What is the appropriate next diagnostic and therapeutic approach for a 47-year-old Black woman with intermittent left upper flank pain and normal computed tomography, ultrasound, urinalysis, and colonoscopy?

Diagnostic Approach for Intermittent Left Upper Flank Pain with Negative Initial Workup

Given that CT, ultrasound, urinalysis, and colonoscopy are all normal, you should now systematically evaluate for non-urologic and extra-intestinal causes, with particular attention to musculoskeletal origins, gynecologic pathology, and functional gastrointestinal disorders.

Immediate Next Steps

Refine the Clinical History

• Determine if pain is position-dependent: Pain occurring after prolonged static positioning or that changes with movement strongly suggests a musculoskeletal origin involving paraspinal muscles, facet joints, or referred pain from lumbar spine pathology. 1

• Assess pain character: Classic renal colic presents as colicky, wave-like severe pain independent of body position, but your patient's normal imaging makes this unlikely. 1, 2 If the pain is constant, dull, or aching rather than colicky, consider alternative diagnoses.

• Evaluate for gynecologic symptoms: In a 47-year-old woman, benign adnexal masses and pelvic congestion syndrome can present as flank pain. 1 Ask about menstrual irregularities, pelvic pressure, or pain with intercourse.

Consider Additional Imaging

• Contrast-enhanced CT or MRI with venography should be obtained if pelvic congestion syndrome is suspected, as this demonstrates dilated pelvic veins and is a recognized imaging diagnosis for left flank pain in women. 1

• MRI of the lumbar spine is warranted if musculoskeletal features are present, particularly if pain is positional or associated with back symptoms. 1

Evaluate for Gastrointestinal Causes Missed by Colonoscopy

• Left-sided colonic diverticulitis can mimic renal colic even with a normal colonoscopy if inflammation is minimal or intermittent; CT abdomen/pelvis with contrast reveals pericolic fat stranding and diverticula. 1

• Inflammatory bowel disease may present with flank discomfort; cross-sectional imaging shows bowel wall thickening and mesenteric edema. 1

• Severe constipation can produce left flank pain; CT may reveal fecal loading and colonic distension in the left colon. 1

• Small-bowel pathology (e.g., partial obstruction, Crohn's disease) may not be visualized on colonoscopy; CT enterography or MR enterography can identify these conditions. 1

Consider Functional Disorders

• Irritable bowel syndrome (IBS) should be considered when structural and biochemical causes are excluded. 3 The Rome criteria require recurrent abdominal pain at least 1 day per week in the last 3 months, associated with two or more of the following: related to defecation, associated with a change in stool frequency, or associated with a change in stool form. 3

• Supportive symptoms include abnormal stool frequency, abnormal stool form, abnormal stool passage (straining, urgency, incomplete evacuation), passage of mucus, or bloating. 3

• If IBS is suspected and pain is the predominant symptom, a plain abdominal radiograph during an acute episode can exclude bowel obstruction and other pathology, followed by a therapeutic trial of an antispasmodic. 3

Common Pitfalls to Avoid

• Do not assume all flank pain is kidney-related: The positional nature of symptoms is a key distinguishing feature between renal and musculoskeletal causes. 1

• Do not delay imaging in women of reproductive age: Gynecologic causes such as ovarian torsion or complicated adnexal masses may require urgent intervention. 1, 2

• Do not miss pelvic congestion syndrome: This vascular condition is frequently overlooked in women with chronic or intermittent flank pain and requires specific imaging (contrast-enhanced MRI or CT venography) for diagnosis. 1

• Do not overlook functional disorders: When extensive workup is negative, IBS or other functional bowel disorders are common explanations, but diagnosis requires meeting clinical criteria and excluding red flags. 3

Red Flags Requiring Urgent Re-evaluation

• Fever, chills, or systemic symptoms suggest infection (e.g., pyelonephritis, diverticulitis with abscess) and mandate immediate imaging and possible admission. 1, 2

• Hemodynamic instability or shock requires emergent evaluation. 1

• New-onset severe or progressive pain warrants repeat imaging, as conditions such as bowel obstruction or vascular events may evolve. 1

Algorithmic Approach

1. Reassess pain characteristics: If positional → pursue musculoskeletal workup (lumbar spine MRI). 1

2. If gynecologic symptoms present → obtain pelvic ultrasound or contrast-enhanced MRI/CT venography to evaluate for adnexal masses or pelvic congestion syndrome. 1

3. If gastrointestinal symptoms predominate (altered bowel habits, bloating) → consider IBS diagnosis per Rome criteria and initiate symptom-directed therapy (antispasmodics for pain, fiber for constipation). 3

4. If none of the above → obtain contrast-enhanced CT abdomen/pelvis to evaluate for subtle inflammatory conditions (diverticulitis, IBD, small-bowel pathology) that may have been missed on non-contrast imaging. 1

5. If all imaging and workup remain negative → diagnose functional disorder, provide reassurance and education, and initiate empiric therapy based on symptom subtype. 3