An Unusual Case of Stump Pyometra

Ashley Magee, DVM, DACVS, discusses a case of stump pyometra and the possible treatment of it, as well as signs and symptoms you may see.

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An eight year old Female spayed French bulldog present for surgical consultation. She was adopted about seven years ago in another state by her current owner. Previous medical history included ovariohysterectomy performed while under the care of another owner, prior to adoption by the current owner. At the time of surgery it was reported that the dog had abnormal anatomy and only one ovary had been found. Over the past seven years, the patient was reported to have occasional false heat cycles associated with behavior changes, weight loss and possible discomfort. During a recent evaluation at the RDVM for dental disease and prophylaxis, a firm mass, initially thought to be the bladder, was palpated in the caudal abdomen. Urine was obtained and evidence of pyuria detected. A complete blood count and serum chemistry evaluation including symmetric dimethyl arginine (SDMA) was within normal limits. An abdominal ultrasound was recommended to evaluate the caudal abdomen.

Ultrasound evaluation revealed an elongated tubular structure to the right and dorsal to the urinary bladder, distended with echogenic fluid, consistent with a uterine remnant (figure 1). Mild sublumbar lymph node enlargement was present and while the left kidney appeared normal, the right kidney was very small and irregular with a length of 1.9 cm and absent corticomedullary distinction (figure 2). No ovarian structures were identified. The patient was referred for a surgical consultation.

On presentation to the surgery service, the patient was quiet, alert and responsive with no abnormalities other than dried discharge at the vulva. The bladder and mass were not palpated due to concerns for rupture of the mass. A 3 cm caudal midline scar was present, consistent with previous ovariohysterectomy. A limited serum chemistry evaluation demonstrated mild hemoconcentration (53% / 6.4 g/dl) and normal electrolytes, glucose, blood urea nitrogen, and creatinine. Due to patient history of heat cycles after OHE, abnormal findings on caudal abdominal palpation, and ultrasonographic confirmation of a fluid filled structure in the caudal abdomen, stump pyometra with retained ovarian remnant(s) was suspected and exploratory celiotomy recommended.  

At surgery, a 3 cm diameter, fluid filled uterine stump was found (figure 3). Mature omental adhesions were present. In the right craniodorsal abdomen just caudal to the liver, the right oviduct, ovary and omental bursa were found (figure 4). The right renal fossa was empty except for a firm 1-2 cm ovoid structure palpable within the retroperitoneal fat. A normal appearing right ureter could be traced from the bladder to this area. The right mid lateral body wall contained several linear smooth muscular defects.  The left kidney, ureter, and bladder appeared normal, and no ovarian remnants were found on the left side. No evidence of peritonitis was noted.

Ovairiectomy and hysterectomy was performed using LigaSure to dissect and remove the ovarian structures, uterine stump and adhesions. The uterus was clamped across the proximal cervix and doubly ligated. The rest of the exploratory, closure and recovery were routine. The patient was discharged from the hospital the following day on amoxicillin-clavulanate and codeine. Avoidance of potentially renal impairing drugs was strongly recommended in the future (no NSAIDs) due to apparent lack of a functioning right kidney, as was monitoring of renal values. A culture of the uterine stump was performed after surgery (figure 5) which recovered methicillin resistant Staphylococcus hominus in small numbersBecause the patient was clinically normal prior to surgery and post-operatively when the results were available, no evidence of peritonitis was present at surgery, and surgical technique did not produce any visible contamination, additional or prolonged antibiotic therapy was not instituted. The patient had an uncomplicated recovery as reported at the two week follow up and again via telephone four weeks post-op.

Stump pyometra is a common sequela to retained ovarian tissue in the female dog. As the ovary continues to produce progesterone and estrogen in cyclical fashion, any remaining endometrium is stimulated and fluid accumulation within the uterine stump occurs, increasing the chance for infection during diestrus. While a unilateral ovarian aplasia is possible, it is rare and if suspected a thorough abdominal exploration via an enlarged approach should be performed to ensure that all ovarian tissue is removed. In this patient, the ovary was displaced cranially to the level of the liver and would not be visible through a standard or even slightly larger approach, resulting in the entire ovarian complex and oviduct to be left within the patient.   

In our patient, abnormal anatomy was reported to the dog’s owner at the time of OHE. Congenital abnormalities of the uterus are reported to occur infrequently in canines. According to a large prospective study,1 abnormalities of the uterine horns occur in about 5/10,000 dogs. In 50% of these cases the ipsilateral kidney was not present and in 93% of cases, both ovaries were present. Often the ovary was displaced either cranially, as in the case of this report, or caudally back towards the bladder. Since the original surgery report is not available for review, we cannot confirm whether a normal right uterine horn is present but a congenital defect of this type is possible in our patient. In patients with defects of the uterine horn found, the clinician should perform a thorough exploration of the patient’s abdomen, assessing both kidneys and looking both cranially and caudally in the dorsal abdomen for the ovary, as it is present in the overwhelming majority of cases.

In a patient displaying evidence of estrus cycles post ovariohysterectomy, vaginal cytology and hormonal assays in conjunction with abdominal ultrasound could be used to confirm the presence of retained ovarian tissue. Ultrasound evaluation alone is not 100 percent successful in locating retained ovarian tissues depending on the amount of tissue present and as illustrated in this patient, abnormal location of the tissue. Measurement of serum anti-Mullerian hormone is a relatively new assay with good sensitivity in detecting patients with ovarian remnant syndrome 2.

Unilateral renal dysplasia (RD) is a congenital abnormality of the kidney that is governed by a specific genetic mutation in many breeds. It can also be due acquired due to fetal or neonatal trauma. The kidney is abnormally small with and often lacks corticomedullary distinction. Biopsy of the affected kidney demonstrates fetal glomeruli. Since bilateral dysplasia is more commonly congenital, and this patient had an apparently normal left kidney and with defects in the body wall that could be consistent with an early traumatic event, it is also possible that this represents an acquired case of RD. Biopsy of the small structure in the retroperitoneal space visible on ultrasound could confirm this theory; however, for this asymptomatic patient it is clinically not appropriate. 

The symmetric dimethyl arginine (SDMA) test is reported to allow detection of renal dysfunction when 25-40% of function is gone3. Further renal function testing could more closely determine the renal capacity remaining in this patient, but in an asymptomatic patient with a normal SDMA at least 60% renal function is likely which would be consistent with one fully functional kidney. Strict avoidance of drugs or situations (hypoxia, urinary tract obstruction, UTI) that could cause additional renal injury is extremely important in patients with any form renal compromise as is close monitoring of urine specific gravity and renal values.

References

  1. McIntyre, RI, Levy, JK, Roberts, JF, Reep, RL.  Developmental uterine abnormalities in cats and dogs undergoing elective ovariohysterectomy. J Am Vet Med. Assoc 237 (5);542-546
  2. Turna Y, Toydemir TS, Kirsan I, et al. Anti-Müllerian hormone as a diagnostic tool for ovarian remnant syndrome in bitches. Vet Res Commun 2015 Sep;39(3):159-62.​
  3. Nabity MB, Lees GE, Boggess MM, et al. Symmetric dimethylarginine assay validation, stability, and evaluation as a marker for the early detection of chronic kidney disease in dogs. J Vet Intern Med 2015 Jul-Aug;29(4):1036-44.

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