American Board of Internal Medicine (ABIM) Certification Practice Exam

In diagnosing ADPKD for individuals aged 15 to 29 with a family history, what is the minimum cyst requirement?

1. One kidney cyst

2. Two kidney cysts

3. Four kidney cysts

4. Five kidney cysts

The correct answer is: Two kidney cysts

In diagnosing autosomal dominant polycystic kidney disease (ADPKD) in individuals aged 15 to 29 with a family history, the minimum cyst requirement is two kidney cysts. The Renal Imaging Criteria for ADPKD recommend this threshold because it allows for the differentiation of ADPKD from other potential renal anomalies. In this age group, the presence of two cysts provides a significant indication of the disease's likelihood, especially when coupled with a family history suggestive of ADPKD. Single cysts can be common and do not necessarily indicate the hereditary nature or progression of polycystic kidney disease. Additionally, as a genetic condition, the identification of multiple cysts strengthens the clinical diagnosis in the context of family history. Other thresholds, such as one or greater counts, may not provide adequate diagnostic accuracy, as one cyst can occur sporadically and is not definitive for ADPKD. Higher thresholds, such as four or five cysts, are generally required for confirming the diagnosis in older individuals, thus emphasizing the importance of the established two-cyst criterion for younger patients.