**Core Concept**
Cryptomenorrhea refers to the condition where there is a lack of visible menstrual bleeding, despite a functioning uterus and ovaries. This condition is often associated with menstrual irregularities and can be caused by various factors, including hormonal imbalances, anatomical abnormalities, and systemic diseases.

**Why the Correct Answer is Right**
In cryptomenorrhea, the menstrual fluid may be absorbed by the body, or it may be retained within the uterus due to a partial or complete obstruction. This can occur due to various reasons such as Asherman's syndrome, where adhesions or scarring within the uterus prevent normal menstrual flow. Another possible cause is a partial vaginal septum or imperforate hymen, which can obstruct the normal outflow of menstrual blood.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it doesn't directly relate to the pathophysiology of cryptomenorrhea. While amenorrhea can be a symptom of various conditions, it's not the underlying cause of cryptomenorrhea.

**Option B:** This option is incorrect because it's a type of amenorrhea, which is a different condition altogether. Primary amenorrhea refers to the absence of menstruation in a woman who has never menstruated, whereas cryptomenorrhea refers to the absence of visible menstruation despite previous menstrual cycles.

**Option C:** This option is incorrect because it's a type of vaginal anomaly, but it's not directly related to the pathophysiology of cryptomenorrhea. While vaginal anomalies can cause menstrual irregularities, they're not the primary cause of cryptomenorrhea.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that cryptomenorrhea can be a symptom of underlying anatomical abnormalities or systemic diseases. A thorough history and physical examination, along with diagnostic imaging studies, are essential to diagnose the underlying cause of cryptomenorrhea.

**Correct Answer: D.**