Clitoral anatomy and sampling the clitoral sinuses

Keywords: equine, clitoris, CEM

Clitoral sinuses are routinely cultured for the CEM organism or CEMO, Taylorella equigenitalis which is able to grow in this relatively anaerobic environment. Image A shows the location of one of the largest clitoral sinuses; usually the central sinus on the dorsal surface of the clitoris.

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Image B shows the approximate depth of the largest sinus, certainly deep enough for an anaerobic environment. The inset between images A and B shows that this central sinus can even stretch and harbor large amounts of smegma. This mass of accumulated smegma is analogous to a “bean” found in a preputial diverticulum in a stallion. In this case, the smegma contents of the sinus have been cleaned out by squeezing the margins of the clitoris.   The smegma itself probably provides an anaerobic environment for the growth of Taylorella equigenitalis.

Due to the small size of the clitoral sinuses, it is best to use small diameter swabs to culture for CEM.  A conventional swab with a blue cap is shown next to a narrow bore swab that is ideal for sampling the clitoris. In the inset image at top left, it is apparent that a large swab cannot easily fit into a clitoral sinus.

The fossa glandis 

Keywords: equine, beans, fossa glandis, CEM

The equine fossa glandis is also called the urethral diverticulum; a somewhat misleading term because it lies completely outside the urethra. Also, it is not a simple fossa but a recess surrounding the urethral process that extends into two diverticulae; one either side of the urethra.  It is in these diverticulae that accumulations of smegma are found. Those accumulations are colloquially referred to as "beans".

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At top left, a yellow arrow indicates the direction in which a digit can be inserted into one diverticulum of the fossa glandis. In this case, the left diverticulum (the stallion's left). Both diverticulae are being explored in the circular images.

In the image at lower left, a penis has been transected sagitally (dorsal to ventral) to expose the diverticulae on either side of the urethra (U). A "bean" has been removed from the right diverticlum . Another "bean" remains in the left diverticulum.  The dorsal aspect of the penis is indicated by the letter D. CC shows the saggital section of the most cranial part of the corpus cavernosum penis. On the lower right, a pair of forceps has been inserted into the left diverticulum of the fossa glandis of this penis.

Smegma "beans" can provide a substrate for bacterial growth and many stallions harbor potential pathogens such as Klebsiella spp. and Pseudomonas spp. in their diverticulae.  The fossa glandis is also a somewhat anaerobic environment (especially deep in the diverticulae) and is therefore an ideal site for the growth of Taylorella equigenitalis, the cause of contagious equine metritis (CEM). Therefore, culturing the diverticulae of the fossa glandis is an important part of screening for CEM.

The stallion is the only domestic animal with a fossa glandis.