All patients fulfilled Ravine’s diagnostic criteria of ADPKD. One hundred and eighty-eight patients with ADPKD gave informed consent to take part in an observational clinical study protocol measuring TKV once a year with simultaneous collection of 24-h urine for determination of creatinine clearance (Ccr) and urinary protein excretion between April 2007 and July 2012. Patients with end-stage renal disease (ESRD) underwent TKV measurement only. Of 188 patients, 70 underwent TKV measurement three times or more. Two patients who received laparoscopic cyst fenestration, one patient with a ureteral stone with hydronephrosis during the study period, and three patients with baseline ESRD were excluded from analysis.
Serum creatinine was measured enzymatically. Kidney function was estimated with Ccr using 24-h urine, reciprocal creatinine and eGFR. eGFR was calculated using the following formula—eGFR (male) = 194 × Cr−1.094 × Age−0.287, and eGFR (female) = eGFR (male) × 0.739. This equation is a Japanese coefficient of the modified Isotope Dilution Mass Spectrometry−Modification of Diet in Renal Disease (IDMS–MDRD) Study [11 (link)]. The staging of kidney function is based on the Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines for CKD [12 (link)] using the final eGFR measurement.
TKV was measured by high-resolution magnetic resonance imaging (MRI) using a volumetric measurement of cross-sectional imaging, as described in the report from the CRISP study [13 (link)]. Gadolinium enhancement was not used for safety reasons. TKV was adjusted by height (ht-TKV, ml/m), body surface area (bs-TKV, ml/m2) and log-converted form (log-TKV, log[ml]). Kidney volume was measured by one radiologist (KK). Intrareader reliability was extremely high—the correlation coefficient was 0.999 for ten different single kidney volume measurements at different times when blind to first measurement. The mean of the % difference between two measurements was 0.29 ± 3.28 (SD) %.
Twenty-four-hour urinary protein excretion was expressed as the mean value of several measurements for each patient. The slopes of TKV, adjusted TKV parameters and kidney function parameters were calculated using linear regression analysis for each patient. %TKV was calculated with baseline TKV as 100 %.
The study protocol was approved by an institutional review board (09-56), and the study was conducted in accordance with the guidelines of the Declaration of Helsinki. All participants gave written informed consent to use their clinical data for medical research.
Serum creatinine was measured enzymatically. Kidney function was estimated with Ccr using 24-h urine, reciprocal creatinine and eGFR. eGFR was calculated using the following formula—eGFR (male) = 194 × Cr−1.094 × Age−0.287, and eGFR (female) = eGFR (male) × 0.739. This equation is a Japanese coefficient of the modified Isotope Dilution Mass Spectrometry−Modification of Diet in Renal Disease (IDMS–MDRD) Study [11 (link)]. The staging of kidney function is based on the Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines for CKD [12 (link)] using the final eGFR measurement.
TKV was measured by high-resolution magnetic resonance imaging (MRI) using a volumetric measurement of cross-sectional imaging, as described in the report from the CRISP study [13 (link)]. Gadolinium enhancement was not used for safety reasons. TKV was adjusted by height (ht-TKV, ml/m), body surface area (bs-TKV, ml/m2) and log-converted form (log-TKV, log[ml]). Kidney volume was measured by one radiologist (KK). Intrareader reliability was extremely high—the correlation coefficient was 0.999 for ten different single kidney volume measurements at different times when blind to first measurement. The mean of the % difference between two measurements was 0.29 ± 3.28 (SD) %.
Twenty-four-hour urinary protein excretion was expressed as the mean value of several measurements for each patient. The slopes of TKV, adjusted TKV parameters and kidney function parameters were calculated using linear regression analysis for each patient. %TKV was calculated with baseline TKV as 100 %.
The study protocol was approved by an institutional review board (09-56), and the study was conducted in accordance with the guidelines of the Declaration of Helsinki. All participants gave written informed consent to use their clinical data for medical research.
