MRI SINOGRAM

MRI Sinogram is a specialized imaging procedure used to evaluate sinus tracts, fistulas, and other abnormal passages within the body by combining magnetic resonance imaging with contrast administration into the tract or cavity. This technique provides detailed information about the course, length, and connections of a sinus or fistulous pathway, along with the condition of surrounding tissues. MRI Sinogram is especially useful when conventional fistulograms or CT-based sinograms are insufficient or when radiation-free imaging is preferred. It offers excellent soft tissue contrast and the ability to visualize associated inflammatory changes or abscess formations.

Purpose of MRI Sinogram

1. Evaluation of sinus tracts

• Identifies the origin, direction, and termination of the tract.
• Helps differentiate between simple and complex sinus pathways.

2. Fistula assessment

• Determines internal openings, multiple branches, and connections with nearby structures.
• Assists in pre-surgical mapping of fistulous tracts.

3. Infection and inflammation

• Detects abscess formation, cellulitis, and inflammatory changes around the tract.

4. Post-surgical follow-up

• Evaluates healing or recurrence of sinus or fistula after surgery.

5. Tumor evaluation

• Identifies underlying neoplastic causes that may result in chronic draining sinuses.

Common Clinical Indications

• Chronic perianal fistulas.
• Non-healing post-surgical wounds with sinus formation.
• Persistent discharging sinus in the chest wall, abdomen, or extremities.
• Evaluation of osteomyelitis-related sinus tracts.
• Complicated pilonidal sinus disease.
• Sinus tracts related to infected implants or orthopedic hardware.

Procedure for MRI Sinogram

Before the scan

• A detailed history is taken to determine the location, duration, and previous treatments for the sinus or fistula.
• Any contraindications to MRI, such as incompatible implants, are assessed.
• The patient is informed about the procedure, especially about local contrast injection into the tract.
• Sterile precautions are followed during contrast administration.

During the scan

• The external opening of the sinus is cleaned and sterilized.
• A small catheter or cannula is inserted into the sinus opening.
• A diluted MRI-compatible contrast medium (usually gadolinium-based) is injected gently into the tract to fill its lumen.
• MRI sequences are performed immediately after contrast administration to avoid leakage or absorption altering the tract visualization.
• The area is scanned in multiple planes to map the tract completely.
• Standard MRI sequences include T1-weighted, T2-weighted, and fat-suppressed images before and after contrast injection.

After the scan

• The catheter is removed, and the opening is cleaned.
• The patient can resume normal activity unless sedation was used.
• The radiologist evaluates the tract course, side branches, internal openings, and any associated pathology.

MRI Sequences in Sinogram Studies

T1-weighted pre-contrast

• Helps assess anatomical details and baseline tract appearance.

T2-weighted images

• Highlight fluid-filled tracts and surrounding edema.

Fat-suppressed T2/STIR sequences

• Improve detection of inflammation and abscesses in the surrounding tissue.

Post-contrast T1-weighted fat-suppressed

• Clearly delineates tract enhancement, side branches, and connections to organs or cavities.

3D sequences

• Allow multiplanar reconstruction for precise surgical mapping.

Advantages of MRI Sinogram

• Superior soft tissue contrast compared to CT sinogram.
• Radiation-free imaging, suitable for repeated studies.
• Better visualization of associated inflammatory changes and abscesses.
• Multiplanar imaging enables accurate mapping in complex cases.
• Ability to detect subtle secondary tracts missed by conventional sinography.

Limitations

• More expensive and less widely available compared to CT.
• Requires careful contrast injection to avoid extravasation.
• Contraindicated in patients with certain metallic implants or severe claustrophobia.
• Longer scan time compared to CT sinogram.

Findings Commonly Detected

Simple sinus tract

• Single straight tract without branching.

Complex sinus tract

• Multiple branches or interconnected tracts.

Internal openings

• Connection to a hollow organ, joint, or other anatomical structure.

Associated abscess

• Localized fluid collection with rim enhancement.

Inflammatory changes

• Edema, soft tissue thickening, and hyperintensity around the tract.

Underlying bone involvement

• Osteomyelitis signs such as marrow edema and cortical destruction.

Tumorous cause

• Mass lesions involving or surrounding the sinus tract.

When MRI Sinogram is Preferred

• In recurrent or complex fistulas where surgical planning is necessary.
• When radiation exposure must be avoided, such as in younger patients.
• For detailed soft tissue evaluation alongside tract mapping.
• When CT findings are inconclusive.

Patient Preparation Tips

• Wear loose, comfortable clothing without metal.
• Inform the radiology team about any allergies, prior contrast reactions, or surgeries in the affected area.
• Follow hygiene measures before the procedure to reduce infection risk.
• Remain still during imaging to ensure clarity.

Applications in Different Body Regions

Perianal region

• Assesses intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric fistulas.
• Identifies secondary extensions that affect surgical approach.

Chest wall

• Evaluates sinus tracts due to post-thoracotomy infection or empyema.

Abdominal wall

• Detects postoperative fistulas connecting to bowel loops.

Extremities

• Maps sinus tracts related to chronic osteomyelitis.

Spine

• Detects cutaneous sinuses in spinal infections or post-surgical complications.

Conclusion
MRI Sinogram is a highly effective, radiation-free imaging technique for evaluating sinus tracts and fistulas with exceptional soft tissue detail. It offers precise mapping of the tract’s origin, path, and termination, along with detection of side branches, internal openings, and associated complications such as abscesses or inflammatory changes. This information is critical for surgical planning, reducing recurrence rates, and guiding appropriate medical or surgical management. Its role is especially important in complex, recurrent, or inconclusive cases where traditional imaging falls short. By combining tract opacification with advanced MRI sequences, MRI Sinogram provides both anatomical and pathological insight in a single study.