What is the most appropriate initial evaluation for a female patient presenting with left upper‑quadrant pain?

Initial Evaluation of Left Upper Quadrant Pain in Female Patients

For a female patient presenting with left upper quadrant (LUQ) pain, CT of the abdomen and pelvis with intravenous contrast is the most appropriate initial imaging study, as it provides comprehensive evaluation of the broad differential diagnosis with moderate sensitivity (69%) and excellent specificity (100%). 1, 2

Immediate Clinical Assessment

Before imaging, several critical steps must be taken:

• Obtain a pregnancy test (β-hCG) in all women of reproductive age to rule out ectopic pregnancy and guide imaging choices, as this is a "can't miss" diagnosis that requires urgent intervention 3, 4, 1
• Assess hemodynamic stability (heart rate, blood pressure) to identify bleeding or sepsis requiring immediate intervention 3
• Examine for peritoneal signs (rigid abdomen, rebound tenderness) suggesting perforation or ischemia 3
• Evaluate pain characteristics: pain out of proportion to physical findings strongly suggests mesenteric ischemia 3

Laboratory Workup

Essential laboratory tests include:

• Complete blood count to assess for infection or anemia 1
• C-reactive protein for inflammatory processes 1
• Hepatobiliary markers (AST, ALT, alkaline phosphatase, bilirubin) 1
• Lipase for pancreatic pathology 1
• Urinalysis to evaluate for urolithiasis or infection 4, 1
• Electrolytes, creatinine, and glucose 1

Imaging Strategy

First-Line Imaging: CT with IV Contrast

CT abdomen and pelvis with IV contrast is the imaging modality of choice for LUQ pain because:

• It has 69% sensitivity and 100% specificity for detecting acute abdominal abnormalities in LUQ pain 2
• It provides 100% positive predictive value when abnormalities are detected 2
• It changes the primary diagnosis in 51% of cases and alters admission decisions in 25% of patients with nonlocalized abdominal pain 5, 3
• It can identify the full spectrum of LUQ pathology including splenic, gastric, pancreatic, renal, and colonic causes 1, 2

Alternative Imaging Considerations

Ultrasonography may be considered as initial imaging in specific scenarios:

• If gynecologic pathology is suspected in premenopausal women, transvaginal ultrasound should be the first-line study 5, 3
• In pregnant patients, ultrasound is preferred initially, followed by MRI (not CT) if ultrasound is inconclusive 5, 1
• Ultrasound can be directed to the area of maximal pain for targeted evaluation 5

MRI is not appropriate for initial evaluation because it is less sensitive for extraluminal air and urinary calculi, more time-consuming, and more subject to motion artifacts in symptomatic patients 5

Plain radiography is not useful as initial imaging because CT is more accurate for all relevant pathologies 5

Differential Diagnosis by Organ System

Gastrointestinal Causes

• Splenic pathology: infarction, abscess, or rupture 3, 1
• Gastric disease: gastritis or peptic ulcer disease 3, 1
• Pancreatic pathology: pancreatitis (epigastric pain radiating to LUQ) 3, 1
• Colonic disease: splenic flexure pathology or early diverticulitis 1

Renal/Urologic Causes

• Nephrolithiasis (renal colic) presenting as LUQ pain 3, 1
• Pyelonephritis or renal abscess 1

Gynecologic Causes (in women of reproductive age)

• Ectopic pregnancy (can present with upper abdominal pain) 3, 1
• Adnexal torsion with referred pain 3, 1
• Pelvic inflammatory disease 3, 1

Vascular Causes

• Mesenteric ischemia: pain out of proportion to examination findings 3, 1
• Splenic infarction 1

Extra-abdominal Causes

• Lower lobe pneumonia with referred pain 3, 1
• Pulmonary embolism with pleuritic chest pain 6, 7
• Abdominal wall pain (musculoskeletal) 8, 1
• Herpes zoster (shingles) before vesicle eruption 8

Critical Pitfalls to Avoid

• Do not skip pregnancy testing in women of reproductive age before imaging, as this can delay diagnosis of ectopic pregnancy and result in unnecessary radiation exposure 3, 4, 1
• Do not dismiss atypical presentations in elderly patients, who commonly present without classic symptoms and have higher likelihood of malignancy, diverticulitis, and vascular causes 3
• Do not over-rely on normal laboratory values early in disease course, as they may not yet reflect the underlying pathology 3
• Do not assume normal CT excludes all pathology: CT has only 69% sensitivity for LUQ abnormalities, and 12% of patients with negative CT may have clinically significant disease 2
• Consider extra-abdominal causes such as pneumonia, which can present with referred abdominal pain 3, 1
• In pregnant patients, recognize that shingles can present as severe LUQ pain before vesicle eruption, and extensive workup may be unrevealing until the rash appears 8

When to Escalate Care

Immediate surgical or emergency consultation is required for:

• Hemodynamic instability (tachycardia, hypotension) 3
• Peritoneal signs (rigid abdomen, rebound tenderness) 3
• Pain out of proportion to examination (suggests mesenteric ischemia) 3
• Free air on imaging (perforation) 5
• Evidence of splenic rupture or intra-abdominal hemorrhage 1