Intrathecal, Intra-articular and Cavitary Contrast

Nonvascular routes require route-specific verification

Intrathecal, intra-articular, bladder, fistula and vaginal contrast examinations place an agent in a defined space rather than relying on vascular delivery. The agent, concentration, total dose, sterility and administration method must match that route. A bottle approved for intravenous use is not automatically approved for injection into cerebrospinal fluid. Before a procedure, confirm the patient, site, indication, allergies, relevant contraindications and the ordered formulation with the procedural team.

Route verification

Intrathecal contrast and CT myelography

CT myelography combines contrast in the subarachnoid space with CT to show the thecal sac and nerve-root sleeves. It can assess selected spinal stenosis, postoperative anatomy or cerebrospinal fluid leaks when MRI is insufficient or unsuitable. The qualified procedural clinician performs the spinal access and determines dose and distribution. The technologist coordinates safe positioning, scan timing, coverage and reconstruction.

Use only the specific nonionic formulation, concentration and presentation labeled for intrathecal administration. The current Omnipaque label warns that wrong intrathecal concentrations can cause severe injury or death; its 140 and 350 mg I/mL injection formulations are not the recommended intrathecal concentrations. Even within an approved agent family, check the exact concentration, age, procedure and dose table. Ionic enteral diatrizoate must never be substituted for an intrathecal agent.

Review anticoagulants, coagulation concerns, infection at the puncture site, relevant neurologic history and medication issues with the procedural clinician. Do not independently stop or restart medication from a memorized list. A timeout and a direct label check before injection prevent wrong-route and wrong-product errors that cannot be detected from the scanner's image settings.

Postmyelographic acquisition and anatomy

Plan cervical, thoracic or lumbosacral coverage according to the question. The contrast outlines the subarachnoid space around the cord or cauda equina; discs, bone and ligaments can displace or narrow that space. Thin acquisitions and sagittal and coronal reformations help show the relationship of a disc or osteophyte to the thecal sac and exiting root sleeve. Use bone and soft-tissue displays because an excellent view of osseous narrowing alone does not fully describe neural structures.

For postoperative imaging, identify hardware and expected surgical changes. For a suspected leak, distribution and timing matter: a routine delayed scan may show extensive extradural contrast without precisely locating a rapid leak. Specialized dynamic techniques require an explicit procedural plan. Do not repeat multiple spinal volumes simply because contrast is visible somewhere outside the thecal sac.

After the procedure, follow the clinician's and product's observation, positioning, activity and hydration instructions. There is no universal proof that aggressive fluid intake or a fixed six-to-eight-hour head elevation prevents every post-dural-puncture headache. Report severe headache, fever, altered mental status, seizures or new neurologic symptoms promptly. Provide written instructions and a contact pathway before discharge.

Intra-articular contrast and CT arthrography

CT arthrography uses direct joint injection to outline cartilage, the joint capsule and selected intra-articular structures. It can be useful when MRI is unsuitable or when the clinical question favors CT. The procedural team confirms the joint, uses aseptic technique and selects the agent, dilution and volume. Joint size, prior surgery and the specific task affect the amount; do not use one injection volume for shoulder, wrist, hip and knee.

After injection, acquire the prescribed thin-section data before contrast disperses enough to reduce the desired contrast. Reconstruct in planes aligned with the joint. In the shoulder, relate the humeral head to the glenoid and labral region; in the knee, assess cartilage surfaces and intra-articular bodies; in the wrist, small carpal compartments make fine spatial sampling important. Avoid forcing an injured joint through a painful position just to reproduce a standard setup. Document injection details, positioning limitations and any delayed imaging.

Bladder and fistulous communications

Retrograde CT cystography requires controlled bladder filling through verified appropriate urinary access. Passive accumulation of intravenously excreted contrast does not provide the distension needed to exclude traumatic rupture. Under AUA guidance, gravity filling in an adult generally uses at least 300 mL or the patient's tolerance, with the procedural team accounting for clinical circumstances. Suspected urethral injury, especially blood at the meatus, requires evaluation before blind catheter placement.

Contrast outlining bowel loops or other peritoneal surfaces supports intraperitoneal leakage; contrast in retropubic or perivesical extraperitoneal tissues supports extraperitoneal leakage. Intraperitoneal traumatic rupture generally requires surgical repair. Uncomplicated extraperitoneal injury may be managed with catheter drainage, while complicated injuries can need repair. Classification guides the clinical team; the technologist does not independently choose treatment.

A sinogram or fistulogram gently opacifies an accessible tract under the clinician's plan. CT then maps the tract and its relationship to bowel, bladder, abscess or skin. Do not inject forcefully against resistance, because false passage or unintended spread can confound the examination and injure tissue.

Vaginal opacification

Selected fistula examinations may use dilute water-soluble vaginal contrast to demonstrate communication with bowel or urinary structures. This is an explicitly ordered specialized technique, not routine contrast for every pelvic CT. Confirm consent, pregnancy assessment when relevant, privacy, aseptic preparation and the clinician's catheter and filling approach. Compare the opacified vaginal lumen with adjacent bladder, rectum and any suspected tract on multiplanar images. A balloon can obscure a low tract, and absence of demonstrated passage does not exclude every fistula. IV enhancement may separately be needed to assess inflammation or a collection.

References: Current Omnipaque prescribing information, ACR myelography parameter, AUA urotrauma guideline, ACR anorectal disease discussion.