The Use of a Low-Profile Cystostomy Tube to Relieve Urethral Obstruction in a Dog

Case Report

A 10-year-old, spayed female Dalmatian was presented to the Louisiana State University Veterinary Teaching Hospital (LSU-VTH) for evaluation of urethral obstruction. Prior to referral, a cystic calculus, which was not submitted for analysis, had been removed during an exploratory laparotomy. During surgery a thickened bladder wall was identified, and a urinary catheter was unable to be passed from the bladder into the urethra; however, a Foley balloon catheter was able to be placed from the urethra into the bladder and was maintained for approximately 12 hours until the dog removed it. At this time, the urinary catheter was unable to be replaced, stranguria was present, and the case was referred.

Physical examination performed at the LSU-VTH suggested mild dehydration based on mucous membrane examination and skin turgor. Rectal palpation revealed a thickened and firm urethra. Based on the signalment and clinical findings in this case, the differential diagnoses considered included urethral transitional cell carcinoma and granulomatous urethritis.

Initial diagnostic evaluation included a complete blood count (CBC), serum biochemical profile, urinalysis, and abdominal radiographs. The laboratory data and radiographs revealed no significant abnormalities. In order to investigate the lower urinary tract of this dog, urethroscopy was performed.

The dog was anesthetized, and urethroscopy with a 14.5-French (F) cystoscope^a revealed a nodular, external urethral meatus with erosive epithelial lesions. Small, hyperplastic nodules were observed in the distal urethra, and in the midurethra the epithelium appeared to not be contiguous and larger mucosal polyps were observed. Under infusion pressure of 80 cm of water, the proximal urethra was not distensible. An opening for further advancement of the cystoscope beyond the midurethra was not discernible, and the proximal urethra and bladder could not be examined. Biopsies were collected for bacterial culture and sensitivity, fungal culture, cytopathology, and histopathology. A transurethral Foley catheter was able to be placed, and the dog was recovered from anesthesia.

The animal was hospitalized in the intensive care unit (ICU) and placed on intravenous fluids^b (60 mL/kg body weight q 24 hours) pending biopsy results. The cytopathology results were nondiagnostic, and the bacterial and fungal cultures were negative. Histopathology was consistent with granulomatous urethritis. Due to the small size of the biopsy sample and the possibility of missing the underlying disease, the dog was scheduled for exploratory laparotomy in order to evaluate the proximal urethra and possibly perform urethrostomy or prepubic cystostomy.

A ventral midline celiotomy was performed 48 hours later, and the proximal urethra and urinary bladder were exposed. The proximal urethra was examined and found to be thickened along its length. A cystotomy was performed, and a full-thickness bladder biopsy was taken. The proximal urethra was distended, and there was redundant mucosa at this site, which was biopsied through the cystotomy exposure. Due to the extensive involvement of the proximal and distal urethra, a urethrostomy was not possible. In order to maintain urine outflow until a definitive diagnosis could be made, a commercially available, silicone, low-profile gastrostomy tube^c was placed as a prepubic cystostomy tube [Figures 1, 2]. A low-profile gastrostomy tube was chosen in order to alleviate the awkwardness of a long tube, such as a Foley catheter, and decrease the possibility of inadvertent removal. The procedure used to place the tube was similar to that previously described,¹ where 3-0 absorbable monofilament suture material^d was used to place a purse-string suture through the serosal and muscular layers of the cranial ventral bladder wall, and a stab incision was made into the center of the purse-string. The cystostomy tube was passed through a paramedian stab incision in the ventral body wall and then into the bladder. Omentum was incorporated into the purse-string as it was gently tightened and tied. The bladder was sutured to the internal abdominal wall using 3-0 absorbable monofilament suture^d in a simple interrupted pattern. The abdominal wall was closed routinely. The tube was secured to the skin using 3-0 nonabsorbable monofilament^e suture in a simple interrupted pattern and was connected to a closed drainage system. The animal was recovered from anesthesia and was monitored for approximately 24 hours in the ICU and then discharged. Histopathology confirmed the diagnosis of granulomatous urethritis. The owners were instructed to keep the cystostomy site dry and clean and to empty the bladder three to four times daily using a 60-cc syringe and a fluid administration extension set.^f

The dog was rechecked 1 week later. During the recheck appointment, the tube was functional and well tolerated by the animal. At this time, the dog was discharged on prednisone (1.0 mg/kg body weight, per os [PO] q 12 hours) for treatment of granulomatous urethritis. A recheck appointment approximately 2 weeks later indicated the dog was doing well, and small amounts of urine were now passing through the urethra. Rectal palpation was performed, and the urethra was still thickened but was subjectively softer. Approximately 3 months following the original surgery, the dog removed the low-profile cystostomy tube and was returned to the LSU-VTH. At this time, a 12-F Foley balloon catheter could be placed via the prepubic cystostomy tube tract. A urinalysis performed at this time revealed the presence of white blood cells, red blood cells, and bacteria. Based on these findings, a bacterial cystitis was suspected and the animal was placed on antimicrobials. A strain of Escherichia coli was isolated from culture, which was sensitive to amoxicillin. Although more urine was able to be voided via the urethra, the owners still had to empty the bladder via the cystostomy tube, and stranguria was still present. Rectal palpation indicated a much less thickened urethra.

Due to the difficulty in chronically managing the cystostomy tube, the owners agreed to repeat the urethroscopy with the possibility of using a urethral balloon dilator on the now softer urethra. The dog was anesthetized, and urethroscopy was performed with a 14.5-F cystoscope. The proximal urethra no longer had a nodular erosive appearance. The urethra immediately proximal to the urethral opening appeared normal, but a stricture was encountered. A 10-cm urethral balloon dilator was passed through the urethral stricture and positioned so the balloon section spanned the anticipated location of the stricture. The balloon was inflated with saline to 180 psi (11 atm), and this pressure was maintained for 2 minutes. After urethral dilatation, the cystoscope was advanced into the urethra through the newly dilated stricture. A narrow, horizontal bridge of tissue divided the distal urethra, and the cystoscope could be advanced into the bladder by passage either over or under this division. This tissue was not affecting urethral patency and was therefore not disrupted. A 2- to 3-cm long region of scar tissue was observed in the distal urethra, and 6 to 7 cm of normal-appearing urethra was observed proximal to the scarred area. A loop of clear suture material was observed protruding into the lumen of the proximal urethra. Immediately following removal of the cystoscope, direct manual pressure on the bladder through the abdominal wall resulted in a strong flow of urine through the urethra. The dog was recovered from anesthesia in the ICU and voided urine through the urethra overnight. The dog was discharged from the hospital the following morning. At this time, the dog was still on prednisone (1.0 mg/kg body weight, PO q 12 hours), and the owners were instructed to taper the dose gradually over a 2-week period (1.0 mg/kg body weight, PO q 24 hours for 7 days, then every other day for 7 days). The dog continued to do well for approximately 8 months with no additional therapy. The dog was again evaluated by the referring veterinarian for stranguria, which continued to worsen over the next month, and was euthanized. Postmortem examination revealed severe granulomatous urethritis, and no etiological agent was identified by histopathology.

Discussion

Due to previous difficulty encountered in managing Foley catheters as prepubic cystostomy tubes, a low-profile gastrostomy tube was used in this case. This tube is easy to use, has a one-way valve, and lies flush with the skin margin, thereby decreasing the likelihood of inadvertent removal. It appeared to provide an excellent alternative to previously described cystostomy tubes. Potential complications associated with the use of this tube include mild urine leakage around the tube exit site immediately postoperatively, urinary tract infection, and one-way valve leakage requiring valve replacement.¹ The dog’s owners were able to empty the bladder three to four times daily using a fluid administration extension set and a 60-cc syringe.

Granulomatous urethritis is an uncommon cause of obstructive urethropathy in the dog.^3–5 It has been treated both medically with immunosuppressive agents³⁴ and surgically with urinary diversion.^3–5 Medical management was effective in 50% of the cases reported in one study.⁵ In this case, urinary diversion was used to palliate the dog while medical management was attempted. The use of urinary diversion using a permanent cystostomy tube has been reported for treatment of urethral transitional cell carcinoma.²⁶

Urethral dilatation has been described to treat urethral stricture and to facilitate passage of cystoscopes.⁷ In this case, a balloon dilator was used; other instruments include metal urethral sounds, nephrostomy tract fascial dilators, and the Otis urethrotome.⁷ Balloon dilators are advanced through the urethra in the deflated state and positioned so that the balloon spans the region to be dilated.⁷ The position of focal obstructions is best checked under fluoroscopy during inflation of the balloon or radiographically after the balloon is inflated.⁷ Fluoroscopy was not used in this case because the obstruction was along an extensive section of the urethra. There are several advantages in using balloons for dilatation. Balloon dilatation minimizes unnecessary trauma to the urethral mucosa, because the dilator is passed through the urethra deflated when the diameter is relatively small;⁷ thus, repeated scraping of oversized instruments against the urethral mucosa is avoided.⁷ The risk of perforation of urethral mucosa and development of a false tract are much less likely than with rigid instruments.⁷

The use of a low-profile gastrostomy tube has recently been described in two dogs and one cat for replacement of conventional cystostomy tubes.¹ Although this tube may be a more expensive alternative, it should be considered in cases where urethral involvement is extensive and when a prepubic cystostomy is indicated. This case is unique in that a low-profile gastrostomy tube was used as a prepubic cystostomy tube, and balloon dilatation was used to relieve stricture caused by granulomatous urethritis.