An otherwise healthy 21-year-old female college student presents to the emergency departme… — USMLE Step 3

An otherwise healthy 21-year-old female college student presents to the emergency department complaining of severe, right-sided pelvic pain with a sudden onset 5 hours prior while she was exercising. The pain is sharp, non-radiating, and accompanied by nausea and two episodes of emesis. Her last menstrual period was 3 weeks ago, and her cycles are regular. Vital signs are temperature $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure $118/76\text{ mmHg}$ , pulse $98/\text{min}$ , and respiratory rate $16/\text{min}$ . Physical examination reveals exquisite tenderness to palpation in the right lower quadrant with voluntary guarding, but no rebound tenderness is elicited. Pelvic examination demonstrates right adnexal fullness and tenderness without cervical motion tenderness. A urine pregnancy test is negative. Complete blood count shows a leukocyte count of $8,500/\mu\text{L}$ . Transvaginal ultrasonography demonstrates a $6.5 \times 5.0 \times 4.5\text{ cm}$ right ovary with a heterogeneous, echogenic central stroma and multiple small, peripherally displaced follicles. Color Doppler evaluation reveals the presence of arterial spectral waveforms within the right ovarian parenchyma, but venous flow is completely absent. The left ovary measures $2.5 \times 2.0 \times 1.5\text{ cm}$ and demonstrates both continuous venous and low-resistance arterial flow. The appendix measures $5\text{ mm}$ in maximal diameter and is compressible. A small amount of simple free fluid is noted in the rectouterine pouch. Based on the interpretation of these imaging findings, which of the following is the most appropriate next step in management?

A
Computed tomography of the abdomen and pelvis with intravenous contrast
B
Discharge home with nonsteroidal anti-inflammatory drugs and outpatient gynecologic follow-up
Diagnostic laparoscopyAnswer
D
Serial pelvic ultrasonography and abdominal examinations every 12 hours
E
Intravenous administration of ceftriaxone and doxycycline

Answer

Diagnostic laparoscopy

The correct next step is diagnostic laparoscopy to evaluate and treat suspected ovarian torsion. The clinical vignette strongly suggests adnexal torsion (sudden severe pelvic pain, nausea, vomiting in an otherwise healthy female). The key to this question is the nuanced interpretation of the transvaginal ultrasound. A common misconception is that the presence of arterial blood flow on Doppler completely rules out torsion. In reality, the twisting of the infundibulopelvic ligament first occludes the thin-walled, low-pressure venous and lymphatic channels while the thick-walled, higher-pressure arteries remain patent. This pathophysiology causes vascular engorgement and stromal edema, which pushes the developing follicles to the edge of the ovary (the 'string of pearls' or peripheral follicular sign). Complete absence of arterial flow is a late finding that often indicates irreversible infarction. Because the imaging shows classic signs of venous obstruction and ovarian edema, emergent laparoscopy with detorsion is required to preserve ovarian function.

Step-by-Step Solution

Analyze the clinical presentation.

The patient has sudden-onset, severe unilateral pelvic pain with nausea and vomiting, which is the classic presentation for adnexal torsion.

Identifying the leading clinical differential guides the interpretation of the subsequent imaging.

Interpret the specific ultrasound findings.

The right ovary is asymmetrically enlarged with an echogenic central stroma and peripherally displaced follicles. Venous flow is absent, but arterial flow is preserved.

Accurate interpretation of Doppler imaging requires understanding that the presence of arterial flow does not rule out torsion. Venous outflow is obstructed first due to lower pressure and thinner vascular walls, leading to engorgement and edema (displacing follicles).

Determine the appropriate management based on the interpretation.

Immediate diagnostic laparoscopy is indicated.

Since the imaging strongly supports ovarian torsion, emergent surgical detorsion is required to prevent irreversible ischemic necrosis of the ovary.

Key Concept

The presence of arterial flow on Doppler ultrasonography does NOT exclude ovarian torsion. Early torsion compresses thin-walled veins, resulting in absent venous flow, ovarian edema, and peripherally displaced follicles, while arterial flow often persists until late in the ischemic process.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic