How should left lower abdominal pain and diarrhea be treated?

Treatment of Left Lower Abdominal Pain and Diarrhea

For left lower abdominal pain with diarrhea in adults, start loperamide 2 mg after each loose stool (maximum 16 mg/day) immediately while simultaneously evaluating for warning signs that require urgent imaging or specialist referral. 1, 2

Immediate Assessment for Red Flags

Before initiating symptomatic treatment, you must identify patients requiring urgent evaluation:

• Check vital signs immediately to assess for hemodynamic instability suggesting bowel ischemia, perforation, or severe dehydration 2
• Examine for peritoneal signs (guarding, rebound tenderness), visible distension, absent bowel sounds, or palpable masses indicating surgical pathology 2
• Warning signs requiring urgent workup include high fever (>38.5°C), frank blood in stools, severe vomiting, obvious dehydration, or age >50 years 1, 2

If any warning signs are present: Order complete blood count, comprehensive metabolic panel, lactate level, and stool for occult blood immediately 2. Obtain CT abdomen/pelvis with IV contrast (rating 8/9 on ACR appropriateness criteria) to evaluate for diverticulitis, abscess, perforation, or malignancy 1.

First-Line Symptomatic Treatment (No Warning Signs)

For otherwise healthy adults aged 12-75 years with sudden-onset diarrhea and left lower quadrant pain but without warning signs:

Antidiarrheal Medication

• Loperamide 2 mg after each loose stool (maximum 16 mg/day) is the drug of choice 1, 2, 3
• Loperamide reduces stool frequency, urgency, and fecal soiling effectively 2, 3
• Critical warning: Use only the prescribed dosage; higher doses can cause fatal cardiac arrhythmias including QT prolongation and Torsades de Pointes 4
• Avoid loperamide in elderly patients taking Class IA/III antiarrhythmics or with underlying cardiac conditions 4

Fluid and Dietary Management

• Maintain adequate fluid intake guided by thirst; use glucose-containing drinks (lemonades, sweet sodas, fruit juices) or electrolyte-rich soups 1
• Oral rehydration solutions are not needed in otherwise healthy adults 1
• Resume solid food guided by appetite with small, light meals; avoid fatty, heavy, spicy foods and caffeine 1
• Consider avoiding lactose-containing foods if diarrhea persists beyond 48 hours 1

Antispasmodic for Pain

• Antispasmodics (dicyclomine or hyoscyamine) are effective for abdominal pain, particularly when pain is exacerbated by meals 2, 3
• Common side effects include dry mouth, visual disturbance, and dizziness 1, 2

When to Seek Medical Evaluation

Patients must seek medical attention if: 1

• No improvement within 48 hours
• Symptoms worsen or overall condition deteriorates
• Warning signs develop (severe vomiting, dehydration, persistent fever, abdominal distension, frank blood in stools)

Diagnostic Workup for Persistent Symptoms

If symptoms persist beyond 48 hours or worsen, obtain:

• Stool studies: Culture for bacterial pathogens (Salmonella, Shigella, Campylobacter, E. coli O157), ova and parasites, and occult blood 1
• Blood work: Complete blood count, sedimentation rate, serum chemistries 1
• CT abdomen/pelvis with IV contrast if diverticulitis suspected (sensitivity 81-98% for detecting diverticulitis and complications) 1

Specific Diagnostic Considerations

For suspected diverticulitis (most common cause of left lower quadrant pain in adults): 1

• CT shows pericolonic fat stranding, colonic wall thickening, and diverticula at the epicenter of inflammation
• CT detects complications including abscess, perforation, fistula, or obstruction that may require surgery or interventional drainage
• Pericolonic lymphadenopathy >1 cm suggests colon cancer rather than diverticulitis and warrants colonoscopy 1

For suspected infectious colitis: 1, 5

• Bloody, purulent, mucoid stools with fever and tenesmus suggest bacterial colitis
• Stool culture identifies Campylobacter, Salmonella, Shigella, E. coli, or Yersinia species
• Fecal lactoferrin or microscopy for leukocytes documents inflammatory colitis 1

Second-Line Treatment for Refractory Symptoms

If symptoms persist despite loperamide and dietary modifications for 4-6 weeks:

• Low-dose tricyclic antidepressants (amitriptyline 10 mg at bedtime, titrated to 30-50 mg daily) are the most effective treatment for persistent abdominal pain and global symptoms 1, 2, 3
• Continue TCAs for at least 6 months if symptomatic response occurs 1, 3
• Low FODMAP diet supervised by a trained dietitian can be considered as second-line therapy, with gradual reintroduction of FODMAPs according to tolerance 2, 3

Psychological Therapy for Persistent Symptoms

Cognitive-behavioral therapy or gut-directed hypnotherapy should be considered when symptoms persist despite 12 months of pharmacological treatment or when symptoms significantly impair quality of life 1, 2

Critical Pitfalls to Avoid

• Do not assume functional disease in patients >50 years without excluding structural pathology; age >50 mandates colonoscopy or CT to rule out malignancy 1, 2
• Do not use antimicrobials empirically for community-acquired diarrhea unless there is high fever (>38.5°C) and/or bloody stools, or the patient is immunocompromised 1
• Do not prescribe loperamide at doses exceeding 16 mg/day due to risk of fatal cardiac arrhythmias 4
• Do not use opiates for chronic abdominal pain in this setting due to risk of dependence and complications 1
• Do not perform colonoscopy or air-contrast enema during acute diverticulitis as colonic distention increases perforation risk 1