- Email: [email protected]
Dysuria associated with urethral caruncle in the dog
j. Comp. Path. 1996 Vol. 115, 77-84
Dysuria Associated with Urethral Caruncle in the Dog j. M. B r a d s h a w , P.J. B r o w n , G. R. P e a r s o n a n d P. E. Holt* Department of Pathology and Microbiology and *Department of Clinical Veterinary Science, University of Bristol, School of Veterinary Science, Langford, Bristol BSI8 7DU
Summary Three cases of urethral caruncle were recognized in bitches with a history of chronic dysuria. Clinical and radiological examinations revealed the presence of inoperable lesions involving much of the urethra in all three cases. At post-mortem examination of Case 1, an oval swelling, 1"5 x l'0cm, was detected within the wall of the urethra close to the vagino-urethral orifice. In Case 2, firm, mottled yellow, white and red tissue formed a thickening between the urethra and vagina. In Case 3, a cylindrical cream mass, 8 cm long and 3 cm in diameter, surrounded the urethra and impinged on the wall of the vagina. Histologically, glandular structures lined by a single layer of epithelial cells and a mixed granulomatous inflammatory reaction were present in the wall of the urethra of all three cases. 9 1996 W.B. Saunders CompanyLimited
Introduction In w o m e n , urethral caruncles are formed from chronically inflamed urethral mucosa associated with glandular structures a n d islands of urethral epithelium e m b e d d e d in the underlying stroma (Beilby a n d Ridley, 1987). T h e y tend to occur in post-menopausal w o m e n as sessile or polypoid growths at the urethral meatus. T h e y m a y be associated with dysuria or bleeding, or m a y be symptomless. Few studies have been u n d e r t a k e n of similar lesions of the lower urinary tract of dogs (Moroffet al., 1991; Norris et al., 1992). Most reported urethral lesions in dogs are neoplastic, usually of epithelial origin, but g r a n u l o m a t o u s urethritis is also recognized (Burk a n d Schaubhut, 1976). M o r o f f e t al. (1991) reported 18 cases o f g r a n u l o m a t o u s urethritis in 60 female dogs with infiltrative urethral disease. Thus, a g r a n u l o m a t o u s condition is not unrecognized, but there have been no gross or histological descriptions in dogs of lesions similar to h u m a n caruncles. T h e purpose of this paper is to report three cases of urethral caruncle in the dog.
MateriMs and Methods Radiographical Studies In each bitch, contrast radiography was performed under general anaesthesia. Plain, lateral abdominal radiographs were made and positive contrast, retrograde vaginourethrography was then performed, as described previously (Holt, 1989). 0021~975/96/050077 +08 $12.00/0
9 1996W.B. SaundersCompanyLimited
78
J.M. Bradshaw
e t al.
Histopathological Studies Relevant tissues collected at post-mortem examination, including urethra and vagina, were fixed in 10% neutral buffered formol saline before routine processing. Sections (4-5 gm) were stained with haematoxylin and eosin (HE). Chemical Analysis The composition of urinary calculi was determined with a Urinary Calculi Analysis Kit (Merckognost; E. Merck, D-6100, Darmstadt, Germany). Results
Clinical Findings Case 1. A 12-year-old female Rough Collie, spayed when 18 months old, had suffered from recurring urinary incontinence and dysuria over the previous 6 years. Clinical and radiographical examinations revealed a grossly enlarged bladder (Fig. 1, top) and a urinary catheter could be inserted only 2 cm into the urethra. A retrograde positive contrast vagino-urethrogram (Fig. 1, bottom) confirmed that urethral obstruction was present with abnormal cavitation of the urethral wall at the site of obstruction. The clinical and radiographical findings were suggestive of urethral malignancy and euthanasia was carried out. Case 2. A 6-year-old entire female Rough Collie was investigated for increasingly severe dysuria of several weeks' duration. Clinical examination revealed a grossly distended bladder and a prominent, firm swelling in the region of the caudal urethra. A vagino-urethrogram (Fig. 2) was suggestive of urethral malignancy and euthanasia was performed. Case 3. A 5-year-old entire female German Shepherd Dog had a vaginal mass which had been causing dysuria for several weeks. Clinical examination confirmed the presence of a diffuse, firm swelling in the ventral vaginal wall, extending around the caudal urethra. No clinical or radiographical evidence of metastatic disease was detected. However, during attempted surgical treatment the lesion was found to be non-resectable and euthanasia was carried out. Post-mortem Findings A full post-mortem examination was performed on the three dogs, which were in good bodily condition. Macroscopical changes were confined to the lower genito-urinary tract.
Case 1. The bladder was grossly distended, filling much of the abdominal cavity, and containing 1200ml of cloudy urine. A small oval swelling (1"5 x 1 cm) composed of cream-coloured tissue was found within the wall of the urethra, 2 cm from the vagino-urethral orifice. The adjacent urethral lumen contained greyish-green fibrous tissue (Fig. 3). The vagina was normal.
Urethral Caruncle in the D o g
Fig. 1.
79
Case 1. Top: Lateral abdominal radiograph with gross bladder enlargement. Bottom: The vaginourethrogram demonstrates urethral obstruction {large arrow) associated with urethral irregularity and spillage of contrast medium into cavities within the urethral wall (small arrow).
80
J.M. Bradshaw
e t al.
Fig. 2.
Case 2. Vagino-urethrogram. Disruption of the caudal urethra (arrow), with spillage of contrast medium into the soft tissues dorsal to the caudal urethra. An increased amount of soft tissue is present between the urethral and vaginal lumina.
Fig. 3.
Case 1. Opened urethra and vagina with thickening of the urethral wall and greyish, green fibrous tissue on its luminal aspect (arrow). B, bladder, V, vagina.
Case 2. The bladder was distended and after evacuation the wall appeared normal but remained distended. The urethra had a dry roughened surface with a diphtheritic exudate. Firm yellow, white and red mottled tissue formed a thickened area between the urethra and vagina.
Urethral C a r u n c l e
Fig. 4.
i n the Dog
g1
Case 3. Opened bladder and urethra. A large mass (arrows) with a roughened cut surface surrounds the urethra. Calculi (C) are present in the bladder.
Case 3. The bladder wall was thickened and the bladder contained cloudy urine and two calculi composed of triple phosphate and calcium phosphate. A cylindrical cream-coloured mass (8 x 3 cm) surrounded the urethra and impinged on the wall of the vagina (Fig. 4). The mass had a roughened cut surface, but the mucosal surfaces of the urethra and vagina appeared normal. Histopathotogical Findings The findings in all three cases were similar. Vascular granulation tissue was present within the urethral wall and was infiltrated by mixed inflammatory cells including plasma cells, lymphocytes and macrophages (Fig. 5). Clefts and cystic spaces, lined by attenuated to cuboidal epithelial cells and scattered throughout the inflamed tissue (Fig. 6), sometimes extended to the mucosal surface. In Case 1, some cyst lumina contained fragmented basophilic concretions, and in Case 2 the inflammatory infiltrate included m a n y neutrophils. Discussion
The clinical and histopathological features in these three cases, all mature female dogs, were those of urethral caruncles, in which epithelial-lined clefts and granulation tissue were present in the wall of the urethra. It is of interest that two of the affected dogs were Rough Collies, but no significance can be attributed to this finding because of the small number of cases.
82
J.M. Bradshaw
e t al.
Fig. 5.
Case 3. Section of urethral mass. A branching cleft lined by epithelium (arrow) is associated with vascular granulation tissue and mixed inflammatory cells. HE. x 300.
Fig. 6.
Case 1. Cleft lined by cuboidal epithelial cells and surrounded by predominantly plasma cells. HE. x 450.
In women, four histological types of so-called urethral caruncle are recognized (Hill, 1989)--papillomatous, angiomatous, granulomatous and mucinous, the latter being rare. The caruncle may be a pedunculated or sessile
Urethral Caruncle in the D o g
83
polypoid fleshy lesion, usually located on the posterior or lateral margin of the external urethral meatus. Patients may show dysuria or bleeding but are often symptomless. Histopathological features include submucosal granulation tissue with an intense inflammatory reaction associated with thinning and ulceration of the overlying mucosa (granulomatous form), and clefts or crypts covered variably by transitional or squamous epithelium and extending deep into the submucosa to give a lobulated glandular appearance (papillomatous form). Thus, there are histopathological similarities between the h u m a n and canine lesions, including both a granulomatous reaction and invaginations of the surface epithelium. H u m a n urethral caruncle tends to develop in post-menopausal women. O f the three adult, dysuric bitches reported here, only one case (Case 1) had been ovariectomized (10 years previously) and could be considered comparable with a post-menopausal h u m a n female. In h u m a n patients the exact aetiology is unclear but may be related to trauma, infection or prolapse, possibly in association with post-menopausal vaginal atrophy (Hill, 1989). In a review of urethral disease in female dogs by Moroff et al. (1991), granulomatous urethritis was commonly identified. These authors suggested that chronic urinary tract disease is not a precursor ofgranulomatous urethritis but that pathological lesions may develop over a period of several days before the appearance of acute clinical signs. However, they gave no description of granulomatous urethritis, made no mention of any epithelial indentations or cystic lesions suggestive of caruncle formation, and provided no conclusive evidence concerning aetiology. A possible cause of the epithelial cysts may be deduced from similar changes that occur in bladder urothelium. It is known that the urothelium of the bladder responds to chronic irritation--caused, for example, by infection, excreted chemicals or calculi--by proliferation and metaplasia (Maxie, 1993). Downward proliferation of bladder urothelium is a c o m m o n reactive change, resulting in the formation of Brunn's nests when groups of proliferating cells become isolated in the submucosa. If the centre of the nest undergoes liquefaction, cystitis cystica or pyelitis cystica results. These types of change have been recognized in the bladder of a cat (Zachary, 1981) and a dog (Cooper and Brearley, 1986). T h e epithelium lining the cyst may undergo mucous metaplasia to produce cystitis glandularis. It is possible that the glandular structures observed in the granulation tissue may have had a similar origin. It appears that most adenomas and adenocarcinomas of the l o w e r urinary tract develop in areas of mucous metaplasia and a few develop in submucosal glands (Maxie, 1993). The potential role of the canine urethral caruncle as a pre-neoplastic lesion is not known. However, in w o m e n they are benign, non-neoplastic lesions with no pre-malignant significance (Beilby and Ridley, 1987). In the three cases reported here the dogs were killed as soon as the urethral and vaginal mass was identified, since resection was not considered possible and the lesions had the radiographical appearance of urethral malignancy. In women, resection is the treatment of choice (Nasah, 1968), but from experience based on our three cases, it would not appear to be feasible in severely affected dogs.
84
J.M. Bradshaw
e t aL
Acknowledgments The authors thank Professor H. Pearson and Dr F. Barr for providing details of their cases; the Radiographic and Anaesthetic sections of the Department of Clinical Veterinary Science for assistance; Mr W. Millard for the chemical analysis; Mr J. Conibear for the photographic prints; and Dr A. McIvor, Southmead Hospital, Bristol, for helpful comments and discussion. References Beilby, J. O. W. and Ridley, C. M. (1987). Pathology of the vulva. In: Obstetrical and Gynaecological Pathology, 3rd Edit., H. Fox, Ed., Churchill Livingstone, Edinburgh, London & Melbourne, pp. 132 133. Burk, R. L. and Schaubhut, C. W. Jr (1976). Obstructive urethritis in the female dog (a report of three cases). VeterinaryMedicine and SmaUAnimal Clinician, 71,898-902. Cooper, J. E. and Brearley, M.J. (1986). Urothelial abnormalities in the dog. Veterinary Record, 118, 513-514. Hill, G. S. (1989). Urethritis. In: Uropathology, Vol. 2, G. S. Hill, Ed., Churchill Livingstone, Edinburgh, London & Melbourne, pp. 463-465. Holt, P. E. (1989). Positive-contrast vaginourethrography for diagnosis of lower urinary tract disease. In: Current Veterinary Therapy. X. Small Animal Practice, R. W. Kirk and J. D. Bonagura, Eds, W.B. Saunders, Philadelphia, pp. 1142-1145. Maxie, M. G. (1993). The urinary system. In: Pathology of Domestic Animals, Vol. 2, 4th Edit., K. V. F. Jubb, P. C. Kennedy and N. Palmer, Eds, Academic Press, San Diego, pp. 447 538. Moroff, S. D., Brown, B. A., Matthieson, D. T. and Scott, R. C. (1991). Infiltrative urethral disease in female dogs: 41 cases (1980-1987). Journal of the American Veterinary Medical Association, 199, 247-251. Nasah, B. T. (1968). Urethral caruncle. Journal of Obstetrics and Gynaecology of the British Commonwealth, 75, 781-783. Norris, A. M., Laing, E.J., Valli, V. E. O., Withrow, S.J., Macy, D. W., Ogilvie, G. K., Tomlinson,J., McCaw, D., Pidgeon, G. andJacobs, R. M. (1992). Canine bladder and urethral tumours: a retrospective study of 115 cases (1980-1985). Journal of Veterinary Internal Medicine, 6, 145-153. Zachary, J. F. (1981). Cystitis cystica, cystitis glandularis, and Brunn's nests in a feline urinary bladder. Veterinary Pathology, 18, 113-116.
Received, October 20th, 1995 ] Accepted, February 29th, 1996]
Dysuria Associated with Urethral Caruncle in the Dog j. M. B r a d s h a w , P.J. B r o w n , G. R. P e a r s o n a n d P. E. Holt* Department of Pathology and Microbiology and *Department of Clinical Veterinary Science, University of Bristol, School of Veterinary Science, Langford, Bristol BSI8 7DU
Summary Three cases of urethral caruncle were recognized in bitches with a history of chronic dysuria. Clinical and radiological examinations revealed the presence of inoperable lesions involving much of the urethra in all three cases. At post-mortem examination of Case 1, an oval swelling, 1"5 x l'0cm, was detected within the wall of the urethra close to the vagino-urethral orifice. In Case 2, firm, mottled yellow, white and red tissue formed a thickening between the urethra and vagina. In Case 3, a cylindrical cream mass, 8 cm long and 3 cm in diameter, surrounded the urethra and impinged on the wall of the vagina. Histologically, glandular structures lined by a single layer of epithelial cells and a mixed granulomatous inflammatory reaction were present in the wall of the urethra of all three cases. 9 1996 W.B. Saunders CompanyLimited
Introduction In w o m e n , urethral caruncles are formed from chronically inflamed urethral mucosa associated with glandular structures a n d islands of urethral epithelium e m b e d d e d in the underlying stroma (Beilby a n d Ridley, 1987). T h e y tend to occur in post-menopausal w o m e n as sessile or polypoid growths at the urethral meatus. T h e y m a y be associated with dysuria or bleeding, or m a y be symptomless. Few studies have been u n d e r t a k e n of similar lesions of the lower urinary tract of dogs (Moroffet al., 1991; Norris et al., 1992). Most reported urethral lesions in dogs are neoplastic, usually of epithelial origin, but g r a n u l o m a t o u s urethritis is also recognized (Burk a n d Schaubhut, 1976). M o r o f f e t al. (1991) reported 18 cases o f g r a n u l o m a t o u s urethritis in 60 female dogs with infiltrative urethral disease. Thus, a g r a n u l o m a t o u s condition is not unrecognized, but there have been no gross or histological descriptions in dogs of lesions similar to h u m a n caruncles. T h e purpose of this paper is to report three cases of urethral caruncle in the dog.
MateriMs and Methods Radiographical Studies In each bitch, contrast radiography was performed under general anaesthesia. Plain, lateral abdominal radiographs were made and positive contrast, retrograde vaginourethrography was then performed, as described previously (Holt, 1989). 0021~975/96/050077 +08 $12.00/0
9 1996W.B. SaundersCompanyLimited
78
J.M. Bradshaw
e t al.
Histopathological Studies Relevant tissues collected at post-mortem examination, including urethra and vagina, were fixed in 10% neutral buffered formol saline before routine processing. Sections (4-5 gm) were stained with haematoxylin and eosin (HE). Chemical Analysis The composition of urinary calculi was determined with a Urinary Calculi Analysis Kit (Merckognost; E. Merck, D-6100, Darmstadt, Germany). Results
Clinical Findings Case 1. A 12-year-old female Rough Collie, spayed when 18 months old, had suffered from recurring urinary incontinence and dysuria over the previous 6 years. Clinical and radiographical examinations revealed a grossly enlarged bladder (Fig. 1, top) and a urinary catheter could be inserted only 2 cm into the urethra. A retrograde positive contrast vagino-urethrogram (Fig. 1, bottom) confirmed that urethral obstruction was present with abnormal cavitation of the urethral wall at the site of obstruction. The clinical and radiographical findings were suggestive of urethral malignancy and euthanasia was carried out. Case 2. A 6-year-old entire female Rough Collie was investigated for increasingly severe dysuria of several weeks' duration. Clinical examination revealed a grossly distended bladder and a prominent, firm swelling in the region of the caudal urethra. A vagino-urethrogram (Fig. 2) was suggestive of urethral malignancy and euthanasia was performed. Case 3. A 5-year-old entire female German Shepherd Dog had a vaginal mass which had been causing dysuria for several weeks. Clinical examination confirmed the presence of a diffuse, firm swelling in the ventral vaginal wall, extending around the caudal urethra. No clinical or radiographical evidence of metastatic disease was detected. However, during attempted surgical treatment the lesion was found to be non-resectable and euthanasia was carried out. Post-mortem Findings A full post-mortem examination was performed on the three dogs, which were in good bodily condition. Macroscopical changes were confined to the lower genito-urinary tract.
Case 1. The bladder was grossly distended, filling much of the abdominal cavity, and containing 1200ml of cloudy urine. A small oval swelling (1"5 x 1 cm) composed of cream-coloured tissue was found within the wall of the urethra, 2 cm from the vagino-urethral orifice. The adjacent urethral lumen contained greyish-green fibrous tissue (Fig. 3). The vagina was normal.
Urethral Caruncle in the D o g
Fig. 1.
79
Case 1. Top: Lateral abdominal radiograph with gross bladder enlargement. Bottom: The vaginourethrogram demonstrates urethral obstruction {large arrow) associated with urethral irregularity and spillage of contrast medium into cavities within the urethral wall (small arrow).
80
J.M. Bradshaw
e t al.
Fig. 2.
Case 2. Vagino-urethrogram. Disruption of the caudal urethra (arrow), with spillage of contrast medium into the soft tissues dorsal to the caudal urethra. An increased amount of soft tissue is present between the urethral and vaginal lumina.
Fig. 3.
Case 1. Opened urethra and vagina with thickening of the urethral wall and greyish, green fibrous tissue on its luminal aspect (arrow). B, bladder, V, vagina.
Case 2. The bladder was distended and after evacuation the wall appeared normal but remained distended. The urethra had a dry roughened surface with a diphtheritic exudate. Firm yellow, white and red mottled tissue formed a thickened area between the urethra and vagina.
Urethral C a r u n c l e
Fig. 4.
i n the Dog
g1
Case 3. Opened bladder and urethra. A large mass (arrows) with a roughened cut surface surrounds the urethra. Calculi (C) are present in the bladder.
Case 3. The bladder wall was thickened and the bladder contained cloudy urine and two calculi composed of triple phosphate and calcium phosphate. A cylindrical cream-coloured mass (8 x 3 cm) surrounded the urethra and impinged on the wall of the vagina (Fig. 4). The mass had a roughened cut surface, but the mucosal surfaces of the urethra and vagina appeared normal. Histopathotogical Findings The findings in all three cases were similar. Vascular granulation tissue was present within the urethral wall and was infiltrated by mixed inflammatory cells including plasma cells, lymphocytes and macrophages (Fig. 5). Clefts and cystic spaces, lined by attenuated to cuboidal epithelial cells and scattered throughout the inflamed tissue (Fig. 6), sometimes extended to the mucosal surface. In Case 1, some cyst lumina contained fragmented basophilic concretions, and in Case 2 the inflammatory infiltrate included m a n y neutrophils. Discussion
The clinical and histopathological features in these three cases, all mature female dogs, were those of urethral caruncles, in which epithelial-lined clefts and granulation tissue were present in the wall of the urethra. It is of interest that two of the affected dogs were Rough Collies, but no significance can be attributed to this finding because of the small number of cases.
82
J.M. Bradshaw
e t al.
Fig. 5.
Case 3. Section of urethral mass. A branching cleft lined by epithelium (arrow) is associated with vascular granulation tissue and mixed inflammatory cells. HE. x 300.
Fig. 6.
Case 1. Cleft lined by cuboidal epithelial cells and surrounded by predominantly plasma cells. HE. x 450.
In women, four histological types of so-called urethral caruncle are recognized (Hill, 1989)--papillomatous, angiomatous, granulomatous and mucinous, the latter being rare. The caruncle may be a pedunculated or sessile
Urethral Caruncle in the D o g
83
polypoid fleshy lesion, usually located on the posterior or lateral margin of the external urethral meatus. Patients may show dysuria or bleeding but are often symptomless. Histopathological features include submucosal granulation tissue with an intense inflammatory reaction associated with thinning and ulceration of the overlying mucosa (granulomatous form), and clefts or crypts covered variably by transitional or squamous epithelium and extending deep into the submucosa to give a lobulated glandular appearance (papillomatous form). Thus, there are histopathological similarities between the h u m a n and canine lesions, including both a granulomatous reaction and invaginations of the surface epithelium. H u m a n urethral caruncle tends to develop in post-menopausal women. O f the three adult, dysuric bitches reported here, only one case (Case 1) had been ovariectomized (10 years previously) and could be considered comparable with a post-menopausal h u m a n female. In h u m a n patients the exact aetiology is unclear but may be related to trauma, infection or prolapse, possibly in association with post-menopausal vaginal atrophy (Hill, 1989). In a review of urethral disease in female dogs by Moroff et al. (1991), granulomatous urethritis was commonly identified. These authors suggested that chronic urinary tract disease is not a precursor ofgranulomatous urethritis but that pathological lesions may develop over a period of several days before the appearance of acute clinical signs. However, they gave no description of granulomatous urethritis, made no mention of any epithelial indentations or cystic lesions suggestive of caruncle formation, and provided no conclusive evidence concerning aetiology. A possible cause of the epithelial cysts may be deduced from similar changes that occur in bladder urothelium. It is known that the urothelium of the bladder responds to chronic irritation--caused, for example, by infection, excreted chemicals or calculi--by proliferation and metaplasia (Maxie, 1993). Downward proliferation of bladder urothelium is a c o m m o n reactive change, resulting in the formation of Brunn's nests when groups of proliferating cells become isolated in the submucosa. If the centre of the nest undergoes liquefaction, cystitis cystica or pyelitis cystica results. These types of change have been recognized in the bladder of a cat (Zachary, 1981) and a dog (Cooper and Brearley, 1986). T h e epithelium lining the cyst may undergo mucous metaplasia to produce cystitis glandularis. It is possible that the glandular structures observed in the granulation tissue may have had a similar origin. It appears that most adenomas and adenocarcinomas of the l o w e r urinary tract develop in areas of mucous metaplasia and a few develop in submucosal glands (Maxie, 1993). The potential role of the canine urethral caruncle as a pre-neoplastic lesion is not known. However, in w o m e n they are benign, non-neoplastic lesions with no pre-malignant significance (Beilby and Ridley, 1987). In the three cases reported here the dogs were killed as soon as the urethral and vaginal mass was identified, since resection was not considered possible and the lesions had the radiographical appearance of urethral malignancy. In women, resection is the treatment of choice (Nasah, 1968), but from experience based on our three cases, it would not appear to be feasible in severely affected dogs.
84
J.M. Bradshaw
e t aL
Acknowledgments The authors thank Professor H. Pearson and Dr F. Barr for providing details of their cases; the Radiographic and Anaesthetic sections of the Department of Clinical Veterinary Science for assistance; Mr W. Millard for the chemical analysis; Mr J. Conibear for the photographic prints; and Dr A. McIvor, Southmead Hospital, Bristol, for helpful comments and discussion. References Beilby, J. O. W. and Ridley, C. M. (1987). Pathology of the vulva. In: Obstetrical and Gynaecological Pathology, 3rd Edit., H. Fox, Ed., Churchill Livingstone, Edinburgh, London & Melbourne, pp. 132 133. Burk, R. L. and Schaubhut, C. W. Jr (1976). Obstructive urethritis in the female dog (a report of three cases). VeterinaryMedicine and SmaUAnimal Clinician, 71,898-902. Cooper, J. E. and Brearley, M.J. (1986). Urothelial abnormalities in the dog. Veterinary Record, 118, 513-514. Hill, G. S. (1989). Urethritis. In: Uropathology, Vol. 2, G. S. Hill, Ed., Churchill Livingstone, Edinburgh, London & Melbourne, pp. 463-465. Holt, P. E. (1989). Positive-contrast vaginourethrography for diagnosis of lower urinary tract disease. In: Current Veterinary Therapy. X. Small Animal Practice, R. W. Kirk and J. D. Bonagura, Eds, W.B. Saunders, Philadelphia, pp. 1142-1145. Maxie, M. G. (1993). The urinary system. In: Pathology of Domestic Animals, Vol. 2, 4th Edit., K. V. F. Jubb, P. C. Kennedy and N. Palmer, Eds, Academic Press, San Diego, pp. 447 538. Moroff, S. D., Brown, B. A., Matthieson, D. T. and Scott, R. C. (1991). Infiltrative urethral disease in female dogs: 41 cases (1980-1987). Journal of the American Veterinary Medical Association, 199, 247-251. Nasah, B. T. (1968). Urethral caruncle. Journal of Obstetrics and Gynaecology of the British Commonwealth, 75, 781-783. Norris, A. M., Laing, E.J., Valli, V. E. O., Withrow, S.J., Macy, D. W., Ogilvie, G. K., Tomlinson,J., McCaw, D., Pidgeon, G. andJacobs, R. M. (1992). Canine bladder and urethral tumours: a retrospective study of 115 cases (1980-1985). Journal of Veterinary Internal Medicine, 6, 145-153. Zachary, J. F. (1981). Cystitis cystica, cystitis glandularis, and Brunn's nests in a feline urinary bladder. Veterinary Pathology, 18, 113-116.
Received, October 20th, 1995 ] Accepted, February 29th, 1996]