Urolithiasis in dogs is common. Cystotomy performed by means of celiotomy (ie, OC) is the traditional surgical method for removing uroliths from the urinary bladder in dogs. Removal of cystoliths is incomplete in as many as 42% of dogs that undergo cystotomy and is more common in dogs that have both cystoliths and urethroliths at the time of surgery.1,2
Laparoscopic-assisted cystotomy is used for removing cystoliths in dogs3,4 and is performed with a rigid endoscope that functions as both a laparoscope and a cystoscope during the procedure.3 Laparoscopic and LAC procedures require smaller incisions and therefore result in less soft tissue trauma, which may reduce postoperative pain and surgical site infection rates, compared with traditional open techniques.5–8 Additionally, there is enhanced visualization of the bladder and proximal portion of the urethra because of the magnification and illumination provided by the endoscope during cystoscopy, which may limit the risk of incomplete cystolith removal.3,9,10 Although laparoscopic-assisted procedures have potential advantages, they also have several potential disadvantages, such as increased expense and technical difficulty, which may increase operative time, compared with open surgery.6,8
Comparison of cost and associated clinical variables between laparoscopic and open surgical techniques is an important consideration in both human and veterinary surgery. Although this analysis is commonly reported in human surgery, similar data are nonexistent in veterinary surgery. For example, laparoscopic removal of the distal portion of the pancreas in humans is associated with similar operative costs but substantial reductions in postoperative pain and analgesic requirements, duration of hospitalization, and total hospitalization cost versus open surgery.11,12 A similar relationship has been reported between laparoscopic colectomy and open colectomy in human surgery.13
Whether these relationships exist in veterinary surgery is unknown, but comparative studies would be useful when discussing surgical options with clients as well as for organizing and assessing cost structure associated with laparoscopic techniques.14 As the economics of veterinary surgery continue to evolve, an understanding of these relationships will be necessary if we are to improve operating efficiency and make informed decisions about surgical techniques.
Consequently, the purpose of the study reported here was to retrospectively compare surgical cost, hospital cost, total cost, and surgical and hospitalization times as well as the prevalence of incomplete urolith removal between dogs undergoing LAC and those undergoing OC. The hypotheses were that surgery costs would be greater for dogs undergoing LAC, compared with those undergoing OC, but that total cost including hospitalization would be similar; surgery time would be greater for dogs undergoing LAC versus OC, but hospitalization stay for LAC would be shorter; and incomplete cystolith removal necessitating revision surgery would be less frequent in the dogs undergoing LAC.
Materials and Methods
Selection of cases and controls—Medical records were searched to identify dogs that underwent OC or LAC between September 10, 2009, and November 14, 2012. Dogs were included in the OC group if an OC was performed as the primary procedure; they were not included in the OC group if an OC was performed after LAC.
Dogs were included in comparative analysis if they underwent pre- and postoperative abdominal radiography, were anesthetized, and had operative records and itemized invoices. Dogs were excluded if they had a major secondary procedure (eg, caudectomy, gastrointestinal tract surgery, urethrotomy, or urethrostomy) performed during the same anesthetic period. Dogs were not excluded if they had minor procedures (eg, liver biopsy, tooth extraction, or castration) performed during the same anesthetic period. Dogs were also excluded if they had complicating concurrent diseases such as urinary neoplasia or clotting disorders.
Medical records review—Data collected from the medical record included age, breed, sex, body weight, surgical treatment, additional surgical procedures, abdominal radiographic findings, surgery time, incomplete cystolith removal, number of doses of analgesics administered IV after surgery, days in hospital, and cost of surgery and hospitalization.
Complete urolith removal was defined as no radiographic evidence of uroliths in the bladder and urethra detected on postoperative caudal abdominal radiographs. If any uroliths were seen on postoperative radiographs, the case was considered an incomplete cystolith removal and an OC was performed to remove the remaining uroliths.
The duration of hospitalization was defined as the time in days from the day of the procedure to the day of hospital discharge (eg, if the dog was discharged the same day as the procedure, the hospitalization time was recorded as 1 day, and if the dog was discharged the day after the procedure, the hospitalization time was recorded as 2 days). Surgery time was defined as the time between skin incision and skin closure.
The number of postoperative IV analgesic injections administered in the hospital was documented. If the patient received a continuous rate infusion of analgesics, it was excluded from this part of the analysis. A shorthand version of the Glasgow Composite Pain Scale15 was used to assess postoperative signs of discomfort in the recovery ward.
Surgery and hospitalization costs were calculated for each dog. Surgery cost included the anesthesia fee, operating room fee, surgical procedure fee, and instrumentation fee. The anesthesia fee was determined on the basis of the duration of the surgery and use of local and epidural analgesia. The operating room fee was a flat fee, and the surgical procedure fee was determined on the basis of competitor costs (market based by comparison with local veterinary practices) in addition to duration of the procedure. The instrument fee was determined on the basis of the initial investment cost of the instruments as well as a resterilization charge based on the cost of sterilization. Use of single instruments or instrument packs incurred separate fees. Additionally, a fee of $235 was charged if the laparoscopic instruments were used. Hospitalization charges consisted of a surgery recovery fee and daily nursing care fee. Hospitalization charges from days in the hospital prior to surgery were not included. All other fees and charges were excluded from the analysis.
Radiography and anesthesia—Preoperative and immediate postoperative, 3-view radiography of the caudal portion of the abdomen including the entire urinary bladder and urethra was performed in all dogs. Anesthetic protocols varied among dogs and were determined by the anesthesiologist for each procedure. Typically, dogs were premedicated with hydromorphone (0.1 to 0.2 mg/kg [0.05 to 0.09 mg/lb], IV or IM) or methadone (0.2 to 0.4 mg/kg [0.09 to 0.18 mg/lb], IV or IM) in combination with acepromazine (0.02 to 0.05 mg/kg [0.01 to 0.02 mg/lb], IV or IM) or midazolam (0.2 to 0.3 mg/kg [0.09 to 0.14 mg/lb], IV or IM). Anesthesia was induced with propofol (3 to 5 mg/kg [1.4 to 2.3 mg/lb], IV) and maintained by administration of isoflurane anesthetic gas. Lactated Ringer's solution was administered IV at 5 to 10 mL/kg/h (2.3 to 4.5 mL/lb/h). Standard intraoperative monitoring was performed during the procedure. After surgery, dogs in both groups typically received either hydromorphone (0.1 to 0.2 mg/kg) or methadone (0.2 to 0.4 mg/kg) IV, IM, SC, or in a combination of these routes for the first 12 to 24 hours after surgery.
OC—Open cystotomy was performed by means of ventral midline celiotomy and ventral cystotomy.16 The bladder was exteriorized and held in place with stay sutures while the cystotomy was performed. Urine and cystoliths were removed with suction and a gall spoon. The bladder and urethra were lavaged retrograde and anterograde with sterile saline (0.9 % NaCl) solution via a red vinyl cathetera and catheter-tip syringe to minimize the chance of incomplete cystolith removal. The bladder was closed in a single layer with absorbable monofilament suture.b–d The abdomen was closed in a routine manner.16
LAC—Laparoscopic-assisted cystotomy was performed similarly as described3 with the exceptions of port location (midline in all cases) and specific laparoscopic portse,f used, which varied among procedures on the basis of the surgeon's preference. Once the abdomen was insufflated and the port was placed, a 5-mm laparoscopeg was inserted and a brief abdominal exploratory was performed. Next, a laparoscopic Babcock forcepsh was passed through a separate 5-mm cannulaf and used to grasp the bladder apex. Once the bladder was grasped, the port or ports were removed and the bladder was elevated to the body wall. A ventral cystotomy was made just large enough to allow removal of the largest cystolith. The incised bladder wall was then temporarily sutured to the abdominal wall port incision with 3-0 monofilament suture.c,d A cystoscopeg-trocar-suction assembly was placed into the bladder, and suction was used to intermittently aspirate urine and cystoliths. A retrograde urethral cathetera was used to distend the bladder with sterile saline solution during the cystoscopy procedure. Large calculi were removed with a narrow gall spoon or a grasping forceps. Prior to completion of cystoscopy, the pelvic portion of the urethra was explored while the retrograde urethral catheter was removed to limit the possibility of incomplete urethrolith removal. The cystoscope and cannula were removed, and the bladder was closed in a simple continuous pattern with monofilament absorbable sutureb–d; the abdominal incision was closed routinely in 3 layers.16
Statistical analysis—Continuous data of normal distribution are presented as mean ± SD values. Nonparametric data are presented as median and range values. One-way ANOVA was used to compare differences among continuous variables. Categorical variables were compared with a χ2 contingency test. Simple linear regression analysis was used to evaluate the effect of date of surgery on surgery time within groups. The ANOVA F test was used to evaluate the predictor effect. Values of P < 0.05 were considered significant for all comparisons. All analyses were performed by means of commercial statistical software.i
Results
Between September 10, 2009, and November 14, 2012, 64 dogs underwent surgery for bladder cystoliths at the University of Florida Small Animal Hospital, with 43 meeting the inclusion criteria. Open cystotomy was performed in 23 dogs and LAC in 20. Mean ± SD body weight of dogs was 14.3 ± 10.6 kg (31.5 ± 23.3 lb) in the LAC group and 10.4 ± 8.1 kg (22.9 ± 17.8 lb) in the OC group (P = 0.18). Mean age of dogs was 6.7 ± 2.7 years in the LAC group and 8.6 ± 1.5 years in the OC group (P = 0.57). There were 17 castrated males, 1 sexually intact male, and 2 spayed females in the LAC group and 15 castrated males, 3 sexually intact males, and 5 spayed females in the OC group (P = 0.33). Breeds in the LAC group included Bichon Frise (n = 3), mixed breed (2), Pomeranian (2), Yorkshire Terrier (2), and 1 each of the following: Australian Cattle Dog, Bassett Hound, Beagle, Boxer, Dalmatian, English Bulldog, German Shepherd Dog, Miniature Poodle, Miniature Schnauzer, Pembroke Welsh Corgi, and Shih Tzu. Breeds in the OC group included Bichon Frise (n = 2), Chihuahua (2), Maltese (2), mixed breed (2), and 1 each of the following: Boston Terrier, Brussels Griffon, Cavalier King Charles Spaniel, Cocker Spaniel, Dalmatian, German Shepherd Dog, Miniature Poodle, Miniature Schnauzer, Pekingese, Pembroke Welsh Corgi, Pomeranian, Pug, Shih Tzu, Silky Terrier, and Yorkshire Terrier.
All surgeries were performed by faculty surgeons or by surgery residents under direct faculty supervision. Secondary procedures were performed in 4 dogs in the LAC group and 3 dogs in the OC group (P = 0.66). Procedures included castration (LAC [n = 2]; OC [1]), liver biopsy (LAC [2]; OC [1]), and tooth extraction (OC [1]). Preoperative radiography revealed uroliths in only the bladder in 11 LAC and 13 OC dogs and in both the bladder and urethra in 9 dogs in the LAC group and 10 dogs in the OC group (P = 0.92).
Surgery cost, hospitalization cost, total cost by group (LAC or OC), surgery time, and hospitalization time by group (LAC or OC) were determined (Tables 1 and 2). One dog in the OC group was not included in the surgery time analysis because the anesthesia record was incomplete. The effect of date of surgery on surgery time for both groups was determined (Figure 1).
Linear regression analyses comparing the effect of date of surgery on surgery time in dogs with urinary cystoliths treated by LAC (upper panel [n = 20]) or OC (lower panel [23]). Solid line indicates regression line; dots indicate individual values.
Citation: Journal of the American Veterinary Medical Association 243, 5; 10.2460/javma.243.5.703
Linear regression analyses comparing the effect of date of surgery on surgery time in dogs with urinary cystoliths treated by LAC (upper panel [n = 20]) or OC (lower panel [23]). Solid line indicates regression line; dots indicate individual values.
Citation: Journal of the American Veterinary Medical Association 243, 5; 10.2460/javma.243.5.703
Linear regression analyses comparing the effect of date of surgery on surgery time in dogs with urinary cystoliths treated by LAC (upper panel [n = 20]) or OC (lower panel [23]). Solid line indicates regression line; dots indicate individual values.
Citation: Journal of the American Veterinary Medical Association 243, 5; 10.2460/javma.243.5.703
Comparison of mean ± SD costs for dogs with urolithiasis treated by OC (n = 23) or LAC (20).
| Variable | OC | LAC | P value |
|---|---|---|---|
| Surgery ($) | 814.9 ± 244.6 | 1,130.1 ± 237.8 | < 0.001 |
| Hospitalization ($) | 267.2 ± 135.5 | 225.2 ± 120.1 | 0.29 |
| Total ($) | 1,088.6 ± 360.0 | 1,347.8 ± 283.3 | 0.013 |
Comparison of the mean ± SD surgery and hospitalization times for dogs with urolithiasis treated by OC (n = 22 [surgery] or 23 [hospitalization]) or LAC (20).
| Variable | OC | LAC | P value |
|---|---|---|---|
| Surgery time (h) | 1.26 ± 0.50 | 1.83 ± 0.70 | 0.004 |
| Hospitalization time (d) | 2.13 ± 0.63 | 1.9 ± 0.64 | 0.24 |
Frequency of incomplete cystolith removal and number of injectable analgesic medications administered in the postoperative period were determined (Table 3). Seven dogs in the OC group and 1 in the LAC group were excluded from the analgesic comparison because they received a continuous rate infusion of analgesics IV in the postoperative period.
Frequency of incomplete cystolith removal (number [%] of dogs; n = 23 [OC] or 20 [LAC]) and IV analgesic administration (median [range] of doses; 16 [OC] or 19 [LAC]) in dogs with urolithiasis treated by OC or LAC.
| Variable | OC | LAC | P value |
|---|---|---|---|
| Incomplete cystolith removal | 4 (17.4) | 1 (5) | 0.21 |
| Postoperative IV analgesic doses | 4 (2–6) | 2 (0–6) | 0.03 |
Discussion
At this academic veterinary hospital, LAC was more time-consuming and, overall, more expensive than OC. Hospitalization time and frequency of incomplete urolith removal did not differ significantly between groups, but the number of injectable analgesic doses administered after surgery was lower in the LAC group versus the OC group.
Faculty surgeons or residents under faculty supervision performed all surgeries in both groups, which is typical of academic institutions. Additionally, the frequency of additional minor procedures was not different between groups. Dogs included in this study were of similar breed, age, sex, and body weight. All dogs had preoperative abdominal radiography, and cystoliths were present in both the bladder and urethra in about 50% of cases; this was not different between groups. Thus, differences detected in this study were most likely related to the differences in surgical treatment rather than selection bias.
Operating cost was significantly greater in the LAC versus the OC group. This finding was not surprising given the established cost structure; it was consistent with some laparoscopic procedures in human surgery.11 The surgery cost was significantly higher in the LAC group for 2 primary reasons. First, the mean procedure time was approximately 50 minutes (30%) longer than for OC, which increased the surgery fee. Second, the procedure and instrumentation fee associated with use of the laparoscopy equipment was approximately 3 times the cost of the OC procedure. The combination of these factors explains the mean increase in surgical cost of approximately $300 (28%), compared with the cost of OC. This cost structure seems reasonable and is similar to what has been recommended.14 In general, the initial cost of the instrumentation, frequency of use, and individual technique were factors in determining pricing for the LAC procedure. We have been performing LAC and many other minimally invasive procedures at our institution for more than 3 years and have most likely recouped the initial cost of the instrumentation, making demand and local competition more relevant determinants of pricing. Although an additional 28% in operating cost might be considered reasonable for LAC, compared with OC, it is possible that some companion animal owners will choose OC over LAC despite the potential benefits of a more minimally invasive procedure. If this were to become common, consideration could be given to a reduction in the procedure or instrumentation fee. However, the present data suggested that the higher operating cost associated with LAC has not been a substantial deterrent for performing LAC at the authors' hospital.
Laparoscopic-assisted cystotomy was not performed at our hospital prior to 2009. Since that time, the procedure has been performed with increasing frequency. Consequently, it was not surprising that the mean operative time was longer for the LAC group, compared with that for the OC group; this was thought to be attributable to the complexity and associated learning curve of performing a new procedure. Supportive of this supposition was the finding of a negative linear relationship between the date of surgery and surgery time in the LAC dogs, but not the OC dogs. Furthermore, the linear regression model suggested that approximately 27% of the improvement in surgery time for the LAC group could be attributed to the date of surgery. Although evaluating the learning curve for LAC was not a primary goal of the study, a prospective study could be considered to better characterize the effect of learning on operative time. Regardless, there did appear to be an effect of learning curve on surgery time in the LAC group, which may be diminished (along with surgical cost) with successive LAC cases.
No significant difference was detected in the number of days in the hospital between groups, which argues against the stated hypothesis. Although a true difference may not exist at our institution, it is also possible that low case numbers and type 2 statistical error prevented identification of this relationship. Results of several human studies11–13,17 indicate that patients who undergo laparoscopy have significantly shorter hospital stays than those who undergo laparotomy. Evaluation of hospitalization time is an important factor not only because of its effect on cost, but also because of the potential effect on patient morbidity. This is a well-evaluated variable in human laparoscopic surgery, which reduces cost as well as iatrogenic complications and patient morbidity.18,19 Although this has not been well evaluated in veterinary surgery, it is possible that a similar relationship exists in canine patients. Prospective or larger retrospective studies are indicated to better answer this question. Interestingly, a recent study by Mayhew et al5 revealed a reduced risk of surgical site infection in dogs undergoing laparoscopic procedures, compared with the risk in dogs undergoing traditional open techniques.5 In the present study, no difference in hospitalization cost between LAC and OC groups was detected. We originally hypothesized that hospitalization costs would be higher in the OC group because of a perceived increase in hospitalization time and need for postoperative administration of injectable analgesic medications. However, because the daily hospitalization fee is the biggest determinant (compared with injection fees) of hospitalization cost and because duration of hospitalization was not different between groups, the total hospitalization costs were also not different. Results of several studies11–13 in human medicine indicate that hospitalization costs are significantly higher in patients undergoing laparotomy than in those having the same procedure performed by laparoscopy. In some of those studies, the difference in median hospital stay was 2 days, which likely accounts for the difference in hospitalization cost, compared with results of the present study.11–13
We also hypothesized that the total surgery and hospitalization cost would be similar between the LAC and OC groups. Results of human studies11,20 indicate that this relationship is true when comparing laparoscopy with laparotomy, and in some instances, the total cost associated with laparoscopy has been less than the total cost for laparotomy.12,13 Because we found no difference in hospitalization cost between groups and because the surgery cost was significantly higher in the LAC group, the total cost was also significantly higher for the LAC group. Perhaps if more LAC cases had been included, a significant difference in hospitalization cost and time might have been identified. It is also plausible that, as surgeons become more familiar with new techniques like LAC, surgery time and therefore operative cost may decrease, eventually reducing total cost to an amount comparable to OC.
One of the purported advantages of LAC is the ability to use the endoscope as a cystoscope, which improves intraluminal viewing of the urinary bladder.3,9,10 A potential benefit of this might be limiting the risk of incomplete cystolith removal, which is reported in up to 42% of dogs undergoing OC.1 Reducing the risk of incomplete cystolith removal has been one of the justifications for LAC at our institution. We did not find a significant difference in the rate of incomplete cystolith removal between the LAC (5%) and OC (17%) groups. However, sample size was small, which likely limited the power of this comparison. It is also possible that with more experience, incomplete cystolith removal would be further minimized or avoided by use of the LAC method. Again, the linear regression analysis results offered some support for this hypothesis and the LAC case with incomplete urolith removal occurred in the first LAC procedure performed at our institution.
Dogs that underwent LAC appeared to be in less pain than dogs that underwent OC because the number of injectable analgesic doses administered after surgery was significantly less in the LAC group. The decision to administer injectable pain medications is based on the comfort of the dog as interpreted by the veterinary surgeon or nurse by use of a short-hand version of the Glasgow Composite Pain Scale.15 In general, dogs are transitioned to orally administered pain medications once they appear to have minor to no signs of substantial discomfort. Quantification of postoperative analgesics administered is a common practice in human surgery; studies21,22 have found significant reductions in the amount of analgesics required after laparoscopic procedures, compared with the amount required after open procedures.21,22 Obviously, other factors such as surgeon preference or impressions of pain will influence the decision whether to administer injectable pain medications.
Several limitations of the study must be acknowledged. The small sample size may have prevented identification of significant differences between groups in some comparisons. The retrospective nature of the study may have limited the accuracy and consistency of collected data. Variation in anesthetic protocol and surgeon experience made interpretation of some results difficult. A prospective study could be considered to offset these limitations. However, retrospective studies can be an important first step in improving the understanding of clinical and economic issues and may lay the foundation for future prospective studies.
In the present study, LAC was more time-consuming and expensive but was associated with fewer doses of injectable analgesics administered after surgery, compared with OC. Although no differences were identified in the frequency of incomplete urolith removal and hospitalization duration, a larger case series or prospective study might be considered to better evaluate these relationships.
ABBREVIATIONS
| LAC | Laparoscopic-assisted cystotomy |
| OC | Open cystotomy |
Red rubber catheter, Covidien Inc, Mansfield, Mass.
Vicryl (polyglactin 910) suture, Ethicon Inc, Somerville, NJ.
Monocryl Plus Antibacterial (poliglecaprone 25) suture with Irgacare MP, Ethicon Inc, Guaynabo, Puerto Rico.
PDS Plus Antibacterial (polydioxanone) suture, Ethicon Inc, Guaynabo, Puerto Rico.
SILS port, 5 mm, Covidien Inc, Mansfield, Mass.
VersaStep 5-mm cannula and dilator with radially expandable sleeve, Covidien Inc, Mansfield, Mass.
Hopkins II telescope, 5 mm, 0°, Karl Storz, Veterinary Endoscopy-America Inc, Goleta, Calif.
Clickline, 5-mm Babcock Forceps, Karl Storz Veterinary Endoscopy-America Inc, Goleta, Calif.
JMP, version 9.0.2, SAS Institute Inc, Cary, NC.
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