open access

Vol 23, No 2 (2020)
Research paper
Submitted: 2020-05-06
Accepted: 2020-08-28
Published online: 2020-09-28
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Kidney Efficiency Index — quantitative parameter of a dynamic renal scintigraphy. I. Theory and preliminary verification

Krzysztof Grzegorz Filipczak1, Pawel Cichocki2, Jacek Kusmierek2, Anna Plachcinska1
·
Pubmed: 33007094
·
Nucl. Med. Rev 2020;23(2):78-83.
Affiliations
  1. Medical University of Lodz, Department of Quality Control and Radiation Protection, Lodz, Poland
  2. Medical University of Lodz, Department of Nuclear Medicine, Lodz, Poland

open access

Vol 23, No 2 (2020)
Original articles
Submitted: 2020-05-06
Accepted: 2020-08-28
Published online: 2020-09-28

Abstract

BACKGROUND: One of the basic clinical indications for dynamic renal scintigraphy (DRS) is a diagnosis of obstructive
uropathy and/or nephropathy. Currently, a basic quantitative criterion for diagnosing nephropathy is the percentage of individual
kidney’s contribution in the global uptake of a radiopharmaceutical from the blood (so-called Split Function - SF).
From a clinical point of view, a parameter evaluating a radiopharmaceutical uptake and reflecting the efficiency of a specific
kidney, determined independently of the total uptake of both kidneys, would be much more useful. Based on a Rutland theory,
a kidney uptake constant K proportional to a radiotracer uptake by individual kidney was introduced and applied to DRS with
99mTc-ethylene-1-dicysteine (99mTc-EC). In addition, a kidney efficiency index (KEi) was also worked out as a new parameter
obtained by dividing the uptake constant K by the surface of the ROI of a given kidney, which can be interpreted as the average
“efficiency” of clearance of a kidney.
MATERIAL AND METHODS: K and KEi values were verified in 72 studies selected retrospectively from patients referred
routinely for DRS, with available current level of blood creatinine, used for calculation of estimated GFR (eGFR) according to
a CKD-EPI formula. After splitting of eGFR values into individual kidneys according to SF, single kidney eGFR values (SKeGFR)
were obtained and then used as a verification method for SF, K and KEi values.
RESULTS: Correlation between SF and SKeGFR values, rsp = 0.64, was significantly weaker (p < 0.0022) than the correlation
of SKeGFR values with K uptake constants and KEi indices: 0.90 and 0.84, respectively.
CONCLUSIONS: Uptake constant K and KEi, as quantitative parameters, give the opportunity to analyze a function of each
kidney separately and in an absolute way. KEi also allows for a reliable assessment of kidneys of atypical sizes (larger or smaller
than average). It also gives the opportunity to create normative values for this parameter and may be useful in a number of
clinical situations where the diagnostic effectiveness of such a relative parameter as SF, is severely limited, e.g. in assessing
a large kidney with hydronephrosis or while differing a cirrhotic from hypoplastic (i.e. a small but properly functioning) kidney.

Abstract

BACKGROUND: One of the basic clinical indications for dynamic renal scintigraphy (DRS) is a diagnosis of obstructive
uropathy and/or nephropathy. Currently, a basic quantitative criterion for diagnosing nephropathy is the percentage of individual
kidney’s contribution in the global uptake of a radiopharmaceutical from the blood (so-called Split Function - SF).
From a clinical point of view, a parameter evaluating a radiopharmaceutical uptake and reflecting the efficiency of a specific
kidney, determined independently of the total uptake of both kidneys, would be much more useful. Based on a Rutland theory,
a kidney uptake constant K proportional to a radiotracer uptake by individual kidney was introduced and applied to DRS with
99mTc-ethylene-1-dicysteine (99mTc-EC). In addition, a kidney efficiency index (KEi) was also worked out as a new parameter
obtained by dividing the uptake constant K by the surface of the ROI of a given kidney, which can be interpreted as the average
“efficiency” of clearance of a kidney.
MATERIAL AND METHODS: K and KEi values were verified in 72 studies selected retrospectively from patients referred
routinely for DRS, with available current level of blood creatinine, used for calculation of estimated GFR (eGFR) according to
a CKD-EPI formula. After splitting of eGFR values into individual kidneys according to SF, single kidney eGFR values (SKeGFR)
were obtained and then used as a verification method for SF, K and KEi values.
RESULTS: Correlation between SF and SKeGFR values, rsp = 0.64, was significantly weaker (p < 0.0022) than the correlation
of SKeGFR values with K uptake constants and KEi indices: 0.90 and 0.84, respectively.
CONCLUSIONS: Uptake constant K and KEi, as quantitative parameters, give the opportunity to analyze a function of each
kidney separately and in an absolute way. KEi also allows for a reliable assessment of kidneys of atypical sizes (larger or smaller
than average). It also gives the opportunity to create normative values for this parameter and may be useful in a number of
clinical situations where the diagnostic effectiveness of such a relative parameter as SF, is severely limited, e.g. in assessing
a large kidney with hydronephrosis or while differing a cirrhotic from hypoplastic (i.e. a small but properly functioning) kidney.

Get Citation

Keywords

dynamic renal scintigraphy; renal clearance; split function; uropathy; nephropathy; kidney efficiency index; uptake constant

About this article
Title

Kidney Efficiency Index — quantitative parameter of a dynamic renal scintigraphy. I. Theory and preliminary verification

Journal

Nuclear Medicine Review

Issue

Vol 23, No 2 (2020)

Article type

Research paper

Pages

78-83

Published online

2020-09-28

Page views

1336

Article views/downloads

1499

DOI

10.5603/NMR.2020.0025

Pubmed

33007094

Bibliographic record

Nucl. Med. Rev 2020;23(2):78-83.

Keywords

dynamic renal scintigraphy
renal clearance
split function
uropathy
nephropathy
kidney efficiency index
uptake constant

Authors

Krzysztof Grzegorz Filipczak
Pawel Cichocki
Jacek Kusmierek
Anna Plachcinska

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