Individual renal function based on 99mTc dimercaptosuccinic acid uptake corrected for renal size.
BACKGROUND
Decreased relative 99mTc dimercaptosuccinic acid (99mTc-DMSA) uptake can be a consequence of abnormal kidney size, associated with normal or impaired function. When there is a small kidney, relative 99mTc-DMSA uptake is decreased, and it is sometimes difficult to distinguish a small, normal kidney from a hypofunctioning kidney. Here, relative renal function was studied by quantifying the relative 99mTc-DMSA uptake corrected for renal size (RCU).


METHODS
Five hundred and fifty-five consecutive patients (184 adults) aged 1 month to 82 years (mean, 14.8 years) underwent a 99mTc-DMSA study for various renal diseases. Results were compared with the relative 99mTc-DMSA uptake without size correction (RUU). Visual evaluation of images was also performed.


RESULTS
In 288 patients (52%) the relative 99mTc-DMSA uptake was normal, either uncorrected or corrected, for renal size; in 184 (33%) it was abnormal by both quantification methods; and in 83 (15%) it was abnormal only by one method. Two hundred and fifty-seven patients (46%) presented with decreased RUU in one kidney, associated with a small kidney in 73 patients (13%). RCU was normal in all of these 73 patients (100%, P<0.0001). The sensitivity and specificity of RCU for evaluating renal function in relation to small renal size and with respect to RUU were 72% and 97%, with positive and negative predictive values of 95% and 80%, and an accuracy of 85%. Visual analysis of the 73 studies with decreased RUU and normal RCU showed a small, normal kidney on 55 occasions (75%), cortical scars in eight (11%), and impaired bilateral function in 10 (14%). Visual analysis of 10 studies with normal RUU and decreased RCU showed dilated pyelocalyceal system in seven occasions (70%) and normal kidneys in three (P<0.0001).


CONCLUSIONS
It is concluded that relative 99mTc-DMSA uptake corrected for renal size is a more accurate method for assessing individual renal function. When there is a small kidney, relative 99mTc-DMSA uptake corrected for renal size can distinguish between a normal and a hypofunctioning kidney.
Estorch
Montserrat
M
Department of Nuclear Medicine, Hospital de la Santa Creu i Sant Pau, Autonomous University of Barcelona, Barcelona, Spain. mestorch@hsp.santpau.es
Torres
Gustavo
G
Camacho
Valle
V
Tembl
Ana
A
Prat
Lourdes
L
Mena
Esther
E
Flotats
Albert
A
Carrió
Ignasi
I
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007668:Kidney / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology*; D007674:Kidney Diseases / Q000000981:diagnostic imaging; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D019783:Technetium Tc 99m Dimercaptosuccinic Acid / Q000493:pharmacokinetics*
D019275:Radiopharmaceuticals; D019783:Technetium Tc 99m Dimercaptosuccinic Acid