Retrograde Urethrogram (RUG) & Voiding Cystourethrogram (VCUG)
The retrograde urethrogram (RUG) and voiding cystourethrogram (VCUG) are the standard contrast studies for urethral and outlet anatomy before reconstruction. RUG maps the anterior urethral lumen. VCUG adds the voiding outlet and the proximal urethra. The AUA recommends urethro-cystoscopy, RUG, VCUG or ultrasound urethrography to diagnose stricture , and states that RUG, with or without VCUG, remains the study of choice for stricture length, location and severity in men.[2] The EAU gives a strong recommendation for RUG to assess stricture location and length before reconstruction.[1][2]
1. Choose the Study
| Question | Useful approach | What may remain unresolved |
|---|---|---|
| Male anterior stricture before reconstruction | RUG; endoscopy as needed | Periurethral fibrosis, very distal narrowing or a non-opacified proximal segment.[1] |
| Near-obliteration or delayed PFUI planning | Combined RUG and VCUG ; add retrograde plus antegrade cystoscopy if further detail is needed | A closed bladder neck may hide the proximal stump, and the apparent gap length can be misleading.[1][2] |
| Bladder neck or vesicourethral anastomotic stenosis | Endoscopy with appropriate contrast imaging | Post-prostatectomy VUAS is anatomically distinct from native bladder-neck stenosis.[2] |
| Female obstructive voiding symptoms | Flow/PVR, examination, cystoscopy and VCUG or video-urodynamics according to the question | Functional obstruction and other causes can mimic a fixed narrowing.[7] |
| Female urethral diverticulum | MRI; double-balloon urethrography if MRI cannot be performed or the ostium is not seen at cystoscopy | VCUG can miss a nonfilling ostium and underestimate complex diverticular anatomy.[17] |
| Suspected vesicoureteral reflux | VCUG when indicated | — |
| Neurogenic bladder | VCUG or video-urodynamics | Detrusor-sphincter relationships need pressure data.[6] |
| Suspected postoperative extravasation | Pericatheter RUG, RUG or VCUG matched to the repair and catheter plan | The significance of a small leak depends on its extent and clinical setting.[4] |
2. Equipment
The parameters below are commonly used values from technique descriptions.
| Item | Typical specification | Notes |
|---|---|---|
| Catheter | 14–18 Fr Foley, tip inserted only into the fossa navicularis | The catheter is not advanced into the bulbar urethra. |
| Balloon | One published adult RUG technique inflates a Foley balloon with 1.5 mL fluid in the fossa navicularis.[19] | Balloon inflation can be painful; EAU weakly favors a clamp over Foley to reduce pain.[1][9] |
| Clamp | Penile clamp (Brodny or Knutson type) | No balloon. The EAU gives a weak recommendation to use a clamp in preference to a Foley catheter, because clamps were less painful. Useful in meatal stricture.[1][9] |
| Contrast | Water-soluble low-osmolality iodinated agent (for example iohexol) | Iohexol is a low-osmolality nonionic agent, not an iso-osmolar agent.[10][11] |
| Dilution and volume | Use enough contrast to distend the lumen; Li et al. cite an approximate anterior urethral volume of 20–30 mL in men as a guide | Concentration and injected volume vary with equipment and patient; avoid excessive pressure.[10] |
| Syringe | A published RUG technique uses a syringe containing 60 mL of contrast.[20] | Allows slow, controlled injection; inject only the volume needed to opacify the urethra. |
| Imaging | C-arm or fluoroscopy table | A C-arm allows oblique positioning. |
3. RUG Technique
Before imaging
Confirm the indication, previous reconstruction, recent instrumentation, catheter route, symptoms suggesting infection and prior contrast reactions. After recent catheterization, self-dilation, dilation or DVIU, allow urethral rest before definitive stricture mapping for urethroplasty; one cited strategy obtains imaging after two months and performs repair after three months, adjusted for infection and inflammation.[4] Explain discomfort and the possibility of an incomplete study. Choose an atraumatic seal and do not force a large catheter through a distal narrowing to obtain an image.[1][9]
Sequence
- Position. The patient lies obliquely, with the lower leg flexed at the knee and the upper leg straight.[12] An oblique of about 30–45° with the penis gently stretched separates the penile and bulbar segments. Inadequate obliquity makes the segments overlap and can hide or shorten a bulbar stricture, so confirm the anatomy on the first image and increase the obliquity if the segments still overlap.[10] Penile stretch, pelvic rotation and body habitus all change the apparent length.[1]
- Seal. Prepare the meatus and seat the catheter tip and balloon in the fossa navicularis, or apply a clamp. Minimize balloon manipulation there. A small randomized comparison (80 men) found that the clamp method was better tolerated than the balloon method and that RUG could be completed in all clamp patients, but device choice still depends on local expertise and anatomy.[9]
- Start fluoroscopy before injecting. Early filling shows the visible distal penile urethra; a Foley balloon or clamp can obscure the meatus and fossa navicularis, which should be assessed by examination or cystoscopy when distal disease is suspected.[1][10]
- Inject slowly. Contrast is introduced gently while observing the leading edge. Forceful injection provokes external sphincter spasm, which produces an artifactual membranous narrowing. Stop and reassess for pain, resistance, extravasation or intravasation, and do not increase force to prove luminal continuity.[1][9]
- Acquire images at three stages. Save an early-fill image of the visible distal penile urethra, a mid-fill image of the penile urethra and penoscrotal junction, and a full-fill image of the bulbar urethra and bulbomembranous junction. Record when the meatus or fossa is obscured by the seal; continue until the bladder neck faintly opacifies if the posterior extent is needed.[1][10]
- Document the limits. Save images that include the relevant distal and proximal margins and record segments that could not be assessed. Obtain complementary imaging rather than labeling an unfilled segment normal.[1][2]
Use collimation and the lowest fluoroscopic exposure consistent with a diagnostic study, for example pulsed fluoroscopy at a low frame rate and acquisition of spot images at key phases. Actual dose depends on technique and equipment. See radiation safety.
Extravasation during the study
A small amount of extravasation from periurethral glands or a minor fossa tear is not a bladder perforation. Withdraw the catheter slightly, reduce the injection pressure and document the finding. Intravasation and contrast reaction are recognized but uncommon risks.[1][2]
Common pitfalls
| Pitfall | Mechanism | Solution |
|---|---|---|
| Apparent membranous narrowing | External sphincter spasm during retrograde injection | Inject slowly and confirm on the voiding phase of VCUG. |
| Stricture appears short | Incomplete filling distal to a dense obstruction | Add antegrade filling (VCUG) or sonourethrography. Do not raise injection force.[1] |
| Extravasation artifact | Balloon not seated in the fossa, prior meatal trauma or high injection pressure | Re-seat the catheter, reduce pressure and reduce balloon volume. |
| Penile and bulbar overlap | Inadequate obliquity | Increase obliquity and stretch the penis further. |
| Poor mucosal detail | Contrast too dense or too dilute | Adjust the dilution to local protocol. |
| Air bubble | Air in the syringe or tubing | Purge the syringe before injection. A bubble mimics a polyp or tumor. |
| Missed distal stricture | Image capture started mid-injection, or the Foley/clamp seal obscured the meatus and fossa | Start fluoroscopy before injecting; assess suspected distal disease by examination or cystoscopy when the seal masks it.[1][10] |
| Distal urethra not filled | Catheter advanced into the bulbar urethra | Withdraw to the fossa navicularis and repeat. |
| Apparent penoscrotal-junction narrowing | Urinal or positioning pressure at the penoscrotal junction, especially in a short-phallus or obese patient | Correlate with cystoscopy or a repeat image before diagnosing a stricture there. |
An external 1-cm radiopaque marker placed alongside the urethra can provide an approximate image scale.[14]
4. VCUG Technique
Fill the bladder through an appropriate established route according to capacity, symptoms and the examination protocol. A fixed adult volume is inappropriate for every child, contracted bladder or recent repair. The Cystografin label describes 25–300 mL for VCUG according to age and bladder irritability and permits larger volumes when bladder capacity allows; fill to urgency or planned capacity rather than a single fixed number.[18] Do not overfill, because urgency may cause involuntary voiding before positioning.[2][9]
- Obtain AP and oblique filling images of the bladder outline, trabeculation and diverticula.
- For a planned voiding study, remove the urethral catheter only when the treating team has confirmed removal is appropriate; after urethroplasty, pericatheter RUG can assess a leak before removal.[4] Keep an existing suprapubic catheter in place and clamp it for the voiding phase.[21]
- Position the patient obliquely, as for RUG, and ask the patient to void.
- Acquire images during active voiding, not at the start or end when flow is intermittent. Include at least one image showing the whole urethra.
- Obtain a post-void AP image to assess residual contrast, delayed filling of a diverticulum and clearing of any reflux.
Acquire the outlet during actual voiding where possible and document failure to void. A suprapubic route gives access when a urethral lesion cannot be traversed.
5. Normal Anatomy and Interpretation
Landmarks by segment
| Segment | Normal appearance | Interpretive point |
|---|---|---|
| Meatus and fossa navicularis | Rounded meatus; slightly wider fossa with smooth walls | Site of lichen sclerosus involvement; missed on a casual study. |
| Penile (pendulous) urethra | Parallel walls, uniform caliber | Extends from the fossa to the penoscrotal junction. |
| Penoscrotal junction | Slight angulation | Transition to the bulbar urethra; common post-hypospadias site. |
| Bulbar urethra | Widest anterior segment; a slightly irregular wall is normal | Longest anterior segment and most common stricture site. A smooth anterior indentation from the musculus compressor nuda (bulbocavernosus fibers) can mimic a stricture; Littre-gland or Cowper-duct opacification is a normal anatomic differential from extravasation.[15] |
| Bulbomembranous junction and membranous urethra | Short, apparently narrowed on RUG because of external sphincter tone | The apparent narrowing is often physiological. The inferior margin of the obturator foramina is an approximate radiographic landmark for this junction when trauma or severe stricture distorts segmental morphology.[15] |
| Verumontanum and prostatic urethra | Posterior midline filling defect; urethra widens proximally | Best assessed on VCUG; retrograde contrast may reach the posterior urethra and bladder when the lumen is patent.[12] |
| Bladder neck | Closed at rest; opens into a funnel on voiding | Failure to funnel on VCUG suggests bladder neck stenosis. |
Caliber estimates from contrast studies are approximate. Cystoscopy or calibration gives the true caliber.
Reporting
| Report element | Include | Avoid inferring |
|---|---|---|
| Location | Meatal/fossa, penile, bulbar, bulbomembranous or other postoperative segment | Etiology solely from its location. |
| Length and multiplicity | Each narrowing, intervening segment, calibration/magnification limitations | A fixed "true length" correction or predetermined graft length. |
| Lumen and proximal extent | Narrowing, passage or nonpassage of contrast, what was not visualized | — |
| Contour | Smooth, irregular or ragged margins; single, multiple or panurethral involvement | — |
| Additional findings | False passage, fistula, diverticulum, extravasation, dilated proximal urethra and bladder findings | A new treatment indication from a small imaging change without clinical context. |
| Comparison | Prior anatomy, interval instrumentation and repair |
Interrater reliability of stricture length, location and caliber on RUG is poor even among urologists, and because RUG image quality and accuracy are operator-dependent, the AUA advises that surgical planning rest on high-quality images from an experienced operator or the surgeon.[1][2][3]
Apparent sphincter-level narrowing during retrograde filling can be physiological. Persistent or clinically concerning narrowing warrants correlation with voiding images or endoscopy. Neither a universal French-size cutoff nor the statement "membranous narrowing is almost always normal" safely resolves that distinction.[2]
Sonourethrography characterizes the anterior periurethral tissues, and the EAU summarizes studies in which it estimated stricture length more accurately than RUG. For posterior urethral stenosis, the EAU strongly recommends considering MRI urethrography as an ancillary test to define length and associated pathology such as fistulae, diverticula, tumors or stones.[1] In a prospective comparison of 55 men, MRU was the most accurate against operative length (mean overestimate about 1 mm), VCUG underestimated by about 1.5 mm and sonourethrography overestimated by about 2 mm.[3] The direction and size of error differed by modality, so no single correction factor applies to every study.[3]
Bladder neck and outlet on VCUG
- The bladder neck normally opens into a smooth funnel on voiding. A shelf-like deformity or absent funnel suggests bladder neck stenosis after outlet surgery or radiation.
- After radical prostatectomy the analogous narrowing is vesicourethral anastomotic stenosis, which affects the anastomosis itself. Membranous urethral stricture lies distal to it.
- Trabeculation on the filling phase indicates chronic outlet obstruction or neurogenic dysfunction. Diverticula fill as saccular outpouchings and may not empty on post-void images.
6. Pelvic Fracture Urethral Injury
Acute assessment differs from elective gap mapping. Resuscitate and manage associated injuries first. The AUA recommends RUG in patients with blood at the urethral meatus after pelvic trauma . For pelvic fracture urethral injury, it recommends prompt urinary drainage, with suprapubic tube placement preferred initially in most cases.[12] Blind catheter passage before RUG is avoided unless exceptional circumstances require emergent drainage. CT findings alone cannot classify every urethral injury.[12]
Trauma-bay technique (ACS 2025). RUG is the preferred study for male urethral injury. When pelvic movement is unsafe in suspected PFUI, rotate the C-arm to a 30–45° oblique position; ACS also describes supine 30–45° patient obliquity with the dependent leg flexed when feasible and accepts AP and oblique views when positioning is limited.[13] Take a scout film first, so that vascular contrast from an earlier IV-contrast CT is not read as urethral extravasation. Seat a 16 Fr Foley about 2 cm into the meatus, inflate the balloon with 2–3 mL, and inject undiluted nonionic contrast (10–30 mL) with the penis on stretch, imaging at 10 mL intervals and stopping once extravasation appears.[13] Extravasation with bladder filling suggests a partial injury, whereas massive extravasation without bladder filling suggests complete disruption.[13][22] When a Foley has already been placed and urethral injury remains suspected, leave it in place and perform a pericatheter RUG with 10–30 mL of contrast through a small catheter or 18-gauge angiocatheter alongside it.[13] In a pelvic fracture, if CT is being used to look for arterial extravasation, the guideline advises doing the CT first because urethral contrast can obscure active bleeding.[13]
AUA’s trauma protocol describes a 12 Fr Foley or catheter-tipped syringe in the fossa navicularis, gentle penile traction and 20 mL of undiluted water-soluble contrast. This differs from the ACS equipment and volume above (Statement 19 discussion).[12]
For delayed urethroplasty after pelvic fracture urethral injury, the AUA recommends RUG with VCUG and/or retrograde plus antegrade cystoscopy for preoperative planning .[2]
Combined RUG and VCUG
The technique below is one commonly described approach.
- With a suprapubic catheter in place, fill the bladder through it with diluted contrast. For VCUG, Cystografin labeling describes 25–300 mL according to age and bladder irritability, with filling adjusted to capacity.[18]
- Position the patient obliquely.
- Insert a Foley catheter or apply a clamp at the meatus and inject contrast retrogradely while maintaining antegrade filling. If the patient can void, imaging during voiding fills the posterior urethra antegradely.
- Acquire images when both columns are maximally filled and measure the gap between the antegrade and retrograde columns.
Assess the proximal and distal segments, bladder neck, fistulae, false passages and prior procedures. Gap length is one input. Access also depends on displacement, scar, tissue mobility and associated injury. The fluoroscopic gap can overestimate the true defect when the proximal stump fills incompletely or a dense scar blocks the retrograde column. MRI or antegrade cystoscopy can supply additional information.[1][2]
The bladder neck deserves specific attention. A smooth funnel suggests that the injury lies distal to the bladder neck. A distorted, deviated or non-funneling bladder neck raises the possibility of bladder neck involvement, which complicates reconstruction and affects continence counseling.[2] If bladder neck integrity would change the reconstruction or counseling, additional assessment resolves it.[2]
7. Female Urethral Assessment
The female urethra is short and mobile. Standard single-catheter retrograde injection fills it inconsistently, so RUG is rarely diagnostic alone in women, and VCUG or video-urodynamics is the usual contrast study.
Female urethral stricture is a fixed anatomic narrowing evaluated in the context of symptoms and examination. Published caliber definitions vary. Proximal urethral dilatation above a narrow segment on voiding images (sometimes called a wine-glass or champagne-flute appearance) has been described. VCUG or video-urodynamics can demonstrate outlet obstruction, but catheterization itself may be difficult and other causes of poor emptying must be considered.[7]
A radiopaque marker placed at the meatus can help identify the urethral course and length on VCUG, where internal radiologic landmarks are otherwise limited; bilateral side-oblique views can also improve depiction of a small bladder or urethral diverticulum and of prolapse.[16]
Urethral diverticulum. MRI with a small-field-of-view T2 urethral protocol defines the extent of a diverticulum, its relation to the sphincter and multilocular or horseshoe configurations that change the surgical approach. The double-balloon (Trattner or Davis type) catheter technique isolates the urethral lumen between a balloon at the bladder neck and one at the meatus, and injected contrast then fills the diverticulum. It is an option when MRI cannot be performed or the diverticular ostium is not seen at cystoscopy.[17] See MRI and female urethral stricture.
8. Vesicoureteral Reflux
VCUG describes the extent of reflux and of ureteral or collecting-system dilatation. The International Reflux Study grades below are based on the extent of filling and dilatation; intrarenal reflux is recorded separately.[23]
| Grade | Description |
|---|---|
| I | Reflux reaches the ureter only, without dilatation |
| II | Reflux fills the ureter, renal pelvis and calyces; no dilatation; normal fornices |
| III | Mild or moderate ureteral dilatation or tortuosity; mild or moderate dilatation of the renal pelvis; no or slight blunting of fornices |
| IV | Moderate ureteral dilatation, with or without kinking; moderate dilatation of the collecting system; blunt fornices with papillary impressions still visible |
| V | Gross ureteral dilatation and tortuosity; gross dilatation of the renal pelvis and calyces; papillary impressions absent in most calyces |
The EAU 2026 guideline gives a weak recommendation to use VCUG to diagnose reflux, with contrast-enhanced voiding urosonography as another option. For infants with prenatal hydronephrosis, the guideline recommends VCUG when ultrasound shows cortical abnormalities, bilateral high-grade dilatation, a duplex kidney with hydronephrosis, ureterocele, ureteral dilatation or an abnormal bladder; otherwise, VCUG to detect reflux is optional.[8]
Age, febrile breakthrough infection, renal parenchymal status, bladder and bowel dysfunction, persistence and family preferences influence pediatric management. Adult secondary reflux needs assessment of the underlying outlet or bladder disorder. High-grade reflux found on pre-reconstruction VCUG in a man with long-standing obstruction warrants upper-tract evaluation and a renal function baseline before urethral repair.[8][6]
9. After Urethroplasty
Before catheter removal
After one-stage urethroplasty or closure of the urethral plate at the second stage, the EAU strongly recommends urethrography before catheter removal to assess extravasation. After perineostomy or the first stage of staged urethroplasty, the catheter can be removed after three to five days without urethrography.[4] The EAU describes RUG, pericatheter RUG and VCUG as options and weakly recommends considering the first urethrogram seven to ten days after uncomplicated urethroplasty to assess whether the catheter can be removed.[4] Persistent substantial leakage usually leads to continued drainage and repeat assessment; the operating team interprets minor findings in the context of the repair.[4]
Recurrence surveillance
Follow symptoms, patient-reported outcomes, flow and residual urine, with anatomical assessment matched to recurrence risk and the postoperative protocol. The EAU weakly recommends flexible cystoscopy three months after urethroplasty and a risk-adjusted follow-up protocol; cystoscopy or urethrography can assess anatomical success.[5]
Typical RUG findings after repair are interpreted as follows.
| Finding | Interpretation |
|---|---|
| Normal caliber at the repair | Patent repair on this study; continue symptom and flow surveillance |
| Smooth narrowing at the repair | Early recurrence or anastomotic scar; correlate with symptoms and flow, and consider cystoscopy or repeat imaging |
| Irregular narrowing | Recurrent stricture; consider cystoscopy |
| Extravasation | Leak; early leaks may need continued catheter drainage |
| Fistulous tract | Assess size, location and drainage |
| Panurethral irregularity | Consider progression of lichen sclerosus or the underlying disease elsewhere |
A Qmax threshold of 12 or 15 mL/s alone neither proves nor excludes recurrence. Not every asymptomatic anatomic narrowing requires treatment. A rising symptom score with falling flow warrants anatomical assessment. Late recurrence can occur after urethroplasty, particularly after substitution repair; the EAU recommends at least one year of routine follow-up and risk-adjusted follow-up thereafter , with instructions to return if symptoms worsen.[5]
Treatment selection is on the urethral reconstruction atlas.
References
1. EAU. Urethral Strictures: diagnostic evaluation. 2026. Guideline. Accessed September 11, 2026.
2. AUA. Urethral Stricture Disease Guideline, amended 2023. Guideline. Amendment.
3. Frankiewicz M, Markiet K, Kozak O, et al. Retrograde urethrography, sonouretrography and magnetic resonance urethrography in evaluation of male urethral strictures. Should the novel methods become the new standard in radiological diagnosis of urethral stricture disease? Int Urol Nephrol. 2021;53(12):2423-2435. doi:10.1007/s11255-021-02994-5. PubMed.
4. EAU. Urethral Strictures: perioperative care of urethral surgery. 2026. Guideline. Accessed September 11, 2026.
5. EAU. Urethral Strictures: follow-up. 2026. Guideline. Accessed September 11, 2026.
6. EAU. Neuro-urology: diagnostic evaluation and urodynamics. 2026. Guideline. Accessed September 11, 2026.
7. EAU. Urethral Strictures: disease management in females. 2026. Guideline. Accessed September 11, 2026.
8. EAU. Paediatric Urology: vesicoureteric reflux. 2026. Guideline. Accessed September 11, 2026.
9. Berná-Mestre JD, Berná-Serna JD, Aparicio MD. Urethrography in men: conventional technique versus clamp method. Radiology. 2009;252:240–246. doi:10.1148/radiol.2522082064. PubMed.
10. Li W, Man L, Huang G. An innovative method for occluding the urethral meatus and accessing urethra strictures in retrograde urethrography in males. BMC Urol. 2023;23(1):158. doi:10.1186/s12894-023-01328-0. Its specific device is not presented here as a standard of care.
11. ACR. Manual on Contrast Media. 2026. Manual. Accessed September 11, 2026.
12. Morey AF, Broghammer JA, Hollowell CMP, et al. Urotrauma Guideline 2020: AUA Guideline. J Urol. 2021;205(1):30–35. doi:10.1097/JU.0000000000001408. Full guideline, published 2014; amended April 2017 and August 2020.
13. Johnsen N, Wessells H, Archer-Arroyo K, et al. Best Practices Guidelines: Management of Genitourinary Injuries. American College of Surgeons Trauma Quality Programs; August 2025. Male urethral imaging protocols, pp. 19–20; RUG sequencing, p. 9.
14. Brandes SB. Decision Making and Surgical Technique in Urethroplasty. In: Brandes SB, Morey AF, eds. Advanced Male Urethral and Genital Reconstructive Surgery. 2nd ed. Humana Press; 2014:1–16. doi:10.1007/978-1-4614-7708-2_1
15. Kawashima A, Sandler CM, Wasserman NF, LeRoy AJ, King BF Jr, Goldman SM. Imaging of urethral disease: a pictorial review. Radiographics. 2004;24(Suppl 1):S195–S216. doi:10.1148/rg.24si045504
16. Nayyar R, Khattar N, Panda A. Working Algorithm for Female Lower Urinary Tract Symptoms. In: Khattar N, Nayyar R, Panda A, eds. Female Bladder Outlet Obstruction and Urethral Reconstruction. Springer; 2021:111–120. doi:10.1007/978-981-15-8521-0_10
17. European Association of Urology. EAU Guidelines on Non-neurogenic Female LUTS: Disease Management. 2026. Guideline.
18. Bracco Diagnostics Inc. Cystografin (diatrizoate meglumine injection): US prescribing information. DailyMed. Revised June 2024. Label.
19. Ramanathan S, Raghu V, Ramchandani P. "Imaging of the adult male urethra, penile prostheses and artificial urinary sphincters." Abdom Radiol. 2020;45(7):2018–2035. doi:10.1007/s00261-019-02356-x
20. Revels JW, Wang SS, Weaver JS, et al. "A multimodality review of male urethral imaging: pearls and pitfalls with an update on urethral stricture treatment." Br J Radiol. 2022;95(1134):20211034. doi:10.1259/bjr.20211034.
21. Choi DK, Kim S, Oh JJ. "Effects of pelvic bone fracture on recurrence-free rate after bulbomembranous anastomotic urethroplasty in men with posterior urethral injuries." Investig Clin Urol. 2020;61(1):99–106. doi:10.4111/icu.2020.61.1.99
22. European Association of Urology. EAU Guidelines on Urological Trauma. Limited update March 2026. Guideline.
23. Kim YJ, Cho BS, Lee J, et al. "The ABCs of Voiding Cystourethrography." J Korean Soc Radiol. 2020;81(1):101–118. doi:10.3348/jksr.2020.81.1.101