Page 235 - WSAVA2017
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L. Gatel1, J. Saunders1 1 Merelbeke, Belgium
Normal appearance
1. Uterus
The uterus is a thin tubular organ from 1 to 6,7 mm in diameter at the level of the horn and 1,6-7,2 mm at the level of the uterus body. The diameter of the uterus correlates with the weight of the queen, the season and probably also with age, previous pregnancies
hours. The corpus hemorrhagicum can be recognized thanks to a more cellular content (= more echoic) compared to the follicle, and easily detected when the previous localisation of the follicle is known. Compared to other species, detection of the corpus luteum is difficult in cats. Ultrasound of the ovaries during a cycle should be repeated several times and is the easiest, most precise and least invasive modality to detect ovulation time.
Abnormal conditions
1. Uterus
1.a. Cystic endometrial hyperplasia
Cystic endometrial hyperplasia (CEH) is a common histological finding in nulliparous queens over 3 years old and in other queens over 5, without correlation with the number of parturitions. On ultrasound, a variable number of anechoic cysts of different sizes can be observed
in the endometrium. The severity of the ultrasound findings correlates with the severity of the disease. Most of the time a CEH is associated with enlarged uterine diameter. Administration of synthetic progesterone for contraception leads to the development of advanced endometrial hyperplasia. CEH is more frequent in indoor than in outdoor cats. When a CEH is observed, there
is high chance of a corpus luteum on the ovaries or an ovarian cyst.
1.b. Pyometra, mucometra and hydrometra
The 3 conditions have a similar appearance on ultrasound: the diameter of the uterus is increased and the lumen is distended by anechoic to echoic fluid.
The amount of fluid located in the lumen depends on
the cervix: with a close cervix, there is a larger amount
of fluid. For differentiation between the 3 processes,
it is important to look for any secondary changes,
such as peri-uterus effusion, steatitis, abdominal lymphadenopathy or pneumo-abdomen. Pyometra
is observed in old queens around 8 years old or in
young queens after administration of contraceptive pills (progesterone). CEH-pyometra complex can be observed with cystic lesions in the endometrium, fluid in the lumen and an enlarged uterus.
1.c. Endometritis and metritis
These disorders are underestimated due to their difficult diagnosis. In dogs, some changes in the thickness and echogenicity of the endometrium can be observed, but the examination could just as well be completely normal.
1.d. Neoplasia
Neoplasia of the uterus are rare (0,29% of neoplasia in cats). Adenocarcinomas seem to be more frequent
An Urban Experience
  and contraceptive treatment. Histologically, the uterus
is composed of 3 layers: the outside serosa, the myometrium and the inner endometrium. The serosa is seen as a thin hyperechoic line surrounding the horn, that can be differentiated from the surrounding mesenteric fat. The apparent inner layer (undistinguished myometrium and endometrium) is iso- to hypoechoic to the surrounding fat. The endometrium and the myometrium can be observed during pro-oestrus, oestrus and dioestrus or pregnancy thanks to the combination of hormones (oestrogens and progesterone) and thickening of the uterus. The endometrium and the myometrium
can be isoechoic to each other, with a thin hypoechoic band to distinguish them, or the endometrium can be hypoechoic compared to the myometrium. The lumen should be empty and is visualized as a thin hypoechoic line (due to a reflection artefact).
1. Ovaries
The ovaries are small in size, from 6,8 to 15 mm in length, ovoid in shape and they produce some edge shadow artefact. In anoestrus, a distinction between the cortex and the medulla is possible, with the medulla being hyperechoic compared to the cortex. With a frequency transducer higher than 15MHz, a primary follicle can be observed as small hypo- to anechoic
foci of less than 1 mm in the cortex. Queens are seasonally polyoestrous, reflex ovulators. Without vaginal stimulations, the cycle can be anovulatory, even if some spontaneous ovulations have been reported. During an anovulatory cycle, the follicles grow during pro-oestrus and oestrus and decrease in size in inter-oestrus. When the queen shows oestrus behaviour, the follicles are about 2,3 mm, and they can grow until 3.5-4,1 mm (follicular grow = 0,2mm/day). No corpus luteum should be observed.
If the cycle is ovulatory, the ovulation will start 23 to 28 hours after the stimulation and continue on at least 10

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