Open Access Study protocol

Predicting the outcome of chronic kidney disease by the estimated nephron number: The rationale and design of PRONEP, a prospective, multicenter, observational cohort study

Toshiyuki Imasawa112*, Takashi Nakazato2, Hiroo Ikehira1, Hiroyuki Fujikawa1, Ryo Nakajima1, Takahito Ito3, Yutaka Ando4, Mitsuhiro Yoshimura5, Masaru Nakayama6, Kensei Yahata7, Osamu Sasaki8, Takaaki Yaomura9, Ritsuko Katafuchi10, Tsuyoshi Yamamura11, Takehiko Kawaguchi1, Motonobu Nishimura1, Hiroshi Kitamura1, Takashi Kenmochi1 and Akira Shimatsu7

Author Affiliations

1 National Hospital Organization Chiba-East Hospital, Chiba, Japan

2 National Hospital Organization Chiba Medical Center, Chiba, Japan

3 National Hospital Organization Osaka Medical Center, Osaka, Japan

4 National Hospital Organization Osaka-Minami Medical Center, Osaka, Japan

5 National Hospital Organization Kanazawa Medical Center, Kanazawa, Japan

6 National Hospital Organization Kyusyu Medical Center, Fukuoka, Japan

7 National Hospital Organization Kyoto Medical Center, Kyoto, Japan

8 National Hospital Organization Nagasaki Medical Center, Nagasaki, Japan

9 National Hospital Organization Nagoya Medical Center, Nagoya, Japan

10 National Hospital Organization Fukuoka-Higashi Medical Center, Fukuoka, Japan

11 National Hospital Organization Hokkaido Medical Center, Hokkaido, Japan

12 Department of Nephrology, National Hospital Organization Chiba-East Hospital, 675, Nitona-cho, Chuoh-ku, Ciba-city Chiba 460-8712, Japan

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BMC Nephrology 2012, 13:11  doi:10.1186/1471-2369-13-11

Published: 10 March 2012



The nephron number is thought to be associated with the outcome of chronic kidney disease (CKD). If the nephron number can be estimated in the clinical setting, it could become a strong tool to predict renal outcome. This study was designed to estimate the nephron number in CKD patients and to establish a method to predict the outcome by using the estimated nephron number.


The hypothesis of this study is that the estimated nephron number can predict the outcome of a CKD patient. This will be a multicenter, prospective (minimum 3 and maximum 5 years follow-up) study. The subjects will comprise CKD patients aged over 14 years who have undergone a kidney biopsy. From January 2011 to March 2013, we will recruit 600 CKD patients from 10 hospitals belonging to the National Hospital Organization of Japan. The primary parameter for assessment is the composite of total mortality, renal death, cerebro-cardiovascular events, and a 50% reduction in the eGFR. The secondary parameter is the rate of eGFR decline per year. The nephron number will be estimated by the glomerular density in biopsy specimens and the renal cortex volume. This study includes one sub-cohort study to establish the equation to calculate the renal cortex volume. Enrollment will be performed at the time of the kidney biopsy, and the data will consist of a medical interview, ultrasound for measurement of the kidney size, blood or urine test, and the pathological findings of the kidney biopsy. Patients will continue to have medical consultations and receive examinations and/or treatment as usual. The data from the patients will be collected once a year after the kidney biopsy until March 2016. All data using this study are easily obtained in routine clinical practice.


This study includes the first trials to estimate the renal cortex volume and nephron number in the general clinical setting. Furthermore, this is the first prospective study to examine whether the nephron number predicts the outcome of CKD patients. The results from this study should provide powerful new tools for nephrologists in routine clinical practice.

Trial registration

UMIN-Clinical Trial Registration, UMIN000004784.

Chronic kidney disease; Nephron number; Birth weight; A prospective; Multicenter; Observational cohort study; Kidney biopsy; Glomerular density; Cortex volume