Laparoscopic-assisted cystotomy for urolith removal in dogs and cats — 23 cases

Abstract

This report describes the outcomes of a modified laparoscopic-assisted cystotomy for urolith removal in dogs and cats. Modifications of the original techniques included a temporary cystopexy to the abdominal wall, utilization of a laparoscope instead of cystoscope, and retrograde flow of saline in the bladder with pressurized saline. The medical records of 23 client-owned animals for which laparoscopic-assisted cystotomy was used for urolith extraction were reviewed. Twenty-six procedures were performed in 23 animals. There were intraoperative complications in 19.2% of cases leading to open conversion in 11.5%. Rate of complications directly related to the procedure was 11.5%. Four cases had documented urolith recurrence with a mean time to recurrence of 335 days.

Introduction

The incidence of calcium oxalate uroliths in dogs has increased in the last 20 to 25 y for reasons that are not clear (1,2). Persistence of uroliths within the lower urinary tract may lead to urinary tract infection, cystitis, hematuria, and/or urethral obstruction. Surgical extraction is the most commonly employed treatment for uroliths not amenable to dietary dissolution and/or those lodged in the urethra or urinary bladder. Frequently, urethroliths can be retropulsed into the bladder avoiding the need for urethrotomy or a urethrostomy for removal. Furthermore, an open cystotomy to remove urocystoliths is the most common urinary procedure in veterinary practice and is associated with a low morbidity and mortality.

A laparoscopic-assisted cystotomy has been described to remove uroliths in the bladder (3). Advantages with this technique were reduction of contamination of the abdominal cavity with urine and better visualization to permit a more thorough evaluation of the bladder and urethra (3–5).

Our objectives for this study are two-fold: to describe several modifications made to the original technique initially developed by Rawlings et al (3,5), and to report on the clinical experience and outcomes encountered with performing laparoscopic-assisted cystotomy for urolith removal in a case series of dogs and cats.

Materials and methods

Case selection

The electronic databases of Colorado State University (CSU) and Florida Veterinary Specialists (FVS) were examined to identify all dogs and cats in which laparoscopic-assisted cystotomy was utilized for the removal of uroliths. Laparoscopic-assisted cystotomy has been used at CSU for urolith removal since early 2005 and at FVS since mid 2008. Records were identified from March 2005 to February 2009. Cases with incomplete medical records (including detailed surgical reports and final diagnoses), or those in which case follow-up could not be done (referring veterinarian or owner phone call), were excluded from further investigation.

Medical records review

Medical records were reviewed to determine signalment, history, final diagnosis (i.e., urolith analysis), type and result of diagnostic imaging, duration of the surgery, intraoperative complications, postoperative management, and time to recurrence. Intraoperative complications were defined as any episode noted in the surgical report that indicated deviation from the expected routine operative procedure (description follows). Cases in which open conversion to laparotomy was performed were also noted. Follow-up time was determined as the most recent time an owner was contacted regarding the urinary status of the animal. Follow-up time was determined by documented telephone communication between the referring veterinarian and owner. The data are presented as mean and range unless otherwise indicated.

Surgical technique

Laparoscopic-assisted cystotomy was performed in a similar manner to the original description by Rawlings et al (3,5). All surgeries were performed by 2 veterinarians, either EM (n = 24) or MR (n = 2). Pneumoperitoneum was established either by Veress needle or open (Hasson) technique (6). The laparoscopic portal was established at the level of the umbilicus. A second portal was established caudal to the first for introduction of a 5-mm cannula and Babcock grasping forceps. The second portal was placed cranial to the prepuce in male dogs and about 2/3 of the way between the pubis and umbilicus in male and female cats and female dogs. The instrument cannula was placed in a location to allow the urinary bladder to be grasped at or near the apex and pulled cranial to the ventral abdominal wall, under laparoscopic guidance. The instrument cannula was removed. An approximately 3 to 4 cm approach was made to the proposed cystopexy site with a scalpel blade. With tension on the urinary bladder and slight eversion of the urinary bladder wall, a 360° temporary cystopexy was performed using 3-0 or 4-0 polydioxa-none suture (PDS II; Ethicon, Somerville, New Jersey, USA) to securely anchor the urinary bladder to the ventral body wall, creating a tight seal to prevent movement of urine and uroliths into the abdominal cavity. The cystopexy suture passed full thickness in the bladder wall and the abdominal wall. The skin was incorporated in the cystopexy for small dogs at FVS only. A small stab incision was made into the ventral mid body of the urinary bladder through which the 5-mm laparoscope within its cannula was then positioned within the urinary bladder. Saline was infused through a preoperatively placed urinary catheter via a manually inflated pressure bag at 300 mmHg. An assistant maintained infusion pressure during the procedure by visually monitoring the pressure gauge. Uroliths were flushed from the urinary bladder under high pressure and removed with suction attached to the ingress/egress portal of the cannula. Uroliths trapped within the lumen of the cannula were removed from the urinary bladder either through the suction via the ingress/egress portal or with the cannula as it was withdrawn from the urinary bladder. For uroliths too large to be removed in this manner, grasping forceps were introduced into the urinary bladder immediately adjacent to the scope. Following removal of all visible cystic uroliths, the urinary catheter was slowly withdrawn and the urethra was examined with the endoscope for remnant uroliths. Frequently, a small portion of the urinary bladder wall was excised and submitted for bacterial culture and sensitivity and/or histopathology. The cystotomy incision, linea alba, subcutis, and skin were closed routinely with single layer appositional patterns. Post-operative imaging was done at the surgeon’s discretion and was often omitted if there was a high confidence in complete urolith removal.

Results

Signalment

Twenty-five records were examined and 23 (17 dogs, 6 cats) were included in this study. Two cases were excluded due to inability to obtain follow-up information. Seventeen dogs, 14 castrated males and 3 spayed females, were included. One dog had surgery twice and one dog had surgery 3 times. The mean age of the dogs at the time of surgery was 8.7 y (range: 3.0 to 15.9 y). The mean body weight of dogs at the time of surgery was 20.1 kg (2.5 to 54 kg). The breeds of dogs included: dalmatian (n = 3), Yorkshire terrier (n = 2), mixed breed (n = 2), and 1 each of basset hound, cairn terrier, Jack Russell terrier, Lhasa apso, Maltese, miniature schnauzer, Newfoundland, samoyed, shiba inu, and West Highland white terrier.

Six cats were included in the study. The mean age of cats at the time of surgery was 6.3 y (range: 0.7 to 10.8 y). The mean body weight of cats at the time of surgery was 4.9 kg (range: 3.9 to 6.1 kg). Three cat breeds were represented: domestic short hair (n = 4), domestic long hair (n = 1), and Siamese (n = 1). Five cats were castrated males, 1 was a spayed female.

Pre-operative diagnostic imaging

All cases had non-contrast abdominal radiographs before surgery (n = 26). Twenty-two of 26 (85%) had evidence of radiopaque uroliths. Preoperative urethrocystograms were performed in 6 cases (4 were positive contrast alone, 2 were double contrast). Urethrocystograms were performed to document the presence of radiolucent uroliths (2), show mucosal filling defects consistent with small radiopaque uroliths (1), or as part of a retrohydropulsion procedure used to move uroliths from the urethra to the urinary bladder (3). All 6 were diagnostic for cystic and/or urethral uroliths.

Four cases required an imaging technique in addition to non-contrast radiographs to diagnose the presence of uroliths. In 3 cases, abdominal ultrasound showed hyperechoic foci with acoustic shadowing (2 discrete uroliths, 1 echogenic sediment) when non-contrast radiographs failed to diagnose the presence of uroliths. Double contrast urethrocystogram diagnosed large radiolucent filling defects in the fourth case.

Preoperative ultrasonographic evaluation of all abdominal structures was performed on 14 cases and 10 (71%) were diagnostic for discrete cystic uroliths.

Surgery

Uroliths were removed in 14 cases through the use of suction applied to the laparoscopic cannula alone (54%). Additional grasping devices (such as laparoscopic Babcock forceps and Alligator grasping forceps) were required to remove larger uroliths in 8 cases (31%).

Intraoperative complications were reported for 5 cases (19.2%) resulting in conversion to an open procedure in 3 cases (11.5%). Puncture of the spleen with mild hemorrhage occurred following placement of the Veress needle in 1 case that did not require conversion to an open procedure. The laparoscopy had to be converted during surgery to a laparotomy because of a problem related to the technique in 3 cases. In 1 case uroliths were large and the window had to be enlarged at the apex of the bladder, then distention of the bladder could not be maintained to pursue the procedure. In another case the urinary bladder was too inflamed and firm to be grasped with Babcock forceps. Tearing of the bladder wall occurred when it was grasped with a Babcock forceps. This cat had previous cystotomies for bladder uroliths and chronic, severe cystitis. In a third case, the laparoscopy in a cat had to be abandoned because the flow of saline through the small urinary catheter was not sufficient to maintain good visualization during the cystoscopy. In 1 case a single urethrolith lodged in the urethra was missed during laparoscopic-assisted cystotomy and was identified on postoperative radiographs. The clinician retropulsed the urolith into the bladder and pursued an open cystotomy instead of repeating a laparoscopic-assisted cystotomy because sterile laparoscopy equipment was not available. This case was not considered as a true conversion since it was related to a lack of instruments to repeat the procedure.

Eleven cases (42%) had an additional procedure performed during the same anesthetic event. Three cases had a laparoscopic liver biopsy, one had laparoscopic-assisted gastropexy, and 3 had urinary bladder wall biopsy performed following the cystoscopy. One case had intraoperative radiation therapy for transitional cell carcinoma of the urinary bladder. One cat had nasal planum biopsy, in which sporotrichosis was diagnosed. One cat received a perineal urethrostomy during the same anesthetic period because of chronic lower urinary tract obstruction. Mean operative time for laparoscopic-assisted cystotomy was 84.3 min ± 35.8 min (n = 17). Operative time for laparoscopic-assisted cystotomy that was converted to open (total surgical time) was 83.3 min ± 65.3 min (n = 3).

Post-operative diagnostic imaging

Postoperative non-contrast radiographs were taken in 10 cases. In one case, a single urethrolith was identified postoperatively that was successfully removed with an open laparotomy as described. No imaging was performed in the remaining cases.

Postoperative complications

Complications are summarized in Table 1. In the post-operative period 1 cat that had urinary incontinence prior to surgery and 1 dog developed urinary incontinence that did not require treatment. The incontinence improved or resolved on its own within 2 wk of surgery. One dog developed stranguria that resolved in 1 wk. No uroliths were present on the post-operative radiographs and no urinary tract infection was present. The dog that received intraoperative radiation therapy developed pancreatitis and aspiration pneumonia after surgery for metastatic transitional cell carcinoma and was euthanized at the owner’s request 3 d after surgery. One cat died of septic peritonitis following a urethral tear during pre-operative management of the case. One cat with tenesmus after surgery developed a rectal prolapse and a herniation through one of the cannula holes. One cat had a seroma at 1 cannula hole. One cat developed renal failure following administration of non-steroidal inflammatory drugs (NSAIDs) after surgery.

Table 1.

Summary of peri-operative case complications of dogs and cats undergoing laparoscopic-assisted cystotomy for urolith removal

Signalmenta	Complication	Conversion	Outcome
8 y MC Mix	Uroliths too large to be removed, laparoscopic-assisted	Yes	Uroliths removed by open cystotomy
11 y MC DLH	Bladder too large/friable to be grasped	Yes	Uroliths removed by open cystotomy
5 y MC DSH	Incomplete bladder distension due to poor saline flow	Yes	Uroliths removed by open cystotomy
9 y FS Mix	Mild post-operative urinary incontinence	No	Resolution without management by 2 wk after surgery
16 y MC Yorkshire terrier	Mild post-operative urinary incontinence	No	Resolution without manangement by 2 wk after surgery
9 y MC Siamese	Chronic urinary incontinence	No	Improved after surgery but did not resolve completely
3 y FS Maltese	Stranguria	No	Resolved by 1 wk after surgery without further therapy
15 y MC West Highland white terrier	Pancreatitis, aspiration pneumonia after surgery	No	Euthanasia after surgery
1 y MC DSH	Septic uroabdomen peritionitis, urethral tear	No	Euthanasia after surgery
5 y FS DSH	Tenesmus, rectal prolapse, cranial port body wall dehiscence	No	Primary herniorrhraphy, colopexy with resolution of prolapse, hernia, tenesmus
5 y MC DSH	Cranial port seroma	No	Resolution with warm compress
7 y MC DSH	Acute renal failure secondary to suspected meloxicam toxicity	No	Resolution with discontinuation of meloxicam, oral gastroprotectants, subcutaneous fluids

^aMC — male castrated, FS — female spayed, Mix — mixed breed dog, DLH — domestic longhair cat, DSH — domestic shorthair cat.

Diagnostic results

Twenty-five bacterial cultures and sensitivities were reported. Sixteen urinary bladder wall samples were cultured alone, 4 uroliths were cultured alone, and in 5 cases, both urolith and urinary bladder wall were cultured. Five positive cultures (20%) were obtained. The urinary bladder wall yielded a positive bacterial culture in 4 cases, and a urolith was positive in the other. In none of the cases were the urolith and urinary bladder wall both positive when submitted together.

Urolith analysis was submitted in 25 of 26 cases. In 13 cases, the urolith was primarily calcium oxalate (52%), in 5 cases they were primarily ammonium urate (20%), in 5 cases they were primarily cystine (20%), and in 2 cases they were primarily struvite (8%). Urinary bladder wall was submitted for histopathology in 4 cases. Biopsy results were: unremarkable (n = 1), interstitial hemorrhagic cystitis (n = 1), and chronic, suppurative cystitis (n = 2).

Follow-up

Eight of the 26 cases (30.8%) were discharged on additional medications for the primary purpose of preventing recurrence of urolithiasis [potassium citrate (n = 5), allopurinol (n = 2), N-(2-Mercaptopropionyl) glycine/Thiola (n = 1)]. Follow-up time was determined by documented telephone communication between the referring veterinarian and owner (n = 6), examination(s) at CSU (n = 5), and telephone contact with the owner (n = 8). Median time of follow-up was 449 d (range: 1 to 946 d).

Time to recurrence

Four cases (6 surgeries) had return of clinical signs and non-contrast radiographs showed urolith recurrence. The mean time to recurrence was 335 d (range: 45 to 856 d). Urolith analysis showed cystine uroliths recovered from 4 surgeries and calcium oxalate monohydrate from the remaining 2.

Discussion

Three primary modifications were developed in this study compared with the previously published technique (3). A temporary complete cystopexy was performed with the abdominal wall instead of placement of 4 stay sutures to secure the bladder. The goal was to limit manipulation of the bladder and limit the risk of contamination of the peritoneal cavity with urine during the surgery. A laparoscope with a 5-mm cannula instead of a cystoscope was used to gain access to the bladder. The laparoscope does not have a working channel in which to place forceps or a basket for capturing uroliths. However, the 5-mm cannula used to gain access to the bladder allows the creation of a flow of saline to flush the uroliths out of the bladder without the need for forceps. Larger uroliths can be grabbed with forceps introduced along the cannula. Unlike the case with the cystoscope, the forceps operate independently of the laparoscope, making its utilization simple. The 5-mm laparoscope provides a larger viewing window and greater image resolution than the 2.7 mm cystoscope. Also, utilization of the laparoscope used for the initial inspection of the abdominal cavity and localization of the bladder minimizes the amount of equipment required during the procedure since a cystoscope is not used. Finally, creation of a retrograde flow of saline helps to flush the uroliths out of the bladder. The flow of saline created with a cystoscope is forward. The high flow of saline also improves visualization because of distension of the urinary bladder wall and dilution of active bleeding. Since placing the largest red rubber or Foley urethral catheter possible is a routine procedure for a cystotomy for urolithiasis in our institutions to either retropulse urethral uroliths into the bladder or to prevent migration of uroliths in the urethra at the beginning of the procedure, maintaining placement of the catheter does not add any extra steps to the procedure (Figure 1). At the end of the procedure the catheter can be removed with a constant high flow of saline and the endoscope simultaneously advanced into the dilated urethra to ensure uroliths are not left in the proximal urethra (Figure 2). The endoscope cannot advance past the ischiatic curvature in male dogs. This procedure cannot be performed in cats because of the size of the urethra. A smaller endoscope might be needed. The high flow of saline combined with a large diameter catheter facilitates displacement of any uroliths lodged in the distal urethra. In 1 male cat, the catheter placed was not sufficient to create an adequate flow of saline to flush the uroliths out of the urinary bladder.

Figure 1.

Intra-operative cystoscopic image of calcium oxalate uroliths in the trigone of a 12-kg miniature schnauzer prior to extraction with graspers. An 8 French Foley urinary catheter is in place to provide high-pressure saline flow and bladder distension.

Figure 2.

Intra-operative cystoscopic image of the same patient as in Figure 1. The Foley catheter has been removed following extraction of the uroliths. Exploration of the proximal urethra can be easily performed with normograde advancement of the laparoscope.

Laparoscopic-assisted cystotomies were all performed with midline incisions even in male dogs and not paramedian as described by Rawlings et al (3), which allows the incisions to be restricted to the linea alba. This reduces hemorrhage and soft tissue trauma compared with an incision through the muscular portion of the rectus abdominis.

Complication rates during laparoscopy in dogs have been reported in 0% to 50% of cases (7–12). The intraoperative complication rate in this study (19%) is well within the range of the complication rates reported. It is difficult to compare complication rates between procedures because the levels of complexity of the procedures are not similar. Also it is difficult to differentiate a complication truly related to laparoscopy (puncture of spleen with Veress needle) from a complication related to the surgery itself (stranguria, or urinary incontinence after urolith removal). For example, Mayhew and Brown (7) reported bleeding for 100% of the ovarian pedicles ligated with clips during ovariectomy; however, the cause of the bleeding was more likely related to the kind of clips and not the laparoscopy. Complications related to laparoscopy in our study were puncture of the spleen by the Veress needle, lack of flow of saline, and uroliths remaining in the urethra at the end of the procedure. Introduction of the Veress needle to establish pneumoperitoneum resulted in splenic laceration in 1 case. Hasson’s technique is an alternative technique to limit trauma to intra-abdominal organs (6). In 1 male domestic shorthair cat, the flow of fluid was insufficient to provide a clear cystoscopic view. It is important to place the largest diameter urinary catheter possible to create a good retrograde flow of saline to maintain the necessary urinary bladder inflation during the procedure; however, this might be difficult in male cats because of the diameter of the urethra. As an alternative, it would have been possible to use a cystoscope in lieu of the laparoscope and use one of the channels to inflate the urinary bladder either in addition to or instead of infusion through the urinary catheter (3–5,13). Unfortunately, this alternative does not produce a retrograde flow of saline that will flush the uroliths out of the urinary bladder easily. On the contrary, it may also create a forward flow of saline that may push uroliths through the urethra. In another cat the urinary bladder could not be grasped due to its thickened chronically inflamed wall. The cat had a history of repeated urinary tract obstruction and had a perineal urethrostomy performed following the cystotomy. The use of a more caudal cystoscopic port, placing and positioning the animal in a Trendelenberg position to allow the urinary bladder to fall as cranial as possible, or placement of stay sutures for traction may help to alleviate this concern (14). Finally, in a mixed breed dog with recurrent cystine urolithiasis, several uroliths were encountered that were too large to be removed through the cystoscopic window, necessitating conversion to open cystotomy and enlargement of the cystotomy. This case was complicated by the chronic cystitis causing significant thickening of the urinary bladder wall. There is a limit to the size of urolith that can be removed with laparoscopic-assisted cystotomy. Patients with uroliths larger than 5 to 10 mm may not be good candidates for laparoscopic surgery.

Postoperative complications were present in 35% of the cases, but none were directly related to the laparoscopy procedures. Rectal prolapse and abdominal wall herniation have been reported previously in cats with urinary obstruction (15,16). The urethral tear likely occurred during catheterization of the urethra to decompress the urinary bladder in the preoperative period. Uroabdomen was not diagnosed before surgery because a urinary catheter was maintained until the time of surgery. The tear was not observed during the cystoscopy. Stranguria and mild urinary incontinence resulting from urethritis and cystitis have been reported (17). The animal that developed an acute pancreatitis underwent intraoperative abdominal radiation therapy at the time of surgery. The etiology of acute pancreatitis in the dog is not entirely understood; however, surgical manipulation/trauma, anesthetic-induced ischemia, or radiation damage may all have precipitated this complication (18).

A single male Newfoundland dog which had 1 previous laparoscopic cystotomy for cystine uroliths, was noted to have a single remnant urolith within the urethra visible on postoperative radiographs. This case was then managed with open cystotomy, allowing successful removal of the urolith. Only 10 cases had follow-up radiographs performed to confirm complete urolith removal because a thorough evaluation of the urinary bladder and 2/3 of the urethra in male dogs or the entire urethra in female dogs could be completed with the endoscope. At the end of the procedure, the urinary catheter was removed slowly with a high flow of saline, and the endoscope was simultaneously advanced in the urethra to evaluate for residual uroliths. In males the endoscope could not pass the ischiatic curvature. Since a large diameter urinary catheter and high flow of saline were used, there was a high level of confidence that there were no uroliths remaining in the urethra. Postoperative radiographs were taken only when the surgeons were suspicious that uroliths could have been left in the lower urinary tract. Previous reports documented incomplete removal of uroliths in 14% to 20% of cats and dogs following routine open cystotomy (19,20). Failure to remove all uroliths was documented in 1 of 10 cases for which postoperative radiographs were obtained. Even after laparoscopic-assisted cystotomy post-operative radiographs are recommended to make sure no uroliths are left in the urinary system.

Long-term postoperative recurrence of urolithiasis may be attributable to remnant uroliths (pseudorecurrence) and reformation of uroliths. Six cases had documented recurrence of cystic uroliths with a mean time to recurrence of 335 d. Two of these uroliths were calcium oxalate and 4 were cystine. The formation of calcium oxalate uroliths typically takes months in the face of persistent lithogenic circumstances. The recurrence of cystine uroliths can be very rapid and recurrence within 1 year of surgical removal is common due to the renal tubular defect that predisposes to urolith formation (21,22). Laparoscopic-assisted cystotomy might help prevent early recurrence/pseudorecurrence of urolithiasis. Magnification of laparoscopy aids visualization of smaller uroliths (Figure 3). Most of the smaller uroliths observed with cystoscopy adhered to the urinary bladder wall, and suction via the cannula was used to remove them.

Figure 3.

The laparoscope provides significant magnification and increased visualization allowing for more accurate urolith identification and extraction. Small calcium oxalate uroliths are noted within the urinary bladder mucosa (black arrows). Compare the urolith size to the tip of the 6 French urinary catheter.

Procedural times for laparoscopic-assisted cystotomy could not be calculated accurately because several other procedures were performed during the same anesthesia in 11 cases. Discrete procedural start and stop times were not always indicated on anesthetic case logs. The time reported in this study is longer than the surgical time reported for open cystotomy (63 min ± 30 min) (19). As with all minimally invasive procedures, there is a significant learning curve that must be overcome by the surgeons and technical staff when implementing new techniques. Different surgeons with various levels of experience performed the procedures. The total operative time was used, likely leading to an overestimate of the procedural time.

Converting to an open procedure is always a possibility during any minimally invasive surgery for the safety of the patient, and should be decided sooner rather than later to minimize surgical time. Technical difficulties such as chronic cystitis preventing correct manipulation of the bladder, inadequate flow of saline, and size of the uroliths were the reasons for converting to an open procedure in this study.

Laparoscopic-assisted cystotomy with 3 modifications of the original technique described by Rawlings et al (3,5) for removal of uroliths was accomplished with relative safety and efficacy in cats and dogs of a wide range of sizes. In future, most complications could be avoided with better case selection; a key factor in the success of minimally invasive surgery. Size of the uroliths, size of the patient (diameter of urethra in cats), and chronic cystitis might be factors to consider before attempting a laparoscopic-assisted cystotomy for treatment of urolithiasis. A prospective clinical trial would be appropriate to compare outcomes between laparoscopic assisted cystotomy and traditional open cystotomy. CVJ