Management of Suspected Calyceal Diverticulum with Posterior Cystic Lesion and Layering Calculi
Proceed with CT urogram (CTU) with IV contrast to confirm the diagnosis of calyceal diverticulum and characterize the communication between the cystic lesion and the collecting system. 1
Diagnostic Confirmation Strategy
Primary Imaging Recommendation
CT urogram is the gold standard for confirming calyceal diverticulum, as it demonstrates the narrow infundibulum connecting the diverticulum to the collecting system and provides detailed anatomical information essential for treatment planning 2, 3
MRI urography serves as an excellent alternative if IV contrast is contraindicated (severe renal impairment or contrast allergy), offering superior soft tissue characterization and the ability to detect subtle enhancement patterns 1
The American College of Radiology specifically recommends MRI for indeterminate renal cystic lesions when CT findings are equivocal, with MRI demonstrating higher specificity (68.1%) compared to CT (27.7%) for distinguishing between different kidney mass types 1
Why CT Urogram is Critical
Delayed phase imaging during CTU reveals the communication channel between the diverticulum and the calyceal system—this is pathognomonic for calyceal diverticulum and distinguishes it from simple cysts, parapelvic cysts, or cystic renal cell carcinoma 3, 4
The presence of layering calculi within the cystic lesion strongly supports calyceal diverticulum, as stones develop in up to 50% of these lesions due to urinary stasis, though this finding alone is not diagnostic 2
CTU provides essential information about stone burden, diverticulum location (anterior vs. posterior, upper vs. lower pole), neck patency, and overlying parenchymal thickness—all critical factors for treatment planning 2
Important Diagnostic Pitfalls to Avoid
Do not mistake this for a Bosniak III cystic lesion: Calyceal diverticula with stones can mimic complex cystic masses, particularly after procedures like shock wave lithotripsy where stone fragments may layer dependently and create a deceptive appearance of a solid component 5
Single imaging modalities are insufficient—ultrasound or non-contrast CT alone cannot reliably differentiate calyceal diverticulum from renal abscess, parapelvic cyst, or cystic neoplasm 4, 6
If CTU remains inconclusive, retrograde pyelography provides definitive visualization of the communication between the diverticulum and collecting system 3, 4
Alternative Diagnostic Approaches if Contrast is Contraindicated
Percutaneous aspiration with creatinine measurement: If the patient cannot receive IV contrast, aspirate fluid from the cystic lesion and measure creatinine—a fluid creatinine level significantly higher than serum creatinine confirms the lesion contains urine, supporting the diagnosis of calyceal diverticulum 3
Retrograde pyelography with methylene blue injection through a ureteral catheter can demonstrate communication with the collecting system when cross-sectional imaging is inadequate 3
Non-contrast MRI with heavily T2-weighted sequences may demonstrate the connecting channel, though less reliably than contrast-enhanced studies 1
Clinical Context and Next Steps
The posterior location of this 3 x 1.7 cm diverticulum is relevant because posterior mid-to-lower pole diverticula are best managed percutaneously if intervention becomes necessary, while anterior diverticula favor ureteroscopic or laparoscopic approaches 2
Most calyceal diverticula are asymptomatic and discovered incidentally—intervention is only indicated for symptomatic patients with pain, recurrent infections, or progressive stone burden 2, 5
After confirming the diagnosis with CTU, asymptomatic patients require no immediate intervention but should be counseled about potential complications including stone formation, infection, and flank pain 2