Diuretic Renal Scan Research Articles

Diuretic Renal Scan: Is It Always Reliable?

The differentiation between significant mechanical obstruction and nonobstructive dilation of the kidneys and ureters is fundamental to patient management. The diuretic renal scan is a useful test in this situation because it usually is reliable and reproducible and is noninvasive and objective, providing information about the function of each kidney. However, this study has given variable results in a small number of patients. We report our experience with five such patients and recommend an algorithm for evaluating patients with equivocal scan results. This report emphasizes the importance of continued follow-up and the need for periodic reevaluation of patients with unexplained urinary symptoms or persistent flank pain, even when the initial diuretic renal scan is normal.

Diuretic Renography in the Evaluation of Neonatal Hydronephrosis: is it Reliable?

Arguments against the use of diuretic renography in the assessment of newborn hydronephrosis include immature function of neonatal kidneys, previously reported poor diuretic response and nonreproducible drainage patterns. To address these concerns we reviewed the initial and followup renal scans of 17 neonates with hydronephrosis without ureterectasis diagnosed by perinatal ultrasonography. All patients were evaluated with an initial diuretic renal scan up to the age of 28 days, and all had normal cystograms. A total of 19 dilated kidneys was studied of which 13 ultimately required pyeloplasty and 6 were managed nonsurgically. Patient study parameters included age and weight at the time of each renal scan, side of hydronephrosis, differential function of each kidney, pre-diuretic and post-diuretic urine output, and drainage half-time of each kidney. The diuretic renal scans followed a standardized protocol.There was no statistically significant difference between neonatal and followup differential function (p>0.05), and the correlation coefficient was highly significant (r = 0.968). Comparison of response to diuretic stimulation (ml./kg. per minute) revealed no statistically significant difference as the patients aged with brisk urine output 3 to 5 times greater than previously reported. The distribution and mean drainage half-times for normal nonhydronephrotic kidneys were similar when comparing those performed as neonates and at followup. Hydronephrotic kidneys managed nonsurgically maintained almost identical patterns. Those repaired surgically demonstrated appropriate improvement in drainage but function remained unchanged. These results refute each of the criticisms against the use of diuretic renography to evaluate neonatal hydronephrosis and demonstrate its reliability in neonates.

Endopyelotomy and endoureterotomy with the acucise ureteral cutting balloon device: preliminary experience.

Endoureterotomy and endopyelotomy usually involve an endoscopic antegrade approach. In an effort to simplify this technique, we designed an 8-mm balloon catheter with a 100-microns electrocautery cutting wire (Acucise) for retrograde incision of the ureter under fluoroscopic control. Twenty-eight patients with ureteral or ureteropelvic junction obstruction of 3.5 cm or less underwent Acucise endoureterotomy or endopyelotomy. The average operating time was 100 minutes, and the average hospital stay was 2.6 days. Follow-up was obtained with a subjective symptom score, intravenous urography, diuretic renal scan, a Whitaker test, or various combinations thereof. All patients had a minimum of 3 months of follow-up (mean 3.8 months; range 3-9 months). Overall, of the 21 patients who had symptoms of upper tract urinary obstruction, 14 (67%) had complete resolution, and another 4 (19%) had partial resolution, of their symptoms. Postoperative studies demonstrated normal upper tracts in 71% and improvement in another 14% of the patients. In our experience, the Acucise ureteral cutting balloon device provides an effective and efficient means for performing a retrograde endoureterotomy or endopyelotomy.

Urinary Tract Obstruction and Infection in the Neonate

Congenital urinary tract obstruction is a common cause of renal failure accounting for up to 20% of end-stage renal disease cases. Intrauterine obstruction often results in parenchymal loss and renal dysfunction. The pathophysiology of obstructive nephropathy and its further depression of renal function is related to severe renal vasoconstriction, which is in large part angiotensin mediated. Signs suggestive of urinary obstruction in the newborn may include an abdominal mass, hypertension, oligoanuria/polyuria, urosepsis, and hyperchloremic acidosis. The combination of renal ultrasound, diuretic renal scans, and voiding cystourethrogram are the main diagnostic modalities in infants with hydronephrosis. Nonsurgical management of ureteropelvic junction obstruction has become more popular, particularly in mild to moderate cases. Early fulguration or bypassing the obstruction of urethral valves is essential and a decrease in serum creatinine to below 1 mg/dL within 1 month of relief of obstruction is a favorable prognostic sign. Obstruction complicated by infection is dangerous and requires prompt intervention. Any newborn with a urinary tract infection, regardless of sex, should be presumed to have urinary obstruction or reflux until proven otherwise.

Renal dynamics after pyeloplasty.

Dismembered pyeloplasty was done on 12 renal units for ureteropelvic junction obstruction. Postoperatively, response of repaired kidney to standard diuretic dose of furosemide (0.3 mg/kg) was evaluated. Also renal pelvic pressures at rest and during diuresis were measured. All renal units responded to the diuretic by increasing their urine output an average of three times over baseline value. Renal pelvic pressure registration revealed no significant change after diuresis over baseline values. Diuretic technetium-99 DTPA renal scans were obtained two to six months postoperatively and compared with preoperative scans; the best results were obtained in renal units whose intrapelvic pressures did not exceed 10 cm of water in the immediate postoperative period.

Diagnostic potential of diuresis renography

Eighty ureterorenal units (65 patients) with upper urinary tract dilatation underwent pressure perfusion studies and diuresis renographies separated by short intervals. Pressure perfusion studies were evaluated as suggested by Whitaker, while wash-out curves of diuretic renographies were analysed quantitatively by calculating peak elimination rates. Upper urinary tract volume was estimated from i.v. urographies and measured directly in 21 cases. Renal function was assessed from base-line renograms and plasma creatinine levels. In patients with minor upper urinary tract dilatation (less than 30 ml) the two procedures agreed in 88% of cases, in those with massive dilatation (greater than 70 ml) agreement was limited to 58%. Diuretic renal scans were more often obstructed than pressure perfusion studies in the latter situation. The effect of severely reduced renal function was less prominent than that of massive dilatation. This was confirmed by the exaggerated response to frusemide reflected by urinary flow measurements in patients with a creatinine clearance of 10 ml min-1 or less. Of the eight patients with severely reduced renal function, who did not show full agreement between the procedures, six had massive dilatation of the upper urinary tract.

Volume Expansion Diuretic Renal Scan in Urinary Tract Obstruction

The diuretic renal scan is used to differentiate the obstructed dilated urinary system from the nonobstructed dilated system. The technique, however, has a false-positive and indeterminate rate of 10%-15%. This usually is due to variables such as the degree of dilatation of the pelvicalyceal system or ureter, the degree of bladder distention, the diuretic dose, and the state of hydration. We developed the volume expansion diuretic renal scan (VEDRS) to overcome these variables and to improve the accuracy of the technique. Twelve patients who had obstructive patterns on the diuretic renal scan were evaluated. Ten patients were shown to be dilated but not obstructed. Two patients were confirmed as obstructed. This technique improves the accuracy of the diuretic renal scan.

Evaluation and Management of Upper Urinary Tract Obstruction in Infancy and Childhood

Our clinical experience over the past 5 years would suggest that both the diuretic renogram and the Whitaker study permit an objective and quantitative assessment of urinary obstruction. The diagnostic accuracy of both studies exceeds 90 per cent, although neither study has proved to be infallible. Both have potential sources of error that must be monitored carefully if their reliability is to be maximized. Potential sources of error in the diuretic renogram include the state of hydration, renal functional status, distensibility and volume of the collecting system, a filled bladder, and ability to respond to the diuretic. Its reliability can be increased if the standard testing protocol is followed, the study closely monitored, and the limitations of the test realized. Interpretation of the diuretic renogram based only upon the appearance of the washout curve without consideration of the calculated half time or the sequential analogue images is unreliable and in our experience would have been responsible for an incorrect interpretation in 40 per cent of patients. The diuretic renal scan is used as the initial testing modality because it is reliable, reproducible, noninvasive, and objective and provides important information concerning individual renal function. Over 80 per cent of children with hydronephrosis can be completely evaluated by the diuretic renogram alone without the need for more invasive testing modalities. Nevertheless, the pressure perfusion study will continue to be necessary for the evaluation of certain individuals. Because of its invasive nature, we prefer to reserve this study for very specific, well-defined circumstances.(ABSTRACT TRUNCATED AT 250 WORDS)