IgG4-related kidney disease: MRI findings with emphasis on the usefulness of diffusion-weighted imaging.
OBJECTIVE
To investigate the imaging findings of immunoglobulin G4 (IgG4)-related kidney disease (IgG4-KD) on magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) and to evaluate the usefulness of DWI in lesion detection.


METHODS
This retrospective cohort study included 31 patients with IgG4-KD who underwent MRI covering both kidneys. Two radiologists reviewed in consensus the MR images to determine the distribution pattern (location, laterality, and multiplicity) and the visually assessed signal intensity (hypointense, isointense or hyperintense) of the renal lesions compared to the normal renal parenchyma on each sequence. Per-patient sensitivity for detecting IgG4-KD and the number of detectable lesions were compared in T2-weighted images, DWI, and dynamic contrast-enhanced images.


RESULTS
IgG4-KD typically manifested as bilateral (83.9%), multiple (93.5%), and renal parenchymal (87.1%) nodules appearing isointense (93.5%) on T1-weighted images, hypointense (77.4%) on T2-weighted images, hyperintense (100%) on DWI (b=1000), and hypointense (83.3%) in the arterial phase and with a progressive enhancement pattern on dynamic contrast-enhanced images. The sensitivity of DWI for detecting IgG4-KD was significantly higher than that of T2-weighted images (100% vs. 77.4%, P=0.034). The median number of detectable lesions was significantly greater in DWI (n=9) than in T2-weighted images (n=2) and dynamic contrast-enhanced images (n=5) (P≤0.008).


CONCLUSIONS
The characteristic MRI findings of IgG4-KD were bilateral, multiple, renal parenchymal nodules with T2 hypointensity, diffusion restriction, and a progressive enhancement pattern. As DWI was useful in the detection of IgG4-KD, adding DWI to conventional MRI for patients suspected of having IgG4-KD may enhance the diagnosis.
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
Bohyun
B
Kim
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea. Electronic address: kimjhrad@amc.seoul.kr.
Jin Hee
JH
Kim
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
Jae Ho
JH
Byun
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
Hyoung Jung
HJ
Kim
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
Seung Soo
SS
Lee
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
So Yeon
SY
Kim
Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil 86, Songpa-Gu, Seoul 138-736, Republic of Korea.
Moon-Gyu
MG
Lee
D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007668:Kidney / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000276:immunology* / Q000473:pathology*; D015588:Observer Variation; D010265:Paraproteinemias / Q000276:immunology* / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
D007074:Immunoglobulin G
Diffusion weighted imaging; IgG4-related kidney disease; IgG4-related systemic disease; MRI