What is the difference between urethral hypermobility and intrinsic sphincter deficiency as causes of SUI?

• A. Urethral hypermobility results from loss of urethral support causing leakage with stress; intrinsic sphincter deficiency is failure of the urethral closing mechanism despite good support
• B. Urethral hypermobility results from failure of closing mechanism; intrinsic sphincter deficiency is loss of support
• C. Both are the same
• D. Neither contributes to SUI

Answer: (A)

Urethral continence depends on two factors: how well the urethra is supported and how well the sphincter closes. In urethral hypermobility, the pelvic floor has weakened support, so the urethra and bladder neck move excessively when pressure rises (like during coughing or sneezing). The sphincter itself may still be capable of closing, but the urethra is pulled open, allowing leakage. In intrinsic sphincter deficiency, the problem is with the closing mechanism itself—the sphincter can’t coapt properly even though there is adequate support—so closing pressure is reduced and leakage occurs with little or no stress. This is why one description emphasizes loss of support causing stress leakage, while the other emphasizes a failing closing mechanism despite good support. Urodynamic or physical tests can help distinguish them: hypermobility shows increased urethral mobility with normal sphincter closing pressures, whereas ISD shows reduced closing pressure with normal or even adequate mobility. Management tends to follow the mechanism: restoring urethral support helps hypermobility, while ISD may require strategies to enhance sphincter closure or augment urethral coaptation.