Kidney scintigraphy

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The kidney scintigraphy , also called isotope nephrography (abbr .: ING), radioisotope nephrography (abbr .: RIN) or renogram, is a nuclear medical examination procedure that allows the assessment of the filterative kidney function under static and dynamic aspects. The blood supply, the filter function and the excretion of each individual kidney are assessed. It is the most suitable test for detecting parenchymal scars , especially in children, and is also used to assess regional and lateral renal function. The ING was first given by CC Winter 1956.

It was also possible to determine the renal function separately before the introduction of renal scintigraphy. It was carried out by examining the excreted urine separately for volume and concentration as a clearance determination with catheters in both ureters .

to form

Basically, there are two forms of kidney scintigraphy: static and dynamic kidney scintigraphy. The tracers used are mostly radioactive.

Static kidney scintigraphy

In static kidney scintigraphy, the functional kidney tissue is shown using the radionuclide 99m Tc -DMSA (DMSA = 2,3-dimercaptosuccinic acid). Static kidney scintigraphy is therefore particularly suitable for displaying kidneys with anomalies ( dystopia , horseshoe kidney , etc.) or the state after inflammation.

The radionuclide is injected about two hours before the measurement with the gamma camera . The kidneys are displayed using a high-resolution collimator .

The functional kidney tissue is recorded by enrichment of the radionuclide, which allows the location, shape, size and mass of the kidneys to be determined. As a result, one kidney stores relatively more radioactivity than the other. The sum of these ratios always results in 100 percent. Further statements on the function of the podocytes , the glomeruli and the tubules are not initially possible. It is usual to state the result, for example, in the form "Partial function left / right = 39% / 61%." If the patient's GFR is now known, the GFR can be quantified in absolute numbers for each individual kidney. In a numerical example with a GFR = 50 ml / min, the GFR of the right kidney is calculated as 0.61 × 50 ml / min = 30.5 ml / min and that of the left kidney as GFR = 0.39 × 50 ml / min = 19.5 ml / min. Control: 30.5 ml / min + 19.5 ml / min = 50 ml / min.

The prerequisite for such GFR information is that the storage of radioactively marked DMSA in the kidney tissue is proportional to the glomerular filtration. However, there is no corresponding evidence for this in the specialist literature. Similarly, the Scottish physiologist and Nestor of Nephrology Thomas Addis described the proportionality between the kidney weight of rabbits and their urea excretion in June 1923 .

Dynamic kidney scintigraphy

Dynamic kidney scintigraphy ( kidney function scintigraphy ) examines kidney function. In this way, the relative glomerular filtration in a right-left comparison, the renal blood flow (RBF = renal blood flow ) and the tubular secretion can be examined with the question of the filtrative kidney function and the renal clearance .

Absolute numerical values ​​for the glomerular filtration rate (GFR) with the unit ml / min are not possible. If necessary, however, a known GFR can be multiplied by the relative numbers of both kidneys. Numerical example: A patient has a GFR = 120 ml / min. If the right kidney filters 60% of the isotope and the left kidney 40% of the isotope glomerularly, then the GFR of the right kidney is 0.6 × 120 ml / min = 72 ml / min and the GFR of the left kidney is 0.4 × 120 ml / min = 48 ml / min. Control: 72 ml / min + 48 ml / min = 120 ml / min. Second numerical example for a premature birth with a body weight of one kilogram, with a GFR = 0.2 ml / min and with a right-sided double kidney: The first kidney filters 20% glomerularly, the second 30% and the left 50%. The glomerular filtration rates of the first kidney are then GFR = 0.2 × 0.2 ml / min = 0.04 ml / min, the second kidney GFR = 0.3 × 0.2 ml / min = 0.06 ml / min and the third kidney GFR = 0.5 x 0.2 ml / min = 0.1 ml / min. Control: 0.04 ml / min + 0.06 ml / min + 0.1 ml / min = 0.2 ml / min.

The following are used as radiopharmaceuticals :

  • 99m Tc-MAG3 (is only eliminated tubular)
  • 99m Tc-DTPA (is only filtered glomerularly)
  • 123 I -OIH (is filtered glomerularly and tubularly secreted)
  • 131 I -OIH

The use of 131 I-OIH (iodine-131-hippurane) for scintigraphy is now advised against. This is justified by the poor imaging properties, the high local radiation exposure and the 131 I input into the wastewater. A ban on the use of 131-iodine hippurane is to be expected in the future. For these reasons, kidney scintigraphy with MAG3 is the most widely used dynamic method today.

Dynamic kidney scintigraphy is performed with adequate hydration of the patient by injecting a suitable radiopharmaceutical. The flooding and the flooding of the radionuclide are determined by recordings with the gamma camera and by activity determinations in the plasma.

Blood samples are taken at intervals of 20 and 25 minutes after the injection to determine the activity of the radionuclide and recordings with the gamma camera at defined time intervals. As a result, a nephrogram curve can be created which allows the function of the kidneys to be assessed separately.

The processing of the radionuclide is divided into three phases when shown in the nephrogram curve:

  • Perfusion phase (flooding of the radionuclide with glomerular filtration)
  • Secretion phase ( tubular secretion of the radionuclide with further accumulation )
  • Excretion phase (excretion outweighs accumulation)

Depending on the course of the curve in the nephrogram, statements can be made about normal kidney function and its limitations, about a condition with a one-sided congestive kidney, about the presence of a shrunken kidney or about a condition after a unilateral nephrectomy . The renal clearance of the radiopharmaceutical, but not the actual glomerular filtration of the individual kidneys with the unit ml / min, can be expressed in absolute values ​​(ml / min). However, the percentage of isotope excretion from the individual kidneys is always given as the sum of 100 percent. As a result, one can only say that one kidney excretes more radionuclides than the other. Possible statements on tubular secretion and renal elimination are, however, without any relevance in everyday clinical practice, especially as they only apply to the radiopharmaceutical used. - As a result, isotope nephrography is of no essential importance for nephrological diagnosis. The side-by-side multiplication of the previously known GFR by the two percentages of the scintigraphy is also rejected because it is not relevant and because it is too inaccurate. If a kidney is missing or has no function, the remaining kidney must excrete all radioactivity; even if this kidney functions only normally, it is then erroneously assumed that this single kidney has a double capacity.

Captopril kidney scintigraphy

In the case of renal artery stenosis , the Goldblatt effect prevents the post-stenotic kidney from underperfusion by activating the renin-angiotensin-aldosterone system (RAAS).

This mechanism can be suppressed by giving an ACE inhibitor (short and fast-acting captopril ). If this is followed by a kidney scintigraphy, the functional relevance of renal artery stenosis can be directly quantified.

Diuresis kidney scintigraphy

After the first dynamic kidney scintigraphy and after the bladder has been emptied, diuresis can be stimulated with the administration of a loop diuretic to clarify postrenal outflow disorders .

When the scintigraphy is repeated, the residual activity in the urinary tract and in the bladder is determined. A distinction can be made between compensated and decompensated outflow disturbance.

Indications

A renal function scintigraphy can be performed in the following use cases:

  • To clarify the laterally separated kidney function in kidney diseases such as kidney stones ( nephrolithiasis ), kidney tumors, dystopic (in the wrong place) or dysplastic (malformed) kidneys
  • to investigate the partial function in double kidneys
  • for the investigation of urinary flow disorders
  • to clarify vesicorenal reflux (an anomaly in the urinary tract)
  • if renovascular arterial hypertension is suspected
  • for testing the kidney function before a living kidney donation
  • if a unilateral renal artery stenosis is suspected and to monitor the progress of surgically treated vascular constrictions or occlusions ( obstructions )
  • for the assessment of transplanted kidneys
  • in emergency diagnostics if an injury to the kidneys is suspected (kidney trauma)
  • in the case of suddenly occurring greatly reduced urine excretion ( anuria ) to rule out kidney embolism or acute urinary obstruction
  • for determining total renal clearance
  • to prove or exclude a urine leak .

Prepare the patient

Except in patients with kidney failure, hydration (drinking mineral water) is carried out 45 minutes before the start of the examination after prior urination with 10 ml / kg body weight.

No other special preparation is necessary.

Risks

The radiation exposure is low, for most examinations significantly lower than with intravenous urography . Renal scintigraphy is the most commonly used nuclear medicine examination in children.

literature

Individual evidence

  1. ^ Isotopic nephrography. ( Memento from August 4, 2012 in the web archive archive.today ) In: Imedo Online Lexicon .
  2. ↑ KW Fritz, H. Leistner: Critical Comments on Isotopennephrographie , in: Karl Julius Ullrich , Klaus Hierholzer (Ed.): Normal and pathological functions of the kidney tubule , Verlag Hans Huber , Bern, Stuttgart 1965, p. 417.
  3. ↑ KW Fritz, H. Leistner: Critical Comments on Isotopennephrographie , in: Karl Julius Ullrich , Klaus Hierholzer (Ed.): Normal and pathological functions of the kidney tubule , Verlag Hans Huber , Bern, Stuttgart 1965, p. 417.
  4. ^ Frank Henry Netter : color atlases of medicine, volume 2: kidney and urinary tract , Georg Thieme Verlag , Stuttgart 1976, ISBN 3-13-524101-7 , pp. 103-106.
  5. ↑ Jörg Dötsch, Lutz T. Weber (Ed.): Kidney Diseases in Childhood and Adolescence , Springer-Verlag, Berlin 2017, ISBN 978-3-662-48788-4 , p. 60.
  6. ↑ FB Taylor, DR Drury, Thomas Addis: The Regulation of Renal Activity: VIII: The Relation between the Rate of Urea Excretion and the Size of the Kidneys , in: American Journal of Physiology , June 1, 1923, 65th volume, p 55-61.
  7. ↑ Markus Daschner, P. Cochat: Pharmacotherapy with renal insufficiency , in: Karl Schärer, Otto Mehls (Ed.): "Pediatrische Nephrologie", Springer-Verlag, Berlin, Heidelberg 2002, ISBN 978-3-642-62621-0 , p 467.
  8. ↑ Markus Daschner: Tabellarium nephrologicum , 3rd edition, Shaker Verlag, Aachen 2009, ISBN 978-3-8322-7967-7 , p. 67.
  9. ↑ a b T. Zajic, E. Moser: procedural instructions for kidney function scintigraphy. German Society for Nuclear Medicine, May 2005.
  10. ↑ KW Fritz, H. Leistner: Critical Comments on Isotopennephrographie , in: Karl Julius Ullrich , Klaus Hierholzer (Eds.): Normal and pathological functions of the kidney tubule , Verlag Hans Huber , Basel, Stuttgart 1965, pp. 420 and 421.
This text is based in whole or in part on the entry kidney scintigraphy in Flexikon , a wiki of the DocCheck company . The takeover took place on August 7, 2007 under the then valid GNU license for free documentation .