Acquired Cystic Kidney Disease Differential Diagnoses

Updated: Mar 13, 2020
  • Author: Manish Suneja, MD, FASN, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Diagnostic Considerations

When more than one renal cyst is found, consider some of the causes of cystic disorders of the kidney (see the Table 1 in Presentation: Physical).

Acquired cystic kidney disease is strictly confined to the kidneys, in contrast to other hereditary cystic disorders, such as autosomal dominant polycystic kidney disease (ADPKD).

Consider malignant transformation. The Bosniak classification, which divides renal cystic masses into five categories based on imaging characteristics on contrast-enhanced computed tomography, predicts the risk of malignancy and can help guide management decisions [9, 16] ; see Table 2, below.

Table 2: Bosniak Renal Cyst Classification [17, 18] (Open Table in a new window)




Percentage Malignant

Management Recommendations

Bosniak I

Simple cyst with fluid attenuation

No calcifications or septa; hairline-thin wall


No further workup needed

Bosniak II

Minimally complex cyst; diameter ≤3 cm; uniform hyperattenuation

A few hairline-thin (< 1 mm) septa or thin calcifications; wall shows minimal regular thickening


No further workup needed

Bosniak IIF

Complexity intermediate between Bosniak II and III

Increased number of septa, minimally thickened with nodular or thick calcifications; contrast may produce perceptible but not measurable enhancement of septa or wall


Ultrasound/CT follow-up

Bosniak  III

Complex cyst; enhanced septations or wall

Thick, nodular, irregular calcification; septa show thick, irregular, measurable enhancement with contrast


Partial nephrectomy or radiofrequency ablation in elderly or poor surgical candidates

Bosniak IV

Cystic mass; enhanced soft tissue and cyst

Thick, nodular, irregular calcification; enhanced nodule in septa and wall


Partial or total nephrectomy

Differential Diagnoses