What could be causing a male patient with a history of anorectal surgery to experience a feeling of weakness or queasiness, similar to a visceral response to fear, in the pelvic area, with altered or numbed sensations to stimuli that normally induce this feeling?

Altered Pelvic Visceral Sensation Following Anorectal Surgery

Most Likely Diagnosis

This patient is experiencing altered anorectal sensory function, most likely due to nerve injury or dysfunction affecting the pudendal nerve pathways or pelvic floor sensory receptors from his previous anorectal surgery. 1, 2

Understanding the Symptom Pattern

The "tingly feeling" in the pelvic area with altered or numbed visceral responses represents disrupted anorectal sensation, which has distinct somatic and visceral components:

• The anal canal has profuse somatic innervation with specialized sensory nerve endings including Meissner's corpuscles (touch), Krause end-bulbs (temperature), Golgi-Mazzoni bodies and pacinian corpuscles (tension/pressure), and genital corpuscles (friction), all transmitted via the pudendal nerve to S2-S4 sacral roots 1

• The rectum processes visceral sensation differently than somatic structures, with greater limbic cortex representation (particularly anterior cingulate cortex), explaining why visceral sensations produce stronger autonomic responses and that characteristic "queasy" feeling 2

• Rectal distension sensation travels via parasympathetic pathways to S2-S4, but the rectum itself is insensitive to stimuli that would cause pain on skin surfaces—it only responds to distension and stretching 1

Mechanism of Post-Surgical Sensory Alteration

The puborectalis muscle contains sensory receptor organs that are critical for normal anorectal sensation, triggering the rectal sphincter reflex mechanism and producing the feeling of fullness 3. Surgical disruption of these structures or their innervation explains the altered sensory experience:

• Tension receptors in parapuborectal tissues normally initiate sensory signals that are transmitted via the lowest rectal ganglion of the mesenteric plexus 3

• Cortical processing of anorectal sensation involves bilateral activation of primary somatosensory cortex, secondary somatosensory cortex, insular cortex, anterior cingulate cortex, and prefrontal cortex 2

• Surgical trauma can damage these sensory pathways, resulting in altered perception of stimuli that normally trigger visceral responses 4, 5

Diagnostic Evaluation

Anorectal manometry (ARM) with sensory testing is the definitive diagnostic test to quantify the sensory dysfunction 4:

• Rectal balloon distension testing should be performed to measure three sensory thresholds: constant sensation of fullness, urge to defecate, and maximum tolerated volume 1

• Mucosal electrosensitivity testing can quantify anal canal sensation using a constant current generator and bipolar electrode probe 1

• ARM provides information on anorectal sensorimotor functions that can identify anal sphincter weakness, poor rectal compliance, or dyssynergic defecation that may coexist with sensory dysfunction 4

Specific Clinical Assessment

Perform digital rectal examination to assess for:

• Tender, indurated areas that might indicate occult abscess or inflammatory process 4, 6

• Anal sphincter tone and voluntary contraction to evaluate motor function alongside sensory complaints 4

• Presence of surgical scars, anorectal deformities, or signs of complications from previous surgery 4

Request laboratory testing if systemic symptoms are present:

• Complete blood count, serum creatinine, and inflammatory markers (C-reactive protein, procalcitonin) if there are any signs suggesting ongoing infection or inflammation 4, 6

• Serum glucose and hemoglobin A1c to exclude diabetes, which can cause diminished anorectal sensation 6

Imaging Considerations

MRI of the pelvis is the preferred imaging modality if structural complications are suspected 4:

• MRI can identify complex fistulas, abscesses, or pelvic floor disorders including rectal intussusception or descending perineum syndrome that may contribute to altered sensation 4

• CT scan with IV contrast is an alternative if MRI is unavailable or contraindicated, particularly if abscess or perforation is suspected 4

Management Approach

Referral to a colorectal surgeon or gastroenterologist with expertise in anorectal disorders is essential for comprehensive evaluation and management 4:

• Biofeedback therapy may be beneficial if ARM reveals dyssynergic defecation or sensorimotor dysfunction, as it can help retrain anorectal coordination 4

• Pharmacologic management with pregabalin may be considered for neuropathic pain if nerve injury is confirmed, though this addresses pain rather than sensory alteration per se 7

Critical Pitfalls to Avoid

• Do not dismiss altered visceral sensation as psychosomatic—it represents real neurophysiological dysfunction that can be objectively measured 1, 2

• Symptoms are frequently diminished in diabetic or immunosuppressed patients, requiring high clinical suspicion for occult complications 4, 6

• Do not delay evaluation if new symptoms develop, as post-surgical complications including abscess formation can present with atypical sensory symptoms 6, 8

• Recognize that day-to-day variability in anorectal pressures exists, particularly during simulated evacuation, so single ARM measurements should be interpreted cautiously 4