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Initially presented to the primary veterinarian for lethargy and decreased appetite. Bloodwork performed at with the primary veterinarian revealed azotemia (BUN 121, Create 6.6, Phos 5). Referred for further workup and additional imaging.

See still images above in the carousel (six total) as well as the video of the right kidney/ureter below

Ultrasound video of the right kidney and ureter

  • Renal asymmetry with the left kidney measuring 3.5 cm in length and the right kidney measuring 4.7 cm. Both kidneys have reduced corticomedullary distinction and strongly shadowing calculi within them.
  • The right kidney has moderate pelvic dilation measuring up to 0.8 cm. The proximal right ureter is moderately dilated (0.75 cm).
  • The proximal dilated ureter has anechoic fluid within it for approximately 3.0 cm at which point the ureter becomes a complex tubular mass of soft tissue and small cystic regions for approximately 8.0 cm in length. The echogenic, mass-like mid-ureter has modest vascular markings with Doppler interrogation.
  • The caudal end of this mass of tissue in the caudal ureter has a focal shadowing calculus in it (0.4 cm).
  • The caudal most ureter is empty.
  • The bladder is normal
  • Right-sided obstructive hydronephrosis and hydroureter
  • Bilateral nephrolithiasis and chronic nephropathy
  • Locally extensive vascularized, complex mass with numerous small cyst-like cavitation, mid-aspect of the right ureter, ending caudally on a shadowing distal ureteral calculus.

The differential diagnosis for the mass of tissue associated with the right ureter includes granulomatous inflammation (granulomatous ureteritis) secondary to chronic obstruction (from the ureteral calculus) and/or infection.  The small pockets of anechoic fluid may be related to trapped urine or cavitation.  Small ureteral abscesses cannot be ruled out, though less likely since the pockets are anechoic and perhaps thin-walled.  Neoplastic etiologies originating from the right ureter (carcinoma, lymphoma, or leiomyoma) cannot be ruled out but are considered less likely.

Conclusions & Outcome

At our institution, radiographs are always made after suspected urinary obstruction to evaluate extent of the calculi. This is a lateral radiograph of the patientcaption
VD radiograph of the patient described above; note the renal asymmetry and calculi; the distal ureteral calculus is difficult to appreciate on either view, especially considering the overlying feces.caption
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Surgery was pursued to remove the right ureter and implant a subcutaneous ureteral bypass.

Intraoperatively the left kidney was normal, the right kidney was large with hydronephrosis and hydroureter. There was diffuse thickening of the right ureter from the distal ureterolith up to the proximal ureter where a ureterostomy catheter was placed. The right ureter was submitted for histopathology. The patient did well during surgery, was hospitalized for a few days, then discharged without complications.  On recheck, the creatnine was improved; clinical signs improved.

The Idexx histopathology results of the right ureter:

The submucosa is expanded by multiple granulomas and pyogranulomas with peripheral aggregates of lymphocytes and plasma cells along with scattered fibrin hemorrhage and immature granulation tissue. Granulomas and pyogranulomas are composed of epithelioid macrophages along with central collections of neutrophils or necrotic debris. The ureteral lining cells have increased mitoses (0-1 per HPF) some of which are outside the basal cell layer.

MICROSCOPIC INTERPRETATION: Marked pyogranulomatous ureteritis with mild transitional cell atypia- changes extend to the margins of the samples submitted

COMMENTS: Changes are inflammatory and non-specific. Special stains for infectious agents are pending and will follow in an Addendum. Based on histologic findings, I suspect changes are either due to ascending infection or potentially secondary to previous lodging of a urolith at this site. There is some mild atypia in the transitional lining cells but in light of the marked inflammation this is strongly favored to be a reactive change rather than evidence of emerging neoplasia.


1. Lamb, C. R., Cortellini, S., & Halfacree, Z. (2018). Ultrasonography in the diagnosis and management of cats with ureteral obstruction. Journal of feline medicine and surgery, 20(1), 15-22.

Intra-operative subcutaneous ureteral bypass (SUB) placement following antegrade pyelogram

Intra-operative photograph of the right ureter; the yellow suture defines the cranial and caudal extent of the mass-like tissue described in mid-right uretercaption
Histology of the granuloma formation attenuating the lumen of the right uretercaption
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