**Core Concept**
The Whitaker test is a diagnostic procedure used to assess the patency of the uterine cavity, specifically in the context of evaluating the integrity of the uterine isthmus. It involves the instillation of a fluid or gas into the uterine cavity through a cannula inserted through the cervical canal, followed by the measurement of the pressure required to achieve a certain level of distension.

**Why the Correct Answer is Right**
The Whitaker test is specifically used to diagnose a uterine anomaly known as a uterine septum. A uterine septum is a congenital abnormality characterized by the presence of a dividing wall or septum within the uterine cavity. This condition can lead to recurrent miscarriages, infertility, and other complications. The Whitaker test involves the measurement of pressure required to distend the uterine cavity, which can help identify the presence of a septum by detecting an abnormal increase in pressure.

**Why Each Wrong Option is Incorrect**
* **Option A:** The Shirodkar test is used to diagnose a cervical incompetence, not a uterine anomaly.
* **Option B:** The Sims-Huhner test is used to evaluate the cervical mucus and its receptivity for sperm, not to diagnose a uterine anomaly.
* **Option C:** The Culdocentesis is a procedure used to diagnose a ruptured ectopic pregnancy, not a uterine anomaly.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the Whitaker test is a diagnostic procedure that requires specialized equipment and expertise, and should only be performed by experienced healthcare professionals in a controlled environment.

**Correct Answer: C. Uterine septum.**