CERVIX
The endocervical canal is spindle shaped. Longitudinal crests of endocervical mucosa protrude into the cavity anteriorly and posteriorly as the plicae palmatae. Secondary branching of the mucosa gives the appearance of a tree and constitutes the arbor vitae. The endocervical mucosa is whitish pink and is thrown into numerous folds or papillae interspersed with clefts (Fig. 1.1). Sometimes one can see small bluish gray bubbles or retention cysts within the canal (Figs 1.2A and B).
The lumen varies from 3–10 mm in diameter depending on individual variation and parity. There is however some resilience to light pressure that may allow 1–2 mm additional space with stretching. During stretching the mucosal folds appear flat and white.
During contact and low pressure CO2 or liquid panaromic hysteroscopy the pink papillary mucosal pattern with its fine branched vessels can be appreciated.
Isthmus
This is a flattened narrowed short canal between the upper portion of cervix and the corpus. The mucosa is smooth compared with the highly folded endocervix. It is 1 cm in length and is marked by a constriction, i.e. internal os where it meets the cervix.
It is narrow in the nulliparous woman but expands to approximately 1 cm after delivery. This is the critical point for entry to uterine cavity. Most nerve points being concentrated here, this is the point where the woman feels pain.
Corpus
This forms the main mass of the uterus and is usually bent anteriorly on the isthmus. The walls are heavily musculatured and 2 cm thick. The uterine cavity is more accurately described as potential. It is flattened and has the shape of an inverted triangle with its base formed by a line drawn between the 2 tubal ostia and apex at the isthmic opening. The length measures 4–5 cm (Fig. 1.3).
The thickness of the mucosa varies between 1–8 cm depending on the phase of the menstrual cycle. During hysteroscopic examination the normal endometrium exhibits hues ranging from tan to pink.4
Fig. 1.3: Uterine cavity seen as inverted triangle. Base is a line drawn between tubal ostia. Vertex is isthmus
It appears rather flattened when viewed during the proliferative phase. During contact hysteroscopy it appears almost translucent with fine vessels. In the secretory phase the endometrium becomes velvety and magenta in color. Under contact hysteroscopy it shows irregular polypoid patterns that protrude into the cavity like stalactites and stalagmites. The thick fundus lies above a line drawn between the two tubal ostia. Frequently this site is marked by a central ridge identifying the point where the mullerian ducts have fused. This normal variant may be confused with an exaggerated subseptate uterus.
Tubal Ostia
The tubal ostia lie recessed in shallow depressions at either ends of the fundus also known as the cornua.
During hysteroscopy there is some variation in the appearance of the ostia as well as in the depth, position and relative location of the corneal recesses and tubal ostia.
They may be seen as flat slits or circles or appear elevated on papilla like pedestals or look completely flat (Fig. 1.4).
The cornual myometrium is thinner than the fundus or corpus muscle. During operative/diagnostic hysteroscopy regardless of location the uterine wall is stretched by the distending medium and thins by a factor of 50–60%.
Regardless of the phase of the menstrual cycle the endometrium is highly vascular and bleeds with the slightest touch of the endoscope. When a focusing magnified telescope is used the submucous capillaries can be seen to form a net-like intricate vascular pattern covering the entire endometrial surface (Fig. 1.5).
The depth of the endometrium can be assessed by allowing the pressure of the endoscope to impact the posterior wall producing a groove into the mucosa. When using the contact hysteroscope depressions representing the mouths of the endometrial glands are readily apparent. Occasionally small holes or diverticula may be observed in otherwise intact endometrium.