A 26-year-old female presents with 8 week amenorrhoea with pain in left lower abdomen. On USG thick endometrium with mass in lateral adnexa is visible. Diagnosis is likely to be:
**Core Concept**
The patient's presentation of amenorrhea and adnexal mass with a thickened endometrium on ultrasound is suggestive of an ectopic pregnancy with an associated corpus luteum cyst. This condition is characterized by the implantation of a fertilized ovum outside the uterus, usually in the fallopian tube, and is often associated with a corpus luteum cyst in the ovary.
**Why the Correct Answer is Right**
The corpus luteum cyst is a functional ovarian cyst that forms during the luteal phase of the menstrual cycle when the ovary fails to resorb the corpus luteum. In this case, the ectopic pregnancy may lead to the persistence of the corpus luteum, resulting in a cystic structure visible on ultrasound. The thickened endometrium is likely caused by the production of human chorionic gonadotropin (hCG) by the ectopic pregnancy, which stimulates the endometrium to proliferate.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a dermoid cyst is a type of ovarian cyst that contains tissue from all three germ layers, but it does not typically present with amenorrhea and adnexal mass in the context of pregnancy.
**Option B:** This option is incorrect because a ruptured ovarian cyst would typically present with acute abdominal pain and not necessarily with amenorrhea and adnexal mass on ultrasound.
**Option C:** This option is incorrect because a uterine fibroid is a benign tumor of the uterus and does not typically present with amenorrhea and adnexal mass in the context of pregnancy.
**Clinical Pearl / High-Yield Fact**
A key clinical feature of ectopic pregnancy is the presence of a corpus luteum cyst in the ovary, which can be visible on ultrasound. This is often associated with a thickened endometrium due to the production of hCG by the ectopic pregnancy.
**Correct Answer:** C. Ectopic pregnancy with corpus luteum cyst.