Differential Diagnosis for Vaginal Bleeding

The patient presents with vaginal bleeding after intercourse, which occurred on September 19, approximately one month after her last known full period on August 18. The bleeding was brief, lasting only a day or two, and differed from her normal menstrual period. Considering these symptoms, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis

  • Implantation Bleeding: This is a common cause of light bleeding or spotting in early pregnancy, occurring when a fertilized egg implants into the uterine lining. Given the timing (about a month after the last period) and the nature of the bleeding (brief and different from a normal period), this is a plausible explanation, especially if the patient has been sexually active without using contraception.

• Other Likely Diagnoses

  • Breakthrough Bleeding: This can occur in individuals taking hormonal contraceptives or experiencing fluctuations in hormone levels, leading to irregular bleeding.
  • Cervical Erosion or Cervicitis: Inflammation or erosion of the cervix can cause bleeding after intercourse due to the mechanical irritation of the affected area.
  • Vaginal Dryness or Trauma: Insufficient lubrication during intercourse can lead to vaginal dryness and minor tears, resulting in bleeding.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: Although less common, an ectopic pregnancy can present with irregular bleeding and must be considered, especially if the patient experiences severe abdominal pain or other concerning symptoms.
  • Molar Pregnancy: A rare condition where abnormal tissue grows in the uterus, which can cause irregular vaginal bleeding.
  • Cervical Cancer: While uncommon in younger individuals, any abnormal vaginal bleeding warrants consideration of cervical cancer, especially if accompanied by other symptoms like pelvic pain or abnormal vaginal discharge.

• Rare Diagnoses

  • Thyroid Dysfunction: Both hyperthyroidism and hypothyroidism can affect menstrual regularity and cause irregular bleeding.
  • Pituitary or Adrenal Gland Disorders: Certain conditions affecting these glands can disrupt normal hormonal balances, leading to irregular menstrual bleeding.
  • Coagulopathy: Bleeding disorders can cause easy bruising, heavy menstrual bleeding, or irregular bleeding, though these conditions are relatively rare.

Each of these diagnoses should be considered in the context of the patient's full medical history, a physical examination, and appropriate diagnostic tests to determine the underlying cause of the vaginal bleeding.