Pudendal Nerve Injury (Pudendal Neuropathy)
This clinical presentation is most consistent with pudendal nerve injury or pudendal neuropathy, likely caused by acute stretch or compression of the pudendal nerve during the straining episode. The triad of altered bladder sensation, blunted sexual sensation, and altered inner rectal sensation directly corresponds to the anatomical distribution of the pudendal nerve, which innervates the perineum, external genitalia, and provides sensory innervation to these regions 1, 2.
Clinical Reasoning
The pudendal nerve (typically originating from S3) is responsible for:
- Sensory innervation to the perineum, including the glans penis/clitoris, scrotum/labia majora, and perianal skin 1
- Motor control of the external urethral and anal sphincters 1
- Sexual sensation and erectile function 1, 2
When a patient strains forcefully during defecation, the pudendal nerve can be acutely stretched or compressed at known anatomical compression points, particularly between the sacrotuberous and sacrospinous ligaments, or within the pudendal canal (Alcock canal) 1, 2.
Key Diagnostic Features
The constellation of symptoms strongly suggests pudendal nerve involvement:
- Altered bladder sensation indicates involvement of the nerve branches supplying the urethra and bladder neck 2, 3
- Blunted sexual sensation reflects compromise of the nerve's sensory fibers to the external genitalia 1, 2
- Altered inner rectal sensation suggests involvement of the inferior rectal nerve branch 1
The acute onset following a single straining episode distinguishes this from chronic pudendal nerve entrapment syndrome, which typically develops gradually from repetitive trauma 4, 5.
Differential Considerations
While chronic straining is a known risk factor for pelvic floor dysfunction and rectal prolapse 4, the acute sensory changes in multiple pudendal nerve territories following a single straining event points specifically to nerve injury rather than structural pelvic floor disorders 2, 3.
Pudendal neuralgia by entrapment typically presents with pain worsened by sitting and is not associated with nighttime awakening 5. However, this patient's presentation focuses on sensory changes without the classic pain pattern, suggesting acute nerve trauma rather than chronic entrapment 2.
Clinical Pitfall
Do not attribute these symptoms solely to pelvic floor dysfunction or constipation without recognizing the neurological component. The American Gastroenterological Association emphasizes that chronic straining can lead to pelvic floor weakness 4, but the acute onset of sensory deficits in the pudendal nerve distribution indicates direct nerve injury requiring specific neurological evaluation 2, 3.
Recommended Evaluation
- Detailed neurological examination including vaginal or rectal palpation to assess for pudendal nerve tenderness 3, 5
- Pinprick sensory testing in the pudendal nerve territory (perineum, genitalia, perianal region) to map the extent of sensory deficit 6
- Consider diagnostic pudendal nerve block if symptoms persist, though complete anesthesia of all six pudendal nerve branches occurs in only 13.2% of cases 6
The diagnosis of pudendal neuropathy is primarily clinical, with no pathognomonic findings on imaging 5. However, if symptoms include urinary dysfunction or concern for structural abnormalities, MR defecography can evaluate pelvic floor anatomy while also assessing for nerve compression 7, 8.