Introduction

Urethral prolapse is the pathologic protrusion of the urethral mucosa through the external urethral orifice.¹ Young, intact male brachycephalic dogs are most commonly affected, with the English bulldog being at the highest risk.^1,2 Other breeds such as Yorkshire terriers and Boston terriers have also been suggested to be prone to urethral prolapse.^3–5 Although the exact etiology of urethral prolapse has not been determined definitively, multiple underlying causes have been suggested, for example, abnormalities in the development of the urethra, increased intraabdominal pressure secondary to chronic upper airway obstruction in brachycephalic dogs, dysuria, sexual excitement, urinary calculi, and urinary or genital infections.^1–3 Owing to the strong breed association, predisposing congenital or genetic defects are favored as an underlying cause of urethral prolapse.^1,6,7 In Yorkshire terriers, congenital factors such as increased intraabdominal pressure secondary to breathing effort caused by tracheal collapse has been suggested as a possible pathophysiology.⁵ Dogs with urethral prolapse typically present with hemorrhage from the penis independent of micturition, excessive licking of the penis, and a characteristic purple mass appearance to the tip of the penis.¹

Because the condition is infrequently diagnosed in clinical practice, studies evaluating the most common corrective surgical procedures, either resection and anastomosis (R&A) or urethropexy, are limited and associated with discrepant recurrence rates.^2,8 Carr et al. examined surgical techniques and outcomes in 37 dogs with long-term follow up, out of which 34 dogs were treated by R&A (56% recurrence rate) but only 3 dogs were treated by urethropexy.² Owing to the small case number of the latter, comparisons of outcome or recurrence rate between procedures was not feasible. A recent study by Healy et al. included 79 dogs with urethral prolapse with longer-term follow-up, out of which 27 dogs were treated by R&A (11% recurrence rate), 44 dogs were treated by urethropexy (39% recurrence rate), and 8 dogs were treated by combined urethropexy and R&A (12.5% recurrence rate).⁸ However, no explanation was given for the lower recurrence rate reported for R&A by Healy et al.

Although a combination procedure of R&A with urethropexy is being performed for urethral prolapse in many clinics, there are few data reported in the literature accessing these outcomes. Healy et al. reported a 12.5% recurrence rate (1/8) following a combined R&A with urethropexy.⁸ However, because of the small case number, comparisons of outcome or recurrence rate between procedures was not feasible.

The purpose of this study was to assess the recurrence rate and outcomes of dogs with urethral prolapse treated with a combined R&A and urethropexy procedure in comparison with R&A alone. We hypothesized that combined R&A with urethropexy would be associated with less recurrence of urethral prolapse compared with R&A alone. Additionally, we assessed a potential influence of surgeon experience and body condition score (BCS) on surgical outcomes.

Material and Methods

Medical records of dogs managed surgically for urethral prolapse were reviewed (February 2013 to September 2023) from three tertiary care hospitals with each corrective surgical technique represented. Data collected included history (clinical signs and duration of clinical signs), signalment (age, breed, sex, and castration status), physical examination findings (including BCS and weight), surgery reports (type of procedure, concurrent procedures performed, type of suture, and suture pattern), short-term postoperative complications, and longer-term follow-up (recheck or phone). Inclusion criteria included documented urethral prolapse within the medical record, no prior corrective procedure, complete records, surgery reports, short-term postoperative complication information, and longer-term follow-up. Any complications noticed up to 2 wk postoperatively were considered short-term. Longer-term follow-up was acquired at a minimum of 3 mo postoperatively. Follow-up phone calls included information on postoperative care provided at home, complications noted postoperatively, and the outcomes of each surgery performed. Dogs with reported recurrence via medical records or phone call interview were included as reprolapses. Dogs were excluded from the study if they had a prior prolapse surgery, no history, no surgery report, or a lack of follow-up, if a surgical laser was used, or if they had a serious comorbidity that affected outcomes.

Surgical techniques are shown in Figure 1. Surgeries were performed by either a board-certified surgeon or surgery resident-in-training (supervised or unsupervised). All prolapses were corrected by R&A, urethropexy, or a combined R&A and urethropexy procedure. Surgical technique was determined based on the discretion of the individual surgeon. Urethral R&A was performed using 4-0 or 5-0 synthetic absorbable monofilament or multifilament suture in a simple continuous or a simple interrupted pattern. Suture types used included short-term or long-term absorbable suture. Short-term absorbable suture included poliglecaprone-25, polyglactin-910, and glycolide/lactide-copolymer. Long-term absorbable suture included polydioxanone. All urethropexies were performed using 2-0 or 3-0 polydioxanone with three to five tacking sutures. The combined R&A and urethropexy procedures were performed using similar techniques and suture material.

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Results

Sixty-nine male dogs were identified. Forty-six dogs successfully met the inclusion criteria (16 castrated; 30 intact). Twenty-three male dogs were excluded from study groups for the following reasons: no surgery report: n = 8, R&A group (RA): n = 13 (prior prolapse surgery: n = 6; lack of follow-up: n = 4; laser use: n = 2; unknown history: n = 1), urethropexy group (UP): n = 2 (prior surgery: n = 1; hemophilia; n = 1).

Brachycephalic breeds were overrepresented in the study (37/46, 80%); specifically, English bulldogs (n = 22), American bulldogs (n = 6), unspecified bulldogs (n = 6), Boston terriers (n = 1), French bulldogs (n = 1), and bull mastiffs (n = 1). Other breeds represented included pit bulls (n = 3) and one of each of the following breeds: border collie, Siberian husky, Australian cattle dog cross, mixed-breed dog, springer spaniel, and a Labrador retriever mix. Median age for all 46 dogs was 10.8 mo (range 1 mo to 9.5 yr). Median age of brachycephalic breeds (n = 37) at presentation was 9.6 mo (range, 1 mo to 9.5 yr) and remaining breeds was 3 yr (range, 6 mo to 9 yr). Median weight for all 46 dogs was 21.5 kg (range 8.8 kg to 72.7 kg) and similar between each surgical group.

The most common presenting clinical sign for these dogs was hemorrhage (n = 38). Other clinical signs included hyperemia and edema of the distal tip of the penis (n = 12), excessive sexual behavior or hyperactivity (n = 7), stranguria (n = 1), purulent discharge (n = 1), vomiting (n = 1), hyporexia (n = 1), and diarrhea (n = 1). Two dogs were diagnosed with urethral prolapse incidentally. The median duration of these clinical signs on initial presentation was 2 days (range 1 day to 5 mo).

There were significant associations between surgical technique and BCS ≥6 (P = .038) and whether a boarded surgeon performed the procedure (P = .007). Specifically, significantly more dogs with BCS ≥6 were in the combined R&A and urethropexy group (UPRA) than the RA group (69.2% and 29.6%, respectively); significantly fewer boarded surgeons performed the combined UPRA than the RA group (15.4% and 63.0%, respectively).

Median postoperative follow-up time for all groups was 1.5 yr (range, 3 mo to 12 yr). Median postoperative follow-up time for RA, UP, and UPRA was 1.7 yr (range, 3 mo to 12 yr), 1.5 yr (range, 3 mo to 6.8 yr), and 1.5 yr (range, 8 mo to 8 yr), respectively.

Recurrence rates for RA, UP, and UPRA groups were 13/27 (48%), 2/6 (33%), and 1/13 (8%), respectively. The median postoperative time to reprolapse for RA was 3 mo (range, 5 days to 4.6 yr), UP was 9.7 mo (range, 7.5 mo to 1 yr), and UPRA was 2 yr (n = 1). Although not statistically significant, in the RA group a higher percentage of recurrence occurred in surgeries performed by a resident-in-training compared with a boarded surgeon, 60% (6/10) versus 40% (7/17). In the UPRA group, 11/13 surgeries performed by a resident-in-training were unsupervised; the one recurrence in the UPRA group was performed by an unsupervised resident.

The only major postoperative complication in the study was a stricture in the RA group. This dog underwent corrective surgery to revise the stricture and did well postoperatively. Minor postoperative complications were seen with 26 dogs. Postoperative hemorrhage from the urethral incision site was the most common minor complication and noted in 16/27 (59%) of RA cases, 0/5 (0%) of UP cases, and 4/13 (31%) of UPRA cases, none of which required additional surgery. Of the 40 dogs who had an R&A performed (27 RA; 13 UPRA), postoperative hemorrhage occurred in 15/31 (48%) using a simple interrupted pattern and 5/9 (56%) using a simple continuous pattern. The only other minor postoperative complication noted was abnormal urination (n = 6; 4 RA, 0 UP, 2 UPRA).

Sixteen dogs had been neutered before presenting for urethral prolapse. Of the 30 intact dogs at presentation, 25 were castrated during their initial surgery (83%), 1 dog was castrated at his recurrence surgery, and 4 dogs were left intact.

Based on BCS (0–9 scale) 19 dogs were overweight (BCS ≥ 6), 25 dogs were of an ideal body condition (BCS 4 to 5), and 0 dogs were underweight. The remaining 2 dogs did not have a BCS recorded. There were significantly more overweight dogs in the UPRA group (9/13) than in the RA group (8/27). Of the overweight dogs, 18/19 (95%) were brachycephalic-breed dogs, and the remaining 1/19 (5%) was a pit bull.

Brachycephalic obstructive airway syndrome grade⁹ was based on physical examination findings and scored as grade 0–I (low) or grade II–III (high). It was noted that 2/20 (10%), 0/5 (0%), and 3/12 (25%) brachycephalic dogs were found to have a high BOAS grade for RA, UP, and UPRA groups, respectively. None of the dogs in this study had upper airway surgery performed before presentation. Upper airway corrective surgery was performed in 7/37 (19%) brachycephalic dogs at the time of their urethral prolapse procedure. Of these 7 dogs, 6/7 (86%) underwent staphylectomy, 5/7 (71%) underwent a laryngeal sacculectomy, and 2/7 (29%) underwent a rhinoplasty. Additional concurrent surgical procedures performed included umbilical hernia (n = 2), cryptorchidism (n = 2), and a fracture repair with a mass removal (n = 1).

Surgery was performed by either a board-certified surgeon or surgery resident-in-training (supervised or unsupervised). For the RA group, 17/27 (63%) were performed by a board-certified surgeon. The remaining 10/27 (37%) RA cases were performed by a surgery resident-in-training, half of which (5/10) were performed unsupervised. All of the UP cases were performed by a resident-in-training, of which 5/6 (83%) were supervised and 1/6 (17%) was unsupervised. In the UPRA group, only 2/13 (15%) cases were performed by a board-certified surgeon. The remaining 11/13 UPRA cases were performed by a surgery resident-in-training, of which 9/11 (81%) were unsupervised.

Surgical duration information was available for all dogs included in this study. Additional procedure time was excluded. The median surgical duration for RA was 13.5 min (range, 7–23 min), for UP was 12.5 min (range, 10–18 min), and for UPRA was 25 min (range, 17–42 min).

RA group surgeries were performed using a simple-interrupted (n = 19) or simple-continuous (n = 8) suture pattern; recurrence rates were 9/19 (47%) and 4/8 (50%), respectively. UPRA group R&A were performed using a simple-interrupted (n = 12) or a simple-continuous pattern (n = 1), with recurrence in 1/12 (8%) surgeries performed using the simple-interrupted pattern. UP group urethropexies were performed using three (n = 1), four (n = 4), or five (n = 1) tacking sutures, with recurrence in 2/4 (50%) surgeries performed using four tacking sutures. UPRA group urethropexies were performed using three (n = 5) or four (n = 8) tacking sutures, with recurrence in 1/8 (13%) surgeries performed using four tacking sutures. Refer to Table 1 (RA), Table 2 (UP), and Table 3 (UPRA) for information including signalment, clinical signs, suture pattern, suture types, surgeon experience, and outcome for each dog included in this study.

TABLE 1 Individual Data: Resection-Anastomosis Group (n = 27)

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TABLE 2 Individual Data: Urethropexy Group (n = 6)

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TABLE 3 Individual Data: Combined Urethropexy and Resection-Anastomosis Group (n = 13)

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Logistic regression analysis was used to determine factors associated with the occurrence of complications (minor and major) and recurrence, when considering possible confounding factors. The initials models were refined by backward-stepwise elimination. The best fit model for recurrence included type of surgery (RA versus UPRA; P = .03) and neuter status at the time of presentation (P = .199; Table 4). Because of the low numbers of dogs treated with a urethropexy, this surgical technique was omitted from statistical comparison. In the multiple-regression model, the only factor associated with an increased risk of recurrence was performing an R&A as the only surgical procedure for urethral prolapse (P = .049; Table 5). No risk factors were found to be significantly associated with major and minor complications.

TABLE 4 Factors Associated with Recurrence: Simple Logistical Regression Analysis

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TABLE 5 Factors Associated with Recurrence: Multiple Logistical Regression Analysis

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Discussion

The current study demonstrated that the recurrence rate of urethral prolapse following combined R&A and urethropexy (8%, 1/13) was lower (P ≤ .05) than R&A alone (48%, 13/27). Interestingly, the lower recurrence rate found with the UPRA group when compared with the RA group occurred within a group having significantly (P < .05) more dogs (69%, 9/13 versus 30%, 8/27) that were overweight (BCS ≥ 6) and fewer board-certified surgeons performing the procedure (15%, 2/13 versus 63%, 17/27). Thus, despite the presence of a higher risk factor for occurrence and lack of surgeon experience, a combined R&A and urethropexy technique demonstrated a low postoperative recurrence rate of urethral prolapse in dogs. A combined technique should be considered for surgical correction of urethral prolapse to decrease recurrence rate.

There are large discrepancies in the few data available currently in the literature reporting recurrence rates following the different surgical techniques used for urethral prolapse, specifically after R&A alone. The recurrence rates for the RA groups are similar between our study (48% 13/27) and that of Carr et al. (56%, 19/34).² However, Healy et al. reported an 11% (3/27) recurrence rate following R&A alone.⁸ Unfortunately, it is difficult to determine why recurrence rate following R&A alone in the Healy study was so much lower than that seen in other studies. Healy et al. state that possible causes for the differences between their study and that of Carr et al. are unclear but may be due to different patient populations (e.g., different breeding pools), surgeons being more aggressive with their resections (e.g., remove as much redundant mucosa as possible when performing an R&A to potentially attenuate the risk for future prolapse), and perioperative management (e.g., use of postoperative sedation); however, none of these factors were assessed. Similar to the study by Healy et al., patient population differences between groups were not assessed in our study. It is possible that the surgeons performing R&A alone in our study were less aggressive at removing as much of the prolapsed tissue as possible compared with the Healy study; however, this would be difficult to assess. Additionally, perioperative management was standard and similar between all groups in our study. The rate of recurrence following the few urethropexy-only procedures in our study (33%, 2/6) was similar to that reported in the study by Healy et al. (43%, 19/44). Interestingly, our recurrence rate of 8% (1/13) following a combined procedure was also similar to that in the study by Healy et al. (12.5%, 1/8).⁸ Importantly, in our study surgeon experience is clearly not a factor in the lower recurrence rate seen with a combined UPRA procedure (11 of 13 performed by a resident-in-training; 9 of the 11 unsupervised) compared with RA (17 of 27 performed by a boarded surgeon).

The signalment of dogs in the present study aligned with those mentioned in previous studies, that is, brachycephalic breeds, specifically English bulldogs, being overrepresented.^1,7 However, the median age at presentation for brachycephalic breeds (n = 37) in our study (10 mo, range 1 mo to 9.5 yr) was significantly (P < .05) less than the median age (3 yr, range 6 mo to 9 yr) for nonbrachycephalic breeds (n = 9). A significant difference in age at presentation for urethral prolapse between brachycephalic dogs and other breeds has not been reported previously. This age difference at the time of diagnosis may represent different etiologies related to the development of urethral prolapse in brachycephalic versus nonbrachycephalic breeds.

The pathophysiology leading to the development of urethral prolapse in dogs is unknown. In humans, prepubescent and postmenopausal women have been found to be most affected by urethral prolapse.^10,11 Thus, the bimodal distribution in women has been theorized to be associated with estrogen deficiency.^10,11 Other proposed inciting factors in humans include an increase in intra-abdominal pressure (IAP) and poor attachment between the two urethral muscle layers where the prolapse occurs.^12–14 The latter theory may be applied to the condition in dogs, as both enhanced inspiratory and expiratory effort have been demonstrated in French bulldogs compared with nonbrachycephalic dogs and shown to be correlated positively with BOAS grade.⁹ One previous study has attempted to analyze the histopathology of urethral tissue acquired from seven dogs with urethral prolapse; however, the small case number and lack of a control group preclude any etiologic conclusions.² Further studies would be required to identify any histopathologic differences between the anatomic connections at the muscle plane involved with urethral prolapse.

The overall median weight of all dogs in the present study aligned with previous studies.² However, when assessing the BCS data, brachycephalic dogs made up the majority of the overweight dogs (BCS ≥ 6) and significantly (P < .05) more dogs with BCS ≥6 were in the UPRA group compared with the RA group. Obesity has been shown in humans and dogs to result in increases in IAP.^13,14 In both species, increased IAP is associated with increased bladder pressure and urethral mobility.^13,14 Considering the predisposition of brachycephalic breeds to BOAS-related increases in IAP, an additional influence such as obesity may be a compounding factor associated with increased IAP resulting in the development of urethral prolapse. It is worth noting that the lower (P < .05) incidence of recurrence found in the UPRA group of the current study occurred despite this group being associated (P < .05) with the categorical variable BCS ≥ 6, a potential risk factor.

Another previously noted factor for urethral prolapse in dogs is being sexually intact.² Although the number of intact dogs (n = 30) diagnosed with urethral prolapse was almost two times greater than that of castrated dogs (n = 16) in our study, this difference was not statistically significant. Of the 30 intact dogs, 25 were castrated during their initial surgery (83%). Although it is difficult to conclude statistically whether castration status and urethral prolapse have a significant relationship from our data, our data are consistent with a recommendation that dogs be castrated at the time of prolapse surgery.

Interestingly, although castration status at the time of diagnosis was found not to be related to postoperative recurrence of urethral prolapse in the current study, this categorical variable did have a P < .2 when analysed with simple logistic regression. Although not significant, the recurrence rate of urethral prolapse in dogs who were neutered versus intact at the time of initial presentation (all groups) was 50% (8/16) compared with 27% (8/30), respectively. Similar calculations within each group were as follows: UP, 67% (2/3) compared with 0% (0/3); RA, 60% (6/10) compared with 41% (7/17); and UPRA, 0% (0/3) compared with 10% (1/10). These trends are consistent with dogs who are already neutered when diagnosed initially with urethral prolapse, that is, dogs who, despite lacking a well-accepted risk factor, may be at a higher risk for postoperative recurrence because other risk factors were sufficient to cause the prolapse.

As expected, hemorrhage and hyperemia of the tip of the penis was the most common presenting clinical sign in the current study. Duration of these signs did not differ greatly from previous studies, with most owners reporting an acute onset of clinical signs of the urethral prolapse. Although in previous studies authors hypothesize that urethral prolapse may be precipitated by chronic vomiting and labored breathing,² in the present study, only one dog presented acutely with vomiting and no dogs presented in active respiratory distress or with labored breathing. However, it is important to also consider the chronic effects of BOAS, that is, expiratory dyspnea and increased IAP, on these dogs’ urethral prolapses even if they do not present in acute distress at the time of their prolapse.¹⁵ Owing to the retrospective nature of this study and the inability of the owners of brachycephalic dogs to recognize dyspnea,⁹ it is difficult to determine whether these dogs truly did have chronic BOAS-related dyspnea that may have contributed to the development of urethral prolapse.

Median time to prolapse recurrence was the shortest for the RA group, followed by the UP and then the combined UPRA group. Given the retrospective nature of this study and that the combined procedure had only one recurrence (2 yr postoperatively), it is difficult to make any conclusions with these data. However, a similar pattern for time to prolapse recurrence (shortest to longest) was reported by Healy et al. (RA: 22 days, range 21–225; UP: 70 days, range 1–1948; UPRA: 465 days [n = 1]). Although purely speculative, if an intramuscular slip plane has formed in the urethra, then after resection of the prolapsed mucosa, some detached muscle layers may remain, which would be unprotected from repetitive shear forces.¹⁶ Conversely, a slip plane opposed and protected from shear forces with a pexy suture may have a chance to adhere, although redundant mucosal tissue, that is, no mucosa being resected with this procedure, may maintain elevated shear forces in the longer term. A combined procedure may both remove damaged, redundant mucosa (i.e., lessen chronic shear forces) and oppose and protect any remaining detached muscle layers, giving them opportunity to adhere.

The type of suture material or pattern had no effect on recurrence rate in any of groups in this study. Poliglecaprone-25 was the most common suture used for R&A (4-0, simple-interrupted) and polydioxanone was the most common suture used for urethropexy (3-0, tacking sutures). No conclusions can be made in the current study with regard to any suture type being associated with any complication or recurrence. Unlike previous studies that showed less hemorrhage following R&A using a simple-continuous pattern,² our data showed there was no difference in postoperative hemorrhage using either a simple-interrupted (48%) or simple-continuous (56%) pattern in the current study. The number of tacking sutures used for urethropexy (three to five) did not show any trends associated with recurrence.

Limitations of this study include its retrospective nature, low case numbers, and reliance on the accuracy of medical records and consistent follow-up. Record information with regard to occurrence and severity of the urethral prolapse and associated diseases was limited and subjective based on the person who assessed the dog. Although relatively few dogs were lost to follow-up, a phone call follow-up also provided an area of bias especially in those dogs with a longer duration of time since their procedures. Median overall postoperative follow-up time for our study (1.5 yr, range 3 mo to 12 yr) was similar to that in the study by Healy et al. (1.2 yr, range 11 days to 9 yr). Additionally, median postoperative follow-up time for each group in our study (RA: 1.7 years, range 3 mo to 12 yr; UP: 1.5 years, range 3 mo to 6.8 yr; UPRA: 1.5 yr, range 8 mo to 8 yr) was longer than (RA and UP) or near (UPRA) our median time to postoperative recurrence (RA: 3 mo, range 5 days to 4.6 yr; UP: 9.7 mo, range 7.5 mo to 1 yr; UPRA: 2 yr [n = 1]) and much longer than median time to recurrence in the study by Healy et al. (RA: 22 days, range 21–225; UP: 70 days, range 1–1948; UPRA: 465 days [n = 1]).

The overall case size represented in this study was also too low to come to conclusions for certain factors, for example, a relationship between castration status and either occurrence or postoperative recurrence. Further prospective studies would be required to assess the significance of this information.

Conclusion

The current study demonstrated that the recurrence rate of urethral prolapse following a combined R&A and urethropexy was lower (P ≤ 0.05) than that following R&A alone. Interestingly, the lower recurrence rate found with UPRA compared with RA occurred within a group having significantly (P < .05) more overweight dogs and fewer board-certified surgeons performing the procedure. Thus, despite the presence of higher risk factors for occurrence and lack of surgeon experience, a combined R&A and urethropexy technique demonstrated a low postoperative recurrence rate of urethral prolapse in dogs. A combined technique should be considered for surgical correction of urethral prolapse to decrease recurrence rates.

The authors would like to thank Kyle Monahan (Tufts Data Science Services) for his assistance with statistical analysis. No ethical approval was required as the study assessed retrospectively data files from client-owned, clinical cases using standard surgical techniques and postoperative management.