effective, minimally invasive alternative to routine open cystotomy, allowing for evaluation of the urethra and bladder and urolith retrieval. This procedure provides some of the benefits of other minimally invasive procedures such as laparoscopic-assisted cystotomy¹¹ and transurethral laser lithotripsy,^7,13 with fewer limitations in regard to patient size or stone size and number and without the requirement for additional laparoscopic equipment. Overall procedure time may be decreased for PCCL, although a comparison between procedure times for the different treatment modalities was not made in the present study. A major procedural limitation is that the penile urethra cannot be adequately visualized with the flexible urethroscope in male cats and small male dogs (< 5.5 kg [12.1 lb]). In our patient population, this was not considered a problem, as no stone was lodged in the area that could not be adequately evaluated with the urethroscope, and in most patients, the entire urethra was visualized. All patients were able to have the transvesicular cystoscopy performed safely and easily. This procedure is modeled after the PCCL technique in humans, which is commonly performed in children with large stone burdens where transurethral laser lithotripsy is considered too difficult for the number of stones present or in countries where laser technology is not readily available.²⁸ This technique was first developed to be used in children with cystoliths that have small urethral lumens. Because veterinary patients have an intraperitoneal bladder, the PCCL was designed by the authors as a modification of the human PCCL procedure to close the entry point into the urinary bladder easily. Percutaneous cystolithotomy is applicable for male and female cats and dogs weighing 1.8 to 42.6 kg, with a urolith diameter of < 1 to 30 mm. This procedure has also been used by the authors for bladder access in dogs and cats for other reasons such as ureteral evaluation, ureteral stent placement, evaluation of proliferative lesions, polyp resection, removal of urethral foreign bodies, and bulking-agent injections in male dogs or cats for urinary incompetence. The procedure time (median, 66 minutes) was considered equivalent to other previously reported⁷ surgical times for routine cystotomy.

During a traditional cystotomy, it may be difficult to closely examine the bladder lumen for residual small calculi. Previous studies^8,a found that radiographs obtained after a cystotomy documented that 14% to 20% of dogs and 20% of cats had uroliths remaining. The residual uroliths seen with traditional surgical cystotomy may result from the inability to carefully examine and visualize the bladder lumen and urethra for calculi and from hemorrhage associated with mucosal manipulation during a cystotomy, which may entrap uroliths within blood clots. Percutaneous cystolithotomy enables full distention of the urinary bladder, allowing for close inspection of the bladder and urethral lumen without excessive manipulation. This results in minimal hemorrhage, mucosal edema, and trauma. In the present study, only 1 (3.7%) patient had evidence of uroliths remaining immediately after the PCCL procedure. This low incidence of remaining calculi may support the benefits of direct inspection of the lumen of the bladder and urethra. In this particular patient, the single large stone present likely fractured during removal, and careful luminal inspection after all stones were suspected to be removed is necessary to confirm a stone-free urethra and bladder.

In contrast to laser lithotripsy in which small patient size, male sex, and excessive stone burdens can limit the practicality of the technique, PCCL did not include these limitations with the patient population in the present study. Percutaneous cystolithotomy enables the visualization of small uroliths that can be embedded within mucosal adhesions, which could otherwise be missed radiographically. Percutaneous cystolithotomy eliminated the need for concurrent urethrotomy or urethrostomy in all patients, which would have otherwise been required in 4 patients. This technique allows a very small abdominal and bladder wall approach, requires minimal peritoneal manipulation without requiring pneumoperitoneum, provides magnification for the visualization and retrieval of various size uroliths regardless of location (bladder and urethra), allows for visualization of the ureteral openings, causes minimal mucosal manipulation or hemorrhage, and allows for close mucosal inspection and biopsy of concurrent polypoid or neoplastic lesions if visualized.

Laparoscopic-assisted cystoscopy¹¹ requires 2 laparotomy incisions and the ability to create and maintain pneumoperitoneum through the use of mechanical insufflation. In the laparoscopic-assisted cystoscopy technique, pneumoperitoneum is created to locate and gain access to the urinary bladder. The urinary bladder is then exteriorized and sutured to the body wall to prevent leakage of urine into the abdomen. The incision over the bladder is ultimately larger than that of the procedure described in the present report. With the PCCL, the need for pneumoperitoneum is avoided by filling and distending the bladder via the urinary catheter with saline solution for safe recognition and manipulation. This allows the surgeon to locate the bladder through a single small incision and avoid the risks^21–27 associated with pneumoperitoneum.

Because PCCL was not directly compared with open cystotomy in the present report, further studies are warranted to evaluate outcome for these 2 techniques. The small incision required for PCCL may be beneficial when compared with larger celiotomy incisions. A recent study²⁹ evaluating open versus laparoscopic ovariectomy by use of accelerometry-based activity monitoring found that small dogs were significantly more active after a minimally invasive procedure. Future studies may show the benefit of minimally invasive procedures in veterinary patients with objective assessment of postoperative activity levels, aside from the suggested benefits of improved visualization, stone retrieval rates, and small incisions.

The present study had several limitations. There are inherent limitations with retrospective review of medical records from patients treated by different clinicians. Both short- and long-term follow-up were attempted, but the long-term follow-up information was available in only 22 of 27 animals, was not standardized, and was limited to the subjective evaluation by the owners. Our patient population was small, and larger numbers may produce different results for procedure times and recurrence rates. The patient population in the present study may also have been biased because most patients were not considered good candidates for lithotripsy (male dogs and cats, small male dogs, and dogs with multiple cystoliths). However, we suggest that this finding further supports the use of PCCL in the more complicated cases for which other minimally invasive procedures are not ideal. The sizes of the cysto-scopes available in veterinary medicine are also a limitation, especially in smaller male patients. In patients with a small urethral lumen, the reach of the larger diameter scopes is limited and may not extend the entire urethral length. With the PCCL approach, the flexible ureteroscope was capable of extending from the bladder to the mid os penis region (dog) or mid to distal penile urethra (male cat), regardless of patient size. Within our institution, the smallest available cystoscopes were rigid 30°, 1.9- or 2.7-mm cystoscopes^d,e with appropriate operating channels as well as a flexible ureteroscope^h that is 7.5F in diameter with a 3.2F working channel for basket retrieval. These are some of the smaller currently commercially available cystoscopes. There are additional limitations with PCCL, however, including the cost of the equipment (rigid and flexible cystoscopes, video equipment, endoscopic trocar, and retrieval baskets), the need for an assistant to facilitate stone retrieval, and the need for specialized training to become familiar and competent with the equipment and procedure. This, in turn, may result in extended surgery times when compared with open procedures. Teaching institutions may have greater resources and personnel to perform this procedure efficiently than do surgeons in a private practice setting. Additionally, larger stones may require some enlargement of the bladder incision, although we suggest that this is not likely to substantially affect procedure time or patient outcome. Percutaneous cystolithotomy may benefit patients that would otherwise be too small for transurethral laser lithotripsy, patients with calculi too large to be removed via urohydropropulsion or transurethral basket retrieval, patients that require direct visualization of the entire lower urinary tract or ureteral openings, patients in which calculi are unlikely to dissolve with medical management, and clients that would like to pursue a minimally invasive option for urolith retrieval or bladder and urethral evaluation. In suitable patients with availability of trained personnel and equipment, we recommend transurethral removal of calculi to avoid a more invasive cystotomy.