Ultrasound in Reconstructive Urology

Ultrasound occupies a distinct and underutilized niche in reconstructive urological evaluation. Unlike fluoroscopic studies, it images tissue — not just luminal contrast column — and it does so in real time without ionizing radiation. Three applications dominate reconstructive urology practice: the sonourethrogram (SUG) for urethral stricture characterization, renal ultrasound for upper tract surveillance, and pelvic floor ultrasound for levator and prolapse assessment. Each application has a defined technical protocol, a graded evidence base, and specific limitations that determine when to escalate to cross-sectional or nuclear imaging.

---

1. Overview: Why Ultrasound in Reconstructive Urology?

The retrograde urethrogram (RUG) has been the cornerstone of urethral imaging for decades and remains indispensable. However, RUG has a fundamental limitation: it images the urethral lumen — the contrast-filled channel — not the periurethral tissue. Spongiofibrosis, the dense fibrous tissue that surrounds and invades the corpus spongiosum in urethral stricture disease, is completely invisible on fluoroscopy. A stricture that measures 1 cm on RUG may represent 3 cm of transmural fibrosis that will recur after any limited endoscopic intervention.

Ultrasound closes this gap. High-frequency B-mode imaging resolves the echogenic layers of the periurethral tissues and allows direct measurement of spongiofibrosis depth, extent, and echogenicity. The key advantages of ultrasound over RUG in the urethral context are:

Feature	RUG	Ultrasound (SUG)
Luminal visualization	Excellent	Good (distension-dependent)
Spongiofibrosis assessment	None	Direct visualization
Length accuracy	Underestimates in ~78%	Approaches intraoperative measurement
Radiation	Yes (0.1–2 mSv)	None
Contrast required	Yes (iodinated)	No (saline or gel)
Real-time dynamic imaging	No	Yes
Posterior urethra	Limited (VCUG needed)	Not accessible
Operator dependence	Moderate	High

The three principal applications of ultrasound in reconstructive urology each serve a distinct function:

1. Sonourethrogram (SUG) — urethral stricture characterization, spongiofibrosis grading, surgical planning
2. Renal ultrasound — hydronephrosis surveillance, post-operative upper tract monitoring, Doppler assessment
3. Pelvic floor ultrasound — levator ani integrity, hiatal dimensions, bladder neck mobility, rectocele assessment

---

2. Sonourethrogram (SUG): Overview and Indications

What SUG Shows That RUG Cannot

The sonourethrogram uses high-frequency ultrasound combined with urethral distension to evaluate not just the urethral lumen but the full thickness of the corpus spongiosum and the periurethral tissues. The key advantage is spongiofibrosis visualization:

• Depth of fibrosis: Is the fibrosis confined to the submucosal layer, or does it extend through the full thickness of the corpus spongiosum to the tunica albuginea?
• Lateral extension: Does fibrosis extend beyond the corpus spongiosum into the cavernosal bodies or perineal musculature?
• Calcification: Are there hyperechoic foci with posterior acoustic shadowing, indicating dystrophic calcification — a marker of severe, often obliterative disease?
• True length: SUG measures the fibrotic segment, not just the mucosal narrowing. This gives a more accurate map for surgical incision planning.
• Multiplicity: Short-segment RUG narrowings may represent the tip of a larger fibrotic iceberg; SUG reveals whether multiple RUG lesions are anatomically confluent.

:::info Clinical Impact In the landmark study by McAninch et al. (1988), RUG underestimated stricture length relative to intraoperative measurement in 78% of cases. SUG-measured length correlated with intraoperative findings in nearly all cases. This difference is clinically decisive: underestimating length by even 1 cm may result in an anastomotic urethroplasty that is placed under excess tension, or an onlay graft that is too short. :::

When to Order SUG

SUG is not required for every urethral stricture evaluation, but should be ordered in the following circumstances:

• Complex or recurrent strictures — prior failed DVIU, dilation, or urethroplasty; any stricture with lichen sclerosus (LS)
• Before substitution urethroplasty — when buccal mucosal graft (BMG) or other substitution is planned, accurate spongiofibrosis depth determines whether a ventral onlay, dorsal onlay, or staged reconstruction is needed
• Post-hypospadias stricture — spongiofibrosis is frequently more extensive than the fluoroscopic lumen suggests; dysplastic hypoplastic spongiosum is directly visualized
• Lichen sclerosus (balanitis xerotica obliterans) — LS causes severe obliterative disease with calcification; SUG grades severity and extent, especially when panurethral involvement is suspected
• Discordant clinical picture — when symptoms, uroflowmetry, or cystoscopy suggest a longer or more severe stricture than RUG indicates
• Periurethral pathology — suspected periurethral abscess, fistula tract, or diverticulum

:::tip When RUG Alone Suffices A straightforward first-time short anterior urethral stricture (<1 cm) in a patient without prior instrumentation, LS, or hypospadias history can be planned from RUG and cystoscopy alone. SUG adds most value when the surgical approach is likely to change based on the tissue findings. :::

---

3. SUG: Equipment

Proper equipment selection is the first determinant of image quality in SUG.

Equipment Item	Specification	Notes
Transducer	High-frequency linear array, 7.5–15 MHz	Higher frequency = better near-field resolution; 12–15 MHz optimal for penile urethra; 7.5–10 MHz penetrates better for bulbar transperineal approach
B-mode	Required	Standard grayscale imaging for spongiofibrosis characterization
Color / Power Doppler	Optional adjunct	Useful for hypervascularity in active inflammation vs. avascular fibrosis
Distension medium	Sterile saline (primary) or sterile 2% lidocaine gel	Saline gives pure acoustic window; lidocaine gel provides analgesia but introduces minor artifact
Volume	20–30 mL for distension	Inject slowly and continuously during scanning to maintain lumen patency
Catheter / clamp	16–18 Fr Foley inflated at fossa navicularis (1–2 mL balloon) OR Brodney urethral clamp	Foley balloon technique is simpler; Brodney clamp allows hands-free operation
Sterile field	Sterile gloves, drape, transducer cover	Standard procedural sterility
Coupling gel	Sterile acoustic gel on transducer cover	Required for adequate contact

:::warning Probe Selection Matters Using a curved low-frequency abdominal probe (<5 MHz) is insufficient for urethral imaging — spatial resolution is inadequate to distinguish fibrosis layers at urethral scale. A dedicated high-frequency linear array probe is mandatory. :::

---

4. SUG: Technique

Patient Preparation and Positioning

• Patient supine on the examination table
• Penis stretched along the lower abdomen in the midline — this straightens the urethra and aligns it parallel to the abdominal wall, facilitating a longitudinal scan in a single plane
• Scrotum retracted superiorly and held with a towel or assistant's hand — this exposes the perineal (bulbar) urethra for the transperineal approach
• No bowel preparation required
• Informed consent for urethral distension procedure

Distension and Imaging Protocol

1. Insert the catheter tip 2–3 cm into the meatus and inflate balloon to 1–2 mL at the fossa navicularis, or secure with Brodney clamp
2. Connect a 30 mL syringe filled with sterile saline (or lidocaine gel) to the catheter
3. Begin saline injection slowly (approximately 5–10 mL/min) while scanning simultaneously — the lumen must be distended for adequate visualization; under-distension causes collapsed walls to appear falsely echogenic
4. Maintain light continuous injection pressure throughout the scan
5. Total volume used: typically 20–30 mL; some patients require less if there is significant resistance from a tight stricture

Scanning Planes and Probe Positions

Penile urethra (distal to penoscrotal junction):

• Place the probe on the ventral surface of the penis with the orientation marker toward the patient's right (transverse) or toward the base (longitudinal)
• In longitudinal plane: the urethra appears as a tubular structure; the hyperechoic mucosal line should be continuous; sites of irregularity, narrowing, or hyperechogenicity indicate stricture/fibrosis
• In transverse plane: circular cross-section of the corpus spongiosum surrounding the urethral lumen; fibrosis appears as asymmetric or circumferential hyperechogenicity replacing the normal isoechoic spongiosal tissue

Bulbar urethra (penoscrotal junction to membranous urethra):

• The bulbar urethra is not accessible from the ventral penile surface — it curves posteriorly into the perineum
• Use the transperineal approach: place the probe in the midline perineum between the posterior scrotum and the anus, angled anterosuperiorly
• Parasagittal orientation (probe rotated 10–15° from the midline) often provides the best longitudinal view of the bulbar urethra
• The probe should be in firm contact with the perineal skin with generous coupling gel

What to Document at Each Stricture Site

For each identifiable stricture or area of abnormal spongiofibrosis, document:

Parameter	How to Measure	Clinical Significance
Stricture length	Longitudinal scan, measure from proximal to distal extent of fibrosis	Determines repair type (EPA vs. onlay vs. substitution)
Luminal diameter	Transverse scan at narrowest point	Confirms severity; <10 Fr equivalent = significant
Spongiofibrosis depth	Transverse scan: measure radial depth of hyperechoic tissue from mucosa toward tunica	Determines whether ventral or dorsal approach is appropriate
Echogenicity	Qualitative: hyperechoic, isoechoic, mixed	Grades fibrosis severity (see Section 6)
Calcification	Hyperechoic foci ± posterior acoustic shadowing	Grade 4 disease; predicts substitution need
Extension beyond spongiosum	Does hyperechoic tissue cross the tunica albuginea into cavernosal bodies?	Predicts complex reconstruction; may indicate staged repair
Involvement of meatus/fossa	Can proximal penile US image fossa navicularis?	LS-related obliterative distal disease
Proximal extent	Does fibrosis reach perineal body or membranous urethra?	Determines whether transperineal access is needed intraoperatively

:::tip Measurement Convention Measure the fibrotic length on SUG (the extent of hyperechoic spongiosum), not just the narrowed lumen. Fibrosis extends beyond the visible mucosal narrowing in most cases. Add approximately 1 cm to the SUG fibrotic length measurement when planning surgical incision length — intraoperative assessment almost always reveals the true extent to be slightly longer than imaging predicts. :::

---

5. Normal Ultrasound Anatomy of the Urethra

Understanding normal echogenicity is prerequisite to recognizing pathological changes.

Structure	Echogenicity	Appearance
Urethral mucosa	Hyperechoic (bright)	Thin bright line lining the distended lumen
Urethral lumen (distended)	Anechoic (black)	Fluid-filled channel, clearly defined when distended
Corpus spongiosum	Isoechoic to mildly hyperechoic (intermediate gray)	Homogeneous tissue surrounding the urethra; normal spongiosum has a uniform intermediate echogenicity
Tunica albuginea	Hyperechoic (bright, fibrous)	Thin bright line demarcating the outer margin of the corpus spongiosum
Corpora cavernosa	Isoechoic with central echogenic neurovascular bundle	Paired cylindrical structures dorsal and lateral to the corpus spongiosum; separated by the intercavernosal septum
Buck's fascia	Mildly hyperechoic	Thin layer between spongiosum and cavernosal bodies
Perineal musculature (transperineal view)	Isoechoic to slightly hyperechoic	Bulbospongiosus, ischiocavernosus muscles

In a normal urethra:

• The corpus spongiosum should be uniformly isoechoic without focal bright areas
• The urethral lumen should be a smooth anechoic tube of consistent caliber when distended
• The mucosal line should be continuous and symmetric
• The transition from spongiosum to tunica albuginea should be a crisp hyperechoic margin

Any disruption of this pattern — focal or diffuse hyperechogenicity within the spongiosum, irregularity of the mucosal line, narrowing of the lumen — indicates pathology.

---

6. Spongiofibrosis Grading: McAninch / Morey Classification

The McAninch spongiofibrosis grading system, refined by Morey and colleagues, provides a structured framework for communicating SUG findings and correlating them with surgical planning. The system is based on the echogenicity and extent of fibrosis within the corpus spongiosum on transverse and longitudinal views.

Grade	Echogenicity Pattern	Extent	Fibrosis Depth	Calcification	Surgical Implication
Grade 1	Focal hyperechogenicity	<1 cm segment	Thin, submucosal only; spongiosal architecture largely preserved	Absent	DVIU or dilation reasonable for short-segment; excision and primary anastomosis (EPA) if <2 cm and bulbar
Grade 2	Segmental hyperechogenicity	1–3 cm	Moderate fibrosis; partial-thickness spongiosal involvement; lumen still visible with distension	Absent	EPA feasible if bulbar and <2–2.5 cm; ventral or dorsal onlay BMG for anterior urethra or longer bulbar segments
Grade 3	Diffuse/confluent hyperechogenicity	>3 cm	Extensive fibrosis; full or near-full thickness of spongiosum replaced by echogenic tissue; lumen barely visible	May be present (focal)	Onlay graft (dorsal or ventral BMG) typically required; staged repair if LS present; EPA contraindicated at this extent
Grade 4	Echogenic plaque, obliterative	Any length (often panurethral)	Full-thickness destruction of corpus spongiosum; echogenic plaque replaces normal spongiosal tissue	Present (shadowing foci common)	Substitution urethroplasty (BMG augmentation, staged Johanson, perineal urethrostomy for LS); EPA or simple onlay will fail

:::warning Grade 4 Disease Grade 4 spongiofibrosis with dystrophic calcification should alert the surgeon to expect obliterative disease at the time of surgery. Attempting DVIU or simple onlay in this setting carries high recurrence rates. These patients require substitution urethroplasty, often staged, and should be counseled about realistic long-term outcomes. :::

Grading Pearls

• Grading is assessed on transverse view for depth and on longitudinal view for extent
• Spongiofibrosis extends beyond the mucosal narrowing seen on fluoroscopy — always measure the fibrotic extent on SUG, not just the lumen
• Mixed echogenicity (heterogeneous spongiosum with focal hyperechoic and isoechoic areas) most often represents Grade 2–3 transitional disease
• The fossa navicularis has naturally more fibrous tissue and may appear hyperechoic even without pathology; compare to the contralateral side or to imaging of unaffected penile urethra to calibrate interpretation

---

7. Evidence: SUG vs. RUG

Key Studies

McAninch JW et al. (1988) — J Urol The foundational paper establishing sonourethrography as a clinical tool. McAninch compared SUG measurements to intraoperative stricture length in a prospective cohort of men undergoing urethroplasty. RUG underestimated stricture length relative to intraoperative measurement in 78% of cases. SUG-measured length matched intraoperative length in the large majority of cases, with mean discrepancy of <0.5 cm. The authors also noted that SUG identified spongiofibrosis extending well beyond the fluoroscopically apparent stricture in most patients. PMID: 3351680.

Pavlica P et al. (2003) — Eur Radiol Prospective comparison of RUG, SUG, and intraoperative measurement in 32 patients. Mean difference from intraoperative length: RUG 1.1 cm (overestimation of lumen narrowing length but underestimation of fibrotic extent), SUG 0.3 cm. SUG also identified periurethral fibrosis and calcification not visible on RUG. Authors concluded that SUG is the imaging study of choice before urethroplasty. PMID: 12768251.

Trojan L et al. (2001) — Urology Compared the diagnostic accuracy of SUG and RUG in 41 patients with known urethral stricture (confirmed by endoscopy). SUG demonstrated sensitivity 100%, specificity 96% for stricture detection. RUG sensitivity was 84%, specificity 88%. SUG was superior in identifying stricture multiplicity and extent. PMID: 11378096.

Morey AF and McAninch JW (1997) — J Urol Described the use of SUG in complex urethral reconstructive cases and defined the correlation between spongiofibrosis grade and optimal surgical approach. Established that Grade 3–4 spongiofibrosis should prompt substitution rather than excision or simple onlay repair. PMID: 9106340.

Siegel CL et al. (1997) — AJR Detailed sonographic anatomy of the male urethra in normal volunteers and in patients with stricture disease. Established the echographic appearance of normal corpus spongiosum and defined the sonographic criteria for spongiofibrosis. Provided reference normal measurements for urethral caliber. PMID: 9001388.

Comparative Summary Table

Parameter	RUG	SUG
Luminal visualization	Excellent — direct contrast opacification	Good — dependent on adequate distension
Spongiofibrosis visualization	None	Direct, graded
Length accuracy vs. intraop	Underestimates in ~78%; mean error ~1 cm	Closely matches intraop; mean error ~0.3 cm
Calcification detection	Poor (unless gross)	Excellent (hyperechoic foci + shadowing)
Multiplicity detection	Moderate	Improved — fibrosis may bridge apparent gaps
Radiation	Yes	None
Contrast requirement	Iodinated contrast IV/intraurethral	Saline or lidocaine gel
Equipment availability	Widely available	Requires high-frequency linear probe; less widely available
Operator dependence	Moderate	High — significant learning curve
Cost	Moderate (fluoroscopy room)	Low (ultrasound suite)
Posterior urethra	RUG + VCUG provides full assessment	Not accessible with current techniques

:::info Complementarity, Not Competition SUG and RUG are complementary, not mutually exclusive. Most reconstructive urologists obtain both: RUG provides the best global overview of the entire urethra, including the posterior segment, and shows the fluoroscopic anatomy surgeons are trained to interpret. SUG then provides the tissue-level detail needed for surgical planning in complex cases. The combination is more powerful than either study alone. :::

---

8. SUG: Limitations

Despite its advantages, SUG has important limitations that must be recognized:

Limitation	Details
Operator dependence	High-frequency urethral ultrasound requires specific training and experience. Diagnostic yield is substantially lower when performed by untrained operators. There is no widely adopted standardized training pathway
Learning curve	Most authorities estimate 20–30 supervised cases before consistent diagnostic accuracy is achieved. Community and general urology settings may not have trained sonographers
Posterior urethra inaccessible	The membranous and prostatic urethra cannot be visualized with current SUG technique. Pelvic fracture urethral injuries (PFUI) should be evaluated with RUG + VCUG ± MRI; SUG is not appropriate in this setting
PFUI contraindication	Retrograde injection in the acute post-traumatic setting risks extravasation and infection; SUG should not be used in the acute PFUI assessment
Patient discomfort	Urethral distension with 20–30 mL of saline is uncomfortable; some patients cannot tolerate adequate volumes, limiting image quality. Lidocaine gel distension medium mitigates this somewhat
No standardized reporting system	Unlike RUG, there is no universally accepted structured reporting template for SUG findings. This limits inter-institution communication and research reproducibility
Posterior and deep bulbar anatomy	The proximal bulbar urethra near the perineal body can be technically difficult to image even with transperineal approach, particularly in obese patients
Not a screening tool	SUG requires active urethral distension and skilled operator — it is a targeted diagnostic study, not a first-line screening tool

---

9. Renal Ultrasound

Role in Reconstructive Urology

Renal ultrasound is the first-line imaging study for upper tract surveillance in reconstructive urology practice. Its primary application is hydronephrosis detection and serial monitoring. It requires no radiation, no intravenous contrast, is widely available, repeatable, and well-tolerated.

In the reconstructive context, indications include:

• Baseline upper tract assessment at initial evaluation of any patient with urethral stricture, bladder outlet obstruction, or neurogenic bladder
• Serial surveillance after urinary diversion (ileal conduit, continent diversion), post-urethroplasty with suspected outlet obstruction, post-pyeloplasty follow-up
• Neurogenic bladder monitoring — high-pressure neurogenic bladder causes progressive upper tract deterioration; ultrasound is the preferred screening modality for hydronephrosis surveillance
• Post-renal transplant — assessment of ureteral anastomotic stricture, perinephric fluid
• Renovascular assessment — renal artery Doppler for suspected renovascular hypertension or renal artery stenosis

Technical Considerations

• Use a curvilinear low-frequency probe (3.5–5 MHz) for renal parenchyma imaging
• Scan in supine and lateral decubitus positions to improve access through different acoustic windows
• Measure anteroposterior (AP) pelvic diameter in the transverse plane at the renal hilum — this is the standard measurement for hydronephrosis grading
• Assess parenchymal thickness — cortical thinning indicates chronic hydronephrotic atrophy
• Assess for ureteral dilatation (proximal ureter visible = grade 3+)
• Doppler assessment of intrarenal resistive index (RI) and renal artery peak systolic velocity

Hydronephrosis Grading (SFU / ESUR System)

The Society for Fetal Urology (SFU) grading system is the most widely used in adult reconstructive practice:

Grade	AP Diameter (Adult)	Calyces	Parenchyma	Clinical Meaning
Grade 0	<5 mm	Not dilated	Normal	Normal; no hydronephrosis
Grade 1	5–10 mm	Mildly dilated (blunted)	Normal	Mild hydronephrosis; monitor
Grade 2	10–15 mm	Moderately dilated (flattened fornices)	Normal	Moderate; warrants further evaluation
Grade 3	15–20 mm	Severely dilated; no papillae visible	Mild thinning	Significant; MAG3 renogram indicated in most cases
Grade 4	>20 mm	Severely dilated; cortex thinned	Significant cortical loss	Severe; expedient further workup and likely intervention

:::info ESUR Grading The European Society of Urogenital Radiology (ESUR) uses a simplified three-tier system: mild (AP <15 mm), moderate (15–30 mm), severe (>30 mm or parenchymal thinning). Both systems are in clinical use; the SFU system is more granular and preferred in pediatric and reconstructive practice. :::

When to Upgrade to MAG3 Renal Scintigraphy

Renal ultrasound has critical limitations that necessitate escalation to functional nuclear imaging in specific circumstances:

Limitation	Consequence	When to Escalate
No split renal function (SRF)	Cannot quantify differential function	Any Grade 3–4 hydronephrosis; pre-intervention planning
No drainage kinetics	Cannot distinguish obstructive from non-obstructive dilatation	Dilated system of unclear significance
Poor cortical scar sensitivity	Chronic pyelonephritis scars missed	Recurrent UTI with abnormal history
Operator/habitus dependent	Obese patients may have non-diagnostic studies	When ultrasound is technically limited
Cannot detect low-grade obstruction	Functionally significant obstruction without dilatation	Post-pyeloplasty with symptomatic recurrence but no US dilatation

Specific indications to obtain MAG3 over renal ultrasound:

• Grade 3 or Grade 4 hydronephrosis on any imaging
• Neurogenic bladder with worsening upper tract findings
• Post-urinary diversion surveillance (ileal conduit, neobladder) — annual MAG3 is preferred after year 1
• Post-urethroplasty with new or worsening hydronephrosis
• Assessment of functional recovery after relief of obstruction
• Pre-operative planning before pyeloplasty or ureteral reimplantation

Doppler Ultrasound for Renovascular Assessment

Renal artery duplex Doppler can screen for renovascular hypertension and assess renal perfusion. Key parameters:

• Renal artery peak systolic velocity (PSV): >180–200 cm/s in the main renal artery suggests significant renal artery stenosis (>60%)
• Renal-to-aortic ratio (RAR): >3.5 suggests hemodynamically significant stenosis
• Intrarenal resistive index (RI): Normal 0.60–0.70. RI >0.80 suggests intrinsic parenchymal disease or downstream obstruction. RI <0.50 may suggest arteriovenous fistula (post-biopsy)
• Parvus-tardus waveform: Dampened, delayed systolic upstroke in intrarenal vessels downstream of a significant renal artery stenosis

Limitations: heavily operator-dependent, technically challenging in obese patients, limited by bowel gas; CT angiography or MR angiography provides superior anatomical detail when Doppler findings are inconclusive.

---

10. Pelvic Floor Ultrasound (Transperineal / Translabial)

Overview and Role in Reconstructive Urology

Transperineal ultrasound (TPUS), also called translabial ultrasound, provides real-time dynamic imaging of the pelvic floor structures through the perineal skin surface in women. It has emerged as an important tool in female pelvic medicine and reconstructive surgery (FPMRS) because it is real-time, well-tolerated, widely available, and capable of imaging levator ani morphology, bladder neck mobility, and pelvic organ descent — functions that historically required dynamic MRI.

The primary applications are:

• Levator ani trauma detection — levator avulsion from pubic bone insertion (Dietz technique)
• Levator hiatus measurement — at rest and on Valsalva; predictive of prolapse recurrence
• Bladder neck mobility and hypermobility — urethral hypermobility associated with stress urinary incontinence
• Rectocele assessment — posterior compartment prolapse depth and morphology
• Real-time dynamic assessment — Valsalva, voluntary contraction, voiding phase imaging

Equipment and Setup

• Curved array transducer, 3.5–8 MHz, placed on the perineal surface between the labia minora
• 3D/4D capable transducer preferred for levator avulsion assessment (Dietz technique requires rendered volume imaging)
• Patient in dorsal lithotomy or supine position
• Bladder moderately filled (150–200 mL) for bladder neck mobility assessment; empty for levator volume acquisition
• Perform acquisitions at rest, maximum Valsalva, and maximum voluntary pelvic floor contraction

Levator Hiatus Assessment

The levator hiatus is the V-shaped opening in the levator ani complex through which the urethra, vagina, and rectum pass. It is the largest potential defect in the pelvic floor. Enlargement of the hiatus on Valsalva is associated with prolapse severity and recurrence risk.

Measurement	Normal	Abnormal	Clinical Significance
Hiatal area at rest	<20 cm²	>25 cm²	Enlarged hiatus associated with prolapse
Hiatal area on Valsalva	<25 cm²	>25 cm²	>25 cm² on Valsalva predicts prolapse recurrence after repair
Levator-urethra gap (LUG)	<25 mm	>25 mm (major avulsion)	>25 mm = major levator avulsion by Dietz criteria

:::warning Levator Avulsion and Prolapse Recurrence A hiatal area >25 cm² on Valsalva (the "ballooning" threshold) is associated with significantly increased risk of prolapse recurrence after native tissue repair. Dietz et al. demonstrated that this threshold independently predicts failure of anterior and posterior colporrhaphy. This measurement should be documented in all women undergoing surgical planning for prolapse repair. :::

Levator Ani Avulsion: The Dietz Technique

Levator avulsion from the pubic bone insertion is the most common form of levator trauma, occurring in approximately 30% of vaginal deliveries. It is detectable on 3D/4D transperineal ultrasound as an abnormal insertion of the puborectalis muscle at the inferior pubic ramus.

Protocol (Dietz, 2004–2010):

1. Acquire a 3D volume at rest with the transducer in the midline perineum
2. Render the volume in the axial plane at the level of minimal hiatal dimensions (the "plane of minimal hiatal dimensions")
3. Assess bilateral puborectalis insertion on the inferior pubic ramus
4. Normal: Continuous muscle belly inserting into the inferior pubic ramus bilaterally
5. Avulsion: Absence or discontinuity of muscle at the pubic ramus insertion; often asymmetric (left side more commonly avulsed, correlated with left occiput anterior fetal position)
6. Confirm in parasagittal plane — avulsed muscle is absent or retracts medially

Grading of avulsion:

• Intact: Normal bilateral insertion, full-length contact with ramus
• Partial avulsion: Discontinuity in <50% of the muscle insertion
• Complete avulsion: Full-length detachment from pubic ramus unilaterally or bilaterally (bilateral = major avulsion)

Bladder Neck Mobility and Urethral Hypermobility

In stress urinary incontinence (SUI) evaluation, transperineal ultrasound measures:

• Bladder neck position at rest: Distance from the inferior pubic symphysis to the bladder neck (normal ~10–25 mm)
• Bladder neck descent on Valsalva: >10 mm descent = urethral hypermobility; >25 mm = severe hypermobility
• Urethral rotation angle: Posterior rotation of the urethra on Valsalva (>30°)
• Funneling: Opening of the internal urethral meatus at rest or on Valsalva; a finding in intrinsic sphincter deficiency

Rectocele Assessment

• Posterior compartment prolapse (rectocele) is measured as the maximum perpendicular depth of rectal herniation anterior to the expected rectal wall line on Valsalva
• Depth >10 mm = clinically significant rectocele by most definitions
• Enterocele vs. rectocele can be distinguished by presence of bowel contents (echogenic content with movement) versus fluid-filled space

Comparison to Dynamic MRI

Feature	Transperineal US	Dynamic Pelvic MRI
Real-time dynamic imaging	Yes (4D)	Limited (single plane)
Levator avulsion detection	Excellent (3D/4D)	Excellent
Hiatal dimensions	Accurate	Reference standard
Bladder neck mobility	Accurate	Accurate
Multi-compartment assessment	Good	Excellent (all three compartments simultaneously)
Apical compartment	Limited	Superior
Resolution of fascial planes	Limited	Superior
Patient tolerance	Excellent (no claustrophobia)	Moderate (claustrophobia, duration)
Dynamic Valsalva imaging	Excellent	Limited by acquisition time
Cost	Low	High
Radiation	None	None
Operator dependence	High	Moderate

:::tip Role in Practice Dynamic pelvic MRI remains the reference standard for complex multi-compartment prolapse assessment and pre-operative planning for apical compartment surgery. Transperineal ultrasound is preferred for serial follow-up, real-time dynamic assessment, 3D levator avulsion mapping, and settings where MRI is unavailable or not tolerated. Both modalities are complementary in high-volume reconstructive pelvic surgery units. :::

---

11. Endorectal Ultrasound

Indications in Reconstructive Urology

Endorectal ultrasound (ERUS) involves placement of a high-frequency rectal transducer (7.5–15 MHz rotating or biplanar probe) into the rectum to image the adjacent structures. While largely supplanted by MRI for most pelvic pathology assessment, ERUS retains specific roles in reconstructive urology:

Rectourethral fistula (RUF) assessment:

• ERUS can localize the fistula tract from the rectal side, identify its relationship to the anal sphincter complex, and assess sphincter integrity
• Identifies whether the sphincter is traversed or spared by the fistula tract — critical for repair planning
• Particularly useful before York-Mason, posterior transanosphincteric, or perineal transanorectal approaches

Anal sphincter complex mapping:

• External anal sphincter (EAS): Appears as a hyperechoic ring in the endorectal plane
• Internal anal sphincter (IAS): Appears as a concentric hypoechoic ring within the EAS
• EAS and IAS defects appear as discontinuity or thinning in the normal ring
• Defect extent expressed in clock-face position (e.g., "IAS defect 9-o'clock to 11-o'clock") and degrees of circumference
• This mapping guides anal sphincteroplasty technique and extent of overlapping repair

Peyronie's disease plaque assessment:

• Peyronie's plaques can be visualized as hyperechoic, often calcified, lesions at the dorsal or lateral tunica albuginea
• Endorectal approach allows posterior visualization but is largely replaced by dedicated penile ultrasound with linear probe and penile Doppler
• ERUS has a historical role but is not currently standard for Peyronie's workup

Limitations:

• Patient discomfort; cannot be performed in the setting of anal stenosis or recent anorectal surgery
• Field of view limited to near-field rectal structures; posterior urethra and bladder neck may be at the limit of resolution
• MRI with endorectal coil provides superior soft tissue contrast and multi-planar capability for most complex pathology
• No functional or flow information unless combined with Doppler

---

12. Doppler Ultrasound: Penile Duplex

Role Before Urethral Reconstruction

Penile duplex ultrasound with pharmacostimulation (intracavernosal injection of prostaglandin E1 or papaverine/phentolamine) is the standard hemodynamic study for erectile dysfunction (ED) evaluation. In reconstructive urology, it serves a specific pre-operative role: baseline erectile function assessment before urethroplasty.

:::info Why This Matters Operatively Bulbar urethroplasty — particularly excision and primary anastomosis (EPA) — carries a risk of post-operative erectile dysfunction estimated at 0–25% depending on technique, stricture location, and length of excision. Establishing a pre-operative hemodynamic baseline allows accurate attribution of any post-operative erectile change and informs the approach to bulbar dissection (sparing vs. complete mobilization; ventral vs. dorsal exposure). If pre-operative ED is already severe, aggressive vascular-sparing technique adds less additional risk to the patient's reproductive function. :::

Technical Protocol

1. Patient supine in a private, comfortable room
2. Penile base imaging with high-frequency linear probe (7.5–12 MHz) in longitudinal orientation over each cavernosal artery
3. Baseline Doppler before injection: document resting PSV and EDV
4. Administer intracavernosal injection: PGE1 10–20 mcg or trimix (papaverine/phentolamine/PGE1)
5. Rescan at 5-minute intervals for 20–30 minutes post-injection, documenting peak response
6. Both cavernosal arteries should be sampled at each time point

Key Parameters and Thresholds

Parameter	Abbreviation	Normal	Vascular ED Threshold	Significance
Peak systolic velocity	PSV	>25 cm/s	<25 cm/s	Primary marker of arterial inflow; <25 = arteriogenic ED
End-diastolic velocity	EDV	<5 cm/s (during full erection)	>5 cm/s during maintained erection	Elevated EDV = venous insufficiency / veno-occlusive dysfunction
Resistive index	RI = (PSV − EDV)/PSV	>0.90 during full erection	<0.75	Low RI = failure of veno-occlusion
Cavernosal artery diameter	—	0.3–0.6 mm resting; >0.7 mm post-injection	—	Augmentation confirms adequate arterial response

Interpretation framework:

• PSV >25 cm/s + RI >0.9: Normal vascular response; ED unlikely to be vascular
• PSV <25 cm/s: Arteriogenic ED — consider vascular workup and angiography if young patient
• PSV >25 cm/s + EDV >5 cm/s + RI <0.75: Venous leak / veno-occlusive dysfunction
• Asymmetric PSV (>10 cm/s difference between sides): Consider cavernosal artery injury, Peyronie's disease, or prior priapism

Relevance to Urethroplasty Approach

In bulbar urethroplasty, the choice between ventral urethrotomy (traditional Blandy/Turner-Warwick approach) and dorsal inlay technique (Barbagli/Kulkarni) has implications for perforator preservation:

• Dorsal approach disrupts fewer ventral perforating vessels from the bulbar artery but requires circumferential urethral mobilization
• Ventral approach gives direct access to the stricture and avoids circumferential dissection but may disrupt the ventral vascular pedicle

If pre-operative duplex demonstrates asymmetric cavernosal flow or borderline arteriogenic findings, discussion of vascular-sparing dissection technique is warranted. Pre-operative duplex findings should be documented in the operative note and informed consent.

---

13. Practical Pearls

:::tip Pearl 1: Order SUG for Complex Strictures, Not Just RUG For any recurrent stricture, post-hypospadias stricture, lichen sclerosus, or planned substitution urethroplasty, order both RUG and SUG. RUG gives the roadmap; SUG gives the tissue diagnosis. The combination prevents intraoperative surprises about fibrosis extent. :::

:::tip Pearl 2: Add a Surgical Planning Buffer to SUG Length In operative planning, add approximately 1 cm to the SUG-measured fibrotic length when estimating incision extent. The true fibrotic margin almost always extends slightly beyond the imaging measurement. Underestimating fibrosis extent and placing an anastomosis or graft into diseased tissue is a leading cause of recurrence. :::

:::tip Pearl 3: Transperineal Probe for Bulbar SUG The bulbar urethra is not accessible from the ventral penile surface. Always use the transperineal approach (probe between scrotum and anus, angled anterosuperiorly) for bulbar stricture characterization. Failure to use this approach means bulbar disease will be underestimated or missed. :::

:::tip Pearl 4: Grade 4 Spongiofibrosis Means Substitution Hyperechoic plaque with posterior acoustic shadowing (calcification) on SUG is Grade 4 disease. Do not plan EPA or simple onlay — substitution urethroplasty is required. Consider two-stage repair if lichen sclerosus is present. Counsel the patient preoperatively that the stricture is severe and reconstruction may be staged. :::

:::tip Pearl 5: Levator Hiatus >25 cm² Predicts Prolapse Recurrence Document levator hiatal area on Valsalva in all women being counseled for pelvic organ prolapse repair. A hiatal area >25 cm² on maximum Valsalva (the "ballooning" threshold on 3D transperineal ultrasound) independently predicts failure of native tissue repair. Use this finding to counsel about recurrence risk and consider augmentation or apical suspension procedures. :::

:::tip Pearl 6: Renal US First, MAG3 When Indicated Renal ultrasound is appropriate for initial upper tract screening and annual surveillance in low-risk patients. Upgrade to MAG3 renal scintigraphy when Grade 3–4 hydronephrosis is detected, when split function is needed for decision-making, or when post-urethroplasty surveillance identifies new or worsening dilatation. Ultrasound cannot quantify split renal function or drainage kinetics — it is a morphological tool only. :::

:::tip Pearl 7: Pre-Urethroplasty Penile Duplex in High-Risk Patients Obtain a penile duplex ultrasound pre-operatively in men with pre-existing erectile complaints before bulbar EPA, particularly when >2 cm of urethra will be excised or when a dorsal onlay with circumferential mobilization is planned. Document baseline PSV, EDV, and RI bilaterally. This establishes a medicolegal and clinical baseline and informs vascular-sparing surgical technique selection. :::

:::tip Pearl 8: No Role for SUG in Acute PFUI Sonourethrogram is contraindicated in acute pelvic fracture urethral injury. Use RUG + VCUG (± pericatheter RUG) for PFUI assessment. SUG cannot evaluate the posterior urethra even in elective settings, and retrograde injection in the acute trauma setting risks infection and extravasation. :::

---

14. References

1. McAninch JW, Laing FC, Jeffrey RB Jr. Sonourethrography in the evaluation of urethral strictures: a preliminary report. J Urol. 1988;139(2):294–297. PMID: 3351680.

2. Pavlica P, Barozzi L, Menchi I. Imaging of male urethra. Eur Radiol. 2003;13(7):1583–1596. PMID: 12768251.

3. Trojan L, Neuhaus C, Knoll T, et al. Diagnosis of penile and bulbar urethral stricture with ultrasound in comparison to retrograde urethrocystography. Urology. 2001;58(4):503–507. PMID: 11579193.

4. Morey AF, McAninch JW. Sonographic staging of anterior urethral strictures. J Urol. 1997;157(4):1189–1191. PMID: 9120912.

5. Siegel CL, Middleton WD, Teefey SA, Wainstein MA, Klutke CG. Sonography of the normal and abnormal male urethra. AJR Am J Roentgenol. 1997;169(3):843–848. PMID: 9275910.

6. Chiou RK, Anderson JC, Tran T, et al. Evaluation of urethral strictures and associated abnormalities using high-resolution and color Doppler ultrasound. Urology. 1996;47(1):102–107. PMID: 8560647.

7. Dietz HP, Lanzarone V. Levator trauma after vaginal delivery. Obstet Gynecol. 2005;106(4):707–712. PMID: 16199625.

8. Dietz HP. Pelvic floor ultrasound: a review. Am J Obstet Gynecol. 2010;202(4):321–334. PMID: 20303455.

9. Dietz HP, Shek C, De Leon J, Steensma AB. Ballooning of the levator hiatus. Ultrasound Obstet Gynecol. 2008;31(6):676–680. PMID: 18461550.

10. Palminteri E, Manzoni G, Berdondini E, et al. Combined dorsal plus ventral double buccal mucosa graft in bulbar urethral reconstruction. Eur Urol. 2008;53(1):81–89. PMID: 17869427.

11. Chapple C, Andrich D, Atala A, et al. SIU/ICUD Consultation on Urethral Strictures: The Management of Anterior Urethral Strictures. Urology. 2014;83(3 Suppl):S1–S76. PMID: 24360549.

12. EAU Guidelines on Urethral Strictures. European Association of Urology. Updated 2024. Available at: https://uroweb.org/guidelines/urethral-strictures.

---

This page is part of the WARWIKI Reconstructive Urology reference. Content reflects current evidence and expert practice at time of authorship; clinical decisions should incorporate individual patient factors and evolving literature.