Luteal cystic ovary disease is characterized by enlarged
ovaries with one or more cysts, the walls of which are thicker than those of
follicular cysts because of a lining of luteal tissue.
Incidence ratios of follicular versus luteal cysts vary
greatly because of diagnostic tendencies of individual veterinarians.
luteal COD is defined as the presence of a
fluid-filled ovarian structure >25 mm diameter persisting >7 days in the
absence of a CL and with a wall diameter >3 mm, usually associated with
abnormal reproductive signs. Normal lacunae formation in CL may be incorrectly
classified as luteal COD
. Etiology and Pathogenesis:
The basic causes of true
luteal cysts are believed to be the same as for follicular cysts. The release
of luteinizing hormone (LH) may be somewhat greater than that occurring when
follicular cysts develop, and sufficient to initiate luteinization of follicles
but inadequate to cause ovulation. Luteal cysts may be an extension of
follicular cysts such that the nonovulatory follicle is partially luteinized
spontaneously or in response to hormonal therapy.
Clinical Findings:
Luteal cysts are
accompanied by normal conformation and anestrous behavior. Rectal palpation
reveals a quiescent uterus characteristic of the luteal phase of the estrous
cycle. Luteal cysts are recognized as smooth, fluctuant domes protruding above
the surface of the ovary. Usually, they are single structures.
Luteal cysts are
differentiated from follicular cysts on the basis of palpable characteristics
of both the structure and the uterus and, to some extent, on the cow’s
behavior. Progesterone assay and ultrasonography can help differentiate
between follicular and luteal cysts, although with either method a final
diagnostic decision remains somewhat subjective.
On attempts to
manually rupture the cystic structure, follicular cysts burst or rupture under
minimal pressure whereas luteal cysts cannot be ruptured with reasonable force.
Both types of cysts
respond to LH or GnRH therapy, but PGF2α will lyse some luteal
cysts and generally all diestrual CL structures.
Treatment and Control:
The treatment of
choice is luteolytic doses of PGF2α if a correct diagnosis can
be ascertained.
A normal estrus is expected in 3–5 days. The major limitation
of this treatment is the difficulty in accurately estimating the amount of
luteal tissue present. If the structure being diagnosed as a luteal cyst is
really a developing CL (as discussed above, sometimes called a cystic CL), it
may not respond because dairy cows do not become highly responsive to the
luteolytic action of PGF2α until day 6 after estrus.
Ultrasound examination is increasingly
common and facilitates diagnosis of ovarian structures. Luteal cysts also
respond to human chorionic gonadotropin and GnRH therapy that is effective in
the treatment of follicular cysts, but the next estrus could occur 5–21 days
after treatment. Manual rupture of luteal cysts is not recommended because of
the risk of trauma and hemorrhage. Because of poor estrus detection practices
on many dairy farms, the treatment of choice for both follicular and luteal
cysts is intravaginal progesterone/prostaglandin
(a fixed timed artificial insemination protocol) (see Treatment of Follicular Cystic Ovary Disease in Large
Animals). Application of this protocol in affected cows promotes timely
breeding after treatment.
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