Histological study of the canine ovarian suspensory ligament and its implications for neutering procedures

The ovarian suspensory ligament (OSL) is routinely manipulated during ovariectomy/ovariohysterectomy in dogs. Despite its surgical relevance, it is traditionally described only macroscopically as a fibrous band, and its microscopic composition has not been characterized.

To provide the first detailed histological and ultrastructural characterization of the canine ovarian suspensory ligament.

OSL samples were collected from twenty female dogs and processed for histology. Sections were stained with Masson's trichrome, Sirius Red, Weigert's resorcin-fuchsin, and anti-α-smooth muscle actin immunohistochemistry. Tissue components were quantified by surface density using a point-counting method. Scanning electron microscopy was performed to assess ultrastructural organization. Comparisons were made between sides and across age, body weight, and reproductive variables (p < 0.05).

The OSL did not resemble a dense collagenous ligament. Instead, it showed a heterogeneous architecture dominated by smooth muscle (46.3 ± 11.7%), followed by collagenous connective tissue (32.9 ± 8.9%), elastic system fibers (5.3 ± 2.1%), adipose tissue (2.7 ± 2.9%), and blood vessels (2.1 ± 2.7%). Immunohistochemistry confirmed the smooth muscle phenotype, and scanning electron microscopy demonstrated a loosely organized collagen network. No significant differences in composition were observed according to side, age, body weight, estrous history, or parity.

The canine OSL is not a classical dense fibrous ligament but a muscular ligament. These findings refine its anatomical characterization and have implications for surgical technique and future studies on pharmacologic relaxation.