How should I evaluate and manage a patient with a one‑year history of persistent left lower quadrant abdominal pain?

Evaluation and Management of Chronic Left Lower Quadrant Abdominal Pain

After one year of persistent left lower quadrant pain, you should obtain CT abdomen/pelvis with IV contrast and colonoscopy to exclude structural pathology before diagnosing a functional bowel disorder, then initiate conservative management with dietary fiber for constipation-predominant symptoms or antispasmodics for pain-predominant symptoms. 1

Initial Diagnostic Workup

Mandatory Imaging and Endoscopy

• CT abdomen and pelvis with IV contrast is the first-line imaging study, rated 8/9 by the American College of Radiology with 98% diagnostic accuracy for detecting diverticulitis, inflammatory bowel disease, malignancy, and other structural pathology 2
• Colonoscopy is required in patients over 50 years with chronic left lower quadrant pain even after negative CT, as functional bowel disorder diagnosis is appropriate only after both modalities have excluded structural abnormalities 1
• Beta-hCG testing must be performed in all women of reproductive age before CT imaging to avoid fetal radiation exposure 2

Critical Red Flags Requiring Emergency Evaluation

• Immediate emergency department evaluation is mandatory if the patient develops fever, inability to pass gas or stool, severe tenderness with guarding, vomiting, bloody stools, signs of shock, or progressively worsening pain 2
• Weight loss, anemia, or change in bowel habits warrant repeat colonoscopy despite prior normal study, as these suggest possible malignancy 1
• New pericolonic lymphadenopathy >1 cm on imaging suggests malignancy rather than benign causes and requires urgent gastroenterology referral 1, 2

Differential Diagnosis for Chronic Left Lower Quadrant Pain

Most Common Structural Causes

• Diverticulitis remains the leading cause in adults over 50 years, though chronic symptoms are atypical for acute disease 2
• Inflammatory bowel disease (Crohn's disease or ulcerative colitis) can present with chronic intermittent pain 2
• Colon cancer must be excluded, particularly when pericolonic lymphadenopathy >1 cm is present on CT 2
• Gynecologic pathology (ovarian cyst, endometriosis, pelvic inflammatory disease) should be evaluated with pelvic/transvaginal ultrasound in premenopausal women 1, 2

Functional Causes After Exclusion of Structural Disease

• Irritable bowel syndrome becomes the most likely diagnosis when CT and colonoscopy are negative, especially if pain relates to bowel movements or dietary triggers 1
• Functional bowel disorders are characterized by visceral hypersensitivity and altered pain processing, where innocuous stimuli are perceived as painful (allodynia) 3

Management Algorithm Based on Findings

If Imaging and Colonoscopy Are Negative

Step 1: Characterize the Pain Pattern

• For constipation-predominant symptoms: Begin therapeutic trial of dietary fiber 1
• For pain-predominant symptoms: Perform plain abdominal radiograph during acute episode to exclude obstruction; if normal, initiate antispasmodic medication 1
• For cyclical pain in women: Obtain pelvic ultrasound to evaluate gynecologic etiology 1

Step 2: Initiate Neuromodulation for Chronic Pain

• Low-dose tricyclic antidepressants or serotonin-norepinephrine reuptake inhibitors can be prescribed by gastroenterologists as baseline therapy for chronic visceral pain 3
• Cognitive behavioral therapy is indicated for patients with no or limited response to medications, particularly those with insight into how thoughts and behaviors relate to pain 3
• Hypnotherapy is effective for patients with visceral hypersensitivity or somatic symptoms, provided they do not have severe PTSD 3

Step 3: Address Risk Factors for Chronic Pain

• Assess for history of early-life adversity, trauma, discrimination, or poverty, as these increase risk of chronic pain development 3
• Evaluate for catastrophizing, pre-existing anxiety, and depression, which predict transition from acute to chronic pain 3
• Screen for substance misuse, disability status, or worker's compensation, as these can reinforce pain behaviors 3

If Structural Pathology Is Identified

Uncomplicated Diverticulitis

• Conservative management without antibiotics is appropriate for immunocompetent patients 2
• Antibiotics for maximum 7 days are reserved for immunocompromised or elderly patients 2

Complicated Diverticulitis

• Small abscess (<4 cm): Antibiotics alone for 7 days 2
• Large abscess (≥4 cm): Percutaneous drainage plus antibiotics for 4 days 2
• Perforation or peritonitis: Emergency surgical consultation 2

Inflammatory Bowel Disease

• Refer to gastroenterology for disease-specific management with immunosuppressive therapy 1

Malignancy

• Urgent oncology referral for staging and treatment planning 1

When to Repeat Imaging

• Repeat CT is generally not indicated unless new symptoms develop or significant time has passed 1
• MRI abdomen and pelvis may be considered if CT was equivocal or concern exists for pathology better visualized on MRI (sensitivity 86-94%, specificity 88-92% for inflammatory conditions) 1

Gastroenterology Referral Indications

• Refer for functional bowel disorder management if symptoms persist despite conservative measures 1
• Refer if colonoscopy has not been performed in patients over 50 years, even after negative CT 1
• Refer for multidisciplinary pain management including psychologist with chronic abdominal pain experience if neuromodulation and self-management strategies fail 3

Common Pitfalls to Avoid

• Do not diagnose functional bowel disorder without excluding structural pathology via both CT and colonoscopy in patients over 50 years 1
• Do not dismiss pain as "functional" or "psychosomatic" without first setting expectations that pain perception is real and multifactorial 3
• Do not perform repetitive testing once functional pain is established; instead, refer for psychological support and pharmacological options 4
• Do not rely on clinical examination alone, as misdiagnosis rates range from 34-68% without imaging 2