Diagnosis of Ovarian Cysts in Dogs and Cats: Role of Ultrasound and Histopathology

Ovarian cysts in bitches and queens can be difficult to recognize clinically because many are small and may remain subclinical. In the available data, most cysts were ≤0.5 cm, making reliable detection and classification an important diagnostic challenge¹. For veterinarians managing reproductive cases, combining imaging with laboratory and pathological assessment can help distinguish ovarian cysts and determine their characteristics. 

Why Diagnosis Can Be Challenging² 

The clinical presentation of ovarian cysts is variable. Some hormonally active cysts may be associated with reproductive abnormalities, whereas others may be detected incidentally during ovarian examination. This makes diagnosis based on clinical signs alone difficult. 

The available evidence also shows considerable variation in diagnostic approaches. Without a consistent diagnostic protocol, the interpretation of an ovarian lesion may depend on the modality used and whether the ovary is subsequently examined histologically. 

Ultrasonography as a Diagnostic Tool 

Ultrasonography was among the most frequently used methods for identifying ovarian cysts, appearing in 8 of 13 included sources. It provides an opportunity to evaluate the ovaries during clinical examination without surgical intervention. 

However, diagnostic performance data remain limited. Only one source reported sensitivity for ultrasonography, with a value of 75%³. For the remaining available sources, sensitivity and specificity were either not reported or could not be calculated. 

This limitation is important in clinical decision-making. A cystic ovarian appearance on ultrasound should therefore be interpreted alongside the animal’s reproductive history, clinical findings and other available diagnostic information rather than being considered definitive on imaging alone. 

Role of Cytology and Hormonal Testing 

Cytology was reported in 7 of 13 sources, while hormonal assays were used in 4. Assays included hormones such as anti-Müllerian hormone (AMH), estradiol and progesterone. 

Hormonal assessment may be particularly relevant when a cyst is suspected to be endocrinologically active. Follicular cysts can produce sustained estradiol, whereas luteinized follicular cysts, luteal cysts, and cystic corpus luteum may be associated with progesterone hypersecretion². 

The available information also highlights a potentially useful but underexplored approach: evaluating peripheral blood and cyst fluid hormone concentrations. Periodic estradiol and progesterone testing may help with early detection of hormonally active cysts in animals that are not scheduled for immediate castration. 

Histopathology for Cyst Classification 

Histopathology was the most commonly reported diagnostic method, used in 11 of 13 sources. It remains particularly valuable for determining the structural characteristics and classification of ovarian cysts. 

Histopathological examination can distinguish among follicular cysts, subsurface epithelial cysts, rete ovarii cysts, and cystic corpus luteum. Specialized staining and immunohistochemical markers can additionally help assess endocrine activity^4,5. 

Key Takeaways 

• Ovarian cysts may be small and clinically silent, so clinical signs alone may not reliably identify them. 

• Ultrasonography is an important non-invasive diagnostic modality, but currently available evidence on its diagnostic performance is limited. 

• Histopathology remains important for definitive cyst classification and characterization. 

• Estradiol, progesterone, and AMH assays may provide additional information, particularly when hormonally active cysts are suspected. 

• A standardized diagnostic pathway incorporating imaging, hormonal assessment and pathological examination is still needed to improve consistency in clinical evaluation. 

References 

1. Knauf Y, Bostedt H, Failing K, Knauf S, Wehrend A. Gross pathology and endocrinology of ovarian cysts in bitches. Reproduction in Domestic Animals. 2014 Jun;49(3):463-8. https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/rda.12311 

2. Domrazek K, Kondratek K, Tobolewski F, Jurka P. Prevalence, diagnosis, and treatment of ovarian cysts in bitches and queens: a meta-analysis. Animals. 2025 Sep 25;15(19):2800. https://www.mdpi.com/2076-2615/15/19/2800 

3. Ball RL, Birchard SJ, May LR, Threlfall WR, Young GS. Ovarian remnant syndrome in dogs and cats: 21 cases (2000–2007). Journal of the American Veterinary Medical Association. 2010 Mar 1;236(5):548-53. https://www.academia.edu/download/99796599/de4d589d979d21e751dcca4fdc970c9b9b5c.pdf 

4. Knauf Y, Köhler K, Knauf S, Wehrend A. Histological classification of canine ovarian cyst types with reference to medical history. Journal of veterinary science. 2018 Nov;19(6):725-34. https://synapse.koreamed.org/upload/synapsedata/pdfdata/0118jvs/jvs-19-725.pdf 

5. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, Shamseer L, Tetzlaff JM, Akl EA, Brennan SE, Chou R. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. bmj. 2021 Mar 29;372. https://www.bmj.com/content/bmj/372/bmj.n71.full.pdf?utm