15.4 Nasopharyngography, Sialography & Fistulography / Sinus Tract Visualization

15.4 Nasopharyngography, Sialography & Fistulography / Sinus Tract Visualization

The Enhanced TOS names nasopharyngography and fistulogram/sinus tract visualization as separate examinable procedures within Special Radiologic Examinations, each carrying items in both the "explain the preparation and types of examinations" competency and the "perform the preparation and procedures for positioning" competency. Sialography belongs to the same head-and-neck contrast family and is examined alongside them. All three are low-volume procedures in a modern department, which is exactly why candidates lose marks on them.

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1. Fistulography (Sinography) — Sinus Tract Visualization

Definitions

• A sinus tract is a blind-ending channel that opens onto a body surface at one end only.
• A fistula is an abnormal channel connecting two epithelialised surfaces — for example enterocutaneous (bowel to skin), rectovaginal, or vesicovaginal.
• Fistulography (also called sinography) is the radiographic demonstration of such a tract by injecting contrast through its external opening.

Indications

• Define the course, length and depth of a post-operative or post-traumatic tract.
• Determine whether the tract communicates with a viscus — bowel, bladder, joint or bronchus — or with bone (chronic osteomyelitis).
• Identify a retained foreign body, an abscess cavity, or a collection at the tract's blind end.
• Plan surgical excision, since a tract must be excised in its entirety to prevent recurrence.
• Assess a persistently discharging surgical wound or a chronic pilonidal or perianal sinus.

Technique

1. Scout image. Always obtain a plain image of the region before contrast. It shows radiopaque foreign bodies, gas in the tract, and bone changes that contrast will subsequently obscure.
2. Mark the external opening with a radiopaque marker so it can be correlated on the image.
3. Aseptic technique. Clean and drape the skin. This is a sterile procedure into a potentially infected space.
4. Cannulate the opening with a small, soft catheter — a paediatric feeding tube, a blunt-tipped needle, or a small Foley catheter whose balloon can be inflated just inside the opening to prevent reflux.
5. Seal the opening around the catheter so that contrast fills the tract rather than running back onto the skin. A purse-string suture, adhesive dressing or the balloon achieves this.
6. Inject water-soluble iodinated contrast slowly under fluoroscopic control, stopping when the patient reports pain, when the tract is fully opacified, or when contrast enters a viscus.
7. Image in at least two projections at right angles to each other — typically AP and lateral, with obliques as needed. This is not optional: a single projection can show a tract's length but never its depth or its true three-dimensional course.
8. Post-procedure: aspirate or express residual contrast where possible, re-dress the wound, and document the volume injected.

Contrast selection

Water-soluble iodinated contrast is used. Barium is absolutely contraindicated — if the tract communicates with the peritoneum, barium causes a severe and potentially fatal granulomatous peritonitis, and it is never absorbed or cleared from soft tissue.

Interpretation points

• Contrast entering bowel confirms an enterocutaneous fistula and identifies the segment involved.
• Contrast tracking to bone with irregular cortical destruction supports chronic osteomyelitis.
• A blind cavity with no visceral communication suggests an abscess or a retained foreign body.
• Multiple branching tracts predict a higher recurrence rate after excision.

Where it sits today

CT fistulography — the same injection with CT rather than fluoroscopic acquisition — and MRI are now preferred for complex, deep or perianal tracts because they show the surrounding soft tissues and sphincter relationships. Conventional fluoroscopic fistulography remains valuable for superficial tracts, for dynamic assessment, and in facilities without ready cross-sectional access.

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2. Sialography

Definition and anatomy

Sialography is the retrograde opacification of the salivary ducts and glands.

Indications

• Sialolithiasis (salivary calculus) — the commonest indication; roughly 80% of calculi occur in the submandibular system because Wharton's duct runs uphill and its secretion is more mucinous.
• Chronic or recurrent sialadenitis; ductal stricture.
• Sjogren syndrome, which produces a characteristic punctate sialectasis ("blossom on a branch" or "cherry blossom" pattern).
• Assessment of a mass and its relationship to the ductal system.
• Suspected ductal injury or fistula after trauma or surgery.

Contraindications

• Acute salivary gland infection — instrumentation and pressure injection can disseminate the infection.
• Known severe iodinated contrast sensitivity.
• Acute allergy or inability to cooperate with cannulation.

Technique

1. Scout images first — AP, lateral and, for the submandibular gland, an intraoral occlusal projection. A radiopaque calculus must be identified before contrast is injected, because contrast will hide it.
2. Give a sialogogue (lemon juice or a lemon wedge) before cannulation to dilate the duct orifice and make it easier to find.
3. Dilate and cannulate the duct orifice with a lacrimal dilator and a fine sialography catheter or blunt needle, under aseptic technique.
4. Inject a small volume of water-soluble iodinated contrast slowly — typically only about 0.5 to 1.5 mL — stopping when the patient reports fullness or pain. Overinjection ruptures acini and produces extravasation.
5. Filling images: lateral, lateral oblique and AP. For the parotid, a tangential projection profiles the lateral aspect of the gland.
6. Evacuation (secretory) images: give a sialogogue again and repeat imaging after about 5 minutes. Retained contrast beyond about 5 minutes indicates obstruction or poor glandular function.

Current status

Ultrasound is first-line for salivary swelling, CT for calculus and abscess, and MR sialography — a heavily T2-weighted sequence needing no contrast and no cannulation — increasingly replaces conventional sialography. Sialendoscopy now offers both diagnosis and calculus retrieval in one sitting.

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3. Nasopharyngography

Definition

Nasopharyngography is the radiographic demonstration of the soft tissues of the nasopharynx after instillation of contrast medium into the nasal cavity, so that the mucosal surfaces, the adenoidal pad, the torus tubarius and the fossa of Rosenmuller are outlined.

Indications (historic and residual)

• Assessment of adenoidal hypertrophy and of nasopharyngeal airway obstruction, particularly in children.
• Suspected nasopharyngeal mass or carcinoma, historically an important indication in Southeast Asia where nasopharyngeal carcinoma incidence is comparatively high.
• Evaluation of the eustachian tube orifice and of velopharyngeal closure during phonation and swallowing.
• Post-operative assessment after adenoidectomy or palatal surgery.

Technique

1. Obtain a plain lateral soft-tissue nasopharynx radiograph first — a well-penetrated lateral with the patient's neck extended and mouth closed, taken during quiet breathing, demonstrates the adenoidal soft-tissue pad and the airway column without any contrast at all. In many cases this alone answers the clinical question.
2. Apply topical anaesthesia and a decongestant to the nasal mucosa.
3. Instil a small volume of contrast medium into the nasal cavity with the patient supine and the head extended, so it coats the nasopharyngeal walls. Both oily and water-soluble preparations have been described historically; water-soluble iodinated contrast is preferred because of the aspiration risk.
4. Projections: lateral (the primary projection), submentovertical (base) view, and AP or Waters as required. Images may be taken during phonation ("E" or "K"), during swallowing, and with the mouth open and closed to assess dynamic closure.
5. Suction any excess contrast and keep the patient upright afterwards; observe for aspiration.

Contraindications and cautions

• Risk of aspiration — the principal hazard; the patient must be able to protect the airway.
• Acute epiglottitis or any condition where instrumentation may precipitate airway obstruction, particularly in children.
• Known iodinated contrast sensitivity.

Current status

Nasopharyngography has been superseded in routine practice by flexible nasoendoscopy, which visualises the mucosa directly and permits biopsy, and by CT and MRI, which show the deep spaces, skull base and nodal disease that contrast fluoroscopy cannot. MRI is the modality of choice for staging nasopharyngeal carcinoma. The correct examination answer names the procedure and its technique, and then states that direct endoscopy and cross-sectional imaging have replaced it.

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4. Comparison Table