International Scientific Committee of Radionuclides in Nephrourology (ISCORN) Consensus on Renal Transit Time Measurements
Section snippets
Methodology
A first draft was discussed by the committee by e-mail. Then, an outline was proposed by Dr. Durand and approved by the other committee members. The whole text was then rewritten based on this outline by Dr. Durand and Dr. Blaufox, including the comments and new references that were proposed and classifying the level of evidence of the references. This version was then submitted to the committee for comments and changes. It is reminded here that a consensus does not mean that all the authors
Basic Facts on Renal TT
In 1956, Taplin and coworkers published the use of 131I-diodrast injected intravenously to produce dynamic acquisitions of kidneys, thus obtaining a time-activity curve.1 These time-activity curves can be used to derive relative renal function,2 but they also provide information on transit, that is, time during which the tracer stays in a given part of kidney. A quantitative analysis of the renogram suggesting the use of deconvolution was proposed as early as 1964.3 Very early, it was suggested
Assessment of Transit
The general technique to assess renal transit in nuclear medicine is to acquire a dynamic scan after a bolus injection. After acquisition, either a qualitative assessment of transit can be done or a quantitative one, which may be either a transit time determination or assessment of a simpler index of transit. (Here, “simple” indices should be understood as “easy to determine.” They may however reflect less simple physiologic parameters.)
Summary
To assess renal transit, two kinds of methods exist. The first one is a measurement of transit time by deconvolution, which was mostly applied to parenchymal transit with DTPA (MAG3 was not introduced until 1986). This measurement provides a parameter that is physiologically relevant (namely, the duration that a molecule stays in the nephron, which is the ratio of the nephron volume to the urine flow). However, a British audit showed a poor intercenter reproducibility of the data processing.81
Application of MTT in Clinical Situations
Renal transit was mostly studied in 3 clinical situations: hydronephrosis, renovascular hypertension (RVHT), and kidney transplantation.
Conclusion
Purest transit parameters (measured transit times) can be obtained by deconvolution but they lack intercenter reproducibility. Simple parameters are more influenced by the input function and do not reflect truly physiological parameters. Moreover, transit is affected by many parameters (hydration state, arterial pressure, reservoir effect, full bladder, posture, etc) More standardization is therefore desirable for both classes of methods. In obstruction, no consensus was reached among the
Appendix
Available online at http://www.ISCORN.org.
Note on References
Only peer-reviewed papers were considered for clinical evidence, not editorials, letters, abstracts, books, or personal communications. Other papers have be taken as useful for their ideas but not for clinical or experimental evidence. The quoted references were classified along the following categories210, 211 (we must however remark that this classification was designed for therapeutic studies, not for diagnostic studies as here). Additional categories were used to adapt the original
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Note: Throughout the text, the symbol “±” stands for standard deviation.
Conflicts of interest: K.E.B. was a consultant to Nuclear Diagnostics Ltd (Hermes work stations) from October 2004 to October 2005; he is no longer involved with this company.
The publication of this paper was made possible by a grant from ISCORN (A. Prigent) and contributions from A.T. Taylor and M.D. Blaufox.