All Radiological investigation techniques for genitourinary systems and it's protocol techniques timing how to do it -Ante grade and retrograde pyelography -Xray ivu protocol -Ct ivu -ct kidney protocol Rgu with normal anatomy Mcu with normal anatomy Voiding cystourthrogram What to see on each study

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IVU X-ray protocol timing steps retrograde antegrade pyelography RGU MCU voiding cystourethrogram technique radiology

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Radiological Investigations of the Genitourinary System

A complete guide to technique, protocol, timing, and findings.

1. Plain X-Ray (KUB - Kidneys, Ureters, Bladder)

Purpose: Preliminary survey film before contrast studies.

What to see:

Renal outlines (normally smooth, bean-shaped)
Renal size: approximately 3.5 vertebral bodies in height (~11-14 cm)
Calcification along the urinary tract (radiopaque calculi)
Bony structures (spine, sacrum, pelvis)
Psoas muscle shadows
Soft tissue masses or abnormal gas patterns

Before every contrast study: Always obtain a plain KUB (scout film) first for baseline comparison.

2. Intravenous Urography (IVU/IVP) - X-ray Protocol

IVU provides simultaneous anatomic and functional information about the entire collecting system. It has largely been replaced by CT urography but remains useful when CT is unavailable or in certain clinical situations.

Preparation

Bowel preparation (mild laxative night before) to reduce overlying gas
Patient nil by mouth for 4-6 hours (mild dehydration improves concentration of contrast)
Pre-procedure check: renal function (creatinine), contrast allergy history
Contraindications: contrast allergy, renal insufficiency (eGFR <30), pregnancy, myeloma with dehydration, metformin use

Contrast

Non-ionic iodinated contrast medium, IV: typically 50-100 mL (e.g., iohexol, iopromide)

Film Sequence and Timing

Time	Film	Phase	What to look for
0 min	Scout/KUB	Pre-contrast	Calculi, renal outlines, bony structures
Immediate	Nephrogram (0-1 min)	Nephrographic phase	Both kidneys enhancing simultaneously - assess size, shape, position
5 min	Full-length abdomen	Pyelographic phase begins	Calyces start filling, renal pelvis opacifying
15 min	Full-length abdomen	Pyelographic phase	Ureters, renal pelvis, calyces; compression can be released if used
30 min	Full-length abdomen	Excretory phase	Ureters and bladder filling, any hold-up or obstruction
Post-void	Bladder	Bladder/urethra	Residual urine volume, bladder outline, any filling defects

Compression: An abdominal compression band at the pelvic brim can be applied after the 5-minute film to distend the upper ureters and improve pyelocalyceal filling. Released at 15 minutes.

Oblique views: Helpful to profile the ureterovesical junction (UVJ) and differentiate calculi from phleboliths.

Delayed films (45, 60, 90 min): Used if there is reduced/delayed nephrogram (hydronephrosis, obstruction, poor renal function). A delayed nephrogram is a hallmark sign of obstruction.

What to Assess on IVU

Kidneys: Number, size, shape, position, axis; smooth vs. scarred cortex; calyceal clubbing (chronic obstruction, reflux nephropathy)
Calyces: Normal cupped shape vs. blunted/clubbed (obstruction, papillary necrosis); filling defects (TCC, blood clot)
Renal pelvis: Size, shape; pelviureteric junction (PUJ) obstruction pattern
Ureters: Smooth-walled, peristaltic; site of hold-up; strictures; filling defects; periureteral notching (collateral vessels)
Bladder: Shape (pear-shaped = extrinsic compression), wall irregularity, filling defects, capacity
Post-void film: Residual volume (>100 mL = significant)
Nephrogram: Asymmetric/delayed = obstruction; absent = non-functioning kidney

(Campbell-Walsh Wein Urology; Smith & Tanagho General Urology, 19th Ed.)

3. CT IVU (CT Urography)

CT urography (CTU) is now the gold standard for evaluating the upper urinary tract, particularly for haematuria investigation and urothelial tumours.

Protocol - Multi-Phase CTU

Phase	Timing After Contrast	Technique	Purpose
Unenhanced	Before contrast	Full abdomen/pelvis	Calculi (HU >100), calcification, baseline density; fat in AML
Corticomedullary (CM)	25-35 seconds	Arterial-dominant	Vascular anatomy, cortical tumours, angiogenesis in clear cell RCC; pseudotumours
Nephrographic	80-100 seconds	Both cortex and medulla enhance	Optimal for renal masses - enhancement >20 HU above baseline = malignancy; maximally conspicuous phase for tumours
Excretory/Pyelographic	5-10 minutes	Collecting systems fill with contrast	Urothelial tumours, filling defects, ureteral strictures, TCC

CT Kidney Protocol (for Renal Mass)

Pre-contrast: Whole kidney, detect calcification or intrinsic density changes
Corticomedullary phase (30 sec): Assess vascularity, identify renal arteries/veins
Nephrographic phase (90 sec): Best phase for solid mass characterization - measure enhancement HU
Excretory phase (5-10 min): Assess pelvicalyceal system, look for TCC involvement

Key HU thresholds:

Enhancement >20 HU (unenhanced vs. nephrographic) = strongly predictive of enhancement = renal neoplasm
Enhancement 10-20 HU = equivocal
<10 HU = non-enhancing (likely cyst)

Split-bolus technique: A single acquisition where two contrast boluses are given at different times, so the nephrographic and excretory phases are captured simultaneously - reduces radiation dose.

Dual-Energy CT (DECT): Can generate virtual unenhanced images, eliminating the need for a pre-contrast scan; also characterizes stone composition (uric acid vs. calcium oxalate).

What to Assess on CT IVU

Kidneys: Renal mass characterization (solid vs. cystic, Bosniak classification for cysts), enhancement pattern, fat content (AML), cortical thickness
Urothelium: Filling defects in pelvis/calyces/ureter = TCC; wall thickening
Ureters: Obstruction level, strictures, ureterocoeles, periureteral disease
Bladder: Wall thickening, tumour, calculi, diverticula; ureteric jets in excretory phase
Adrenals, lymph nodes, adjacent organs: Staging purposes
Stones: All stone types visible (uric acid indistinguishable from calcium oxalate on standard CT but separable on DECT)

(Grainger & Allison's Diagnostic Radiology; National Kidney Foundation Primer on Kidney Diseases, 8e)

4. Antegrade Pyelography

What it is

Contrast is injected into the renal collecting system percutaneously (via a needle or nephrostomy tube already in situ), travelling downward (antegrade = with the flow of urine).

Indications

Retrograde pyelography not technically feasible
Failed or non-diagnostic CT/IVU
Nephrostomy tube already in place
Need to precisely define the level of ureteral obstruction for surgical planning
Severe contrast allergy (can use dilute contrast)

Technique

Patient positioned prone
Ultrasound or fluoroscopic guidance to puncture a posterior calyx percutaneously with a 22-gauge Chiba needle
A small volume of diluted contrast (or CO2) injected under fluoroscopy
The "air pyelogram" trick: inject air to delineate posterior calyces in prone position
X-ray images taken in AP and oblique projections
For the Whitaker test (functional assessment): infuse contrast at 10 mL/min; measure intrapelvic pressure
- <15 cm H2O = normal
- 15-22 cm H2O = indeterminate
- 22 cm H2O = obstruction

What to Assess

Level and cause of obstruction
Anatomy of the renal pelvis and ureter above the obstruction
Ureteric strictures, extrinsic compression, TCC
UPJ anatomy prior to pyeloplasty

(Campbell-Walsh Wein Urology)

5. Retrograde Pyelography (RGP)

What it is

Contrast is injected retrograde (against urinary flow - upward) into the ureteral orifice via a cystoscopic approach.

Indications

Define upper tract anatomy when CT/IVU inadequate
Contraindication to IV contrast (allergy, renal failure)
Localise radiolucent calculi
Evaluate ureteral/renal pelvis filling defects
Plan surgery on the collecting system
Adjunct to ureteral stent placement, ureteroscopy

Technique

Patient under spinal or general anaesthesia
Cystoscopy first - identify ureteral orifices
Ureteral catheter (open-tipped or Braasch bulb catheter) advanced 2-3 cm into the ureter
Diluted non-ionic contrast (15-30% solution) injected gently under fluoroscopic guidance (avoid over-distension to prevent pyelo-venous or pyelo-lymphatic backflow which causes pain/sepsis)
A bulb ureterogram (Braasch catheter) is easier but leaks back into bladder - may be suboptimal; an angiographic exchange catheter advanced higher gives better opacification
Images taken in AP, oblique, and sometimes prone positions
Retrograde catheter withdrawn slowly while injecting for a "pull-back ureterogram"

Risks

UTI / urosepsis (especially with obstructed system - must drain if obstructed)
Ureteral perforation
Backflow artefacts

What to Assess

Ureteral filling defects (TCC, clot, radiolucent stone)
Ureteral strictures and their level
PUJ anatomy
Mucosal irregularity (TCC/papillary lesion gives a "stippled" or "goblet sign")
Compare to contralateral ureter

(Campbell-Walsh Wein Urology; Grainger & Allison's Diagnostic Radiology)

6. RGU - Retrograde Urethrogram

What it is

Contrast is injected in a retrograde direction (opposite to flow) into the urethra to outline the male urethra. Used almost exclusively in males.

Indications

Suspected urethral stricture
Urethral trauma (pelvic fracture - "Don't pass a catheter until RGU done!")
Urethral tumour
Urethral fistula/diverticulum
Pre-operative assessment for urethroplasty
Post-traumatic urethral disruption

Normal Male Urethral Anatomy on RGU

The male urethra is divided into:

Fossa navicularis - within the glans penis
Penile (pendulous) urethra - extends to the penoscrotal junction
Bulbar urethra - from penoscrotal junction to the urogenital diaphragm (widest part - the bulb)
Membranous urethra - shortest, narrowest segment; passes through the external sphincter (urogenital diaphragm)
Prostatic urethra - widened segment within the prostate; the verumontanum (seminal colliculus) is visible as a filling defect on its posterior wall

Key normal landmarks:

The bulbo-membranous junction is where most traumatic ruptures occur (below the UG diaphragm)
The verumontanum is the midpoint of the prostatic urethra
Normal caliber is widest at the bulb (~8-10 mm)

Technique

Patient supine (or 30-45° oblique - right posterior oblique preferred to profile the entire urethra without overlap)
Penile meatus cleaned; Knutsson (Foley) clamp or a Foley catheter (inflated with 2 mL in fossa navicularis) used to occlude the meatus
Diluted water-soluble contrast (20-30% iodine) injected under gentle pressure using a syringe or pressure injector
Fluoroscopic images and spot films taken in oblique position (45° RPO) as contrast fills the urethra
Volume: approximately 20-30 mL

What to Assess on RGU

Strictures: Narrowing with shouldering effect; site (penile, bulbar, membranous)
Diverticula: Outpouchings from the urethral lumen
Fistulae: Abnormal tracks filling with contrast
Traumatic rupture: Extravasation of contrast - below UG diaphragm (bulbar) = extraperitoneal; above UG diaphragm (posterior) = more serious
Filling defects: Tumour, urethral polyp, or calculi
Prostatic impression on the posterior wall of prostatic urethra (BPH)
Posterior urethral valves (in males - best seen on MCU/voiding)

7. MCU - Micturating Cystourethrogram (Voiding Cystourethrogram/VCUG)

What it is

The bladder is filled retrogradely with contrast via a catheter, and images are taken both during filling and while the patient voids (urinates). This is the forward (antegrade) imaging of the urethra.

Indications

Vesicoureteral reflux (VUR) - primary indication in children
Posterior urethral valves (PUV) - characteristic appearance
Bladder outflow obstruction (BPH, urethral stricture, neurogenic bladder)
Urethral stricture (shows anterior urethra less well than RGU but shows posterior urethra better)
Bladder diverticula
Bladder fistulae (vesicovaginal, vesicoenteric)
Bladder capacity and compliance
Post-traumatic evaluation
Ureterocele assessment

Technique

Preliminary KUB
Urethral catheter inserted (12F Foley in adults; smaller in children)
Diluted water-soluble contrast (15-20% iodinated contrast) instilled by gravity (bag height ~60 cm above patient) - do not use pressure injection during filling phase
Bladder filled to capacity:
- Adults: ~300-400 mL
- Children: Estimated capacity = (Age + 2) x 30 mL, or weight-based
Filling films: AP pelvis during filling - look for VUR, bladder outline
Catheter removed; patient asked to void
Voiding films: Oblique (45°) or AP view during micturition - critical for urethra
Post-void film: AP of kidneys and bladder for residual urine and late VUR

What to Assess on MCU / VCUG

Bladder:

Shape: normal smooth ovoid; trabeculated (neurogenic/"pine tree" bladder, BOO); "Christmas tree" = neurogenic; pear-shaped = extrinsic compression
Capacity
Diverticula (Hutch diverticulum near UVJ)
Ureteroceles (oval filling defect at ureteral orifice)
Bladder neck: smooth funnel (normal voiding) vs. failure to open (DSD)

Vesicoureteral Reflux (VUR) - International Grading:

Grade	Description
I	Reflux into ureter only - no dilation
II	Reflux to renal pelvis - no dilation
III	Mild/moderate dilation of ureter and pelvis - minor calyceal blunting
IV	Moderate dilation/tortuosity - obliterated fornices
V	Gross dilation, tortuous ureter, no calyceal impressions

Urethra (during voiding):

Posterior urethral valves (PUV): In boys - "sail-like" or "wind-sock" filling defect in posterior urethra; dilated posterior urethra; "spinning top" deformity; VUR
Urethral stricture: Narrowing with proximal dilation
Normal female urethra: Short, wide; no strictures
Normal male posterior urethra: The verumontanum is seen as a posterior indentation

8. Voiding Cystourethrogram (VCU) vs MCU

These terms are essentially synonymous - MCU = Micturating Cystourethrogram (UK/Commonwealth terminology); VCUG/VCU = Voiding Cystourethrogram (North American terminology). The technique and findings are identical.

Key distinction from RGU:

RGU = retrograde injection into meatus - best for anterior urethra (strictures)
MCU/VCUG = voiding phase - best for posterior urethra (PUV, BPH impression), bladder, VUR
Combined RGU + MCU gives complete urethral assessment - the two studies meet at the external sphincter level

Summary Comparison Table

Study	Route of Contrast	Radiation	Sedation/GA	Primary Use
KUB	None (plain)	Low	No	Calculi screen, pre-contrast scout
IVU	IV injection	Moderate	No	Upper tract anatomy + function
CT IVU	IV injection	High	No	Gold standard haematuria workup, TCC, RCC staging
CT Kidney	IV injection	High	No	Renal mass characterization
Antegrade pyelography	Percutaneous injection into renal pelvis	Moderate	Yes (sedation)	Obstruction level when retrograde fails
Retrograde pyelography	Cystoscopic ureteral catheter	Moderate	Yes (GA/spinal)	Upper tract when IV contrast contraindicated
RGU	Retrograde via meatus	Low	No	Anterior urethral strictures, trauma
MCU/VCUG	Catheter into bladder	Low-moderate	No (local)	VUR grading, posterior urethra (PUV), bladder

Sources:

Campbell-Walsh Wein Urology, 12th Ed. - Retrograde/Antegrade Pyelography, Whitaker Test sections
Smith & Tanagho's General Urology, 19th Ed. - Radiologic Investigations chapter
Grainger & Allison's Diagnostic Radiology - CT Urography, Renal/Urothelial Tumour Imaging
National Kidney Foundation Primer on Kidney Diseases, 8th Ed. - IVU/IVP section

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