Renal Scintiscanning a Review

Postgrad Med J: first published as 10.1136/pgmj.46.531.52 on 1 January 1970. Downloaded from Postgraduate Medical Journal (January 1970) 46, 52-62. Renal scintiscanning A review E. RHYS DAVIES M.A., M.B., M.R.C.P.E., F.F.R. Consultant Radiologist, United Bristol Hospitals Summary 1963; Desgrez, Raynand & Kellersohn, 1964; Izen- Renal scintiscanning is a simple investigation that stark et al., 1964; McEwan & Rosenthall, 1966; does not require special preparation and is well Winter, 1966; Gottschalk, 1967; Chisholm, Aye & tolerated by patients. Evans, 1967; Graham et al., 1967). Experience has Radiopharmaceuticals used in linear scanning are helped to clarify the indications for renal scintiscan- accumulated in the renal cortex. This accumulation ning and the value and application of the results will is diminished: (a) when the cortex is destroyed, e.g. be discussed in this review. by pyelonephritis, injury, etc.; and (b) when the Details of the physical aspects of scanning can be amount available to the cortex is reduced, e.g. by found elsewhere (Mallard, 1966, 1969) and the avail- ischaemia. The scintigram depicts the kidneys un- able instruments will be mentioned only briefly. The impeded by bowel contents, gives a qualitative most widely used is the linear scanner in which a assessment of renal function and shows the distribu- detecting crystal collimated to a small area moves copyright. tion of zones of normal function. Recent technical continuously to and fro across the area being scanned, improvements show great promise in deriving a taking some 40 min to scan both renal areas. It can quantitative measure of renal function in some be used only with radiopharmaceuticals that are circumstances. accumulated in the kidneys, because the speed of The location of normally functioning cortex is scanning is relatively so slow. A multiprobe scanner often important in the management of renal diseases has been designed which improves the speed of and the value of scintiscanning is then considerable. scanning considerably (Hayes, Swanson & Taplin, It is occasionally useful in planning surgery. 1968; Hindel, Gilson & Swanson, 1969) but maxi- The anatomy of the renal collecting system can be mum improvement in speed is obtained with the http://pmj.bmj.com/ shown only by urography. High dose techniques gamma camera, a static detector that can produce achieve this even in the face of renal failure, and an image in a matter of seconds (Gottschalk & scintiscanning has few indications in investigating Auger, 1965a, b). Lesions are detected as readily as lesions that distort the renal anatomy, e.g. tumours with a linear scanner (McCready, 1967) and because and cysts. rapid serial images can be produced, compounds Renal scintiscanning is a very valuable additional that traverse the kidney as well as those that are method to urography, arteriography and accumulated can be used. Linear scanning data are renography on October 2, 2021 by guest. Protected in investigation of renal disorders. recorded on paper by coloured dots, or a radiograph by a photo scan. Gamma camera data are recorded Introduction in black and white by Polaroid camera. Evaluation Scintiscanning is an attractive method of investi- of the data can be enhanced by the use of an image gation, because it is simple and well tolerated and intensifier (Ter-Pogossian, Kastner & Vese, 1963) requires no special patient preparation. The stimulus and digital computer (Tauxe, 1969). to increase the use of techniques with such an appeal is so great that it is desirable from time to time to Radiopharmaceuticals reflect how well they answer the clinical problems, The first compounds chosen for renal scanning and what place they have achieved alongside more were 1311-labelled pyelographic contrast media, e.g. established methods. sodium diatrizoate (Hypaque) but as these are During the past decade many uses have been excreted by glomerular filtration they disappear too claimed for renal scintiscanning, usually in clinical rapidly from the field of a linear scanner to be usable situations where radiological methods had been the (Denneberg & Hedenskog, 1959). They were dis- methods of choice (McAfee & Wagner, 1960; Sodee, carded in favour of compounds accumulated in the Postgrad Med J: first published as 10.1136/pgmj.46.531.52 on 1 January 1970. Downloaded from Renal scintiscanning 53 kidneys. Typical of these are the mercurial diuretics serial renal images from these compounds are more which are accumulated by the tubule cells and akin to the nephrogram and pyelogram phase of excreted slowly (Borghgraeff & Pitts, 1956). The excretion urography than to a chlormerodrin image, greatest renal accumulation is achieved by 3-chlor- with the advantage that they are a better test of mercuric - 2 - methyl propylurea (chlormerodrin) function than urography (Hayes et al., 1968). (Kessler, Lozano & Pitts, 1957), which has become Finally the distribution of renal vasculature can be the agent of choice. recorded with the gamma camera and compounds After intravenous injection, a variable amount of like 99mTc which outline the body blood pool, and chlormerodrin which is protein-bound is transferred this can be used in conjunction with conventional to the tissues, mainly to the kidneys (60%) but also chlormerodrin scintigraphy (Rosenthall, 1967). to liver, spleen and muscles. In the kidney, animal The choice of radiopharmaceuticals is influenced studies have shown that all the chlormerodrin is most by the equipment available, and also by the located in the renal cortex, mainly in its inner third, availability and shelfhalf-life of the agents. Many will within the cells of the distal convoluted tubule prefer chlormerodrin to 99mTc or 113mIn compounds (Laakso, Lindgren & Rekonen, 1965). for routine scanning because it can be injected Accumulation increases slowly over 1-2 hr and directly from its ampoule without preparation and remains steady for about 6 hr before it begins to fall has an economical shelf half-life. as some of it is excreted in the urine. Ten per cent of accumulated chlomerodrin is retained permanently Technique in the tubule cells (Gottschalk, 1967). The usual dose of 197Hg chlormerodrin for an Chlormerodrin can be labelled with either 203Hg adult is 100-150 ,uCi given intravenously. The or 197Hg, the choice being determined by important quantity of diuretic injected is too small to have any biophysical differences between these isotopes detectable pharmacological effect. The patient lies (Table 1). The relatively penetrating gamma photons so that the head can be as of 203Hg are an advantage in overcoming tissue prone scanning brought close as possible to the kidneys. If an undercouch copyright. attenuation in a thick-set patient, but because of its head is available it is more convenient for the patient longer half-life and beta emission it gives a much to lie supine, and this position is used also when an higher renal radiation dose (20-30 rads/100,iCi) anterior scan is needed, e.g. in outlining the isthmus than 197Hg (3-4 rads/100 ,lCi) which is, therefore, of a horse-shoe kidney or a pelvic kidney. The generally preferred (Blau & Bender, 1964; Quinn & optimal time for scanning is 1-2 hr after injection Maynard, 1965). 197Hg may also be used as a chelate, when the renal accumulation is maximal. A delayed with ethylenediamine-tetra-acetate which is accumu- scan may show better accumulation in renal failure. lated in the same way as chlormerodrin (Kraszhai, Each Pal & Foldes, 1965). Other chelates, e.g. 99mTc-iron scan takes 3-40 min and the whole investigation takes 2-3 hr of the patient's time. The gamma http://pmj.bmj.com/ complex (Harper et al., 1965) have even more favour- camera produces each image in a matter of seconds able physical characteristics (Table 1) and improve and it is as the quality of the image without increasing the important in saving time as in conducting radiation hazard. Because it produces serial images dynamic studies. so quickly the gamma camera can also be used with compounds not accumulated by the kidney, e.g. Normal appearances ll3mIn diethylenetriamine-penta-acetic acid, filtered The scintigram of chlormerodrin and similar the Hosain & by glomeruli (Reba, Wagner, 1968), compounds shows the distribution of functioning on October 2, 2021 by guest. Protected or 131I hippuran, filtered by glomeruli and excreted renal cortex, without any contribution from the by tubules. The renal radiation hazard is then medulla or collecting system. The count rate is minimal (Hayes, Swanson & Taplin, 1968). The highest over the centre of the image and falls quite quickly towards the margins, which are often TABLE 1. Physical properties of isotopes used in renal unsharp (Fig. 1). The count rate is usually equal over scanning two normal but attenuation of Gamma kidneys, activity Compound Emission keV Half-life could occur from the deeper of two kidneys, making Isotope the images unequal. The difference in renal depths is Chlormerodrin 203Hg Beta, gamma 279 47 days probably less than 1 cm (Britton & Brown, 1968) 197Hg Gamma 77 65 hr which is Hippuran 131I Beta 360 8 days probably not significant but a difference of Neohydrin Gamma up to 155% maximum count rate has been found Indium-DTPA l3lmIn Gamma 392 1-7 hr between normal kidneys (Morris et al., 1967). Pertechnetate 99mTc Gamma 140 6 hr The shape and position of a scintigraphic and a technetium- radiographic image correspond well. The length of iron complex the scan image is 1 cm or so less, so that renal size Postgrad Med J: first published as 10.1136/pgmj.46.531.52 on 1 January 1970. Downloaded from 54 E. Rhys Davies FIG. 1. Normal renal scintigram. Note the high slightly asymmetrical central count rate over both kidneys. Their margins are moderately sharp. cannot be measured accurately from it, but changes Renal ectopia should always be sought in this way if copyright.

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