Left Flank Pain with Normal CT Urogram: Gynecologic Evaluation is Mandatory
The left flank pain in this patient is most likely caused by the 5.7 cm left adnexal cystic lesion, not urolithiasis, and requires immediate pelvic ultrasound for further characterization as recommended in the CT report. 1
Primary Diagnosis: Adnexal Pathology
The CT scan definitively ruled out urolithiasis—no stone, no hydronephrosis, no hydroureter—making renal colic extremely unlikely as the pain etiology. 2 The presence of a 5.7 cm left adnexal cystic lesion is the only significant abnormality identified that could explain left-sided flank pain. 1
Why the Adnexal Mass is the Culprit:
- Benign adnexal masses are a recognized cause of flank pain in women, particularly when they reach this size (5.7 cm). 1
- Large ovarian cysts can cause pain through several mechanisms: capsular distension, torsion (partial or complete), rupture, or hemorrhage into the cyst. 3
- The location (left adnexa) directly correlates with the symptom location (left flank). 1
Immediate Next Steps
Obtain a dedicated pelvic ultrasound within 7 days to characterize the adnexal lesion and assess for complications. 1 This imaging will determine:
- Whether the mass is ovarian or paraovarian in origin
- Presence of solid components, septations, or internal blood flow patterns
- Signs of torsion (absent or decreased Doppler flow)
- Free fluid suggesting rupture or hemorrhage
Red Flags Requiring Urgent Evaluation:
- Sudden worsening of pain with nausea/vomiting suggests ovarian torsion—this requires emergent gynecologic consultation within hours, not days. 1
- Fever or signs of systemic infection could indicate infected cyst or abscess formation. 1
- Hemodynamic instability may indicate ruptured hemorrhagic cyst. 1
Why This is NOT Urolithiasis
The CT findings make stone disease virtually impossible:
- Non-contrast CT has 98-100% sensitivity and specificity for detecting urinary stones. 1, 4, 5
- Absence of hydronephrosis makes stones >5 mm extremely unlikely (ultrasound is 100% sensitive for hydronephrosis). 6
- Classic renal colic presents as colicky, wave-like pain radiating to the groin/genitals—if the pain pattern differs from this, alternative diagnoses become more likely. 1, 7
Common Pitfalls to Avoid
Do not assume all flank pain is renal in origin—approximately one-third of patients with flank pain have non-urologic causes identified on CT. 1, 4 In women of reproductive age, gynecologic pathology must always be considered. 1
Do not delay gynecologic imaging in young females—some adnexal pathologies (torsion, ectopic pregnancy, hemorrhagic cyst rupture) require urgent intervention. 1
Do not miss ectopic pregnancy—although this patient has an IUD in place (which reduces but does not eliminate ectopic risk), obtain a pregnancy test if there is any menstrual irregularity. 1
Other Incidental Findings Requiring Follow-up
The 2.9 cm hepatic cyst is benign and requires no intervention. 4 The umbilical hernia and L4 Schmorl's node are incidental and unrelated to the acute presentation. 8