Comparison of bidirectional barbed versus conventional monofilament suture material for closure of feline perineal urethrostomies

Abstract

Objective

A retrospective comparison of bidirectional barbed absorbable suture material to conventional absorbable monofilament suture for closure of feline perineal urethrostomies.

Animals

Client-owned cats (N = 26) that underwent perineal urethrostomy.

Procedure

Medical records for cats that underwent perineal urethrostomy surgery at BluePearl Veterinary Specialty and Emergency Center Conshohocken between 2018 and 2021 were reviewed. Information regarding signalment, perioperative conditions, surgical procedures, treatments, and postoperative complications were identified. Long-term follow-up information was obtained using owner questionnaires and referring veterinarian records.

Results

Mucocutaneous apposition in 15 cats was accomplished using bidirectional barbed suture material followed by 11 consecutive cats sutured using conventional suture material. The mean (± SD) surgery time in the bidirectional barbed group was 31.6 (± 5.8) minutes and in the conventional group was 34.5 (± 7.1) minutes. Short-term complications included urine extravasation, licking, hemorrhage, stranguria, bruising/erythema, diarrhea, and hemorrhage. The short-term complication rate in the bidirectional barbed group was 80% (12/15) compared to 55% (6/11) in the conventional group. Long-term complications included recurrent urinary tract infections, suture migration, recurrent feline lower urinary tract disease signs, excessive licking, and stricture. The long-term complication rate in the bidirectional barbed group was 47% (7/15) compared to 36% (4/11) in the conventional group.

Conclusion

The use of bidirectional barbed suture was comparable to the conventional absorbable suture technique with no significant differences in surgical time or complication rates.

Clinical relevance

The use of bidirectional barbed suture is an acceptable option for closure of perineal urethrostomies.

Introduction

Urethral obstruction is a common cause of morbidity in male cats (1,2). Of male cats with feline lower urinary tract disease (FLUTD) 18 to 58% progress to urethral obstruction. The incidence of feline urethral obstruction has decreased significantly over the last 20 y (3). Recurrent urethral obstructions caused by FLUTD in cats is the most common indication for perineal urethrostomies (PU) but may also be considered in cases of anatomic abnormalities and trauma. The technique initially described by Wilson and Harrison in 1971 is still the most common procedure for perineal urethrostomies (4). This technique has been modified to minimize intrapelvic dissection preserving urethralis muscle function and increase visualization via sharp transection of the ischiourethralis and ischiocavernosus muscles for pudendal nerve preservation (5–7). Initially, a nonabsorbable simple interrupted pattern was used to suture the urethral mucosa to the skin. The nonabsorbable sutures would remain in place to achieve primary wound healing and then were removed after 2 wk (8). Facilitation of suture removal often required repeat general anesthesia or sedation. A simple continuous suture pattern using absorbable suture material described and evaluated in 2004 proved to be a viable alternative to the use of nonabsorbable suture material (9).

Advances in suture technology have provided veterinary medicine with knotless and bidirectional barbed suture material, which are characterized by protruding barbs in various geometrical positions along a monofilament suture to provide self-anchoring. Barbed suturing devices have been described for skin, enterotomy, and gastrotomy closures (10–12). Barbed suture can be either monodirectional with a loop or tag to prevent the need for a knot at initiation or bi-directional with double swaged needles (13). Key benefits to barbed suture include the ability to eliminate knots which may cause irritation, decrease in surgery time, subjective improvement in cosmesis, and minimization of tissue entrapment which may lead to local ischemia (14). Conventional suture knots create high tension in focal areas as opposed to the purported even dispersal of tensile forces through the entire closure as seen with barbed suture (15). Smooth and barbed sutures are distinctly different biomechanically. When comparing the breaking strength of various sizes of conventional smooth polypropylene suture to 2-0 barbed polypropylene suture, the breaking strength was not significantly different from the conventional smooth 3-0 polypropylene suture. Barbed suture had less elongation and was significantly stiffer than any other conventional smooth suture (14,16). A disadvantage of using a bidirectional barbed suture is the opportunity for the barbs to cause persistent migration upon patient movement. This has been documented in human plastic surgery causing pain and irritation to the patient thereby requiring suture removal (17).

Our objective was to evaluate the use of bidirectional barbed suture as an alternative to conventional suture material for mucosa to skin closure of feline perineal urethrostomies and to compare postoperative complication rates. We hypothesized that the use of a bidirectional barbed suture would reduce urethrostomy closure times with minimal to no significant difference in short- or long-term complications.

Materials and methods

Electronic medical records were searched for all cats admitted to BluePearl Veterinary Specialty and Emergency Center at Conshohocken, Pennsylvania, USA that underwent perineal urethrostomy surgery between 2018 to 2021. All cats brought in for urethral obstructions secondary to feline lower urinary tract disease were unblocked and stabilized before surgery. Methods of unblocking were not reported and remained at the discretion of the emergency veterinarian. Cats were considered eligible for inclusion provided appropriate records were maintained, a 2-week recheck examination was performed, and long-term follow-up were recorded. Long-term follow-up was defined as a minimum of 1 y following surgery. Long-term follow-up consisted of a telephone interview with owners and/or through using referring veterinarian records. All cats had signalment, weight, history, baseline laboratory tests, concurrent infections, radiographic evaluation of the bladder/urethra, and duration of hospital stay recorded. All surgeries were completed in entirety by the same Board-certified veterinary surgeon. Cats were divided into 2 groups for consecutive surgeries: 15 bidirectional barbed suture and 11 conventional monofilament suture. Exclusion criteria included concurrent surgical procedures required at the time of perineal urethrostomy and/or cats undergoing revision of a previous PU.

Surgical procedure

All cats had perineal urethrostomy surgical procedures based on the technique described by Wilson and Harrison (4). All surgical procedures were carried out in entirety by the same ACVS Board-certified surgeon (N.S.). All cats were placed in sternal recumbency with perineal elevation. The ischiocavernosus muscle attachments to the pelvis were transected. Once the urethra was mobilized, dissection was made proximal to the level of the bulbourethral glands for landmark visualization. A #11 blade was used for incision of the urethra using a semi-rigid polypropylene urinary catheter for guidance. Adequate urethral diameter was determined if passage of a closed Halsted mosquito hemostat to the level of the box locks could be achieved (17). Tension free, accurate tissue apposition of the urethral mucosa to the skin was performed. The subcutaneous tissues were not closed. For the bidirectional barbed suture group, the spatulated urethral mucosa was sutured to the skin using bidirectional barbed 3-0 poliglecaprone (Quill Monoderm, Surgical Specialties Corporation, Westwood, Massachusetts, USA) starting at dorsal midline. The first needle was passed through the urethral mucosa on dorsal midline and through the skin along the median raphe. The suture was passed through until the suture barbs were noted to engage, as evidenced by tension on the suture. The second needle was passed similarly ~1 mm lateral to the first suture passage. Each suture end was continued ventrally along its respective edge of the lateral urethral mucosa and skin in a simple continuous horizontal suture pattern. This was continued until the urethral mucosa was apposed 1.5 cm in length where the distal penis was transected and a circumferential ligature was placed using 4-0 poliglecaprone 25 (Monocryl Ethicon, Somerville, New Jersey, USA). Both barbed suture ends were cut flush to the skin. The remaining skin apposition ventral to the urethral mucosa was apposed with 4-0 poliglecaprone 25 in a simple interrupted pattern. For the conventional suture group, the spatulated urethra was initially tacked to the skin on dorsal midline with two simple interrupted sutures using 4-0 poliglecaprone 25 to ensure proper dorsal apposition of the mucosa to the skin. The 4-0 poliglecaprone 25 was continued distally until all mucosa was sutured in a simple interrupted suture pattern. The remaining skin ventral to the urethral mucosa was apposed with 4-0 poliglecaprone 25 in a simple interrupted pattern. All cats recovered routinely from anesthesia and were monitored closely in hospital. Postoperative urinary catheters were not placed. Records were noted to be complete if appropriate documentation of urination, incision evaluation, and use of Elizabethan collar were maintained during the entirety of the postoperative hospitalization period. Postoperative treatment for all cats included intravenous fluid therapy, a partial mu opioid, non-steroidal anti-inflammatory medication, and a cephalosporin antibiotic. Cats were discharged with a partial mu opioid, non-steroidal anti-inflammatory medication, and an antibiotic when indicated by the culture and sensitivity obtained on admission. Cats were discharged with the recommendation to be placed on a prescription diet to minimize recurrent FLUTD signs.

Follow-up evaluation

Information from the immediate post-operative hospitalization was obtained via electronic medical record. A 2-week recheck examination (range: 10 to 16 d after surgery) was carried out in person by the surgeon of record to ensure adequate healing, evaluate for dehiscence, and appropriate stoma size. In person questionnaires were completed at that time for review of the recovery period. The immediate post-operative period was defined as the time from surgery to the 2-week recheck examination. All owners were contacted for long-term follow-up and medical records from referring veterinarians were requested. Long-term follow-up was performed at > 1 y following surgery. Owners were asked about complications related to perineal urethrostomy surgery including stricture formation, recurrence of FLUTD signs, bacterial urinary tract infections, behavioral changes, hemorrhage, and suture migration. A review of referring veterinarian records was performed if records were obtained.

Data analysis

All analyses were performed using SAS 9.4 (Cary, North Carolina, USA). A significance threshold of 0.05 was used. Binomial proportions with two-sided exact 95% confidence intervals (CI) were calculated for short-term and long-term complication rates for each group. Logistic regressions were used to compare odds of complications between groups. Log-likelihood ratio test P-values were recorded. Risk differences between groups were calculated along with 95% CI. A Student’s t-test was used to compare surgical times between groups. Q-Q plots and histograms of surgical times by group were examined and supported the assumption of normality.

Results

Thirty cats were admitted to the hospital throughout the study period for evaluation of urethral obstruction secondary to FLUTD signs. Four cats were excluded due the presence of cystoliths noted on radiographs necessitating cystotomy in addition PU. Fifteen cats in the bidirectional barbed absorbable suture group and 11 cats in the conventional monofilament absorbable suture group met inclusion criteria. All cats survived to follow-up. None of the cats in either group was noted to have incisional dehiscence. Six cats were noted to have urinary tract infections when brought to the hospital; diagnosed by the emergency department upon unblocking based on positive urine culture or bacteriuria discovered on urinalysis. Pathogens were identified as Escherichia coli (n = 2), Pasturella multocida (n = 1), Serratia plymuthica (n = 1), alpha hemolytic Streptococcus (n = 1), and cocci (culture and sensitivity declined). A urethral tear was noted in 1 cat in the bidirectional barbed suture group at the time of surgery due to the unblocking procedure performed on admission to the emergency department. This cat experienced self-limiting urine extravasation with excessive peri-incisional bruising in the immediate post-operative period. No further complications were identified in this cat following the 2 wk recheck examination. The mean (± SD) overall surgery time in the bidirectional barbed group was 31.6 (± 5.8) min and in the conventional group was 34.5 (7.1) min (P = 0.27). Mean duration of hospitalization after surgery was 1.7 d (range: 1 to 3 d with an outlier of 9 d for the cat with urine extravasation).

Minor complications noted during the immediate postoperative period included urine extravasation (n = 1), licking at the surgical site (n = 4), hemorrhage (n = 8), stranguria (n = 9), persistent bruising/erythema (n = 4), and diarrhea suspected secondary to concurrent antibiotic therapy (1). Major complications noted during the immediate post-operative period included hemorrhage requiring transfusion (n = 1) (Tables 1, 2). The short-term complication rate in the bidirectional barbed group was 80% (12/15; 95% CI: 52 to 96%) compared to 55% (6/11; 95% CI: 23 to 83%) in the conventional group (P = 0.17; odds ratio (95% CI) 3.3 (0.6 to 19). The difference in short-term complication rates (bidirectional barbed versus conventional) was 25% (95% CI: −10 to 61%). Incidence of short-term complications in the presence of urinary tract infections at the time of diagnosis was 50% (3/6 cats). All complications in these cats were minor and were not significantly associated with identification of preoperative urinary tract infection.

Table 1.

Number of cats with short-term complications.

Complications	Conventional	Bidirectional barbed
Urine extravasation	1	0
Licking	0	4
Hemorrhage	2	6
Stranguria	2	7
Bruising/erythema	2	2
Diarrhea	0	3
Hemorrhage requiring transfusion	0	1

Table 2.

Postoperative complications.

	Conventional		Bidirectional barbed
	Number of cats	Percentage of complications	Number of cats	Percentage of complications
Short-term (< 2 weeks)	6/11	55%	12/15	80%
Long-term (> 2 weeks)	4/11	36%	7/15	47%
Hemorrhage requiring transfusion	0/11	0%	1/15	7%
Urethral stricture/reobstruction	1/11	9%	0/15	0%

Minor complications identified between the immediate postoperative period and the 1-year follow-up included recurrent urinary tract infections confirmed via urine cultures (n = 2), suture migration (n = 1), recurrent FLUTD signs (n = 5), and excessive licking of the surgical site (10). Major complications between the immediate post-operative period and at the 1-year follow-up included stricture with secondary obstruction (n = 1) (Tables 2, 3). The cat with a stricture was evaluated 5 mo after surgery for excessive licking and recurrent FLUTD signs. This cat was diagnosed with a urinary tract infection on urinalysis (culture declined). One month after treatment for the urinary tract infection, the cat was presented again for recurrence of FLUTD signs. A stricture was diagnosed, and revision surgery was recommended; however, euthanasia was elected. The long-term complication rate in the bidirectional barbed group was 47% (7/15; 95% CI: 21 to 73%) compared to 36% (4/11; 95% CI: 11 to 69%) in the conventional group (P = 0.60; odds ratio: 1.5; 95% CI: 0.3 to 8). The difference in long-term complication rates (bidirectional barbed versus conventional) was 10% (95% CI: −28 to 48%).

Table 3.

Number of cats with long-term complications.

Complications	Conventional	Bidirectional barbed
Urinary tract infection	2	0
Suture migration	0	1
Recurrent FLUTD signs	2	3
Excessive licking	4	6
Stricture	1	0

Discussion

The results of this study suggest that closure of feline perineal urethrostomies using bidirectional barbed absorbable suture material reveal no statistically significant increases in complication rates compared with using conventional absorbable monofilament suture material. The use of bidirectional barbed absorbable suture material, therefore, can be considered an appropriate closure material for PU surgeries. The complication rates, both short-term and long-term, for the bidirectional barbed suture group in this retrospective evaluation of cats with mucocutaneous closure were comparable to those of conventional absorbable suture. The potential for the presence of minor increases in complication rates amongst the bidirectional barbed suture group may be identified in larger studies with greater power. The overall results of this study were uncertain as evidenced by the large 95% CI. Variables were minimized by conducting all surgeries by the same Board-certified veterinary surgeon in one hospital. All surgeries were carried out at a newly established specialty hospital; this attributed to the small case numbers presented. The findings of this study resulted in similar long-term complication rates but considerably higher short-term complication rates when compared to previous studies. Short-term complication rates of 20 to 25% and long-term complication rates of 28 to 57% have been previously reported (2,8,9,18–23). This is in contrast to the short-term complication rate of 55% for the conventional group and 80% for the bidirectional barbed group, and the long-term complication rate of 36% for the conventional group and 47% for the bidirectional barbed group reported in this study. Previous studies report dysuria and incisional inflammation but not hemorrhage, excessive licking of the surgery site, and stranguria (17). Inclusion of post-operative hemorrhage, excessive licking of the surgery site, and stranguria as short-term minor complications may be the cause of this disparity.

One cat in the bidirectional barbed suture group had excessive postoperative hemorrhage requiring a packed red blood cell transfusion. Excessive bleeding may occur from the ischiocavernosus muscle transection or accidental laceration to deeper vessels. Hemorrhage from these structures should be identified and rectified before mucocutaneous closure. The authors consider this cat’s complication potentially related to the horizontal suture pattern used in this study compared with a vertical simple continuous suture pattern. Consideration of a simple continuous vertical suture pattern in the future is recommended as this may assist with improved blood vessel tamponade. Another potential cause of excessive hemorrhage requiring transfusion may be the use of reverse cutting PS-2 needles present on the bidirectional barbed absorbable suture as opposed to a tapered SH needle of the conventional monofilament 4-0 poliglecaprone 25 as no excessive hemorrhage from either the ischiocavernosus muscle or surrounding area was noted prior to mucocutaneous closure (13,17).

The absorbable suture material poliglecaprone, a copolymer of epsilon-caprolactone and glycolide, was used in both groups. Each has similar degradation and absorption periods. This absorbable material is rapidly degraded via hydrolysis. After 14 d, the suture material loses approximately 2/3 of its tensile strength and is completely absorbed by 120 d (13,17). A 1-year follow-up period was chosen to ensure complete absorption of suture material along with ample time for the possible development of complications related to the surgical procedure. A 3-0 sized bidirectional barbed suture has an outer diameter of 3-0; however, with consideration of the barbs, the suture is similar to a 4-0 diameter conventional suture (13,14). A 4-0 sized conventional monofilament was chosen for comparison with the 3-0 sized bidirectional barbed suture for this reason. Overall surgical times were comparable with a statistically insignificant decrease in time for the novel approach closing with bidirectional barbed suture material. Decreases in surgical times may be achieved with further experience using the bidirectional barbed suture material. Start to finish surgical times were recorded in the medical record in each case included in this study. Mucocutaneous suture closure time was not documented. Further studies evaluating the mucocutaneous closure times in relation to the suture material used are warranted to delineate the protentional for decreases in duration of surgical time.

Urinary tract infection may be related to early suture degradation and incisional dehiscence with use of poliglecaprone suture for closure of PU surgeries (17). Poliglecaprone has rapid degradation when continuously immersed in urine; this may also lead to incisional dehiscence when used for PU surgeries (24,25). All cats herein with urinary tract infections diagnosed at the time of presentation to the hospital by the emergency department (6/26 cats) recovered from surgery with only minor complications. None of the cats with urinary tract infections developed dehiscence or stricture. Two of 26 (7.7%) cats were diagnosed with urinary tract infections during the long-term period. One cat which was initially diagnosed with an Escherichia coli infection after surgery was brought to the clinic for recurrent urinary tract signs 9 mo after PU surgery. A methicillin-resistant Staphylococcus urinary tract infection was diagnosed and treated with complete resolution. No further complications were noted in this cat. The other cat had a urinary tract infection diagnosed on urinalysis (culture declined by owner) 5 mo after surgery. This cat was initially urinary culture negative at the hospital before surgery. One month after treatment for a urinary tract infection, the cat was again evaluated for licking and recurrent FLUTD signs. A stricture was diagnosed, and euthanasia was elected. The cause of stricture formation is unknown; however, the urinary tract infection in this case may have been a contributing factor. Urinary tract infection alone is considered less likely the cause in the presence of self-mutilation.

In the study by Frem et al (17), only 2/61 cats had incisional dehiscence and both cats were noted to have self-trauma. Other studies have also shown self-mutilation as a complication after PU surgery and may be a cause of urethral dehiscence and/or stricture formation (17). Excessive licking to the point of self-trauma (self-mutilation) after surgery was recorded in this study as a complication to monitor for potential causes of dehiscence and stricture. In the authors’ experience, use of bidirectional barbed suture material in cutaneous closures for abdominal and stifle incisions has the potential for suture migration. To the authors’ knowledge, cutaneous barbed suture migration has not been previously documented as a complication in the postoperative period for cats. Human patients with suture migration were noted to have marked pain requiring suture removal (18). Clinically, cats with cutaneous barbed suture migration may experience similar irritation and/or pain which may lead to excessive licking. No cats in either group of this study were noted to have incisional dehiscence. Only 1 cat (1/26 cats, 3.8%) was noted to form a stricture in the long-term. This cat, in the conventional absorbable monofilament group, was also noted to have excessive licking at the time of and following treatment for a urinary tract infection. It is difficult to attribute the stricture in this cat solely to the self-mutilation; however, it may be considered a contributing factor. This finding is similar to previously reported rates of stricture formation ranging from 0 to 18.1% of cases after PU surgery (2,8,17,22). No cats in the present study had urethral catheters placed after surgery. This was based on surgeon preference as this has been suggested as a potential cause for stricture formation and ascending urinary tract infection (17,23).

Limitations of this study include the small sample size, comparison of bidirectional barbed horizontal suture pattern to a simple interrupted suture pattern, comparison of a tapered needle with a reverse cutting needle, the retrospective nature, and reliance on long-term follow-up via owner questionnaire and referring veterinarian records. The overall results of this study may be inconclusive as type II error is likely. Further studies with larger inclusion groups are recommended for evaluation of the bidirectional barbed absorbable suture. Consideration of use of a taper needle instead of the reverse cutting needle is recommended along with use of a simple continuous suture pattern for both groups.

In conclusion, the use of bidirectional barbed absorbable suture for closure of feline perineal urethrostomies may be an acceptable and viable alternative to the use of conventional suture material; however, further studies are required to elucidate the significant benefits and complications. The bidirectional barbed suture did not prove to significantly decrease surgical time; this did not support our original hypothesis. Postoperative complications of the conventional monofilament to bidirectional barbed suture, both short- and long-term, within this study are comparable, which supports our original hypothesis.