The advantages of 99mTc DTPA(Sn) in dynamic renal scintigraphy and measurement of renal function

Comparison of methods for determination of glomerular filtration rate in hypertensive subjects with normal serum creatinine

BACKGROUND

Glomerular filtration rate (GFR) measured through technetium-99m diethyl triamine penta-acetic acid (Tc(99m)DTPA) renal scintigraphy (rsGFR) was compared with that estimated (eGFR) from 24-h creatinine clearance (CrCl) and, using both the Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas, in a population of hypertensive subjects (HTs) with normal serum creatinine (SCr) levels.

PATIENTS AND METHODS

In 200 normoalbuminuric (<30 mg/24 h) HTs 55-75 years old, without diabetes and history of coronary and cerebrovascular diseases, Pearson's correlation assess the relationship between rsGFR and eGFR. The Bland-Altman method was used to assess the agreement between rsGFR and eGFR, separately in subjects with low (<60 ml/min/1.73 m(2)) and normal (≥60 ml/min/1.73 m(2)) rsGFR. The span between -1.96 and +1.96 standard deviations of mean difference (bias) was calculated and used for this purpose.

RESULTS

In 76 subjects, an unknown low renal function was found by Tc(99m)DTPA renal scintigraphy. In subjects with normal rsGFR the Bland-Altman analysis showed that the smallest span between rsGFR and eGFR was evident for ClCr values (26.0 ml/min/1.73 m(2)), whereas higher values were detected with the CG and MDRD formulas (41.0 and 40.4 ml/min/1.73 m(2), respectively). The same results were observed for low rsGFR, where a smaller span was found for ClCr (21.2 ml/min/1.73 m(2)), whereas CG and MDRD methods gave greater results (30.4 and 31.8 ml/min/1.73 m(2) respectively); no differences were found between genders. The degree of agreement for eGFR estimated with the CG and MDRD formulas was wider than that derived from ClCr, reflecting a greater between-methods variability and a considerable discrepancy of rsGFR values in the former than in the latter.

CONCLUSIONS

In HTs with normal SCr values, Tc(99m)DTPA renal scintigraphy discovered un known renal organ damage in 38% of cases. If this methodology is not available, ClCr measurement should be preferred to estimate GFR whereas CG and MDRD formulas are of limited efficacy.

RENAL EVALUATION IN THE HEALTHY GREEN IGUANA (IGUANA IGUANA): ASSESSMENT OF PLASMA BIOCHEMISTRY, GLOMERULAR FILTRATION RATE, AND ENDOSCOPIC BIOPSY

Plasma biochemistry, iohexol clearance, endoscopic renal evaluation, and biopsy were performed in 23 clinically healthy 2-yr-old green iguanas (Iguana iguana). Mean (+/- SD) values for packed cell volume (30 +/- 3%), total protein (62 +/- 7 g/L, 6.2 +/- 0.7 g/dl), albumin (25 +/- 2 g/L, 2.5 +/- 0.2 g/dl), globulin (37 +/- 6 g/L, 3.7 +/- 0.6 g/ dl), total calcium (3.0 +/- 0.2 mmol/L, 12.0 +/- 0.7 mg/dl), ionized calcium (1.38 +/- 0.1 mmol/L), phosphorus (1.32 +/- 0.28 mmol/L, 4.1 +/- 0.9 mg/dl), uric acid (222 +/- 100 micromol/L, 3.8 +/- 1.7 mg/dl), sodium (148 +/- 3 mmol/L or mEq/ L), and potassium (2.6 +/- 0.4 mmol/L or mEq/L) were considered within normal limits. Values for urea were low (< 1.4 mmol/L, < 4 mg/dl) with 70% of samples below the detectable analyzer range. After the i.v. injection of 75 mg/ kg iohexol into the caudal (ventral coccygeal or tail) vein, serial blood collections were performed over 32 hr. Iohexol assays by high-performance liquid chromatography produced plasma iohexol clearance graphs for each lizard. A three-compartment model was used to fit area under the curve values and to obtain the glomerular filtration rate (GFR) using regression analysis. The mean GFR (SD) was 16.56 +/- 3.90 ml/kg/hr, with a 95% confidence interval of 14.78-18.34 ml/kg/hr. Bilateral endoscopic renal evaluation and biopsy provided tissue samples of excellent diagnostic quality, which correlated with tissue harvested at necropsy and evaluated histologically. None of the 23 animals demonstrated any adverse effects of iohexol clearance or endoscopy. Recommended diagnostics for the evaluation of renal function and disease in the green iguana include plasma biochemical profiles, iohexol clearance, endoscopic examination, and renal biopsy.

Scintigraphy and Doppler ultrasonography for the evaluation of obstructive urinary calculi

Forty-seven patients with unilateral obstructive calculi (12 males and 35 females) were submitted to 99mTc-diethylene triamine pentaacetic acid (DTPA) or 99mTc-dimercaptosuccinic acid (DMSA) scans for assessment of renal function. The scans revealed unilateral functional deficit in 68 and 66% of the patients, respectively. A calculus size of 1.1 to 2.0 cm was significantly associated with deficit detected by DTPA, but duration of obstruction and calculus localization were not. After relief of the obstruction, the mean percent renal function of the affected kidney was found to be significantly increased from 25 +/- 12% to 29 +/- 12% in DTPA and from 21 +/- 15% to 24 +/- 12% in DMSA. Initial Doppler ultrasonography performed in 35 patients detected an increased resistive index in 10 (29%). In the remaining patients with a normal resistive index, ureteral urinary jet was observed, indicating partial obstruction. The high frequency of renal function impairment detected by DTPA and of tubulointerstitial damage detected by DMSA as well as the slight amelioration of unilateral renal function after relief of obstruction suggest that scintigraphy assessment may help evaluate the unilateral percentage of renal function and monitor renal function recovery when it occurs. The presence of a urinary jet detected by Doppler ultrasonography further indicates the severity of obstruction and the recovery prognosis.

Radionuclide quantitation of renal function

Quantitation of renal function may be performed with a variety of radiopharmaceuticals which reflect slightly different renal functions. Plasma sampling techniques and imaging techniques have been used to derive absolute measurements of renal function. The addition of imaging permits the determination of relative or "split" function. Time-activity curves from renal studies provide other quantitative parameters of function reflecting arterial supply, renal cortical function, and patency of the renal collecting system. Quantitative radionuclide studies of the kidneys provide comprehensive, reproducible, and objective assessments of renal function.

99mTc-DTPA and 99mTc-DMSA renal gamma imaging in the surveillance of patients with conduit urinary diversion

We studied renal anatomy and function using 99mTc-2-3 dimercaptosuccinic acid (DMSA) and 99mTc-diethylenetriaminepentaacetic acid (DTPA) in 27 patients with conduit urinary diversion. In this condition, free ureteral reflux is often associated with bacteriuria, and these factors are thought to precipitate progressive renal deterioration. Gamma-camera images provided valuable information concerning the structure of the renal parenchyma, the function of individual kidneys and possible ureteral obstruction, thus helping us to decide whether or not to instigate further treatment. The information gained using renal gamma imaging with 99mTc-DTPA and 99mTc-DMSA was complementary and partly overlapping. We preferred the use of 99mTc-DTPA because of its ability to visualise the ureters and the region of ureteroconduit anastomosis. Using diuretic medication, we were able to differentiate true ureteral obstruction from atony in 9 patients using 99mTc-DTPA.

Radionuclide scanning--new applications in urology

The current status of nuclear renal scanning and function evaluation is summarized. The indications for renal imaging are discussed. Techniques for measurement of split and total renal function are reviewed. Special attention is given to the role of renography (conventional and diuretic) in the evaluation of the obstructed kidney.

Quantitative assessment of individual renal function. A comparison between creatinine excretion and a radionuclide method

Individual renal function was evaluated in 21 patients. Two methods were used in each case, namely gamma camera renography and measurement of creatinine excretion in urine collected via a nephrostomy. The scintigraphic technique utilized measurement of renal parenchymal radionuclide uptake in an early phase. Good agreement was found between the results from both methods in most patients. Gamma camera renography was found to be clinically useful for assessing the function of individual kidneys.

Renal function after urinary diversion. A study of continent caecal reservoir, ileal conduit and colonic conduit

Total and separate renal function, renal parenchymal thickness and dilatation of the upper urinary tract were studied in 40 patients preoperatively and 24 to 67 months after urinary diversion, using 51Cr-EDTA clearance test, scintillation camera renography and urography. In ten patients a continent caecal reservoir was used for diversion. In the other patients, an ileal or a colonic conduit (15 patients with each method) was used, one ureter being implanted with an anti-reflux method and the other with direct technique. Renal function following urinary diversion showed little or no deterioration in most patients. The functional outcome was not related to the method of diversion or, in the conduit groups, to the mode of ureteral implantation. Serum creatinine tests and urography were not adequate for determining loss of renal function. Radionuclide studies proved to be valuable for assessing renal function after urinary diversion.

Acute effects of full urinary bladder and full caecal urinary reservoir on regional renal function. A study with scintillation camera renography

Scintillation camera renograms were recorded in six patients without a history of bladder function disturbances and in eight patients with caecal urinary reservoir. Each patient was studied once with empty bladder/reservoir and once with full bladder/reservoir. Renograms were obtained from parenchyma, pelvis and whole kidney. Time was measured from injection of isotope to peak of the renogram curve (Tmax) and to the point corresponding to the centre of gravity of the area under the curve (Tg). A full reservoir gave longer Tmax and Tg for both parenchyma and pelvis than an empty reservoir. With full bladder the only significant change was Tg increase for renal pelvis. In the patients with full caecal reservoir, the elimination of radioisotope from the renal pelvis was significantly slower, reflected as longer Tmax and Tg, than in the subjects with full bladder. In comparisons between empty and full bladder/reservoir, Tg permitted clearer separation between the groups than did Tmax. The higher Tmax and Tg values for full than for empty reservoir indicated obstruction to urinary flow and could be ascribed to the high intrareservoir pressure. Regularly occurring pressure waves with amplitudes of 30-65 cm H2O were recorded in the reservoirs, sometimes reflected as transient increases in radioisotope activity in the renograms. In some patients the two kidneys differed considerably in their response to a full urinary bladder or reservoir. The cause may have been difference in the dynamics of the two ureterovesical junctions or of the ureterointestinal anastomoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of modern radiological investigations in obstructive uropathy

Obstructive uropathy in its various forms accounts for much of the work load in urological units and general hospitals. Until recently, laboratory tests and excretion urography were the only procedures available for its assessment. The past few years have seen the development and refinement of ultrasound, examination by computer tomography, nuclear medicine, antegrade pyelography, and perfusion pressure flow studies. This paper examines the particular qualities of these modern procedures and their role in the clinical assessment of the obstructed urinary tract.

The influence of renal prostaglandins on glomerular filtration rate (GFR) and calcium excretion in urolithiasis

In a clinical study of 275 idiopathic stone formers the GFR was significantly raised in hypercalciuric patients compared with normal controls P less than 0.001). The possibility that the mechanism underlying hypercalciuria and raised GFR may be prostaglandin-mediated was considered because it is now well established that prostaglandins regulate intra-renal haemodynamics and influence tubular electrolyte excretion. Experiments were performed in conscious Sprague Dawley rats to determine the changes in calcium and sodium excretion following prostaglandin synthetase inhibition with indomethacin. Both calcium and sodium excretion together with urine flow were significantly reduced (P less than 0.002). Further experiments were performed in anaesthetised monkeys (Macacca fascicularis) to see if the inhibitory effect of indomethacin was reversible. Exogenous prostaglandin (PGE2) infusion resulted in a marked calciuretic response without producing changes in GFR or blood pressure. Selected hypercalciuric patients were treated with indomethacin, which resulted in a significant fall in urinary calcium excretion (P less than 0.001). This clinical and experimental study suggests that PGE2 is the hormone which determines the renal handling of calcium by controlling renal tubular function.