What could be causing me to have stool incontinence, especially when I urinate?

Stool Incontinence During Urination: Causes and Evaluation

You need urgent evaluation for a possible rectovesical or rectovaginal fistula, which is an abnormal connection between your bowel and bladder or vagina that allows stool to pass when you urinate. This is a serious condition requiring immediate medical attention and imaging studies 1.

Primary Diagnostic Considerations

Fistulous Connections (Most Urgent)

• Rectovesical fistula causes the pathognomonic symptoms of fecaluria (stool in urine) or pneumaturia (gas in urine), which directly explains stool passage during urination 1
• Rectovaginal fistula in women presents with stool, gas, or odorous discharge from the vagina, often confused with incontinence 1
• Common causes include diverticulitis, Crohn's disease, colorectal or pelvic malignancies, radiation therapy, and surgical complications 1
• CT pelvis with IV contrast is the initial imaging study of choice, with water-soluble rectal contrast administered to opacify the fistulous tract 1
• MRI provides superior visualization of complex fistulous anatomy when CT findings are equivocal 1

Pelvic Floor Dysfunction

• Defecatory disorders involve impaired rectal evacuation from inadequate propulsive forces or paradoxical pelvic floor contraction during attempted defecation 1
• Increased intra-abdominal pressure during urination may trigger involuntary stool passage if pelvic floor coordination is severely impaired 1
• Look for prolonged straining, sensation of incomplete evacuation, and need for digital assistance to pass stool 1

Neurologic Causes

• Spinal dysraphism with tethered cord presents with combined urinary and bowel dysfunction, particularly when associated with sacral dimple or other cutaneous markers 2
• Diabetes mellitus causes bladder dysfunction in 43-87% of type 1 diabetics and 25% of type 2 diabetics, with associated bowel denervation 1
• Multiple sclerosis, stroke, and spinal cord lesions disrupt coordinated sphincter control 3

Critical Red Flags Requiring Immediate Workup

• Fecaluria or pneumaturia (stool or gas in urine) - pathognomonic for rectovesical fistula 1
• Recurrent urinary tract infections - may indicate fistulous connection or anatomical abnormality 1
• History of diverticulitis, Crohn's disease, pelvic radiation, or recent pelvic surgery - high-risk factors for fistula formation 1
• Sacral dimple with combined day/night urinary and bowel symptoms - requires immediate spinal MRI to exclude tethered cord 2

Diagnostic Algorithm

Step 1: Detailed History

• Characterize the exact timing: Does stool pass only during urination or also at other times? 3, 4
• Assess stool consistency: liquid versus solid incontinence has different implications 4
• Document urge versus passive leakage: urge incontinence suggests neurologic dysfunction, passive suggests sphincter damage 4
• Review obstetric history: vaginal deliveries with instrumentation increase risk of occult sphincter injury 3, 4
• Medication review: diarrheal states from medications worsen underlying sphincter weakness 3

Step 2: Physical Examination

• Digital rectal examination assessing sphincter tone, squeeze strength, and presence of fecal impaction 1, 3
• Neurologic examination of lower extremities: strength, reflexes, gait, and sensory deficits 2
• Perineal inspection for scars from obstetric trauma, fistulous openings, or sacral dimples 2, 3
• Vaginal examination in women to assess for rectovaginal fistula openings or severe pelvic organ prolapse 1

Step 3: Initial Imaging

• CT pelvis with IV contrast and water-soluble rectal contrast is the first-line study when fistula is suspected 1
• CT cystography (retrograde bladder filling with contrast) may be needed if bladder perforation or rectovesical fistula is suspected 1
• MRI of the spine if neurologic examination is abnormal or sacral dimple present with combined urinary/bowel dysfunction 2

Step 4: Specialized Testing (If Initial Workup Negative)

• Anorectal manometry measures sphincter pressures and rectal sensation 4
• Endoanal ultrasound visualizes sphincter defects from obstetric or surgical trauma 4
• Defecography assesses pelvic floor coordination during simulated defecation 1, 4

Management Approach

If Fistula Confirmed

• Urgent surgical consultation is mandatory for fistula repair 1
• Treat underlying cause (diverticulitis, Crohn's disease) before definitive repair 1
• Temporary fecal diversion may be necessary for complex cases 1

If Pelvic Floor Dysfunction

• Biofeedback therapy is first-line treatment for defecatory disorders, teaching proper pelvic floor coordination 1, 4
• Aggressive treatment of constipation with fiber supplements and osmotic laxatives to reduce straining 1
• Pelvic floor physical therapy for muscle retraining 4

If Neurologic Cause

• Treat underlying condition (optimize diabetes control, manage multiple sclerosis) 1
• Bowel regimen with scheduled toileting and stool consistency management 3, 5
• Consider sacral neuromodulation if conservative measures fail 4, 6

Common Pitfalls to Avoid

• Do not assume simple fecal incontinence when stool specifically passes during urination - this pattern strongly suggests fistula 1
• Do not delay imaging in patients with risk factors for fistula (prior pelvic surgery, radiation, inflammatory bowel disease) 1
• Do not miss spinal dysraphism in younger patients with combined urinary and bowel symptoms plus sacral dimple 2
• Do not treat empirically with antidiarrheals before establishing the diagnosis, as this may worsen symptoms if obstruction or fistula is present 3, 4