What is the initial workup for a patient presenting with left lower quadrant pain?

Initial Workup for Left Lower Quadrant Pain

Contrast-enhanced CT of the abdomen and pelvis is the preferred initial imaging modality for patients presenting with left lower quadrant pain, particularly when diverticulitis is suspected, due to its superior diagnostic accuracy (98%) and ability to detect complications and alternative diagnoses. 1

Clinical Assessment

• Key history elements:

  • Pain characteristics (onset, duration, severity, radiation)
  • Associated symptoms (fever, nausea, vomiting, changes in bowel habits)
  • Past medical history (previous diverticulitis, inflammatory bowel disease)
  • Medication history
  • In women of reproductive age: last menstrual period and pregnancy status

• Physical examination focus:

  • Vital signs (fever suggests infection)
  • Abdominal examination (tenderness, guarding, rebound)
  • Digital rectal examination
  • Pelvic examination in women

• Laboratory tests:

  • Complete blood count (leukocytosis suggests inflammation/infection)
  • C-reactive protein
  • Basic metabolic panel
  • Urinalysis
  • Pregnancy test in women of reproductive age (before imaging)

Imaging Algorithm

General Population:

1. CT Abdomen and Pelvis with IV contrast (first-line)

   • Highest appropriateness rating (8/9) by ACR 1
   • Nearly 100% sensitivity and specificity for diverticulitis 1
   • Can identify complications (perforation, abscess, fistula)
   • Helps risk-stratify patients for operative vs. non-operative management 1
   • Can diagnose alternative causes with similar presentation 1

2. CT Abdomen and Pelvis without contrast

   • Alternative when IV contrast is contraindicated
   • Lower appropriateness rating (6/9) 1

3. Abdominal ultrasonography

   • May be used to reduce CT examinations without affecting patient care 1
   • Can identify patients with diverticulitis who don't have surgical abdomen
   • Less common in US for initial imaging of non-gynecologic LLQ pain 1
   • Operator-dependent and technically difficult in obese patients 1

Special Populations:

1. Premenopausal women:

   • Transvaginal ultrasound first if gynecologic cause suspected 1
   • Followed by CT if gynecologic causes excluded

2. Pregnant patients:

   • Ultrasound first
   • MRI if ultrasound inconclusive 2

3. Patients with renal failure:

   • Non-contrast CT or MRI (avoid gadolinium with GFR <30 mL/min/1.73m²) 1

4. Immunocompromised patients:

   • Lower threshold for CT imaging as clinical signs may be unreliable 2

Common Causes of Left Lower Quadrant Pain

1. Diverticulitis

   • Most common cause in adults over 40
   • Classic triad: left lower quadrant pain, fever, leukocytosis (present in only 25% of cases) 1
   • Clinical diagnosis alone has error rates of 34-68% 1

2. Other colonic causes:

   • Colitis
   • Fecal impaction
   • Epiploic appendagitis 3

3. Urologic causes:

   • Left-sided urolithiasis 3

4. Gynecologic causes (in women):

   • Ovarian cysts/torsion
   • Pelvic inflammatory disease
   • Ectopic pregnancy

Management Considerations

• Imaging may not be required in patients with:

  • Typical symptoms of diverticulitis
  • Prior history of diverticulitis with similar symptoms
  • No evidence of complications 1

• Early CT for acute diverticulitis can:

  • Reduce hospital admission by >50%
  • Shorten hospital length of stay 1
  • Prevent unnecessary admissions for uncomplicated cases

• Treatment depends on severity:

  • Medical therapy for uncomplicated diverticulitis
  • Catheter drainage for abscesses ≥3 cm
  • Surgery for free perforation and peritonitis 1

Common Pitfalls to Avoid

1. Relying solely on clinical assessment for diagnosis (high error rates)
2. Overlooking gynecologic causes in women of reproductive age
3. Missing atypical presentations in elderly patients
4. Delaying imaging in immunocompromised patients
5. Attributing all post-surgical pain to the surgical site without considering other etiologies 2

Remember that plain abdominal radiography has limited utility as an initial imaging test for left lower quadrant pain, as CT is more accurate for identifying pathology 1.