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Exam category: Procedures → Thorax and Abdomen (GU Studies), Head/Spine/Pelvis (Myelography), Extremity (Arthrography)
Why it matters: IVU vs. retrograde urography is the cleanest functional/nonfunctional contrast pair in the whole Procedures domain — once that distinction clicks, several other "why this study over that one" questions get easier too.
Each of these studies puts contrast somewhere specific — the urinary system, the subarachnoid space, the uterus, a joint capsule — and the reason for the specific route (IV vs. catheter, lumbar puncture vs. cervix) is almost always the real test question, not just the anatomy shown.
| IVU (intravenous urography) | Retrograde urography | |
|---|---|---|
| Contrast route | IV injection | Catheter, introduced backward via cystoscopy |
| Functional? | Yes — contrast is filtered/excreted by the kidneys, showing physiologic function | No — bypasses normal physiology entirely |
| Best for | General urinary tract evaluation, functional assessment | Precisely locating calculi/obstruction when function isn't the question |
Memory cue: IVU tests function (the kidneys have to actually filter and excrete the contrast). Retrograde is purely anatomic — contrast placed directly where you want to look, no physiology involved.
Ureteric compression — what it does and when you must not use it. During an IVU, a band with two inflatable paddles is placed across the abdomen and the paddles are positioned over the outer pelvic brim on each side, where the ureters cross the psoas muscles. Inflating them compresses the ureters and holds contrast back in the upper tract: the pelvicalyceal system and proximal ureters fill more completely, and the collecting system retains the contrast longer, so the pelves, infundibula and calyces are better seen. Placement matters — paddles in the wrong position simply let the contrast drain at its normal rate.
It is contraindicated in a recognisable list of situations, and the reasoning is the same each time — either the compression could do harm, or it could imitate a finding:
| Contraindication | Why |
|---|---|
| Abdominal aortic aneurysm | Compression could cause the aneurysm to leak or rupture |
| Possible ureteric stones | Compression's appearance is hard to tell apart from a stone |
| Abdominal mass | Can look the same on the image as compression does |
| Recent abdominal surgery, severe abdominal pain, acute abdominal trauma | Compression is unsafe or intolerable |
Memory cue — compression dams the upper tract. It holds contrast back so the calyces and renal pelves fill and stay filled. Don't apply it over an aneurysm, a mass, a suspected stone, or a fresh abdominal injury or incision.
These study the lower urinary tract — the bladder and urethra — and both are nonfunctional (contrast placed directly, not filtered by the kidneys), the same idea as retrograde urography above.
Memory cue — voiding shows the urethra and reflux: plain cystography images the filled bladder; the voiding in VCUG is what opens the urethra and exposes vesicoureteral reflux.
Contrast injected into the subarachnoid space via lumbar or cervical puncture, to visualize the spinal canal's soft tissue structures — nerve roots, intervertebral disks, spinal canal lesions. Largely superseded by CT/MRI, but still a real registry topic.
Aftercare is tested more than the procedure itself. The complication to manage is the post-puncture headache, and three measures reduce it: increased fluid intake, elevating the head, and limited activity afterwards. Keeping the head up rather than flat also uses gravity to keep the contrast down in the lumbar region instead of letting it travel toward the head. So the post-procedure instruction is the opposite of what students often guess — not lying flat, and not getting straight up and moving about.
Memory cue — head up, fluids up, activity down. After myelography the patient stays with the head elevated, is encouraged to drink, and keeps activity limited. Flat-on-the-back and up-and-walking are both wrong.
Contrast injected through the cervix to outline the uterine cavity and assess patency of the fallopian tubes — if contrast spills into the peritoneal cavity through the tubes, they're patent (open). A common infertility workup tool, and occasionally therapeutic (contrast injection can dilate/straighten tubes).
Contrast injected directly into a joint capsule under sterile conditions, to evaluate tendinous, ligamentous, and capsular pathology in diarthrodial joints (wrist, elbow, shoulder, ankle, knee). Like myelography, largely reduced in use by MRI, but still tested.
What it actually shows is soft tissue, not bone. Arthrography images the articular cartilage, menisci, bursae and ligaments — the structures that don't appear on a plain radiograph. So the indication is internal derangement of a joint, and at the knee that means the menisci and cruciate ligaments. It is the fallback when MRI is unavailable or contraindicated; a question describing a cortical fracture, a bone tumour or joint-space narrowing is describing something you would not order an arthrogram for.
Three contrast techniques, distinguished only by what's injected: pneumoarthrography (gas), opaque arthrography (water-soluble iodinated medium), and double-contrast (both). The shoulder is the most frequent site; shoulder, knee and hip are the joints usually studied.
The sequence at the table. Any joint effusion is aspirated first, then the radiologist injects the contrast and manipulates the joint so the medium distributes evenly and leaves a thin, even coating on the soft-tissue structures before imaging begins. Imaging is usually fluoroscopy with spot images.
Memory cue — aspirate, inject, move the joint. The joint is drained first, contrast goes in, and then the joint is moved — an immobile joint gives you a puddle of contrast, not a coating.
Endoscopic retrograde cholangiopancreatography — contrast introduced via endoscope into the bile ducts and pancreatic duct, combining endoscopy with fluoroscopic contrast imaging.
Two more biliary studies image the ducts with water-soluble iodinated contrast around gallbladder surgery, differing by when they happen:
Memory cue — operative during, T-tube after: operative cholangiography is on the table during surgery (C-arm, surgeon injects, hunting residual stones); T-tube (postoperative) comes after, injecting through the drainage tube to be sure the ducts are clear before it's removed.
Source: Bontrager, Textbook of Radiographic Positioning and Related Anatomy, 10th ed., Ch. 19 (arthrography, myelography, HSG), Ch. 14 (urography, cystography, VCUG); cholangiography — operative (immediate) in Ch. 15, postoperative (T-tube/delayed) in Ch. 19. Ureteric compression — its purpose (filling the pelvicalyceal system and proximal ureters, and retaining contrast longer in the collecting system), the paddle placement over the outer pelvic brim where the ureters cross the psoas muscles, and the full contraindication list including abdominal aortic aneurysm — is Bontrager Ch. 14. Arthrography — the soft-tissue structures it shows (menisci, ligaments, articular cartilage, bursae), the pneumo/opaque/double-contrast distinction, and the aspirate-inject-manipulate sequence — is Merrill, Atlas of Radiographic Positioning and Procedures, 15th ed., Ch. 13 (Contrast Arthrography). Post-myelography aftercare (increased fluid intake, head elevation, limited activity to minimise the post-puncture headache) is Ehrlich, Patient Care in Radiography, 10th ed., Ch. 19.
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