Canine Stump Pyometra

Writing about the stuff of urban legends, Coby Richter, DVM, DACVS, describes a pyometra and subsequent surgery in a previously spayed dog.

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A one-year-old female spayed Labrador presented to the referring veterinarian for 24 hours of inappetence, polydipsia and diarrhea. She was adopted the day before from a rescue organization. The dog had been spayed three weeks earlier at an unknown veterinary clinic. The surgery and recovery were described as routine on the adoption papers, and the dog had been otherwise healthy (updated on vaccinations and deworming). At presentation to the referring clinic, the dog was painful upon caudal abdominal palpation. CBC and chemistry panel were unremarkable aside from a neutropenia (4700 cells/microliter) and a lymphocytosis (3700 cells/microliter). She was referred to DoveLewis for an ultrasound with the primary differentials of a stump pyometra or intestinal foreign body.

Upon presentation at DoveLewis, the dog exhibited a normal TPR, adequate hydration, normal blood pressure and was alert and ambulatory. Other than the painful caudal abdomen and dark brown diarrhea, her physical exam was unremarkable. An ultrasound examination showed the body of the uterus extending 2.5 cm cranial to the cranial aspect of the urinary bladder. A 2.8 cm heterogeneous mass involving the cranial aspect of the uterus was visualized with fluid pockets in the region of the mass. No evidence of diffuse peritonitis was observed, and the remainder of the abdomen was unremarkable. The primary differentials based on ultrasound included abscess or granuloma.

Exploratory celiotomy was performed shortly after ultrasound examination. A dark red to black cystic structure was found associated with the amputated end of the uterine body. Omentum was adhesed to the abscess, colon, spleen and ovarian pedicles. Omentum was resected using electrocoagulation to allow complete excision of the uterine body and associated abscess. Both ovarian pedicles were inspected and no gross evidence of ovarian tissue was found. Both pedicles were ligated deep to the existing ligatures and approximately 0.5cm of tissue removed. The abdomen was lavaged and closed in routine fashion. The dog recovered well from surgery and went home the following morning on amoxicillin-clavulanate and tramadol for pain management. Seven months following surgery, the dog was doing well.

Site of colonic omental adhesion following electrocoagulation to free the colon. Cranial is to the right. Uterine stump abscess. Cranial is to the right. Mature omental adhesion to the abscess and spleen is visible.

Uterine stump abscess, often referred to as stump pyometra, is inflammation and bacterial infection of the portion of uterine body left behind after ovariohysterectomy. Reports of dogs presenting with stump pyometra show a window of opportunity anywhere from days to years following OHE. Potential causes include suture reaction (both absorbable and non-absorbable suture have been implicated), poor surgical technique (rough tissue handling or failure of asepsis), residual infection (pyometra present at OHE), excessive devitalized uterine stump (tissue cranial to the ligatures), ascending infection, and activity of endogenous or exogenous reproductive hormones (progesterone +/- estrogen). An open cervix and favorable uterine conditions during proestrus and estrus means that even healthy dogs have bacteria within the uterus in these two estrous phases. In the dog of this report, her estrous stage at the time of OHE was unknown, as were any details of the surgery itself. The clients declined culture of the abscess and histopathology of the ovarian pedicle remnants. Close inspection of the excised ovarian pedicle remnants following surgery did not suggest any glandular tissue; however, microscopic evaluation was not pursued. Sharp dissection of the excised abscess demonstrated a knotted loop of monofilament suture (suspected absorbable) no longer encircling the uterine stump but still loosely attached to the wall of the uterus. The material within the cystic portion of the abscess was dark purple and viscous. A brief microscopic exam of the purulent debris demonstrated cocci and degenerate neutrophils.

Clinical signs for uterine stump abscess can mirror pyometra in an intact female dog, including depression, lethargy, inappetence, vomiting, abdominal pain, PU/PD, and vaginal discharge. CBC and chemistry changes are similarly non-specific and may include a neutrophilia (with or without a left shift), monocytosis, non-regenerative anemia, hyperglobulinemia and azotemia. Ultrasonography is the diagnostic of choice; however, conclusive evidence of infection (as opposed to inflammation alone) may require exploratory celiotomy.

The recommended treatment of stump pyometra is excision of all infected tissue to the level of the cervix (or including the cervix in some cases). If excision of the entire abscess is not possible due to involvement of other critical structures (e.g. neurovascular supply for the bladder), drainage and omentalization is an acceptable alternative. Ovarian pedicles should be closely inspected and any tissue of questionable glandular origin (retained ovarian tissue) excised. Complications are the same as any other abdominal surgery involving the female reproductive tract, including hemorrhage, septicemia, endotoxemia, peritonitis, dehiscence, urinary tract injury, incontinence, and other organ system disease secondary to septicemia. Prognosis is good with early surgical intervention and complete excision. Patients in which the uterine stump abscess has ruptured resulting in septic peritonitis and/or septicemia have a guarded prognosis with aggressive therapy.

Selected References:
•    Stone EA. Ovary and Uterus. In: Slatter D. ed. Textbook of Small Animal Surgery. 3rd ed. Philadelphia: W.B. Saunders Co., 2003;1487-1502.
•    Campbell BG. Omentalization of a nonresectable uterine stump abscess in a dog. JAVMA 2004;224:1799-1803.
•    Boza S., et al. Late abscess formation caused by silk suture following hysterectomy in a female dog. Reprod Domest Anim. 2010;45(5):934-6.
•    Nelson RW, Feldman EC. Pyometra. Vet Clin North Am Sm
Anim Prac 1986;16:561-576.

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