In a 60‑year‑old patient with flank pain and a contrast‑enhanced CT showing widened hepatic fissures with steatosis, splenomegaly, an adrenal mass, and multiple renal cysts, what imaging modality should be used for follow‑up?

Follow-Up Imaging for Incidental Findings in a 60-Year-Old with Flank Pain

The most appropriate next step is to obtain dedicated MRI of the abdomen without and with contrast to characterize the adrenal lesion, followed by ultrasound to further evaluate the renal cysts if they appear complex on the initial CT. 1, 2

Prioritized Imaging Strategy

1. Adrenal Lesion (Highest Priority)

The adrenal mass requires immediate characterization because it has the highest potential for malignancy and mortality impact:

• Non-contrast CT of the abdomen should be obtained first if not already performed, as lesions measuring <10 HU are diagnostic of benign adenomas and require no further workup 1
• If the initial contrast CT did not include non-contrast images, or if the lesion measures >10 HU, proceed directly to MRI with chemical shift imaging 1
  • Chemical shift MRI has 96-100% accuracy in distinguishing benign adenomas from malignant lesions and is superior to CT for indeterminate lesions (10-30 HU) 1
  • Signal loss on out-of-phase imaging compared to in-phase imaging confirms benign adenoma 1
• If MRI is contraindicated or inconclusive, delayed contrast-enhanced CT (10-15 minute washout protocol) is the alternative 1
• For lesions 3-5 cm (as in this case), initial follow-up imaging at 3-6 months is recommended if initial characterization suggests benignity 1

2. Renal Cysts (Second Priority)

Multiple kidney cysts require assessment for complexity and potential complications:

• Ultrasound is the first-line modality for characterizing renal cysts if the initial contrast CT did not adequately define their features 1, 2
  • Simple cysts (anechoic, thin-walled, posterior acoustic enhancement) require no follow-up regardless of size 1, 2
  • If >10 cysts are present, this defines polycystic kidney disease and warrants renal function testing 2
• MRI without and with contrast is indicated if ultrasound shows complex features such as septations, wall thickening, mural nodularity, or debris 1
  • MRI is superior to CT for detecting enhancement in indeterminate renal masses, with optimal enhancement threshold of 15% 1
  • Homogeneous lesions measuring 10-20 HU on portal venous phase CT are benign cysts and need no further imaging 1
• In the context of flank pain, assess for cyst hemorrhage or infection 3
  • Hemorrhagic cysts appear as high-density lesions on non-contrast CT with sharp contours 3
  • Infected cysts show wall thickening, enhancement, and perinephric fat stranding 3

3. Liver Findings (Lowest Priority for Imaging)

The hepatic steatosis and widened fissures are likely benign and related to metabolic syndrome:

• No specific follow-up imaging is indicated for simple hepatic steatosis 1, 4
• Widened liver fissures do not require dedicated imaging unless there are septated cysts or mass lesions 1
• If incidental liver cysts were noted, ultrasound can confirm their simple nature, but routine follow-up is not recommended for asymptomatic simple cysts 1, 4

4. Splenomegaly

• Splenomegaly warrants clinical correlation with complete blood count, liver function tests, and consideration of portal hypertension workup, but does not require dedicated imaging follow-up unless there are focal splenic lesions 1

Critical Pitfalls to Avoid

• Do not assume all adrenal lesions are benign adenomas without proper characterization—failure to obtain non-contrast CT or chemical shift MRI may miss adrenal metastases or primary malignancy 1
• Do not use contrast-enhanced CT alone to characterize adrenal lesions discovered on contrast studies—chemical shift MRI is superior for indeterminate lesions 1
• Avoid mistaking hemorrhagic renal cysts for malignancy—true enhancement (>15-20 HU) must be documented on multiphase imaging 1
• Do not order routine follow-up imaging for simple hepatic or renal cysts—this leads to unnecessary healthcare costs and patient anxiety 1, 4
• Beware of pseudoenhancement on CT of small renal lesions—MRI or dual-energy CT can overcome this limitation 1

Practical Algorithm Summary

1. Obtain non-contrast CT of abdomen (if not already done) to measure adrenal lesion density 1
2. If adrenal lesion >10 HU: Order MRI abdomen with chemical shift imaging 1
3. Order renal ultrasound to characterize cyst complexity 1, 2
4. If cysts are complex on ultrasound: Upgrade to MRI with contrast 1
5. No dedicated imaging needed for steatosis or simple liver/renal cysts 1, 4
6. Clinical workup for splenomegaly (labs, not imaging) 1