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  • 12-year-old female spayed Chihuahua presented to the University of Pennsylvania’s Ryan hospital emergency service for further evaluation of sudden onset blood-tinged vulvar discharge and frequent urination.
  • The patient had a previous history of a urinary tract infection, which resolved with medical treatment.
  • On physical exam, the mammary glands and vulva were prominent and active bloody vulvar discharge was appreciated.
  • AFAST indicated large fluid filled loops within the mid to caudal abdomen.
  • Hematology revealed an inflammatory leukogram with a reactive thrombocytosis.
  • Differentials for the discharge and fluid distended tubular structures included pyometra, mucometra, or hematometra.
  • Abdominal radiographs and an abdominal ultrasound were recommended for further evaluation.

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  • Markedly distended bilateral short tubular structures with moderately echogenic fluid, noted immediately caudal to the ovaries. Mild echogenic sediment layer within the left-sided structure, presumed uterine horn. These structures abruptly taper within the mid to caudal abdomen.
  • Mild cystic mural changes along the luminal surface of the dilated fluid-filled structures.
  • A cystic, mildly thickened uterine body with minimal luminal fluid is present. This structure does not communicate with the cranially located distended tubular structures.
  • Few small anechoic follicles are present within the right and left ovaries. A well-defined mildly hyperechoic nodule is immediately adjacent to the left ovary.
  • The combination of findings is consistent with a prior partial hysterectomy, in which the proximal uterine horns and ovaries were not removed.
  • The cystic and dilated proximal uterine horn segments are suggestive of cystic endometrial hyperplasia with secondary mucometra given the echogenic luminal fluid. Other causes such as pyometra are less likely given the absence of communication of the uterine horns with the uterine body.
  • The uterine body changes are most consistent with cystic endometrial hyperplasia. Minimal fluid could represent mucometra or pyometra and may explain the reported bloody vulvar discharge.
  • Suspect peri-ovarian nodule may represent an ovarian mass (e.g. adenoma, adenocarcinoma) vs. regional fat necrosis.
  • Moderate cystitis, which is most likely secondary to a urinary tract infection.
  • An abdominal exploratory surgery was performed, revealing remaining left and right ovaries with fluid filled and distended uterine horns still attached to both ovaries. The uterine body was not attached to the uterine horns but was tightly attached to the small intestine via adhesions. The ovaries and remnant uterine horn tissue was removed.
  • Histopathology of the ovaries showed normal folliculogenesis with small corpora lutea and a single small cyst. Histopathology of uterine horns revealed a variably dilated lumen and revealed multifocal cystic endometrial hyperplasia without evidence of pyometra.
  • Histopathology of the left ovarian nodule revealed a papillary adenoma.
  • Cystitis is likely based on urinalysis results, which revealed a moderate amount of bacterial rods, 1-2 white blood cells and 5-10 red blood cells per high power field.

Intact female dogs with cystic endometrial hyperplasia (CEH) and sterile seromucous fluid in the uterine lumen (hydrometra or mucometra) are sonographically difficult to differentiate from patients with pyometra and CEH. However, it is important to differentiate the two, for patients with the CEH-mucometra complex are not regarded as potential emergencies while patients with the CEH-pyometra complex have an increased risk for endotoxic shock (De Bosschere et al. 2001; Hagman & Kuhn, 2006). Most cases of pyometra in canine patients are derived from fecal flora, resulting in ascending infection of the urinary tract. Progesterone primes the endometrium and myometrium, allowing for the establishment of ascending opportunistic bacterial infection (Sandholm et al. 1975). Moreover, in cases of simultaneous urinary tract infection and pyometra, the urinary tract and uterus are often affected with the same bacterial strain of E. coli (Hagman et al. 2002).

Because our patient was systemically stable, and there was no communication between uterine horn segments and the uterine body, we suspected the CEH-mucometra complex, confirmed with histopathology.

Many female dogs exhibiting a sudden onset of bloody vaginal discharge, hematuria and frequent urination will have an ascending bacterial infection. Most bacterial urinary tract infections (UTIs) occur from ascending migration of pathogens from the rectum or perineum, spreading to the urethra and bladder (Johnson et al. 2003). On ultrasound, the most common presentation of a bladder with cystitis is irregular hypoechoic or hyperechoic bladder wall thickening along the cranioventral aspect (Penninck & d’Anjou, 1991, pp 369). Other findings, such as necrotic debri, calculi or blood clots, are also commonly seen with cystitis (Penninck & d’Anjou, 1991, pp 369). This patient’s ultrasound findings, combined with urinalysis results, is supportive of bacterial cystitis.

  1. De Bosschere, H., Ducatelle, R., Vermeirsch, H., Van Den Broeck, W., & Coryn, M. (2001). Cystic endometrial hyperplasia-pyometra complex in the bitch: should the two entities be disconnected?. Theriogenology, 55(7), 1509–1519. https://doi.org/10.1016/s0093-691x(01)00498-8
  2. Hagman, R., Kindahl, H., Fransson, B. A., Bergström, A., Holst, B. S., & Lagerstedt, A. S. (2006). Differentiation between pyometra and cystic endometrial hyperplasia/mucometra in bitches by prostaglandin F2alpha metabolite analysis. Theriogenology, 66(2), 198–206. https://doi.org/10.1016/j.theriogenology.2005.11.002
  3. Hagman, R., & Kühn, I. (2002). Escherichia coli strains isolated from the uterus and urinary bladder of bitches suffering from pyometra: comparison by restriction enzyme digestion and pulsed-field gel electrophoresis. Veterinary microbiology, 84(1-2), 143–153. https://doi.org/10.1016/s0378-1135(01)00449-7
  4. Johnson, J. R., Kaster, N., Kuskowski, M. A., & Ling, G. V. (2003). Identification of urovirulence traits in Escherichia coli by comparison of urinary and rectal E. coli isolates from dogs with urinary tract infection. Journal of clinical microbiology, 41(1), 337–345. https://doi.org/10.1128/JCM.41.1.337-345.2003
  5. Penninck, D., & d\’Anjou, M. (Eds.). (1991). Atlas of small animal ultrasonography. John Wiley & Sons, Incorporated.
  6. Sandholm, M., Vasenius, H., & Kivistö, A. K. (1975). Pathogenesis of canine pyometra. Journal of the American Veterinary Medical Association, 167(11), 1006–1010.