Lower urinary tract obstructions – a case-based approach

Introduction

This article can be read in conjunction with the paper by the same authors entitled “Practical tips and tricks for lower urinary tract obstruction” which reviews various minimally invasive techniques commonly used and accessible to veterinarians in general practice. This article presents five clinical cases in which these techniques were implemented to treat patients with lower urinary tract diseases, in particular urethral obstruction.

Case #1 

A one-year-old male neutered Highland Lynx cat 

This cat was referred to the authors’ hospital with dysuria, stranguria, pollakiuria and urinary incontinence. Two months prior to this he had presented at his local practice with recurrent lower urinary tract signs, followed by a urethral obstruction. Urethral catheterization was difficult, but he was successfully unblocked. He had then represented a few days later straining to urinate; physical examination revealed a distended bladder and suspected urethral obstruction, with severe azotemia on bloodwork. A perineal urethrostomy was performed without further diagnostics, but the dysuria returned again 3 weeks later, hence the referral.

Physical examination was unremarkable other than a large, firm urinary bladder and some urine soiling around the urethrostomy site. Urinalysis was also unremarkable, with a urine specific gravity of 1.041, urine pH of 6, and an inactive sediment. Abdominal radiographs and urinary ultrasound showed no abnormality. Given the pollakiuria, dysuria and hematuria, along with the previous history of perineal urethrostomy, initial differential diagnoses included urethral stone(s), sterile or bacterial cystitis, stricture, or (less likely) neoplasia; urethral spasm was also considered. The distended urinary bladder and the persistent pollakiuria/dysuria were consistent with a urethral outflow obstruction. A contrast cystourethrogram was recommended; and this was achieved (under general anesthetic) via a percutaneous antegrade technique, as a urinary catheter could not be passed retrograde (Figure 1). This imaging demonstrated a distal urethral stricture, confirmed to be at the site of the perineal urethrostomy, and additionally a distended pelvic urethra up to the site of the stricture. The stricture resulted in overflow incontinence and hence the dysuria and urine soiling, so revision surgery was successfully performed.

Figure 1. A positive contrast lateral urethrogram showing a well distended urethra with a distal stricture (white arrow) at the site of the previous perineal urethrostomy. Minimal abdominal extravasation of contrast following the percutaneous antegrade approach is noted (blue and red arrows). A marker catheter is placed in the colon. Note that a radio-opaque glove (on the left of the image) is used for voiding cystourethrograms. © Dr. C. Vachon/Dr. M. Dunn

Case #2 

A 6-year-old female spayed Shih Tzu 

This dog was presented for investigation of bladder stones. Three months prior to this she had been seen by her family veterinarian for hematuria, dysuria and pollakiuria, with urinalysis (cystocentesis) revealing significant hematuria and pyuria. Urine pH was 9, and a culture was positive for Staphylococcus spp. The patient was prescribed 10 days of amoxicillin. Upon recheck 2 months later, her urinalysis (again via cystocentesis) remained abnormal, with a pH of 9, 50 red blood cells/HPF, 3+ cocci and no white blood cells. Urine culture was positive for Staphylococcus pseudintermedius. Abdominal radiographs revealed numerous round-to-oval, slightly radiopaque stones in the bladder and urethra (Figure 2).

Figure 2. A lateral abdominal radiograph demonstrated slightly radiopaque bladder stones on initial presentation. © Dr. C. Vachon/Dr. M. Dunn

Based on signalment, the previous history of a positive urine culture with a urease-producing bacteria, high urine pH, the radiographic appearance of the stones, and the short course of antibiotics, struvite calculi were highly suspected. The patient was prescribed 4 weeks of antibiotics (based on the results of urine culture and sensitivity) and fed a urinary diet. The hematuria, pollakiuria and dysuria resolved within a few days of treatment, and the patient was clinically well at recheck 4 weeks later. Follow up radiographs showed that the bladder stones had reduced in size but remained visible (Figure 3). An additional 4 weeks of antibiotics was prescribed, and the urinary diet was continued.

Figure 3. A lateral abdominal radiograph showing mildly radiopaque bladder stones after 4 weeks of treatment with an antibiotic and dissolution diet. © Dr. C. Vachon/Dr. M. Dunn

A further check a month later noted that the patient was doing well; urinalysis was unremarkable, with a urine pH of 6 and an inactive sediment. The stones were no longer visible on radiography. However, ultrasound evaluation of the bladder revealed numerous small (< 1.2 mm) stones with ongoing mild to moderate thickening of the bladder wall (Figure 4). The owner was instructed to continue antibiotic therapy and diet for an additional 2 weeks, but on recheck the stones were unchanged on ultrasound. Urohydropulsion was performed and the remaining stones successfully expulsed. Mineral analysis revealed the stones to be composed of 100% silica.

Figure 4. At the time of ultrasound-guided cystocentesis, numerous very small bladder stones were noted, with ongoing mild to moderate thickening of the bladder wall. © Dr. C. Vachon/Dr. M. Dunn

This combined approach (i.e., medical dissolution and urohydropulsion) allowed minimally invasive removal of the bladder and urethral stones. The initial stones were composed of silica; interestingly, the owner performed regular toothbrushing on the dog with a silicate-based toothpaste, which may have predisposed it to silicate stones. The urinary tract infection with a urease-producing bacteria led to a struvite shell developing over the silicate nidus. The stepwise approach for this patient allowed for complete dissolution of the struvite portion of the stone and voiding of the remaining silicate stones. 

Case #3 

A 4-year-old male neutered domestic shorthair cat

This cat had no previous medical history but presented to the emergency service for pollakiuria and dysuria. Physical examination revealed a firm and distended urinary bladder, with an edematous and inflamed penis. Urethral obstruction was suspected, and a retrograde urinary catheter was passed and stitched in place for 48 hours. However, following removal of the urinary catheter the cat was pollakiuric, dysuric and unable to urinate. A second retrograde urethral catheterization was attempted unsuccessfully. Decompressive cystocentesis was performed and placement of a retrograde urinary catheter was again attempted; however, radiographs revealed that the urinary catheter had passed through the urethral wall (Figure 5). As urethral catheterization was now deemed essential, this was achieved by antegrade placement of an angled tip hydrophilic 0.018’’ (cat) guidewire passed through a 22G intravenous catheter inserted through the bladder apex and advanced until it exited the penile urethra. A 3Fr open-ended urethral catheter was then passed over the guidewire in a retrograde manner until positioned in the bladder lumen, and sutured in place. This was left in place for 5 days to allow healing of the urethral tear while ensuring bladder drainage. On day 5 a contrast cystourethrogram was performed to evaluate urethral patency (Figure 6). This confirmed a persistent urethral tear, with leakage of contrast from the mid-pelvic urethra into the caudal peritoneal space and pelvic canal. The catheter was therefore replaced via retrograde passage of a guidewire and left in place for an additional 10 days. At this point, with the catheter still in place, contrast cystourethrogram was repeated, revealing persistent contrast accumulation in the pelvic canal (Figure 6) but reduced in comparison to the previous exam. The urinary catheter was left in place for an additional 6 days, and repeat contrast cystourethrogram on day 21 (Figure 6) failed to show any leakage of contrast. The cat was discharged from the hospital and remains free of clinical signs at the time of writing, 14 months following initial presentation.

Figure. 5. A lateral abdominal radiograph showing evidence of a urethral tear following the unsuccessful catheterization. The catheter’s distal portion can be seen in the distal urethra (large arrow), but as it enters the abdomen it is superimposed on the colon, then courses ventrally, and can be seen to be overlying the bladder before progressing cranially into the ventral abdomen (small arrows). Air bubbles are noted in the urinary bladder, likely from previous urethral catheterization. © Dr. C. Vachon/Dr. M. Dunn

Figure. 6. Successive evaluations of the urethral tear via positive contrast urethrograms. Accumulation of contrast in the pelvic canal (arrows) is noted to decrease between the urethrograms performed on days 5 and 15. There is no evidence of contrast extravasation by day 21. © Dr. C. Vachon/Dr. M. Dunn

Case #4 

A 5-year-old female spayed Yorkshire Terrier 

This dog presented to the authors’ hospital after falling off and being rolled over by a golf kart. 48 hours after the accident the owners realized she had not urinated since the fall. Upon presentation, she was dehydrated (7%) with abdominal pain on palpation. Bloodwork revealed severe azotemia (urea: > 120 mg/dL (20 mmol/L or 42.8 mmol/L BUN), creatinine: 6.32 mg/dL (559 μmol/L)). An abdominal ultrasound revealed moderate abdominal effusion which was confirmed to be urine (potassium, urea and creatinine levels were all higher in the effusion than the blood) and cytology revealed septic inflammation. A retrograde urinary catheter was placed and sutured in place; the bladder was then filled with saline and on ultrasound the abdominal effusion was noted to progress. Uroabdomen secondary to bladder rupture was suspected, however a tear of the proximal urethra could not be ruled out. Three options were considered for this patient: 

1. a minimally invasive option, with placement of a percutaneous abdominal drain and urethral catheterization to stabilize the patient. If improvement was noted clinically, the urinary catheter would be left in place for a minimum of 3-5 days to allow the bladder and/or proximal urethra to heal;
2. cystourethrography to document the location of the rupture and potential surgical bladder/urethral repair; or 
3. surgical exploration. 

The minimally invasive option was chosen and the patient’s blood abnormalities improved. On day 6, while removing the urinary catheter, a “pull-out” contrast cystourethrogram was performed (Figure 7) and no extravasation of contrast was noted (In order to prevent creating further damage to a suspected recently healed bladder/urethra, the bladder was only moderately filled, and a voiding phase was not performed). The dog was discharged from the hospital and remains free of clinical signs at the time of writing (2 years later).

Figure 7. A “pull out” contrast cystourethrogram following treatment for the traumatic uroabdomen. There is no evidence of contrast extravasation from the bladder or proximal third of the urethra. The urinary catheter tip is positioned in the mid-urethra (arrows). © Dr. C. Vachon/Dr. M. Dunn

Case #5 

An 11-month-old male neutered Manx cat 

This cat was referred to the authors’ hospital for investigation of urinary incontinence, which had been noted since adoption at the age of 4 months. The incontinence was present throughout the day (walking, resting, sleeping), but the cat also urinated normally and did not present with pollakiuria, dysuria, stranguria or hematuria. Numerous treatments had been administered (prazosin, meloxicam, gabapentin, buprenorphine, urinary diet) with no improvement, although at each clinic visit he was noted to have a large and firm bladder, and manual voiding was partially successful, with a markedly decreased urine stream.

Initial investigations on referral included complete bloodwork and urinalysis, all of which were unremarkable. Abdominal ultrasound revealed a large urinary bladder. Based on the history (no pollakiuria/dysuria), physical examination (large bladder, difficultly voiding, decreased urine stream), unremarkable urinalysis (no hematuria/pyuria) and ultrasound (except for the large bladder), an infectious, inflammatory or neoplastic process was considered unlikely. The primary suspicion was therefore an outflow obstruction secondary to a congenital stricture and/or a sacral malformation.

Abdominal radiographs revealed a large bladder and anomalies compatible with sacrocaudal dysgenesis (1). Manx cats with a congenital sacral malformation will typically present with a urinary bladder that is easy to express, and concurrent fecal incontinence. In order to further investigate the primary cause for the urinary incontinence, a neurologic examination, a contrast cystourethrography and an MRI were recommended (with the latter declined by the owner). In the absence of fecal incontinence and the presence of good bladder tone and the difficulty in manually emptying the bladder, a sacral malformation was deemed less likely, and a contrast cystourethrogram (Figure 8) revealed a pelvic urethral stricture. This was suspected to be congenital in origin, since clinical signs had been present since adoption and there was no history of previous urethral catheterization or pelvic trauma. Treatment options included serial ballooning of the stricture under fluoroscopic guidance and/or urethral stent placement, but both options were declined. 

Figure. 8. Ventrodorsal (a) and lateral (b) contrast cystourethrography studies showing an enlarged proximal urethra (small arrow) cranial to a pelvic urethral stricture (large arrow). On both images iatrogenic urethral kinking is visible during manual voiding of the bladder. © Dr. C. Vachon/Dr. M. Dunn

Conclusion

Minimally invasive interventional procedures are the new standard of care in veterinary medicine. They can be performed in general practice with the aid of various imaging modalities (plain or contrast radiographs and ultrasound) and minimal equipment. These procedures help both in the diagnosis and management of many cases with lower urinary disease and obstruction. For further understanding of the usefulness of these techniques, the reader is directed to the associated article entitled ‘’Practical tips and tricks for lower urinary tract obstruction‘’.

References

1. Westworth DR, Sturges BK. Congenital spinal malformation in small animals. Vet Clin North Am. 2010;40(5):951-981.
2. Butty E, Vachon C, Dunn M. Interventional therapies of the urinary tract. Clin. North Am. Small Anim. Pract. 2019;49(2):287-309.