Abdominal Masses and Pelvic Masses in Obstetrics

Introduction

Understanding abdominal and pelvic masses in obstetrics is crucial for success in the Medical Council of Canada Qualifying Examination Part I (MCCQE1). This comprehensive guide focuses on the Canadian perspective, aligning with MCCQE1 objectives and the CanMEDS framework.

Types of Abdominal and Pelvic Masses in Obstetrics

Uterine Fibroids (Leiomyomas)

Uterine fibroids are the most common benign tumors of the female reproductive system. They are particularly relevant in the Canadian context due to their prevalence among diverse ethnic groups in Canada's multicultural population.

Ovarian Cysts and Masses

Ovarian masses are common findings in obstetric patients and require careful evaluation to rule out malignancy.

Ectopic Pregnancy

Ectopic pregnancy is a critical diagnosis in early pregnancy and a significant cause of maternal morbidity and mortality in Canada.

Key Abbreviations:
- βhCG: Beta Human Chorionic Gonadotropin
- TVUS: Transvaginal Ultrasound

Canadian Epidemiology

• Incidence: 1-2% of all pregnancies in Canada
• Risk factors: Previous ectopic, pelvic inflammatory disease, smoking, assisted reproductive technologies

Diagnostic Approach

Management Options

1. Expectant management (for select cases)
2. Medical management with methotrexate
3. Surgical management (laparoscopy preferred)

Key Points to Remember for MCCQE1

• Differentiate between physiological and pathological causes of abdominal/pelvic masses in pregnancy
• Know the Canadian guidelines for managing uterine fibroids, including fertility-sparing options
• Understand the diagnostic criteria and management options for ectopic pregnancy in the Canadian context
• Be familiar with the classification and management of Gestational Trophoblastic Disease
• Recognize the importance of βhCG monitoring in early pregnancy complications
• Understand the role of imaging modalities (ultrasound, MRI) in diagnosing obstetric masses
• Be aware of the multidisciplinary approach in managing complex cases, aligning with CanMEDS roles

Sample Question

A 28-year-old woman, G2P1, presents to the emergency department at 7 weeks gestation with vaginal bleeding and right lower quadrant pain. Her last menstrual period was 7 weeks ago, and she has a history of pelvic inflammatory disease. Vital signs show BP 100/60 mmHg, HR 100 bpm. On examination, there is right adnexal tenderness. Transvaginal ultrasound shows no intrauterine gestational sac, and serum βhCG is 1800 IU/L. Which of the following is the most appropriate next step in management?

• A. Expectant management with serial βhCG measurements
• B. Administer methotrexate
• C. Perform a diagnostic laparoscopy
• D. Repeat transvaginal ultrasound in 48 hours
• E. Perform a dilatation and curettage

Explanation

The correct answer is:

• C. Perform a diagnostic laparoscopy

Explanation: This patient presents with signs and symptoms suggestive of an ectopic pregnancy: vaginal bleeding, unilateral pelvic pain, and a history of pelvic inflammatory disease (a risk factor for ectopic pregnancy). The absence of an intrauterine gestational sac on transvaginal ultrasound with a βhCG level above the discriminatory zone (typically 1500-2000 IU/L in Canada) raises high suspicion for an ectopic pregnancy.

In the Canadian context, given the patient's symptoms, vital signs showing mild tachycardia, and the high suspicion for ectopic pregnancy, the most appropriate next step is a diagnostic laparoscopy. This approach allows for both definitive diagnosis and potential treatment in a single procedure, which is crucial given the potential for rupture and life-threatening hemorrhage.

Option A (expectant management) is inappropriate given the high suspicion for ectopic pregnancy and the patient's symptoms. Option B (methotrexate) is not suitable without a definitive diagnosis and in the presence of significant symptoms. Option D (repeat ultrasound) would delay definitive diagnosis and treatment unnecessarily. Option E (dilatation and curettage) is contraindicated when ectopic pregnancy is suspected, as it would not address the ectopic gestation and could lead to complications.

This question tests the candidate's ability to recognize the signs of ectopic pregnancy, understand the significance of βhCG levels and ultrasound findings, and make appropriate management decisions in an emergency setting, aligning with the CanMEDS roles of Medical Expert and Decision-maker.

References

1. Society of Obstetricians and Gynaecologists of Canada. (2015). SOGC Clinical Practice Guideline No. 318: Management of Uterine Fibroids in Women with Otherwise Unexplained Infertility. Journal of Obstetrics and Gynaecology Canada, 37(3), 277-285.

2. Dodge, J. E., et al. (2020). SOGC Clinical Practice Guideline No. 414: Gestational Trophoblastic Diseases. Journal of Obstetrics and Gynaecology Canada, 42(10), 1266-1285.e1.

3. Lefebvre, G., et al. (2018). SOGC Clinical Practice Guideline No. 341: Diagnosis and Management of Adnexal Masses. Journal of Obstetrics and Gynaecology Canada, 40(3), e22-e39.

4. Shen, O., et al. (2019). Ectopic pregnancy: A Canadian overview. Journal of Obstetrics and Gynaecology Canada, 41(10), 1480-1487.

5. Vilos, G. A., et al. (2015). The management of uterine leiomyomas. Journal of Obstetrics and Gynaecology Canada, 37(2), 157-178.

6. Medical Council of Canada. (2023). Objectives for the Qualifying Examination. Retrieved from MCC website (opens in a new tab)