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Dogs
Urethral defect with suspected corpus spongiosum herniation as a cause of stranguria and urethral haemorrhage in a dog
  1. Mark Newman,
  2. Natashia Evans,
  3. Juan Podadera,
  4. Niek Beijerink and
  5. Katja Voss
  1. University Veterinary Teaching Hospital—Sydney, University of Sydney, Sydney, New South Wales, Australia
  1. Correspondence to Dr Mark Newman, mark.newman{at}sydney.edu.au

Abstract

A male neutered Staffordshire bull terrier presented for evaluation of urethral haemorrhage of three days duration. A urethral mass was identified on contrast radiography, ultrasonography and urethroscopy. An open excisional biopsy was performed and the mass appeared to arise from the vascular tissue beneath the urethral wall. Histopathology revealed evidence of ulceration and granulation; coupled with the clinical findings the mass appeared to be a herniation of corpus spongiosum through a defect in the urethral mucosa. Removal and closure of the urethral defect, along with postoperative propranolol, effected a clinical resolution. To the author's knowledge, a urethral mucosal defect as a cause of urethral haemorrhage has not been previously described in the dog.

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Background

Urethral haemorrhage in the dog is most often associated with prostatic disease, urolithiasis, foreign bodies, urethral trauma and neoplasia (Baldwin 2009). Non-neoplastic masses causing urethral haemorrhage are poorly described in the dog. In a case description of transpelvic urethrostomy in a dog, a ruptured vascular structure was found to be responsible for urethral haemorrhage; similar lesions have also been seen in male horses (Schumaker and others 1995, Liehmann and others 2010).

Urethral masses in dogs are most often neoplastic, and include transitional cell carcinoma, adenocarcinoma, squamous cell carcinoma, undifferentiated carcinoma, adenoma and chondrosarcoma (Norris and others 1992, Davis and others 2003). The majority of neoplastic masses are malignant; in a study of 115 dogs with bladder and urethral neoplasia, all urethral neoplasms were malignant (Norris and others 1992). Other potential causes of mass-like lesions within the canine urethra include urolithiasis, urethral stricture, foreign bodies and granulomatous (proliferative) urethritis.

This report describes the clinical history, diagnosis and treatment of an unusual cause of urethral bleeding in a dog.

Case presentation

A six-year-old male neutered Staffordshire bull terrier (37.8 kg) presented with a two weeks history of stranguria. Relevant history included an episode of urolithiasis of uncertain aetiology two years previously. A moderate-sized bladder was palpable and rectal examination revealed a normal prostate. The remainder of physical examination was unremarkable.

Investigations

Urinalysis, sediment examination, and culture and sensitivity were unremarkable. Abdominal ultrasonography revealed no significant abnormalities, and no uroliths were identified. A presumptive diagnosis of reflex dyssynergia was reached. Treatment was started with phenoxybenzamine (10 mg orally twice daily) (Dibenyline, Smith Kline Beecham) and diazepam (5 mg orally three times daily) (Valium, GlaxoSmithKline). Some improvement was noted, however the dog remained intermittently stranguric.

One month later the dog represented with a three-day history of urethral bleeding. Frank, clotted blood was noted dripping from the prepuce. A complete blood count, biochemistry and coagulation profile were unremarkable. Following sedation, an 8 Fr Foley urethral catheter was placed without difficulty. A retrograde contrast urethrogram was performed with iohexol (Omnipaque, GE Healthcare), and a persistent urethral filling defect was observed 20 cm into the urethra (Fig 1). The defect was approximately 0.2 cm long and smoothly demarcated. On urethral ultrasound, a 0.53 cm×0.2 cm mass was identified at the level of the proximal region of the pars spongiosa (Fig 2). The mass appeared to be contained within the urethral wall without evidence of extension to the surrounding soft tissues. The proximal bulbourethralis muscle appeared normal in size, shape and echotexture.

FIG 1:

Lateral retrograde positive contrast urethrocystogram showing a 2.5 cm long filling defect in the proximal urethra, immediately caudal to the ischial arch (arrow)

FIG 2:

Urethral ultrasound demonstrating the urethral mass (arrow) within the urethral lumen (*). The urethral lumen has been dilated with saline

Differential diagnosis

The primary differential diagnoses at this point included neoplasia (transitional cell carcinoma), polyp and blood clot. Diagnostic traumatic catheterisation was performed with a rigid 8 Fr urinary catheter, and cytology was collected and submitted for analysis. Cytology revealed numerous rounded and angular, small to medium sized, transitional/squamous epithelial cells. There was no evidence of neoplasia or infection.

Treatment

Urethroscopy was performed with a 3.0 mm flexible cystoscope (Specialty Fibrescope, Storz) and a smooth, broad-based mass was visualised at the location identified on urethrography. Urethroscopic biopsy of the mass was not attempted due to the small size and the risk of haemorrhage. Open excisional biopsy was recommended, with a view to either urethral stenting or penile amputation/urethrostomy if malignant.

The dog was positioned in the Trendelenburg position with the hindlegs abducted and drawn cranially. A sterile 10 Fr rigid urinary catheter was passed to the level of the obstruction. A 5 cm incision was made over the perineal urethra, midway between the anus and scrotum. The subcutaneous tissues were bluntly dissected, and the retractor penis and bulbospongiosus muscles were separated. A 3 cm urethrotomy was made over the urinary catheter. A 3 mm pink, fleshy, spherical mass was visualised on the far (dorsal) wall of the urethra (Fig 3). The mass appeared to protrude through the mucosa and was attached to, and easily reducible into, the corpus spongiosum beneath the urethral wall. A circumferential ligature of 5/0 polydioxanone (PDS II, Ethicon) was placed around the base of the mass, and it was excised and submitted for histopathology. The defect in the dorsal urethral mucosa was closed with a single horizontal mattress suture of 5/0 polydioxanone (PDS II, Ethicon). An 8 Fr Foley catheter was placed, and the ventral urethral wall was closed with 5/0 polydioxanone (PDS II, Ethicon) in a simple continuous pattern. The muscles overlying the urethra were reapposed using 5/0 polydioxanone (PDS II, Ethicon) in a simple continuous pattern. The subcutaneous tissue and skin were closed routinely.

FIG 3:

After urethrotomy a smooth bulging mass was visible behind the concave surface of the urethra. A defect with protrusion of presumably vascular tissue, attached to the underlying corpus spongiosum, was present in the centre of this mass (arrow). The protruded tissue was ligated, excised and submitted for histopathology. The edges of the defect were closed as described

Outcome and follow-up

Histopathology of the mass revealed a variable thickness of transitional epithelium, with some ulceration. Under the ulcerated area there was a moderate amount of haemorrhage, fibrin and cellular debris. The submucosa was of moderate cellularity with numerous large plump spindle cells interspersed with small capillaries and some areas of haemorrhage. These changes were consistent with acute urethral ulceration with submucosal haemorrhage and granulation, with no evidence of an underlying neoplastic cause.

The Foley catheter was left in place for 48 hours following surgery. Following removal of the catheter, the patient was able to produce only drops of urine or a thin stream at best. Meloxicam (0.1 mg/kg orally once a day) (Metacam, Boehringer Ingelheim) and prazosin (2 mg orally three times a day) (Minipress, Pfizer) were commenced, and the Foley catheter replaced. The Foley catheter was removed three days later, and normal urination was observed. No stranguria or urethral bleeding was observed prior to discharge from hospital seven days following surgery. The dog returned for removal of the skin sutures 14 days postoperatively; the owners reported no complications at home and no bleeding from the urethral orifice had been seen. Physical examination was unremarkable, and the wound had healed uneventfully. At six weeks postoperatively the owners reported that the dog was having occasional episodes of urethral bleeding occurring with excitation. Propranolol was prescribed at 10 mg orally twice a day in an attempt to reduce penile blood flow. This was continued for three months, and the dose was reduced to 10 mg once a day. At a final revisit 11 months following surgery, no episodes of penile haemorrhage had been noted for several months. At that stage, the dog had not received propranolol for approximately three weeks.

Discussion

Based on the clinical and histopathological findings, the offending mass in this case appeared to be a vascular lesion arising from the urethral or penile tissue. One potential explanation is herniation of the corpus spongiosum through a defect in the urethral mucosa; this is consistent with a history of previous obstruction (urolithiasis) which may have resulted in urethral damage. This has been reported in the horse, and is suspected to be subsequent to trauma (Schumaker and others 1995). In a case series of 10 horses, the clinical and intraoperative findings closely paralleled those in this case, except that the location of the urethral defect in the equids was on the ventral (convex) surface of the urethra and was visible as a slit-like defect on urethroscopy (Schumaker and others 1995). All geldings in this case series made a full recovery with either subischial urethrostomy or a ‘pressure-releasing’ incision into the spongiosa. The stallions showed a less predictable response, likely due to the increased pressure within the corpus spongiosum seen with sexual activity.

In the case presented here, postoperative urethral haemorrhage appeared to be responsive to administration of propranolol. Interestingly, erection in the dog is mediated by α-adrenergic fibres and is unresponsive to β-adrenergic blockade (Matsumoto and others 2000). Thus; any potential benefit of propranolol in this case was likely via another mechanism, such as through its negative inotropic and chronotropic action, or a local vasoconstriction (Muir and Sams 1984). However, it is also possible that any improvement seen with propranolol was purely coincidental.

Another potential explanation for this pathology is a vascular malformation in the urethral wall. The clinical findings in this case are similar to a previously reported case, also involving a Staffordshire bull terrier with urethral haemorrhage and a urethral mass (Liehmann and others 2010). On the suspicion of carcinoma, that patient was treated by subtotal penile amputation and transpelvic urethrostomy. Subsequent histopathology revealed a ruptured vascular structure with thrombosis, haemorrhage and repair tissue, with no evidence of neoplasia. It is interesting to note that the signalment, clinical signs, lesion location and radiographic lesion appearance in that case are almost identical to our case, and the histopathology supports a similar lesion. In the case reported here, resolution was achieved with a less invasive surgical approach.

Non-invasive diagnosis of urethral masses can be challenging. Positive contrast retrograde urethrography is potentially the most useful modality to confirm an intraluminal mass, and allows precise localisation (Ticer and others 1980). Ultrasound can allow characterisation of the architecture and layering of the urethra, but requires prior localisation. To achieve a cytological or histological diagnosis, cells may be collected by urinalysis, traumatic catheterisation, or urethroscopic or open biopsy; in a study of open versus cystoscopic biopsies of cystic transitional cell carcinoma, endoscopic biopsy yielded a diagnostic sample in only 65 per cent of male dogs (Childress and others 2011). This figure is likely to be lower for urethral masses, although such studies are lacking. The high proportion of urethral masses that are malignant often leads to an assumption of malignancy, and may preclude biopsy. In this case an open excisional biopsy was elected as an intermediate approach between cystoscopic biopsy and penile amputation.

Acknowledgments

The authors would like to thank Dr Iris Reichler, Clinic for Reproduction Medicine, Vetsuisse Faculty, University of Zurich, Switzerland, for her assistance with this case.

  • Received July 1, 2014.
  • Revision received August 8, 2014.
  • Accepted August 19, 2014.

References

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Footnotes

  • Contributors I can confirm that all authors have contributed equally to preparation of this manuscript, outside of normal clinical duties. All authors consent to publication of this manuscript.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Author note Dr Natashia Evans' current address is UW-Madison School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706, USA.

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