Editorial Type: Case Reports
 | 
Online Publication Date: 01 Mar 2004

Unusual Urethral Calculi in Two Male Dogs

DVM,
BVMS, PhD, Diplomate ACVS,
MS, Diplomate ACVS,
DVM, Diplomate ACVS,
DVM, Diplomate ACVS, and
DVM
Article Category: Other
Page Range: 157 – 161
DOI: 10.5326/0400157
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The clinical presentation and advanced size of the two calculi described in this report are both atypical and noteworthy. Both dogs were presented initially with signs of hematuria, stranguria, and perineal discomfort. Each calculus was visible on survey abdominal radiographs and was present in the region of the ischial arch. Both dogs underwent a perineal urethrotomy to retrieve the calculus. Resolution of clinical signs was obtained in one case, which was referred within 2 months of the onset of clinical signs. The second dog was medically managed for approximately 2.5 years before referral. Surgical intervention failed to restore urinary continence in this second dog. Early detection of similar cases may be important in optimizing clinical outcome following appropriate treatment.

Case Reports

Case No. 1

A 4-year-old, intact male, terrier-type mixed-breed dog was referred for a 2-month history of stranguria. Four weeks prior to presentation, the owners reported normal urinary posturing but the production of only drops of blood-tinged urine. The skin over the urethra immediately ventral to the anus was reddened. A urinalysis performed by the referring veterinarian revealed a urine specific gravity (USG) of >1.045, a pH of 6.5, and a protein of 300+ mg/dL. Microscopic examination of the urine sediment revealed red blood cells (RBC) that were too numerous to count, leukocytes of 3 to 5 per high-power field (hpf), rod-shaped bacteria, and a moderate amount of struvite crystals. Survey radiographs taken at that time showed an oval, radiopaque mass that was 5 × 3 cm in size, dorsal to the pelvic floor and 3 cm distal to the prostate gland, in the region of the ischial arch. A 3-week course of enrofloxacin was prescribed, but stranguria persisted.

On presentation to the authors’ hospital, the dog was bright, alert, and responsive. Body condition was acceptable, with a body weight of 8.6 kg. Physical examination was unremarkable except for a hunched posture while standing. A digital rectal examination and body temperature measurement were performed after sedation, because the dog manifested extreme discomfort upon manipulation of the perineal region. Body temperature was within normal limits. Externally, a firm, ovoid mass was palpable in the ischial area between the anus and the scrotum.

Under sedation, a urinary catheter was passed from the penis into the urinary bladder with very little resistance, and a urine sample was obtained. Significant findings included USG of 1.045, pH of 6.5, 3+ protein, 1+ bilirubin, and 4+ hemoprotein. Rod-shaped bacteria were seen. Urine culture revealed growth of large numbers of Corynebacterium spp. as well as Actinomyces viscosus. Pelvic radiographs revealed a smooth, marginated, calcified density along the midline at the ischial arch [Figure 1]. To delineate the exact relation of this density to the urethral lumen, a contrast urethrogram was performed under general anesthesia. The infused contrast medium flowed around the calcified mass, confirming its location within the urethral lumen [Figure 2]. Abdominal ultrasonography was performed to assess the rest of the urinary tract. The prostate gland was enlarged and had a mottled appearance, with numerous hypoechoic regions consistent with small, intraprostatic cysts. A fine-needle aspirate of a representative cyst was obtained. The fluid was analyzed for cytopathological abnormalities and cultured for bacteria. Culture results were negative, and cytopathological abnormalities were not apparent.

Surgery was performed 3 days later. The dog was placed in sternal recumbency on a perineal stand. A midline incision was made over the intraurethral mass between the anus and scrotum. The retractor penis muscle was retracted laterally, and the paired bulbospongiosus muscles were separated to reveal the underlying urethra. The urethral wall was incised over the mass, and a single urethral calculus was removed. The lumen was lavaged with sterile saline, and closure of the urethral mucosa was performed using 4–0 polydioxanonea in a simple interrupted pattern. Subcutaneous as well as subcuticular tissues were closed with 3–0 polydioxanonea in a simple continuous pattern. The skin was closed with 3–0 nylonb suture in a simple interrupted pattern.

The dog recovered uneventfully and by the next morning was voiding a normal stream of urine. He was discharged 2 days postoperatively on a 2-week course of amoxicillinclavulanic acid (13 mg/kg per os [PO] q 8 hours). The dog was returned 2 weeks later for suture removal, and the owners reported that micturition was normal at home. Urine was obtained by cystocentesis for culture, and results revealed no bacterial growth. The dog remained free of clinical signs associated with the urinary tract for >1 year, at which time he was lost to follow-up.

Quantitative crystallographic analysis of the calculus was performed. It measured 29.1 × 20.6 × 15.5 mm and weighed 7.66 g [Figure 3A]. The surface was roughened and gold in color. After the calculus was cracked into cross-sections, concentric layers were evident [Figure 3B]. The outer layer was composed of 99% apatite (i.e., calcium phosphate) and 1% struvite (i.e., magnesium ammonium phosphate hexahydrate). The next underlying layer from outside to inside was composed of 50% struvite and 50% apatite. The third layer was composed of 99% apatite and 1% struvite. The central core layer was composed of equal parts of apatite and struvite. A plant awn (i.e., foxtail) was found in the center of the calculus. Culture of the calculus was negative for growth of bacteria.

Case No. 2

A 10-year-old, male castrated German shepherd dog weighing 46 kg was presented for assessment of suspected urinary incontinence. Signs of urinary dysfunction had begun 2.5 years before, and the owners had noted periodic hematuria and stranguria of increasing severity since that time. The dog was periodically examined by the referring veterinarian during this time. Various antibiotics were prescribed, which generally resulted in temporary resolution of clinical signs. A recent rectal examination revealed a firm, elongated mass on the floor of the pelvic canal, extending over the ischial arch. The dog exhibited signs of pain during this examination. Survey radiographs of the pelvic area revealed a mineral-dense opacity in the caudal pelvic canal, extending past the margin of the ischium. This mass was approximately 9 × 4.5 cm. Several attempts to pass a urinary catheter were unsuccessful. A fine-needle aspirate of the mass was attempted and yielded a small amount of fluid containing bacteria, neutrophils, and erythrocytes. The mass itself was too hard to be penetrated by the aspiration needle.

Upon presentation to the authors’ hospital, the dog dribbled urine continuously. According to the owners, he had not voided a normal stream of urine for >1 year. The dog was predominately an outdoor dog in a rural area, and he had a history of medical problems such as draining tracts associated with migrating grass awns. The owners also reported a progressive decrease in activity and a reluctance to sit.

Physical examination revealed a bright, alert, responsive dog, with a body condition score of 5/9. Abdominal palpation was unremarkable. The bladder was not palpable. The prepuce was soaked with urine, and continuous dribbling was apparent. A large (4 × 3 cm) swelling was noticeable between the anus and the scrotum. The entire perineum was extremely sensitive to any manipulations; therefore, a rectal examination was performed under sedation. A complete blood count (CBC) revealed a slight leukocytosis of 13.8 × 103/μL (reference range, 6 to 13 × 103/μL) with a mature neutrophilia of 11.1 × 103/μL (reference range, 3 to 10.5 × 103/μL). A serum biochemical profile revealed a blood urea nitrogen (BUN) of 40 mg/dL (reference range, 8 to 31 mg/dL) and an albumin of 2.4 g/dL (reference range, 2.9 to 4.2 g/dL). Serum creatinine concentration was normal at 1.2 mg/dL (reference range, 0.5 to 1.6 mg/dL). Urine was obtained by cystocentesis for urinalysis and culture. The urinalysis revealed a USG of 1.030 with 3+ protein and 3+ hemoglobin. Urine culture yielded a small number of a Helcococcus-like species (a gram-positive cocci) and a small number of Mycoplasma spp. The gram-positive cocci were susceptible to all antibiotics tested.

Survey radiographs confirmed the presence of a large, radiopaque mass ventral to the rectum and dorsal to the ischium [Figure 4]. Attempts to catheterize the urethra under sedation in order to perform a contrast urethrogram were not successful. Multiple fistulae consistent with foreign body draining tracts were present at the tip of the penis and made catheterization difficult.

The dog was anesthetized. With some difficulty, a polypropylene catheter was successfully advanced into the penile urethra, and contrast medium was infused into the urethra and bladder [Figure 5]. Retrograde urethrography revealed a large filling defect in the urethra at the location of the mineralized opacity in the area of the ischial arch. A focal filling defect consistent with a urethral stricture was also detected just distal to the mineral opacity.

The dog was operated using a surgical approach identical to that for case no. 1. A large, mineralized concretion was removed from the lumen of the urethra. The surface was tan/white and covered with irregular, verrucous projections. The urethral mucosa was very inflamed, and after the stone was removed, a distended pelvic urethra was evident. Closure of the surgery site was identical to that for case no. 1.

The dog recovered uneventfully and was placed on doxycycline (5 mg/kg PO q 12 hours) and cephalexin (22 mg/kg PO q 8 hours). He was discharged 48 hours after surgery. The incontinence persisted despite pharmacological intervention with sustained-action phenylpropanolamine (2.2 mg/kg PO q 12 hours). One month after surgery, a urethral pressure profile showed a complete lack of normal urethral sphincter function. Eight months after surgery, the owners reported a tremendous increase in activity and energy, but persistence of the urinary incontinence.

The urethral calculus measured 78.9 × 43.2 × 27.2 mm in size and had a weight of 99.15 g [Figure 6A]. The surface was roughened and was a chalky tan in color. Once cracked open, concentric laminations were evident on cross section [Figure 6B]. Crystallographic analysis revealed the outer layer was composed of 99% apatite and 1% struvite. The wart-like nodules on the surface were composed of 50% apatite and 50% struvite. A focal area of unique-appearing material was also found within the calculus and consisted of 80% struvite and 20% apatite. The three innermost layers were all composed of 99% struvite and 1% apatite. A specific nidus was not found. Culture of the calculus yielded no bacterial growth.

Discussion

Urethral calculi are commonly seen in dogs, especially in male dogs. The most common site for calculi to lodge in the male canine urethra is immediately proximal to the os penis.12 The second most common location for urethral calculi to lodge is at the level of the ischial arch.2 The atypically large calculi present in these two dogs were found in this more proximal location. The pathophysiology of urinary calculi has been well described.1–4 The formation process often begins in the presence of a nidus. A definitive nidus (i.e., foxtail) was found in case no. 1 but not in case no. 2. The presence of multiple fistulae at the tip of the penis in case no. 2 was consistent with foxtail migration, and this dog had a prior history of medical problems attributed to migrating foxtails. Foxtail migration is usually retrograde up the urethra, and they are rarely passed during micturition because of their “open umbrella” shape.

Both of the calculi found in these dogs had a mixed-mineral composition (i.e., apatite and struvite). Struvite calculi may form in either a sterile (rare) or an infected environment (common), and they are common in dogs.2–5 Pure apatite calculi are very rare in dogs.56 The combination of struvite and apatite is the most commonly reported mineral mixture.6 Layering of the compounds (as seen in both cases presented) has been reported before but has occurred predominately in female dogs.7 Some published reports indicate an increased risk of urolithiasis in mixed-breed and German shepherd dogs, while others indicate a decreased incidence in German shepherd dogs.89

To the authors’ knowledge, calculi approaching the size encountered here have not been reported in the canine urethra. Urethral calculi are commonly believed to originate in the bladder and subsequently pass into the urethra.11 It is not known whether a small cystic calculi initially became lodged in the ischial urethra of case no. 1, or whether the calculus primarily formed around a migrating foxtail that served as a nidus. The calculus in case no. 1 may have enlarged in the urethra over time, as it was bathed in mineral-rich urine. The short time course of the clinical signs in this case would argue against the foxtail scenario and support the supposition that the calculus originally formed in the urinary bladder.

The clinical course in case no. 2 was more chronic in nature, and it supported the supposition that gradual development and enlargement of the calculus occurred within the urethra. This dog’s incontinence may have developed secondary to progressive dilatation of the urethral lumen and loss of normal sphincter function from slow enlargement of the calculus. Alternately, this dog may also have been plagued with a preexisting urinary incontinence. If the dog was also incontinent, urine would have constantly bathed the developing calculus, contributing to its progressive enlargement. Unfortunately, the long duration of the clinical disease at the time of referral made the sequential course of events difficult to determine. The protracted clinical course and extreme dilatation of the urethra at the level of the calculus may also have contributed to the persistence of incontinence after surgery.

Although medical management of urolithiasis has been well described,5 both cases presented here fit the criteria for surgical intervention.1–311 Reasons for recurrence of clinical signs following surgical intervention include stricture at the diseased or surgical site, hemorrhage at the surgical site, urethral fistula formation, and recurrence of the calculi.112–14 Resolution of all clinical signs was achieved in case no. 1, but incontinence persisted in case no. 2.

Conclusion

The cases presented here describe the occurrence of atypical urethral calculi in two male dogs. Both dogs presented with signs of dysfunction of the lower urinary tract. Early diagnosis and surgical intervention may have contributed to the excellent outcome in the first case. The other case had a more chronic course, and urinary incontinence persisted despite surgical intervention. Early diagnosis and correction of large urethral calculi may be important to achieve a desirable clinical outcome.

a

PDS II; Ethicon Inc., Somerville, NJ

b

Ethilon; Ethicon Inc., Somerville, NJ

Figure 1—. Plain lateral abdominal radiograph of a 4-year-old, male, terrier-type mixed-breed dog (case no. 1) presented for evaluation of a 2-month history of stranguria. Note the large, radiopaque calculus located in the region of the pelvic brim.Figure 1—. Plain lateral abdominal radiograph of a 4-year-old, male, terrier-type mixed-breed dog (case no. 1) presented for evaluation of a 2-month history of stranguria. Note the large, radiopaque calculus located in the region of the pelvic brim.Figure 1—. Plain lateral abdominal radiograph of a 4-year-old, male, terrier-type mixed-breed dog (case no. 1) presented for evaluation of a 2-month history of stranguria. Note the large, radiopaque calculus located in the region of the pelvic brim.
Figure 1 — Plain lateral abdominal radiograph of a 4-year-old, male, terrier-type mixed-breed dog (case no. 1) presented for evaluation of a 2-month history of stranguria. Note the large, radiopaque calculus located in the region of the pelvic brim.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

Figure 2—. Contrast urethrogram from the dog in Figure 1. Contrast material has flowed around the calculus into the proximal urethra, confirming its presence in the urethral lumen.Figure 2—. Contrast urethrogram from the dog in Figure 1. Contrast material has flowed around the calculus into the proximal urethra, confirming its presence in the urethral lumen.Figure 2—. Contrast urethrogram from the dog in Figure 1. Contrast material has flowed around the calculus into the proximal urethra, confirming its presence in the urethral lumen.
Figure 2 — Contrast urethrogram from the dog in Figure 1. Contrast material has flowed around the calculus into the proximal urethra, confirming its presence in the urethral lumen.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.
Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.Figures 3A, 3B—. Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.
Figures 3A, 3B — Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

Figure 4—. Plain lateral radiograph of a 10-year-old, male castrated German shepherd dog (case no. 2) presented for evaluation of urinary incontinence. Note the large, radiopaque mass above and extending ventral to the pelvic brim.Figure 4—. Plain lateral radiograph of a 10-year-old, male castrated German shepherd dog (case no. 2) presented for evaluation of urinary incontinence. Note the large, radiopaque mass above and extending ventral to the pelvic brim.Figure 4—. Plain lateral radiograph of a 10-year-old, male castrated German shepherd dog (case no. 2) presented for evaluation of urinary incontinence. Note the large, radiopaque mass above and extending ventral to the pelvic brim.
Figure 4 — Plain lateral radiograph of a 10-year-old, male castrated German shepherd dog (case no. 2) presented for evaluation of urinary incontinence. Note the large, radiopaque mass above and extending ventral to the pelvic brim.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

Figure 5—. Contrast urethrogram from the dog in Figure 4. As in case no. 1, contrast material outlines the urethral lumen along the sides of the urethral calculus, confirming its location within the urethra.Figure 5—. Contrast urethrogram from the dog in Figure 4. As in case no. 1, contrast material outlines the urethral lumen along the sides of the urethral calculus, confirming its location within the urethra.Figure 5—. Contrast urethrogram from the dog in Figure 4. As in case no. 1, contrast material outlines the urethral lumen along the sides of the urethral calculus, confirming its location within the urethra.
Figure 5 — Contrast urethrogram from the dog in Figure 4. As in case no. 1, contrast material outlines the urethral lumen along the sides of the urethral calculus, confirming its location within the urethra.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).
Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).Figures 6A, 6B—. Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).
Figures 6A, 6B — Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400157

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    Ling GV. Part VII: disorders of urination. In: Lower Urinary Diseases of Dogs and Cats. Diagnosis, Medical Management, Prevention. St. Louis: Mosby Year Book, 1995:191–206.
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    Osborne CA, Lulich JP, Bartges JW, et al. Canine and feline urolithiases: relationship of etiopathogenesis to treatment and prevention. In: Osborne CA, Finco DR, eds. Canine and Feline Nephrology and Urology. Baltimore: Williams & Wilkins, 1995:798–888.
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    Osborne CA, Lulich JP, Polzin DJ, et al. Medical dissolution and prevention of canine struvite urolithiasis: twenty years of experience. Vet Clin North Am Small Anim Pract 1999;29:73–112.
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    Ling GV, Franti CE, Johnson DL, et al. Urolithiasis in dogs III: prevalence of urinary tract infection and interrelations of infection, age, sex, and mineral composition. Am J Vet Res 1998;59:643–649.
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Copyright: Copyright 2004 by The American Animal Hospital Association 2004
<bold> <italic toggle="yes">Figure 1</italic> </bold> —
Figure 1 —

Plain lateral abdominal radiograph of a 4-year-old, male, terrier-type mixed-breed dog (case no. 1) presented for evaluation of a 2-month history of stranguria. Note the large, radiopaque calculus located in the region of the pelvic brim.

<bold> <italic toggle="yes">Figure 2</italic> </bold> —
Figure 2 —

Contrast urethrogram from the dog in Figure 1. Contrast material has flowed around the calculus into the proximal urethra, confirming its presence in the urethral lumen.

<bold> <italic toggle="yes">Figures 3A, 3B</italic> </bold> —
Figures 3A, 3B —

Photographs of the calculus removed from case no. 1. Note the irregular surface of the intact stone (3A) and concentric lamellae of the calculus on its cut surface (3B). A grass awn can be seen in the center of the calculus, just above the arrow.

<bold> <italic toggle="yes">Figure 4</italic> </bold> —
Figure 4 —

Plain lateral radiograph of a 10-year-old, male castrated German shepherd dog (case no. 2) presented for evaluation of urinary incontinence. Note the large, radiopaque mass above and extending ventral to the pelvic brim.

<bold> <italic toggle="yes">Figure 5</italic> </bold> —
Figure 5 —

Contrast urethrogram from the dog in Figure 4. As in case no. 1, contrast material outlines the urethral lumen along the sides of the urethral calculus, confirming its location within the urethra.

<bold> <italic toggle="yes">Figures 6A, 6B</italic> </bold> —
Figures 6A, 6B —

Photographs of the calculus from case no. 2. Note the irregular projections on the surface of the intact stone (6A) and the concentric layers visible along the cut surface (6B).

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