Pelvic CT Recognition Pattern

Systematic approach to interpreting pelvic CT scans with focus on genitourinary, gastrointestinal, and musculoskeletal structures

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1. Pelvic CT Protocols

A. Standard Techniques

• Trauma protocol:
  - IV contrast required
  - 2.5-3mm slice thickness
  - Includes entire pelvis to lesser trochanters
• Oncology staging:
  - Triple-phase (non-contrast/arterial/venous)
  - Rectal/vaginal contrast optional
  - Extended FOV to L3 for nodes
• Renal colic protocol:
  - Non-contrast only
  - Low-dose technique
  - From top of kidneys to pubic symphysis

B. Key Anatomical Planes

• Dividing landmarks:
  - Sacral promontory (true vs false pelvis)
  - Obturator internus (pelvic sidewall)
  - Piriformis (sciatic foramen)

2. PELVIS Systematic Approach

Step	Assessment	Key Elements
P	Prostate/uterus	Size, masses, enhancement
E	Extraluminal air	Bowel perforation, abscess
L	Lymph nodes	Obturator, iliac chains
V	Vessels	Iliac veins, aneurysms
I	Intestines	Wall thickening, obstruction
S	Skeleton	Fractures, metastases

3. Organ-specific Patterns

A. Genitourinary

Structure	Normal CT Features	Pathology
Bladder	Wall <5mm when distended	Tumors, rupture, diverticula
Prostate	Homogeneous 30-50HU	Nodules, abscess, calcifications
Uterus	Zonal anatomy post-contrast	Fibroids, malignancies
Ovaries	Follicular cysts <3cm	Torsion, masses, endometriomas

B. Gastrointestinal

• Diverticulitis:
  - Colonic wall thickening
  - Pericolonic fat stranding
  - Abscess formation
• Appendicitis:
  - Dilated appendix ≥7mm
  - Periappendiceal inflammation
  - Appendicolith (30% cases)

4. Pelvic Trauma Evaluation

A. Fracture Classification

• Young-Burgess:
  - APC (anteroposterior compression)
  - LC (lateral compression)
  - VS (vertical shear)
• Tile Classification:
  - Type A: Stable
  - Type B: Rotationally unstable
  - Type C: Vertically unstable

B. Critical Findings

• Arterial bleeding:
  - Active contrast extravasation
  - Pseudoaneurysms
• Visceral injury:
  - Bladder rupture (intra/extraperitoneal)
  - Rectal wall discontinuity

5. Pelvic Lymph Node Stations

Station	Location	Drainage
Internal iliac	Pelvic sidewall	Bladder, cervix, prostate
Obturator	Along obturator internus	Prostate, uterine corpus
Presacral	Anterior to sacrum	Rectum, anal canal

Abnormal criteria:
- Short axis ≥8mm (except inguinal ≥10mm)
- Round shape (loss of reniform)
- Necrosis or irregular margins

6. Pelvic CT Reporting Template

1. Technique: Contrast phase, reconstruction
2. Bones:
   - Fractures (classification)
   - Lytic/sclerotic lesions
3. Genitourinary:
   - Bladder/prostate/uterus
   - Abnormal fluid/air
4. Gastrointestinal:
   - Bowel wall thickening
   - Diverticula/appendicitis
5. Vascular:
   - Iliac vessels
   - Active bleeding
6. Soft tissues:
   - Abscesses/masses
   - Lymphadenopathy

Always correlate with clinical history (e.g., trauma mechanism, oncologic history). For female patients of reproductive age, note intrauterine devices or pregnancy when present. In trauma cases, carefully evaluate the sacral foramina and SI joints for subtle fractures. For oncology staging, measure lesions according to RECIST 1.1 criteria and document relationship to adjacent organs.

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