- Case report
- Open Access
Radiographic and ultrasonographic findings in a dog with emphysematous pyometra
© The Author(s) 2018
- Received: 8 April 2018
- Accepted: 20 October 2018
- Published: 29 October 2018
Emphysematous pyometra is a rare canine disease characterized by gas-forming bacteria infecting the uterus and causing an accumulation of both gas and infectious exudate in the uterine lumen. While radiological features of emphysematous pyometra have been previously described in dogs, the ultrasonographic appearance has not been reported.
A 7-year-old intact female Labrador Retriever was presented because of a 1 day history of vomiting, anorexia, mild polyuria/polydipsia and signs of fatigue. On physical examination the dog had a swollen vulva with a sparse amount of yellow discharge. Lateral and ventrodorsal radiographs showed a dilated predominantly gas-filled tubular structure located in the mid and cranial abdomen traversing from left to right and ending dorsally at the level of the 12th thoracic vertebra. A small intestinal ileus was initially suspected. Following the radiographic examination, abdominal ultrasound was performed. In the left mid and caudal abdomen there were two thin-walled gas-containing tubular structures. One had the typical layered appearance of an intestinal wall and represented the descending colon. The second structure had a similar thickness but homogenously hypoechoic wall and contained gas and echogenic fluid in the lumen. By use of several positional changes of the dog aiming to alter the location of the intraluminal gas, the second structure was traced to the right ovary cranially and the uterine body caudally, confirming that the structure was the right uterine horn. A final diagnosis of emphysematous pyometra was made.
Ultrasound can be used as a non-invasive diagnostic method to differentiate between small intestinal ileus and emphysematous pyometra.
Emphysematous pyometra in the dog is a rare, life threatening disease, characterized by gas-forming bacteria infecting the uterus and causing an accumulation of both gas and infectious exudate in the uterine lumen . To date, only six case reports have been described in dogs [1–6], and they all focus on the radiological features of emphysematous pyometra, which include large tubular structures containing gas or mixed gas and soft tissue/fluid opacities. The main differential diagnosis for emphysematous pyometra is small intestinal ileus. The previously reported radiological cases were conclusive mainly because of the bilateral involvement of the uterine horns, that created a bifurcating gas-filled tubular structure, or because of the severe degree of distension, that resembled a uterine horn rather than a small intestinal loop. Contrast radiography (upper gastrointestinal and barium enema) was also successfully used in some cases [4, 5] to distinguish between uterus and intestines.
We describe an unusual case of emphysematous pyometra, predominantly affecting one uterine horn that was in an unexpected anatomical position.
A 7-year-old intact female Labrador Retriever was presented because of a 1 day history of vomiting, anorexia, mild polyuria/polydipsia and signs of fatigue. The owner had noticed some discharge from the vulva, as well as mucus and helminths in the feces. The dog had been in estrus 2 weeks before presentation but was not mated. The owner reported episodes of vomiting and weakness during the dog’s previous estrus cycles. On physical examination the dog was normothermic, had a swollen vulva with a sparse amount of yellow discharge and showed signs of pain on abdominal palpation. Hematology showed mild leukocytosis (18.96 × 109 cells/L, reference 5.05–16.76 × 109 cells/L). A serum chemistry panel identified mild metabolic hypochloremia and respiratory alkalosis and mildly elevated lactate.
Because of the position and the gas content in the structure, the main radiological suspicion was small intestinal ileus likely due to mechanical intra- or extraluminal obstruction, despite that no foreign body or mass could be seen.
The radiological diagnosis was emphysematous pyometra, predominantly affecting the right uterine horn.
Pyometra is a bacterial infection that leads to accumulation of pus in the uterus, and commonly affects intact female dogs. Its pathogenesis is related to the repeated exposure of the endometrium to progesterone during the long luteal phase of the estrus in bitches . The progesterone-sensitized uterus is suitable not only for pregnancy, but also for bacterial infection, because progesterone stimulates endometrial glandular secretions, induces functional cervical closure, decreases myometral contraction and suppresses local immune responses . Escherichia coli is the most commonly isolated organism  but a wide range or other species have also been found [1, 2, 7–9]. Rarely the uterus is colonized by gas-producing bacteria, which lead to emphysematous pyometra. In previous cases of canine emphysematous pyometra Staphylococcus spp., Pseudomonas aeruginosa, Citrobacter diversus, Clostridium perfringens and Enterococcus avium have been isolated [1–5].
The radiological features of emphysematous pyometra have been described in dogs [1–5], and include tubular structures containing gas or mixed gas and soft tissue/fluid, which had to be differentiated from small intestinal gas . In the previously published case reports, the radiological studies were conclusive mainly because of the bilateral involvement of the uterine horns, creating a bifurcating gas-filled tubular structure, typical for the uterus, or for the severe degree of distension, that fit more a uterine horn than a small intestinal loop. Upper gastrointestinal and barium enema contrast radiography was successfully used in some cases [4, 5] to distinguish between uterus and intestines.
In cases of pyometra, the uterine horns are usually symmetrically affected, but this is variable and only one horn may be affected . The described case was misleading because only one horn was significantly enlarged and fluid and gas-filled, while the other horn was only mildly affected. The primary radiological diagnosis was a segmental dilated small intestine, since the gas-filled structure could not be clearly connected to the uterine body and the position was atypical for a distended uterine horn. The unusual location of the right uterine horn was probably because of the gas content causing it to be more fluctuant and moveable compared to the classic fluid-filled heavy horns. Furthermore, the contracted appearance of the tubular structure was interpreted as an increased intestinal peristalsis, possibly related to obstruction, another feature more typical for the gastrointestinal than the genital tract.
The ultrasonographic appearance of a pathologically altered uterus varies, but luminal fluid is commonly found and ultrasound is of great use to detect mild accumulation of fluid, even if differentiation of the type of fluid is not possible .
In this case the ultrasound examination was performed to localize the area of and the reason for the suspected obstruction (foreign body, mass, focal functional ileus) since this could not be established based on the radiographs. Usually ultrasound gives limited information when a large amount of gas is present in the investigated organ, since gas is a strong reflector and prevents transmission of ultrasound waves, creates reverberation artifacts and inhibits diagnostic information from being obtained . Despite the gas content, the wall of the hollow structure could be clearly evaluated and gave valuable information. The wall was not typical for an intestinal loop, since the layered pattern was missing. The proximity of the structure to the colon highlighted the different wall appearance, homogenously hypoechoic for the uterine wall, histologically composed of a mucosa and a muscularis, which cannot be differentiated with ultrasound , and alternating hyper- and hypoechoic layered for the intestinal wall, which is normally differentiated with ultrasound.
Severe inflammatory bowel disease can significantly affect the intestinal wall layers, even causing their complete loss, thereby making it difficult to differentiate between an abnormal intestinal segment and a gas-filled uterus. The peristaltic movement can help distinguish intestinal tract from genital tract, but altered motility is often present with severe enteritis, making this parameter less useful for distinguishing between intestines and a gas-filled uterus. Crucial to this case was the continual change in position of the dog during the examination, that allowed both the gas in the uterus to move and the superimposed colon to change position. These positional changes of the dog were repeated until a clear connection of the tubular structure with the right ovary and uterine body was identified, allowing for the definitive diagnosis.
In conclusion, as previously stated , radiological differential diagnosis of a dilated gas-filled structure in an intact female dog has to include emphysematous pyometra, even when no clear connection to the uterine body can be seen and the unusual position and unilateral affection of the organ seem to make this diagnosis less likely. In cases of uncertain radiological diagnosis, ultrasound represents a non-invasive and relatively rapid diagnostic method for differentiating between small intestinal ileus and emphysematous pyometra. A gas-filled hollow organ with thin, uniformly hypoechoic wall, lacking the typical intestinal layers and peristaltic movements, should raise the suspicion of emphysematous pyometra. To confirm the diagnosis of emphysematous pyometra the gas-filled structure should be clearly connected to the uterine body or ovaries.
CM interpreted the diagnostic imaging materials, prepared the manuscript and is the main author. MF conceived the idea of the manuscript and contributed with ideas to the discussion. KH made an intellectual contribution, reviewed the paper and was the main supervisor. All authors read and approved the final manuscript.
The authors would like to thank Maria Norell for the contribution to case management and Charles J. Ley for the language revision.
The authors declare that they have no competing interests.
Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
Ethics approval, consent to participate and consent for publication
Written informed consent for publication of the clinical details and/or clinical images was obtained from the dog’s owner.
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