History
A 9-year-old 7.0-kg (15.4-lb) spayed female Shih Tzu was referred for a 1.5-year history of vaginal discharge, polyuria, polydipsia, and urinary tract infections. Four months prior to the referral examination, abdominal radiography performed by the referring veterinarian revealed numerous mineral opacities in the region of the urinary bladder, and struvite crystals were identified on urinalysis. At that point, cystotomy was performed because of the suspicion of urocystoliths but revealed only minimal urinary debris. The urinary debris was removed; however, the abnormal clinical signs persisted, and the dog was referred for further evaluation.
On referral examination, the dog had mild seromucoid vulvar discharge, and the dog's abdomen felt tense on palpation. Findings for the rest of the physical examination were unremarkable. Abdominal radiography was performed (Figure 1).
Right lateral (A) and ventrodorsal (B) abdominal radiographic images of a 9-year-old 7.0-kg (15.4-lb) spayed female Shih Tzu with a 1.5-year history of vaginal discharge, polyuria, polydipsia, and urinary tract infections.
Citation: Journal of the American Veterinary Medical Association 257, 11; 10.2460/javma.2020.257.11.1113
Formulate differential diagnoses and treatment strategies from the history, clinical findings, and Figure 1—then turn the page →
Radiographic Findings and Interpretation
Abdominal radiography revealed a large, tubular soft tissue opacity that extended from the region of the urinary bladder and pelvic inlet, along the sagittal midline, ventral to the descending colon, and to the ventral aspect of the mid-abdominal area (Figure 2). Randomly distributed throughout this structure were multiple stippled mineral opacities. Also evident were multiple minuscule nephroliths in the right kidney, mild hepatomegaly, a moderate volume of soft tissue intraluminal gastric material (likely representing recently ingested food), and 8 lumbar vertebrae. The lack of urinary bladder visualization was attributed to a lack of urinary bladder distension. On the basis of radiographic findings, a uterine stump mass with intralesional dystrophic mineralization was suspected; however, chronic stump pyometra or endometritis could not be completely ruled out. A urinary bladder origin for the abnormal soft tissue stucture was considered much less likely because of the location and radiographic characteristics of this lesion.
Same radiographic images as in Figure 1. A tubular soft tissue opaque structure with multiple stippled mineral opacities randomly distributed throughout (arrowheads) extends from the region of the urinary bladder and pelvic inlet, along the sagittal midline, ventral to the descending colon, and to the ventral aspect of the mid-abdominal area. Mineral opaque foci are evident in the region of the right kidney (arrows), consistent with minuscule nephroliths.
Citation: Journal of the American Veterinary Medical Association 257, 11; 10.2460/javma.2020.257.11.1113
Positive-contrast retrograde vaginourethrography was performed for further evaluation of the urogenital tract (Figure 3). Findings indicated that there was marked enlargement of the uterine stump, with numerous randomly dispersed foci of mineralization and multiple lobulated, irregularly margined deffects filled with contrast medium. The urinary bladder, distended with contrast medium, was cranially and ventrally displaced and compressed by the enlarged uterine stump. On the basis of these findings, a uterine stump neoplasm was prioritized, with carcinoma or smooth muscle neoplasm (eg, leiomyoma or leiomyosarcoma) suspected. A uterine intraluminal origin (eg, focally mineralized large intraluminal uterine stump blood clots) could not be ruled out but was considered unlikely.
Right lateral (A) and ventrodorsal (B) positive-contrast retrograde vaginourethrographic images of the dog described in Figure 1. The uterine remnant is markedly enlarged, has numerous randomly dispersed foci of mineralization, and has multiple lobulated, irregularly margined, contrast medium–filled defects (arrowheads), consistent with endometrial polyps diagnosed on histologic examination. The urinary bladder (asterisks) is distended with contrast medium and cranially and ventrally displaced by the enlarged uterine remnant. Mineral foci in the region of the right kidney (arrows) are evident.
Citation: Journal of the American Veterinary Medical Association 257, 11; 10.2460/javma.2020.257.11.1113
Treatment and Outcome
Partial hysterectomy was performed without complication. There was no remnant ovarian tissue found during the laparotomy. The dog recovered from surgery without complication, and its vaginal discharge resolved. The following day, the dog was released to its owner with prescriptions of amoxicillin–clavulanic acid (18 mg/kg [8.2 mg/lb], PO, q 12 h for 7 days) and buprenorphine (0.013 mg/kg [0.006 mg/lb], oral transmucosally, q 12 h for 3 days). In addition, the owner was instructed to monitor for signs of urinary incontinence and return the dog for a recheck examination in approximately 1 week. However, the owners did not do so, and further follow-up information was unavailable.
Bacterial culture performed on a vaginal swab sample yielded Enterococcus spp, and bacterial culture of urine yielded no growth. Results of histologic examination of the uterine stump indicated multiple endometrial polyps and a large leiomyoma (size not reported) that arose from within one of the polyps. There were no histologic criteria identified that suggested malignancy, and no mineralization was noticed within the uterine stump structure submitted.
Comments
In retrospect, the pinpoint mineral opacities evident radiographically in the caudoventral aspect of abdomen in the dog of the present report were initially mistakenly interpreted as urocystoliths, which prompted a cystotomy. On the radiographic images obtained at our institution, the caudoventral midline soft tissue structure with mineral opacities was tubular and ventral to the descending colon, suggestive of a genital tract origin. Further, the mineral opacities were not centrally located, indicative of a mural, rather than intraluminal, localization.
Positive-contrast retrograde vaginourethrography, as performed in the dog of the present report, is a high-yield, noninvasive procedure that is widely available and can easily be performed by general practitioners. Contrast radiography has been useful in veterinary medicine in diagnosing urolithiasis, strictures, and ruptures along the urinary tract; prostatic disease; and congenital anomalies such as ectopic ureters.1,2 In the dog of the present report, this procedure allowed differentiation between the urinary bladder and uterine stump, and the use of positive-contrast retrograde vaginourethrography was instrumental in confirming that the mineral opacities observed in the caudal aspect of the abdomen were not urocystoliths.
Because the dog of the present report had previously been spayed, a possible reproductive tract abnormality was not originally considered. Although uncommon, dogs can have disease of their uterine body remnant after ovariohysterectomy, and stump pyometra can occur in remnant cervical and uterine tissue, especially when ovarian tissue is incompletely removed. Even without remnant ovarian tissue, an ascending vaginal infection can lead to stump pyometra. Clinical signs and laboratory findings are similar to a typical pyometra, but the condition can be difficult to diagnose in the absence of vaginal discharge.3
Dogs with uterine tumors may have radiographic and ultrasonographic evidence of dystrophic mineralization, osseous metaplasia, or both, and the mineralization is usually focal, rather than disseminated within the uterine wall. However, multifocal areas of uterine mural mineralization were observed ultrasonographically in a sexually intact female mixed-breed dog with chronic cystic endometrial hyperplasia and pyometra, likely as a consequence of prolonged synthetic progesterone administration.4,5 In the dog of the present report, the disseminated mural mineralization evident radiographically was suspected to have been secondary chronic endometrial inflammation. In dogs, endometrial polyps are infrequent and usually identified as solitary, proliferating, small, broad-based sessile or pedunculated masses with stalks; however, larger polyps that compromise the uterine lumen have been described.6 The underlying cause of endometrial polyps is still not fully understood but has been associated with mature age and estrogen-modulating medication in women and with progestin-containing contraceptives in zoo animals.6 Because hormone concentrations were not measured in the dog of the present report, ovarian remnant syndrome could not be ruled out as a possible underlying cause. Further, the dog of the present report had a leiomyoma that arose from within an endometrial polyp. Leiomyomas are the most common uterine neoplasia in dogs but rarely arise from the uterine stump in spayed dogs.7,8 It is debated whether endometrial polyps represent a precancerous state or whether endometrial malignancy develops concurrently.9 In women, endometrial polyps are considered preneoplastic, with an estimated 1% to 29% risk of progression to endometrial carcinoma10; however, this association has not been shown in dogs.11 Regardless, the recommended treatment for benign or malignant uterine neoplasia is surgical removal.
References
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