Origins of the Guidelines Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease, with approximately half of the patients experiencing end-stage renal disease by age 60. Bilateral cysts progressively proliferate and enlarge, even as complications such as hypertension, hepatic cysts, and intracranial aneurysms lead to more lethal events such as cyst infections and ruptured intracranial aneurysms prior to end-stage renal disease. Early-stage diagnosis and intervention are recognized as being vital. Autosomal recessive polycystic kidney disease (ARPKD) is estimated to occur in 1 in 10,000~40,000 births, with symptoms present neonatally. Due to early detection and management as well as improvements in end-stage renal disease treatment, long-term survival is currently possible in patients other than neonates with severe pulmonary hypoplasia. In Japan, Clinical Guidelines for Polycystic Kidney Disease in 1995 was published by the Progressive Renal Diseases Research, Research on intractable disease, from the Ministry of Health, Labour and Welfare of Japan, followed by a 2002 revision, the ADPKD Guidelines (second edition). Both serve as protocols for daily treatment of ADPKD in Japan. However, subsequent advancements in PKD expertise led to the 2010 Clinical Guidelines for Polycystic Kidney Disease, which were aimed at physicians and other health practitioners. These events provided the backdrop for the 2014 Clinical Practice Guidelines for Polycystic Kidney Disease, which were drawn up to answer the questions of physicians specializing in renal care. 2. The Intended Purpose, Anticipated Users, and Predicted Social Significance of the Guidelines The 2014 Clinical Practice Guidelines for Polycystic Kidney Disease were drawn up to assist renal care specialists with daily diagnosis and treatment of ADPKD and ARPKD. These Guidelines offer descriptive and exhaustive coverage of PKD diagnosis and definition, epidemiology, and screening. Moreover, routine treatment by renal specialists is addressed through clinical questions (CQs) and responses. Each response is accompanied by a recommendation grade reflecting the level of evidence the response embodies. Our objective is to convey standardized care through specific responses to renal specialists’ questions, thereby supporting these professionals as they face daily clinical decisions. We anticipate that general practitioners using the current Guidelines along with the 2010 Clinical Guidelines for Polycystic Kidney Disease will deepen their understanding of PKD and liaise more smoothly with renal specialists. The Guidelines should also enhance patients’ understanding of the disease and serve as a reference in answering their questions concerning current treatments. Professional literature and international conferences afford renal specialists fragmented bits of information about the field, while the specialists are expected to have an integrated understanding of the expertise level and medical environment in Japan, and to provide optimal care for each patient. The current Guidelines incorporate the wisdom of experienced specialists, offering not only evidence, but also practical and standardized views communicated to readers through the CQ responses. However, the degree to which information in these Guidelines may be applied to individual patients requires the judgment of each specialist. Patients do not expect uniform, rigid treatment. Indeed, these Guidelines are not intended to restrict the treatment options available to renal specialists, but rather to facilitate treatment based on their own flexible insights and expert understanding. We must also clarify that the Guidelines are not designed for use in resolving medical practice disputes or as evaluation criteria in malpractice lawsuits. 3. Patients within the Scope of the Guidelines These Guidelines apply to any and all PKD patients. Sections 1~4 address ADPKD, whereas Sections 5~9 cover ARPKD. The Guidelines provide an outline and definition (Sections 1 and 5) for each of the two diseases, along with information on diagnosis (Sections 2 and 6), epidemiology (Sections 3 and 7), and treatment (Sections 4 and 9). Each section applies to patients regardless of gender or age. However, the Guidelines do not generally take pregnancy into account. 4. Preparation procedure Guidelines on four diseases (IgA nephropathy, nephrotic syndrome, RPGN, and polycystic kidney disease [PKD]) were created simultaneously by a research group on progressive kidney disorders (led by Seiichi Matsuo) funded by the Ministry of Health, Labour, and Welfare’s research project for overcoming intractable diseases. All of these guidelines have the same chapter structure. PKD is a genetic disease, so Shinshu University professor Yoshimitsu Fukushima assisted by serving on the drafting committee as a representative of the Japan Society of Human Genetics. Keiichi Furukawa of the Division of Infectious Diseases in the Department of Internal Medicine at St. Luke’s International Hospital provided assistance regarding cyst infections. We would like to take this opportunity to thank these two