What is the diagnostic approach for scrotal lymphedema?

Diagnostic Approach for Scrotal Lymphedema

Scrotal ultrasound with Doppler is the primary diagnostic modality for evaluating scrotal lymphedema, as it can differentiate between various causes of scrotal edema and exclude emergent conditions like testicular torsion. 1, 2

Initial Clinical Assessment

The clinical evaluation should focus on:

• Onset and duration of symptoms – Gradual onset over months to years is typical for lymphedema, distinguishing it from acute conditions like torsion (abrupt onset) or epididymitis (subacute onset) 1
• History of predisposing factors – Prior surgery (especially inguinal or pelvic procedures), radiation therapy, filariasis exposure, or congenital lymphatic abnormalities 3, 4, 5
• Extent of involvement – Whether edema is isolated to scrotum or extends to penis and lower extremities 3, 5
• Associated symptoms – Pain, chronic irritation, recurrent infections, drainage, or sexual dysfunction 3
• Age considerations – Congenital forms present in childhood, while acquired forms (post-surgical, filarial) typically present in adults 4, 5

Imaging Protocol

Ultrasound with Doppler (First-Line)

The American College of Radiology recommends scrotal ultrasound with Doppler as the initial imaging study for all scrotal abnormalities. 1, 2

The examination should include three components:

• Grayscale imaging – Assesses scrotal wall thickening, testicular homogeneity, and identifies underlying masses or fluid collections 1, 2
• Color Doppler assessment – Evaluates testicular perfusion to exclude torsion (96-100% sensitivity) and identifies increased flow in inflammatory conditions 1, 2
• Power Doppler – More sensitive for low-flow states and particularly useful in prepubertal patients 1, 2

Advanced Imaging When Indicated

• MRI of pelvis/scrotum – May be appropriate for very large scrotal masses where ultrasound is limited, or when differentiating intratesticular from extratesticular pathology is unclear 6, 1
• CT or MRI of abdomen/pelvis – Consider when evaluating for underlying malignancy, pelvic lymphadenopathy, or retroperitoneal pathology that may cause secondary lymphedema 6

Critical Differential Diagnoses to Exclude

The diagnostic workup must rule out emergent conditions that mimic or coexist with lymphedema:

• Testicular torsion – Requires surgical exploration within 6-8 hours; ultrasound shows absent/decreased flow and "whirlpool sign" 1, 2
• Epididymo-orchitis – Most common cause of acute scrotum in adults; shows enlarged hypoechoic epididymis with increased flow 2
• Testicular rupture – After trauma; shows loss of testicular contour and heterogeneous echotexture 2
• Acute idiopathic scrotal edema – Self-limiting condition in children; shows marked scrotal wall thickening with striated appearance and normal testes 6
• Underlying malignancy – Penile or testicular cancer with lymphatic obstruction; requires assessment for inguinal lymphadenopathy 6

Diagnostic Pitfalls to Avoid

• False-negative Doppler can occur with partial torsion or spontaneous detorsion; if clinical suspicion remains high despite normal ultrasound, surgical exploration should be considered 1, 2
• Chronic lymphedema may mask underlying pathology – Always assess testicular parenchyma for masses despite overlying edema 6
• Do not rely on clinical examination alone – Significant overlap exists in clinical presentation between different causes of scrotal swelling 1

Establishing the Diagnosis of Lymphedema

Once emergent conditions are excluded, the diagnosis of scrotal lymphedema is established by:

• Characteristic ultrasound findings – Marked scrotal wall thickening with preserved testicular architecture and normal testicular perfusion 6, 1
• Chronicity of symptoms – Progressive swelling over months to years, often with fibrotic changes 4, 5
• Identification of etiology – History of filariasis (most common worldwide), prior surgery/radiation, or congenital lymphatic abnormalities 5, 7
• Exclusion of other causes – Normal testicular parenchyma, absence of infection, no evidence of malignancy 4, 5

When to Obtain Urgent Surgical Consultation

Immediate urological consultation is required for:

• Any suspicion of testicular torsion, even with normal imaging if clinical suspicion is high 1, 2
• High TWIST score (≥6) in pediatric patients, which warrants surgical exploration without imaging 6, 1
• Testicular rupture confirmed or suspected on imaging 2
• Giant scrotal lymphedema causing functional impairment, as surgical debulking with reconstruction is the definitive treatment 3, 4, 5