Pyometra in a 13-year-old neutered queen

A 13-year-old, 3.2 kg, spayed female domestic shorthair was referred for weight loss of 1.4 kg over 4 months. The owner also reported that the cat was eating and drinking but hiding more than usual. The cat was neutered as a kitten, and signs of estrus had not been noticed by the owner since this surgery. The rectal temperature was 40.0°C. An electrocardiogram was performed and revealed normal rhythm, normal complexes and a heart rate of 174 beats per minute. A mass was palpated in the mid-abdomen.

The cat had leukocytosis (25.7×10³/mm³; normal 5.5–19.5×10³/mm³) and moderate non-regenerative anemia (packed cell volume: 19%; normal: 30–45%). Feline leukemia virus and feline immunodeficiency virus tests were negative. Serum biochemistry tests showed increased creatinine 2.3 mg/dl (reference range 0.3–2.1) and hypokalemia 3.4 mmol/l (reference range 3.7–5.8). The total T4 was normal. Thoracic radiographs revealed mild cardiomegaly. Abdominal ultrasound revealed a tubular fluid-filled mass (Fig 1). Differential diagnoses included a small bowel tumor, hydrometra and pyometra; pyometra was considered the most likely. Lactated Ringer's solution was administered intravenously at 1.5 times maintenance, and an exploratory laparotomy was performed. The preanesthetic medications were morphine (0.1 mg/kg IM) and acepromazine (0.09 mg/kg IM). Induction was by mask using sevoflurane. An endotracheal tube was placed, and anesthesia was maintained by sevoflurane. A midline surgical approach was performed. Pyometra was diagnosed when a tortuous, pus-filled, tubular structure with absence of gross evidence of ovarian tissue was identified (Fig 2). The structure was carefully dissected from the surrounding tissue and removed. The abdomen was closed routinely. The cat was given ampicillin sodium (20 mg/kg q12h SC) and enrofloxacin (5 mg/kg q12h SC) postoperatively.

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Fig 1.

Tubular fluid-filled mass in abdomen noticed by ultrasonographic abdominal evaluation.

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Fig 2.

Pyometra diagnosed when a tortuous fluid-filled structure was identified during surgery.

Histopathology of the excised tissue was not performed. Aerobic culture of the fluid revealed Escherichia coli (>100,000 cfu/ml) which was sensitive to amikacin, ampicillin, amoxycillin/clavulanate, enrofloxacin, gentamicin, tetracycline and doxycycline. Marbofloxacin (8 mg/kg q24h PO) and amoxycillin/clavulanate (20 mg/kg q12h PO) were prescribed at discharge, to be given for 3 weeks. The patient recovered fully.

Pyometra has been observed in queens older than 8 years and in younger queens after progesterone administration, even if they have been ovariectomized (Agudelo 2005). Most intact females are known to have experienced an estrous cycle within 1 week to 2 months before the onset of clinical signs (Johnson 1992). In this case, to the best of the owner's knowledge, this cat had been neutered as a kitten, and the cat had never experienced estrus or received estrogen or progesterone compounds. The mammary glands could have been a source of estrogen or progesterone, but no mammary neoplasia was found. Adrenal neoplasia may also cause elevated progesterone or estrogen levels, but the glands were grossly normal in this cat. The source of elevated estrogen or progesterone was not determined.

Pyometra may occur with incomplete removal of the uterine body or horns (Tobias and Wheaton 1995), as in this case. A progesterone source is thought to be necessary and is typically from ovarian remnants or exogenous administration (Agudelo 2005). The affected animal may have a history of estrous behavior after ovariohysterectomy (Tobias and Wheaton 1995) that was never noticed by the owner. Pyometra must be suspected in a neutered queen with purulent or hemorrhagic vulvar secretion; however, it is more of a diagnostic challenge in cases with closed-cervix pyometra (Agudelo 2005).

Physical examination usually reveals vaginal discharge in a mildly depressed, dehydrated cat with a normal or increased rectal temperature and a palpably enlarged uterus (Feldman and Nelson 2004). The most common clinical finding is vaginal mucopurulent to hemorrhagic discharge occurring in about 75% of the cases. However, this symptom can be inapparent due to fastidious habits of queens (Agudelo 2005). Moreover, only the cats with open-cervix pyometra have an obvious watery or thick and viscous vaginal discharge. Cats with closed-cervix pyometra have no vaginal discharge, but they may have significant uterine distention causing abdominal enlargement and severe illness (Feldman and Nelson 2004). Although this queen had a closed-cervix pyometra and moderate uterine distention, it did not show abdominal expansion or apparent disease.

In most of the cases, blood progesterone levels are increased, although normal levels may occur (Agudelo 2005). Moreover, according to Potter et al (1991), serum concentrations of estrogen and progesterone do not correlate with clinical disease or with histologic lesions in the uterus. Therefore, plasma concentrations of those hormones were not performed. Cytologic examination can be performed if the diagnosis is in doubt which was not the case.

Diagnosis is based on history, the clinical signs, and is usually confirmed by radiography and/or ultrasound. A tubular fluid-dense structure is observed on abdominal radiographs of 81–87% of animals with pyometra (Tobias and Wheaton 1995). In most cases ultrasound is preferred (Agudelo 2005). The uterine wall was thin (approximately 1.5 mm), and the lumen (approximately 3 cm in diameter) was filled with homogeneous hypoechoic material. Luminal distension with flocculent material of variable echogenicity is typical (Grundy and Davidson 2004).

Surgical examination of the abdomen showed a partial uterine horn approximately 3 cm×3 cm×7 cm. It was removed and contained thick yellowish pus. Before closure, urine collection by cystocentesis should be performed for culture because 30–79% of animals with pyometra have bacteriuria (Tobias and Wheaton 1995).

Medical therapy with prostaglandin F-2α and antibiotics has been proposed for elderly patients because of higher surgical and anesthetic risk (Agudelo 2005). However, in some references it is mentioned that this is not useful and must be avoided in geriatric patients older than 8 years (Agudelo 2005). Moreover, medical therapy should be avoided if the pyometra is closed (Biddle and Macintire 2000). Therefore, surgery without medical therapy was preferred, and the cat made an uneventful recovery. Although the owner did not observe severe clinical signs before the operation, she subsequently stated that the queen became much more alert and active following surgery.

This case appears to be unusual because of the age of the cat and the absence of ovaries. Moreover, it serves to emphasize the importance of carrying out a total ovariohysterectomy when neutering cats. Additionally, it illustrates why one must be open-minded when diagnosing feline patients.