Spontaneous Urethral Catheter Kinking or Knotting in Male Dogs: Four Cases
Four dogs were diagnosed with urethral catheter malfunction. The catheter was kinked in three dogs and knotted in one dog. In two dogs, kinking of the catheter was associated with presence of urethroliths in the perineal urethra. Diagnosis was based on the difficulty encountered retrieving the catheter in all dogs and swelling in the scrotal or perineal area in two dogs. Diagnosis of catheter kinking or knotting was confirmed after catheter retrieval. Catheter removal was achieved in two dogs after traction under anesthesia, whereas scrotal or perineal urethrotomy were used in the other two dogs. No complications associated with urination were reported in any of the dogs after 7 to 12 mo.
Introduction
Urethral catheterization is a frequently used technique in small animal practice. Intermittent catheterization is indicated for obtaining urine samples, relieving urethral obstruction, and performing radiographic contrast studies of the bladder and/or urethra. Indwelling catheter placement is indicated for urine production monitoring in critically ill patients, relieving urinary retention, bypassing urethral trauma, or preventing urine scalding in neurologically impaired animals.1–3 The most common complications associated with catheterization include urethral or bladder trauma, hematuria, ascending infections, and urethral stenosis.3,4 Spontaneous catheter knotting or kinking is not a commonly reported complication in human patients.5–7 Catheter kinking and knotting is briefly included in veterinary clinical textbooks.2,3,8 To the authors' knowledge, there was only one case in veterinary literature reporting catheter kinking in a dog.9 The purpose of this case series was to report the clinical signs, diagnosis, treatment, and outcomes of four male dogs that were admitted with catheter kinking or knotting after urethral catheterization.
Case Report
The medical records of dogs that were diagnosed with urethral catheter kinking or knotting in the Department of Clinical Sciences, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece and in VCA Veterinary Specialists of Northern Colorado, Loveland, Colorado, between 2001 and 2009 were reviewed. Four dogs were identified and are described herein.
Case 1
A 5 yr old, intact male Yorkshire terrier weighing 5.5 kg was presented after being hit by a car the day before with a history of depression and nonambulation associated with a fractured scapula and presumed thoracolumbar spinal cord trauma. Complete blood count and serum biochemical analysis were within normal limits.
The dog was hospitalized in the critical care unit and received Ringer's lactated solution IV (70 ml/kg q 24 hr) and prednisolone (0.5 mg/kg q 24 hr) along with morphine (0.5 mg/kg 3 times/day intramuscularly [IM]) for analgesic purposes because of suspected spinal cord injury; an 8 French and 50 cm long indwelling polyethylene urethral cathetera was inserted half of its length to the bladder for urine production monitoring and urine scald prevention. Difficulty was encountered during catheter advancement at the level of the ischial arch. Because of the small size of the patient, urine production was just a few milliliters per hour. Two days after admission excess, urine leakage around the catheter was noticed, whereas the urine bag remained empty. Catheter failure was suspected, and an attempt to remove the catheter with gentle traction was made 3 days after admission after acepromazine (0.05 mg/kg IM) and morphine (0.5 mg/kg IM) administration, but removal was unsuccessful. Palpation of the perineal area just caudal to the scrotum revealed bulging under the skin. Catheter kinking was suspected, but plain abdominal radiography failed to define the cause of the bulge. An attempt to perform retrograde urethrography was unsuccessful because infusion of the contrast media through the catheter met with resistance. A skin incision was made over the swelling, and the urethra was incised through the ventral midline, revealing double kinking of the catheter in an “N” shape just ventral to the ischial arch (Figure 1). The kinked part of the catheter was cut and the rest of the catheter removed in retrograde fashion through the urethral orifice. The urethrotomy was closed with simple interrupted sutures of 4/0 glycolide, ɛ-caprolacton, and trimethylene carbonate suture (Monosyn)b and the subcutaneous tissue and skin were closed with 3/0 Monosyn and polyamidec sutures, respectively, in a continuous pattern. Three days after surgery, although some hind limb function and ambulation was gained, the dog had the fractured scapula surgically stabilized. The dog recovered uneventfully from the two surgeries and was discharged from the hospital 10 days after admission. Telephone communication with the owner 7 mo after surgery revealed that the dog was doing well with no difficulty urinating.
Citation: Journal of the American Animal Hospital Association 47, 5; 10.5326/JAAHA-MS-5672
Case 2
A 1.5 mo old intact male Caucasian mountain dog weighing 5 kg was referred for further investigation and treatment of septic peritonitis after having an intestinal resection and anastomosis performed for the management of an intussusception. On abdominal exploration, dehiscence was identified at the anastomosis side, and a new resection and end-to-end anastomosis were performed followed by copious peritoneal lavage. The abdomen was managed open for peritoneal drainage. The dog received cefuroxime (20 mg/kg twice daily IV) and butorphanole (0.1 mg/kg q 4 hr IM) and recovered in the critical care unit. During hospitalization a flexible 6 French and 48 cm long polyvinyl chloride indwelling tubed was placed in the urethra for urine production monitoring and to prevent bandage soiling. The catheter was inserted with most of its length placed within the bladder. The animal recovered uneventfully from anesthesia and improved gradually. Seven days after surgery, gentle traction was applied to the catheter for withdrawal, but resistance was encountered and, in every attempt, the animal showed signs of pain. Under general anesthesia with isoflurane in oxygen, careful and gentle traction was applied and the catheter was removed. A simple knot was evident 3 cm from the tip of the catheter (Figure 2). The abdomen was closed 8 days after the initial surgery in three layers using 2/0 polydioxanonee for abdominal wall, 3/0 polydioxanone for subcutaneous tissue, and 3/0 polyamide suture for skin closure, all in a continuous pattern. The dog was discharged from the hospital 14 days after the initial surgery. Nine months later after telephone communication with the owner, the dog was reported to be in good health, having no difficulty urinating.
Citation: Journal of the American Animal Hospital Association 47, 5; 10.5326/JAAHA-MS-5672
Case 3
A 6 mo old intact male shih tzu weighing 6.4 kg was referred for further examination and treatment of a portosystemic shunt and ammonium biurate urolithiasis in the bladder diagnosed with ultrasound. A portoazygous shunt was detected on abdominal exploration and a 3.5 mm ameroid constrictor was placed around the shunt. Multiple 2–4 mm uroliths were removed from the bladder through a ventral cystotomy incision. Several attempts to pass a 3.5 French and 40 cm long polyvinyl chloride flexible red catheterf in retrograde fashion during surgery were unsuccessful because of a urethral obstruction. Catheter removal was attempted but was not possible. A firm swelling was detected in the urethra just caudal to the scrotum under the skin; catheter kinking was suspected. After a bilateral orchidectomy was performed, a urethrotomy was made over the swelling, and several urethroliths were revealed. The distal end of the catheter was folded and kinked over the stones (Figure 3). The stones and catheter were removed, and the urethra was flushed anterograde and retrograde several times with normal saline to ensure patency. The cranial and caudal aspects of the skin incision were sutured with 3/0 polyamideg in a simple interrupted pattern, leaving a 0.5 cm opening in the center to heal by second intention.10 The cystotomy incision was closed in two layers with a continuous Cushing pattern using 4/0 polydioxanone suture material. Abdominal incision was closed in three layers; 2/0 polydioxanone for abdominal wall, 3/0 polydioxanone for subcutaneous tissue, and 3/0 polyamide sutureg for skin closure, all in a continuous pattern. The animal recovered well from anesthesia and had hematuria for 3 days. The dog was discharged from the hospital 3 days after surgery. The dog was given meloxicam (0.2 mg/kg q 24 hr per os) for 4 days. Amoxicillin- clavulanate (12.5 mg/kg twice daily per os) was administered for 7 days and a special liver diet was provided for 1 mo for the treatment of hepatoencephalopathy. One year after surgery after communication with the owner and referring veterinarian, the dog was reported to be well, the urethrotomy incision healed uneventfully, and no urethral stricture or dysuria were noted.
Citation: Journal of the American Animal Hospital Association 47, 5; 10.5326/JAAHA-MS-5672
Case 4
A 5.5 yr old intact male French bulldog weighing 16.5 kg was referred for dysuria, stranguria, and hematuria after having a perineal urethrostomy performed in a different facility 4 mo previously for the management of calcium oxalate urolithiasis. On presentation, a urethrolith was detected at the perineal urethrostomy site. Radiographic examination revealed urethroliths in the perineal urethra and several cystic calculi. Complete blood count and serum biochemistry were within normal limits. The dog received dexmedetomidine (5 μg/kg IM) and butorphanole (0.2 mg/kg IM), and an attempt was made to establish urethral patency by passing an 8 French and 50 cm long polyethylene urethral cathetera through the urethrostomy site; flushing the stones back into the bladder resulted in catheter entrapment. More than half of the catheter's length was passed through the urethrostomy. Attempts to remove the catheter were unsuccessful. The dog was anesthetized with isoflurane in oxygen and gentle traction on the catheter resulted in its dislodgment, revealing a kink 6 cm away from the tip of the catheter (Figure 4). A ventral cystotomy was performed through a ventral midline celiotomy and all of the stones from the urethra and bladder were removed. The cystotomy incision was closed in two layers using 4/0 polydioxanone suture in a continuous Cushing pattern. The celiotomy had a three layer closure: 2/0 polydioxanone for abdominal wall, 3/0 Monosyn for subcutaneous tissue, and 3/0 polyamide sutureg for skin closure, all in a continuous pattern. The dog recovered uneventfully from anesthesia and had hematuria for 3 days. The dog received carprofen (4 mg/kg q 24 hr per os) for 4 days and cefalexin (15 mg/kg 3 times/day per os) for a presumed urinary tract infection. It was discharged from the hospital 4 days after surgery. One year after surgery, the dog had no difficulty urinating.
Citation: Journal of the American Animal Hospital Association 47, 5; 10.5326/JAAHA-MS-5672
Discussion
Knotted soft urethral catheters can cause considerable morbidity in human patients; however, there is a paucity of information concerning the true incidence and morbidity of this complication in small animal patients.7,11 The mechanism of urethral catheter spontaneous knot formation was recently elucidated in humans, and risk factors were identified, including catheter size <10 French, bladder overdistention, and placement of >10 cm of catheter length inside the bladder.7 Catheter insertion into an overdistended bladder might produce a low-pressure zone around the catheter tip, resulting in a hydrodynamic imbalance and formation of a water current. Under the influence of the water current, excessive catheter length within the bladder might result in catheter coiling, forming an open-loop knot that could become a true knot when the distal end of the catheter passes through it. When the catheter is withdrawn, the loose knot that forms might tighten.7,11 Kinking is another less common complication associated with catheter placement, and very little has been published in both humans and animals.5,8,9 Inserting an excessive length of a catheter into the bladder might follow the bladder curvature, making a complete loop with the tip directed back toward the urethra. When pulled, the catheter loop could become smaller to a point where the catheter kinks, usually at a hole.8,9 In the three cases reported here, catheter kinking occurred, reflecting a possibly different mechanism. In one dog, possible forceful catheter insertion through the urethra at the ischial arch, where difficulty was encountered, resulted in catheter kinking in two sites. In the two other dogs, urethroliths blocking the urethra resulted in catheter bending and, ultimately, kinking.
It was reported that catheter kinking occurred at side holes that were weak points; however, in the cases reported here all kinks occurred at other locations.8,9 Although knotting might be seen in soft catheters, kinking might occur with both soft and hard catheters, as shown in this case series. The diagnosis of catheter kinking or knotting might be based on the difficulty encountered in catheter removal, and confirmation of diagnosis was made on radiographic or ultrasonographic examination of the abdomen and perineal area.7,9,12–14 Radiographic signs of kinking depended on the severity of catheter bending and the beam angle relative to the bend plane; however, the presence of these signs might be necessary but not sufficient to establish the diagnosis of catheter malfunction.5 In this study, diagnosis of catheter malfunction was based on physical examination in all the dogs, and confirmation was made after carefully retrieving the catheter in two dogs or by surgical exploration of the urethra in the other two dogs. Radiography was used in only one of four dogs and was not helpful. The catheters of two dogs (cases 1 and 4) were made of radiolucent material, and, in one, any attempt to visualize the double kinked catheter by infusing contrast medium was unsuccessful, possibly because of the excessive resistance met during infusion.5 Several techniques were described for retrieval of knotted catheters in humans. These included sustained traction under general anesthesia, untangling the knot using a guidewire, endoscopic retrieval, and open cystotomy.6,7,11–17 The general anesthesia that was administered in cases 2 and 4 might have allowed urethral relaxation and dilation, permitting catheter withdrawal with traction. In the other two dogs, an exploratory urethrotomy established the diagnosis. In one of the dogs of this report (case 1), the small volume of urine produced associated with the small size of the patient might have contributed in a 24 hr delay for confirming a diagnosis of catheter failure, which resulted in a delayed attempt to remove the catheter. Traction on kinked urethral catheters might be achieved in dogs under anesthesia by infusing sterile saline or a viscous solution through the catheter, resulting in urethral dilation.8,9 The cause of kinking in one dog was associated with urethroliths. Urethrotomy allowed removal of the kinked catheters in both dogs; however, sustained traction might have resulted in serious damage to the urethral wall in these two dogs. The authors recommend that traction on the urethral catheters be applied with caution and performed under general anesthesia.
Conclusion
Catheter kinking and knotting are uncommon complications of urinary catheter placement in dogs. They might result from inserting an excessive length of the catheter in the bladder. Kinking might be caused by the presence of stones in the urethral lumen. Catheter kinking or knotting might be suggested if the catheter does not come out easily and if there is a palpable swelling along the perineal or scrotal urethra. Gentle and careful traction under general anesthesia or urethrotomy allowed for catheter removal with no long-term complications in all cases.
Intraoperative appearance of a polyethylene urethral catheter kinked in the form of an N (black lines superimposed over catheter) in a 5 yr old male Yorkshire terrier viewed through a perineal urethrotomy (case 1).
Photograph of a knotted polyvinyl chloride urethral catheter after removal from a 1.5 mo old male Caucasian mountain dog (case 2).
Intraoperative view of a folded and kinked polyvinyl chloride catheter in a 6 mo old male shih tzu as viewed through a scrotal urethrotomy incision (case 3).
Photograph of a polyethylene urethral catheter kinked 6 cm away from its tip after withdrawal from a 5.5 yr old male French bulldog (case 4).
Contributor Notes
