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28

Reproduction
Judith Hudson and Aime Johnson

Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA

28.1 Radiographic Anatomy In the nongravid cat, the uterus appears in the transverse
of the Female Cat plane as a hypoechoic circular structure or ellipse, measur­
ing about 0.5–1.0 cm (Figure 28.2a). In the longitudinal
The normal nongravid uterus is occasionally visible in cats plane (Figure 28.2b), it is seen as a slightly undulant, tubu­
because of the cranial location of the feline bladder. In one lar organ. The myometrium and endometrium are best dis­
study using digital radiography, the uterus was seen as a tinguished in the postpartum period, but one study found
longitudinal fluid opacity between the bladder/urethra that layering was apparent in 4/8 cats imaged, with the
ventrally and the colon dorsally in 14/50 cats, particularly myometrium being the less echogenic of the two layers [2].
when compression was applied using a wooden spoon Fluid was not seen in the lumen but a thin hyperechoic line
(Figure 28.1) [1]. Iodinated contrast can be placed in the noted centrally was attributed to echoes originating from
vagina using a Foley catheter to check for fistulae or tears the adjacent wall surfaces [2]. A hyperechoic peripheral
but ultrasonography is more useful for imaging other por­ line on longitudinal images most likely represented the
tions of the female reproductive tract. Normal ovaries are serosa [2]. The uterus is more apparent during estrus or
not radiographically visible. early pregnancy when it becomes slightly enlarged and less
echogenic, and might contain a small amount of fluid in
the lumen.
The aorta, caudal vena cava (CVC), and small intestine
28.2 Ultrasonography of the Female Cat can be mistaken for the uterus (Figures 28.3 and 28.4). If
available, Doppler ultrasonography can be used to differen­
A high‐frequency transducer (7–12 MHz) should be used for tiate vascular structures from the uterus. Care should be
evaluation of the reproductive tract with the cat positioned taken to ensure that the gain setting is optimal so that vas­
in either lateral or dorsal recumbency. The uterine horns are cular structures appear anechoic in comparison to the
more symmetrically located when the cat is in dorsal recum­ uterus. Additionally, pulsatility may be noted in the aorta
bency and the urinary bladder can serve as an “acoustic win­ and both vessels branch caudally whereas the uterus bifur­
dow.” On the other hand, the uterus is more superficial cates cranially. Larger vessels like the aorta and CVC are
when imaged from the lateral aspect. A useful procedure is relatively straight compared to the undulating structure of
to find the ovary first and then scan between the ovary and the uterus. Applying moderate pressure to the probe will
urinary bladder to identify the uterus. Scanning should be cause the CVC to collapse, allowing it and the adjacent
avoided after administration of an enema because the proce­ aorta to be identified. Watching for branches extending to
dure increases the amount of gas in the colon, which will or from various organs can be helpful.
obscure visualization of other organs. Lateral recumbency is Intestinal loops have well‐defined wall layers, unlike the
best for detection of the ovaries since each is dorsally located uterus (Figure 28.4). Peristalsis and hyperechoic gas or
near the caudal pole of the ipsilateral kidney. Ovaries are ingesta can further aid in identification of intestinal loops.
more difficult to find when the cat is in dorsal recumbency Diseased bowel is more difficult to differentiate from the
because intestinal gas is more likely to interfere with visuali­ uterus, particularly if loss of wall layering has occurred. In
zation of these small organs. these cases, the abnormal area may be followed proximally

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.