Silk Sign (Silk Glove Sign)
The phenomenon of scrotal contents retracting inward on coughing or straining is called the "silk sign" or "silk glove sign," which is pathognomonic for an inguinal hernia with a patent processus vaginalis.
Clinical Significance
This sign occurs when increased intra-abdominal pressure from coughing forces herniated contents (typically bowel or omentum) back through the inguinal canal into the abdomen, creating a palpable impulse or visible retraction of the scrotal bulge 1, 2.
Mechanism and Pathophysiology
- The sign results from incomplete involution of the processus vaginalis, creating a patent communication between the peritoneal cavity and the scrotum through which intra-abdominal structures can herniate 1, 2
- When the patient coughs or strains, the sudden increase in intra-abdominal pressure temporarily reduces the hernia, causing the scrotum to appear to "pull inward" 3, 4
- This is the opposite of what occurs with a typical hernia examination, where coughing produces an outward bulge or impulse 3
Diagnostic Approach
Physical examination should specifically assess for an inguinal bulge that increases with crying or straining and may extend into the scrotum in males or labia in females 2.
Key examination findings include:
- Palpating for a bulge or impulse while the patient coughs or strains 3, 4
- The bulge may disappear when the patient is in the prone position 3
- In males, palpate the testis to ensure it is present in the scrotum and not involved in the hernia 2
- Evaluate both groins bilaterally, as contralateral patent processus vaginalis occurs in 64% of infants younger than 2 months 2
Clinical Context and Urgency
- All inguinal hernias require surgical repair to prevent bowel incarceration and gonadal infarction/atrophy 2, 5
- Urgent surgical referral for repair within 1-2 weeks of diagnosis is recommended 2
- Assess for signs of complications such as incarceration or strangulation, including irreducibility, tenderness, erythema, or systemic symptoms 2
- Risk factors for hernia incarceration/strangulation include female gender, femoral hernia, and a history of hospitalization related to groin hernia 6
Common Pitfalls to Avoid
- Failing to examine both sides for hernias can miss contralateral hernias, which develop in 25-50% of children with patent processus vaginalis 2
- Missing femoral hernias, which have a higher risk of strangulation and may present similarly 2
- Not assessing for complications that require urgent intervention, such as incarceration or strangulation 2
- Delayed treatment (>24 hours) of complicated hernias is associated with higher mortality rates 5