Urinary System Radiographic Procedures

General Physiology and Anatomical Markers of the Urinary System

• Urine Excretion Rate: The kidneys normally excrete between $1\,liter$ and $2\,liters$ of urine per day.

• Kidney Location: In individuals of sthenic build, the kidneys extend from the level of the superior border of $T12$ to the level of the transverse processes of $L3$.

• Mobility:

  • Kidneys exhibit a respiratory movement of approximately $1\,inch$.

  • When changing from a supine to an upright position, the kidneys normally drop no more than $2\,inches$ ($5\,cm$).

• Bladder Capacity:

  • The adult bladder can hold approximately $500\,ml$ of fluid when completely full.

  • The desire for micturition (urination) typically occurs when the bladder contains about $250\,ml$ of urine.

Radiographic Indicators and Contrast Media Safety

• Diagnostic Lab Indicators: Before administering contrast media (CM), the Radiologic Technologist (RT) must check the following values:

  • Normal BUN (Blood Urea Nitrogen): $8-25\,mg/100\,ml$.

  • Normal Creatinine: $0.6-1.5\,mg/dl$.

• Metformin (Glucophage) Protocol:

  • Iodinated CM should not be given if the patient took metformin within $48\,hours$ before the procedure.

  • Metformin must be withheld for $48\,hours$ after the procedure.

  • Lactic Acidosis: This is a potentially fatal adverse effect occurring in patients who take metformin and receive radiologic contrast media.

• Common CM Side Effects: Temporary hot flashes and a metallic taste in the mouth are common occurrences after the IV injection of iodinated CM.

• Contrast Media Administration Safety:

  • Patients should never be left alone after an IV injection of CM.

  • Most reactions to CM occur within the first $5\,minutes$ after administration.

  • A physician must be summoned immediately for any moderate or severe reaction.

  • Vial Protocol: Before withdrawing CM, the RT must confirm correct contents, check the expiration date, and read the label carefully. Empty bottles must be shown to the radiologist.

• Equipment:

  • For $50-100\,ml$ of CM: Use an $18-20\,gauge$ butterfly needle.

  • For pediatric patients: Use a $23-25\,gauge$ needle.

Contrast Media Timing and Dynamics

• Pelvocalyceal System Appearance: CM appears in the system within $2-8\,minutes$ post-injection.

• Greatest Concentration: The peak concentration of CM in the kidneys occurs $15-20\,minutes$ after injection.

• Nephrogram Timing: For a nephrogram demonstration, exposure is taken at $30\,seconds$ after bolus injection.

• Whitaker Test: A procedure utilized to measure pressure gradients across the kidneys and bladder.

• Long’s Research: Imaging of cutaneous urinary diversions was described by LONG.

• Sensation of Fullness: Indicators for complete filling of the pelvocalyceal system include a sense of fullness at the back.

Intravenous Urography (IVU) / Excretory Urography

• Definition: The most common special radiographic examination of the urinary system. It is a true functional test demonstrating renal cortical tissue saturated with CM.

• Historical Development:

  • 1923: Excretory urography was first reported by ROWNTREE ET AL using a $10\%$ solution of chemically pure sodium iodide. It was discarded because it excreted too slowly and was too toxic.

  • 1929: ROSENO AND JEPKINS introduced a compound of sodium iodide and urea, which caused considerable patient distress.

  • 1929: SWICK developed the organic compound Uroselectan, which had an iodine content of $42\%$.

• Indications:

  • Visualizing the collecting portion of the urinary system.

  • Assessing functional ability of the kidneys.

  • Evaluating pathology (Calculi, Hematuria, Hypertension, Renal Failure, UTIs, masses, or trauma).

• Contraindications: Hypersensitivity to CM, anuria, multiple myeloma, diabetes mellitus, severe hepatic/renal disease, congestive heart failure, pheochromocytoma, sickle cell anemia, and metformin use.

• Patient Preparation:

  • Light evening meal and NPO after midnight.

  • Bowel cleansing cathartic and a morning enema.

  • Patient must empty the bladder before the exam to prevent rupture and avoid diluting the CM.

Standard Projections for IVU

• AP Projection (Scout Film):

  • Position: Supine, knees flexed to reduce the lordotic curve.

  • CR: Perpendicular ($\perp$) to iliac crest.

  • Rationale: Checks anatomy, reveals calculi, establishes technique, and confirms preparation.

• AP Nephrogram:

  • Timing: $1\,minute$ after start of injection.

  • CR: $\perp$ midway between xiphoid tip and iliac crest. Uses a $10 \times 12\,inch$ IR crosswise.

  • Rationale: Demonstrates the renal parenchyma (blush of the kidneys).

• AP Pyelogram:

  • Timing: $5\,minutes$ after start of injection.

  • CR: $\perp$ midway between xiphoid tip and iliac crest.

• AP Ureteric Compression Device:

  • Rationale: Best demonstrates the pelvocalyceal system and proximal ureters by retarding urine escape. Performed after the $5\,minute$ radiograph.

• Trendelenburg position:

  • Alternative to compression; prevents CM from escaping into ureters.

• PA Projection (Prone):

  • CR: $\perp$ to iliac crest.

  • Rationale: Best for the ureteropelvic region, hydronephrosis, and resolving gas shadows in the stomach (BERDON ET AL recommended this for infants).

• 15-minute AP Projection: Performed for maximum opacification of contrast-filled kidneys and ureters.

• AP Oblique Projection (RPO and LPO):

  • Rotation: $30\,degrees$.

  • Rationale: Identifies exact sites of opacities.

  • RPO: Best for Right Ureter and Left Kidney (Left kidney is parallel to IR; Right kidney is perpendicular).

  • LPO: Best for Left Ureter and Right Kidney (Right kidney is parallel to IR; Left kidney is perpendicular).

• Lateral Projection: Best for demonstrating rotation or pressure displacement of kidneys.

• Dorsal Decubitus (Cook Method): Shows if extrarenal mass is intra- or extraperitoneal.

• Ventral Decubitus (Rolleston-Reay Method): Demonstrates ureteropelvic region while prone.

• Post-Void PA Recumbent: Specifically used for residual urine, tumors, or detecting an enlarged prostate.

• Post-Void AP Erect: Best for mobility or positional changes (Nephroptosis).

Variations and Specialized Techniques in IVU

• Infants and Children:

  • Fluid must NOT be restricted due to dehydration risk.

  • Dosage: $2\,cc/kg$ (adults/less than $5\,kg$); $20\,cc$ for $8-30\,kg$.

  • Hope and Campoy Technique: Giving carbonated drinks to distend the stomach with gas ($2\,ounces$ for newborns, $12\,ounces$ for a $7-8\,year$ old).

• Renal Failure: No preparatory fluid restriction; use high dose CM and delayed radiographs up to $24\,hours$ or more.

• Hypertensive IVP: Series of x-rays at timed intervals ($1$, $2$, and $3\,minutes$) before compression.

• Drip Infusion/Gravity Method: Full dose CM mixed with $200\,cc$ or $5\%$ dextrose water. Fluid is opened "full blast."

• Tomography: EVANS introduced tomography of the renal parenchyma; it blurs intestinal gas.

Antegrade and Retrograde Urography

• Antegrade Urography: CM enters in the normal direction of flow via percutaneous puncture of the renal pelvis.

• Retrograde Urography (RGU):

  • Nature: Non-functional exam.

  • Technique: CM introduced backward via catheterization of the ureter.

  • History: $1904$ (air), $1906$ (colloidal silver), $1911$ (silver iodide), $1918$ (sodium iodide and bromide).

  • Position: Modified lithotomy.

  • Contrast Concentration: $10\,cc$ of CM mixed with $10\,cc$ distilled water.

  • Projections:

    • AP Pyelogram (Trendelenburg $10-15\,degrees$ head down to prevent escape).

    • AP (Fowler’s $35-40\,degrees$ head up to fill ureters).

Retrograde Cystography and Voiding Cystourethrography (VCUG)

• Retrograde Cystography:

  • Non-functional exam of the bladder.

  • Procedure: Bladder drained, then filled with dilute CM ($150-500\,ml$) via gravity (never use pressure).

  • Projections:

    • AP Axial: $10-15\,degrees$ caudad (clears symphysis) or $20-25\,degrees$ caudad (shows prostate).

    • PA Axial: $10-15\,degrees$ cephalad (bladder neck).

    • AP Oblique: $40-60\,degrees$ rotation.

    • Chassard-Lapine Method: Axial view of posterior bladder surface.

• Voiding Cystourethrography (VCUG):

  • Used for vesico-ureteric reflux, stress incontinence, and obstruction.

  • Contrast: $10-15\%$ water soluble CM.

  • Volume: $700-1000\,ml$ to fill bladder full.

  • Gravity height: Bottle must be $36\,inches$ above the table.

Specialized Examinations and Procedures

• Renal Puncture: Used for diagnosing cystic disease vs. space-occupying lesions. Observations include NPO for $6\,hours$ and a final chest radiograph to rule out pneumothorax.

• Percutaneous Nephrostomy: Insertion of a catheter skin-to-renal pelvis to relieve pressure.

• Double Contrast Cystography:

  • Uses Negative (Air/Gas) and Positive ($120\,ml$ sterile barium sulphate/steripaque).

  • Barium coats tumors/ulcers while carbon dioxide distends the bladder.

• Urethrography:

  • Injects viscous CM (Umbradil viscous) or water soluble ($60\%$ Urografin for ruptures).

  • Uses a Knutson clamp or Foley catheter.