Pelvic CT

Emergency pelvic computed tomography

Computed tomography is strongly recommended for any suspected pelvic bone trauma. If a patient presents with polytrauma, the pelvic region is scanned as part of the overall pan-CT protocol.

The primary target audience for this diagnostic algorithm includes patients with signs of pelvic ring instability accompanied by hemodynamic disturbances. The examination is organized as quickly as possible, ideally in a trauma bay or intensive care unit (ICU).

A critical organizational rule: the patient is transported for CT only after adequate infusion therapy has been initiated in the emergency operating room. Concurrently with CT, specialists perform a focused assessment with sonography for trauma (FAST) protocol to immediately detect hematomas and potential sources of ongoing hemorrhage.

Radiography as an alternative method

In situations where CT is technically impossible, diagnostic imaging relies on conventional radiography. The baseline examination is the anteroposterior projection, supplemented by inlet and outlet views (with the X-ray tube angled at 30–45 degrees).

Acetabular fractures (acetabulum) require special attention. For their detailed evaluation, iliac, obturator, and oblique projections are obtained. Emergency traumatology enforces a strict rule: do not position a severely injured patient by rotating the torso 30–45 degrees to the left or right. The radiologist must only change the angle of the central beam of the machine while keeping the patient's pelvic position completely motionless to avoid exacerbating the injury.

Radiation anatomy and hip joint evaluation

For diagnosing hip joint disorders such as coxarthrosis, a baseline radiograph is usually sufficient. However, for fine differential diagnosis—for instance, to rule out inflammatory arthritides—CT or MRI is prescribed. Image analysis evaluates key anatomical relationships:

1. Wiberg angle (Wiberg): indicates the depth of femoral head coverage within the acetabulum. It is formed by a line passing through the center of the femoral head perpendicular to the transverse axis of the pelvis, and a line from the center of the femoral head to the superolateral edge of the weight-bearing (sclerotic) zone of the acetabulum. Normal in adults is 26–35 degrees.
2. Shenton's line: an arc extending from the medial contour of the femoral neck to the superior border of the obturator foramen. A disruption in this smooth line is a definitive sign of dysplasia or compromised joint integrity.
3. Vertical-center-peripheral angle: formed between the line connecting the edges of the acetabulum and the line from the center of the femoral head to the middle of the femoral neck (normally 70–90 degrees).
4. Femoral head coverage: the ratio of the diameter of the femoral head to the distance from its medial edge to the lateral border of the acetabulum. Normal coverage is 70–90%.

The role of CT and PET/CT in oncogynecology

Although CT plays a leading role in traumatic pelvic bone injuries, MRI is the method of choice for staging pelvic tumors (such as cervical or endometrial cancer). It surpasses CT due to its exceptionally high soft-tissue resolution, allowing precise measurement of invasion depth and involvement of adjacent structures.

Computed tomography is frequently combined with positron emission tomography (PET/CT) using fluorodeoxyglucose (FDG). This method detects areas of accelerated glycolysis characteristic of malignant cells. PET/CT is used to search for recurrences, though potential pitfalls must be kept in mind. False-negative results occur if the metastasis is smaller than 0.5 cm or if the tumor has low metabolic activity. False-positive responses are often associated with inflammatory processes, infections, and postoperative changes.

Class and exam questions

What else to study on this topic

• Radiological criteria for dysplasia: Wiberg angle, Shenton's line, and vertical-center-peripheral angle.
• Imaging of intra-articular calcaneal fractures and measurement of Bohler's angle.
• MRI protocols for precise staging of endometrial and cervical cancer.
• Differential diagnosis of coxarthrosis and inflammatory arthritides using diagnostic imaging.

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Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.