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When to operate on neonatal hydronephrosis
EDITORIAL
WHEN TO OPERATE ON NEONATAL HYDRONEPHROSIS JOHN W. DUCKETT, JR., M.D. From the Division of Urology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
Prenatal ultrasound detects hydronephrosis in as many as 1.4 percent of fetuses, with it persisting postnatally in half.’ As this is a serendipitous finding, when to intervene surgically remains one of the most controversial issues in pediatric urology. Since surgical correction carries a high success rate with minimal morbidity in the neonate, it is very tempting to take an aggressive position of “conserving” all renal function that might be compromised by achieving optimum drainage early Admittedly, since our diagnostic techniques are not as precise as we would like, it is difficult to find a “comfort” level for the urologist when observing urinary dilatation in the neonate and hoping for its improvement.
Evaluation Our current recommendation is to use ultrasound on the baby at two days of life. If it is a male with hydronephrosis and a thick-walled bladder, urethral valves should be suspected; a voiding cystourethrogram and immediate attention are required. With persistent renal dilatation without bladder involvement, we wait for four to six weeks while transitional renal function improves dramatically and then perform a diethylenetriaminepenta-acetic acid (DTPA) scan usually with furosemide (Lasix) washout. At the same time, a conventional voiding cystourethrogram is done to detect and grade reflux. The babies are maintained on antibacterial prophylaxis prior to this six-week evaluation. In the case of unilateral hydronephrosis, a pyeloplasty is performed if the function is less than 35 percent. A repeat DTPA scan at three to six months compared with the neonatal scan in the babies operated on usually confirms anticipated improvement and confirms that the observational course was a good choice. At The Children’s Hospital of Philadelphia, the early uptake of technetium DTPA by each kidney is measured at three minutes and used to estimate individual renal function. The percent of the total
UROLOGY
/ DECEMBER1993 I VOLUME42, NUMBER6
isotope injected which is taken up by each kidney at three minutes, prior to any accumulation of isotope in the collecting system, is expressed as the “extraction factor.“2 For instance, in a two-week old baby, the total extraction factor for 9gTC DTPA should be greater than 2.5 percent, or 1.25 percent per kidney. For a one-year-old baby, it should be 2.5 percent for each or 5 percent total. Since we have accumulated thirteen years of data using 9gTC DTPA, we are reluctant to switch to MAG 3, a newer radionuclide used for renograms. In unilateral hydronephrosis, this is not as important as with bilateral hydronephrosis. If bilateral dilatations are present, a total extraction factor below the expected norm for that infant with a delayed furosemide washout will prompt us to perform bilateral pyeloplasties. The extraction factor study is particularly helpful in evaluating bilateral megaureters also. Excretory urography (IVU) has limitations in the neonate, but still has a role in demonstrating caliceal anatomy and the kinks and folds of the ureter in the older infant. Koff et a1.3 showed that pressure flow measurements, as with the Whitaker test, often reflect mainly the response of the renal pelvis to distention and that the test may be positive in the absence of obstruction. This is a convincing reason to avoid this invasive test in the evaluation of the neonate. Pathophysiology of the high incidence of transient dilatations in the neonate detected antenatally is explained well in the embryology section of our recent review article.4 We believe that the natural kinks and folds in the ureters that were described by Ostling in 19425 explain why hydronephrosis improves with time. “Hydronephrosis and hydroureters in the fetus are manifestations of a disturbance in normal growth and in differentiation and caliber. The boundary lines between physiological and pathological variations in the ureters and renal pelvis in the fetus are ureteral folds comvague. “5 These transverse monly seen at the ureteropelvic junction and
617
ureterovesical junction may disappear with time, and the dilatation may improve dramatically Indications for surgery when unilateral hydronephrosis presents with a percent function of less than 35 percent is our relative cutoff point for early intervention. It is nevertheless arbitrary. Ransley et aI have chosen 40 percent as a cutoff point. Koff,7 on the other hand, has demonstrated in a group of patients with an average of 25 percent of total renal function in the dilated kidney that there was improvement to better than 40 percent of total function in all cases without surgery In our series, 85 percent of the patients we followed improved their extraction factor while 15 percent (6 patients) required surgical intervention for decreasing function, urinary tract infection, or otherwise unexplained colic.* The eventual differential renal function improvement in these patients was no different than a group of 12 patients who were agematched with greater than 35 percent function but who had undergone pyeloplasty at an earlier date. Bilateral hydronephrosis, however, is a different entity Differential functions (EF) will indicate if both kidneys are depressed and with furosemide washout delay will guide us to bilateral pyeloplasty T-‘/2 for Lasix This is usually done simultaneously washout has not been a reliable marker for surgical intervention in the neonate. The accumulation of isotope in the dilated collecting system is quite variable so that the timing of the Lasix stimulus may easily be premature or delayed in regard to maximum isotope excretion. Thus, the standard T’/2 greater than twenty-minute cutoff for “obstruction” is often misleading. When function is very poor, we have not felt that percutaneous drainage of a kidney preoperatively to determine the return of function is warranted. In these cases, we proceed with a pyeloplasty, taking a biopsy of the kidney at the beginning of the case. While the pathologist is processing the biopsy, the pyeloplasty is completed. The histology determines whether we do a nephrectomy or leave the kidney. If a poorly functioning kidney is left, we place a drainage tube for assessment of the anatomy with contrast media in follow-up. A recent review of our experience with ureteropelvic junction obstruction at Children’s Hospital of Philadelphia over ten years (1982-1993) showed that 43 percent of neonates (70 of 163) with antenatally diagnosed hydronephrosis had surgical correction.9 All had good results with improved function with no complications. Only one was treated by nephrectomy. In the postnatally diagnosed group (139), 85 percent (119) had surgi-
618
cal correction. Three cases (2.6%) came to reoperation, but only 1 had renal deterioration. These overall excellent results, however, do not justify an operation for prophylactic indications. If we look at the last five years’ experience compared with the previous five years, we see that our “comfort level” has changed. The pyeloplasty rate in the neonates was only 40 percent in the last five years while it was 60 percent before.9 The early pyeloplasty advocates argue that early relief of obstruction will lessen the stimulus for contralateral compensatory hypertrophy. However, the clinical support for this theoretical consideration is still lacking.4J0 King et al. in 198411 reported on 11 patients less than three months old who underwent pyeloplasty and compared the relative increase in renal function with that of older patients undergoing pyeloplasty. The mean increase in relative function was 19 percent in the younger patients compared with only 4.6 percent in the older group. However, the final relative function values were 36.5 and 32.5, respectively; not a significant difference. The larger increase noted in the younger group only reflects the expected maturation in renal function with age, not that early surgical intervention is better. For infants with hydronephrosis secondary to ureterovesical junction narrowing, or possible primary obstructed megaureter, similar recommendations are presently made. In these cases, impressive dilatation of the ureters have resolved. In our series of 34 renal units, only 6 percent required operation for diminishing renal function.12 Early surgical intervention, however, is clearly indicated in other obstructive causes of neonatal hydronephrosis such as ureterocele, ectopic ureter, or urethral valves. The debate concerning early surgical correction of neonatal hydronephrosis is less of an issue today than it was ten years ago. This is due to our current extensive experience with observation of significant dilatation of the pelvis and calices in the presence of reasonable renal function detected by 9gTC DTPA scans or MAG 3. Since our “comfort” level is now based on more experience, we are on firmer ground in opposing those who wish to make the x-ray film look better, preserve every possible nephron from deterioration, and avoid the theoretical consequences of renal compensatory hypertrophy by subjecting a lot of neonates with dilated kidneys to surgery that might not be necessary As Frank Hinman, Sr., showed years ago with the counterbalance theory of the two-kidney model, when one side is “hurting,” its function
UROLOGY
/ DECEMBER 1993 I VOLUME42, NUMBER6
will be taken over by its mate; the hurting side will recover once the obstruction is corrected. Claesson et ~1.‘~ have shown with the reflux nephropathy model that the “good” kidney will demonstrate hypotrophy when the scarred kidney begins to grow. We believe the same process is occurring in the hydronephrosis model with two kidneys. On the other hand, when a spot check of renal function is made in a patient with a solitary kidney with partial obstruction, its moment-bymoment measure of function is quite variable.14 Our renal function studies today are not valid in this setting and may give us a false sense of confidence. There is, therefore, still more of an indication to repair a solitary kidney with a partial UPJ obstruction. John
W. Duckett,
Jr., M.D.
Division of Urology Children’s Hospital
of Philadelphia Philadelphia,
Pennsylvania
REFERENCES 1. Livera LN, Brookfield DS, Egginton JA, and Hawnaur JM: Antenatal ultrasonography to detect fetal renal abnormalities: a prospective screening programme. BMJ 298: 1421-1423,1989. 2. Heyman S, and Duckett JW: The extraction factor: an estimate of single kidney function in children during routine radionuclide renography with 99’” technetium-diethylenetriaminepenta-acetic acid. J Urol 140: 780-783, 1988.
UROLOGY
/ DECEMBER1993 / VOLUME42, NUMBER6
3. Koff SA, Hayden LJ, Cirulli C, and Shore R: Pathophysiology of ureteropelvic junction obstruction: experimental and clinical observations. J Urol 136: 336-338, 1986. 4. Blyth B, Snyder HM, and Duckett JW: Antenatal diagnosis and subsequent management of hydronephrosis. J Urol 149: 693-698,1993. 5. &tling K: The genesis of hydronephrosis particularly with regard to the changes at the ureteropelvic junction. Acta Chir Stand (Suppl72) 86: 1, 1942. 6. Ransley PG, Dhillon HK, Gordon I, Duffy PG, Dillon MJ, and Barratt TM: The postnatal management of hydronephrosis diagnosed by prenatal ultrasound. J Ural 144: 584-587,199O. 7. Koff SA: The case for nonoperative management of apparent UPJ obstruction. Dial Pediatr Urol 14: l-8, 1991. 8. Cartwright PC, Duckett JW, Keating MA, Snyder HM, Escala J, Blyth B, and Heyman S: Managing apparent ureteropelvic junction obstruction in the newborn. J Urol 148: 122+1228,1992. 9. Canning D, et al: Unpublished data. 10. Chevalier RL, and El Dahr S: The case for early relief of obstruction in young infants, in King LR (Ed): Urologic Surgery in the Neonates and Young Infants, Philadelphia, WB Saunders Co, chap 6, pp 95-l 18,1988. 11. King LR, Couglin PW, Bloch EC, Bowie JD, Ansong K, and Hanna MK: The case for immediate pyeloplasty in the neonate with ureteropelvic junction obstruction. J Urol 132: 725-728,1984. 12. Keating MA, Escala J, Snyder HM 3rd, Heyman S, and Duckett JW: Changing concepts in management of primary obstructive megaureter. J Ural 142: 636-640, 1989. 13. Claesson 1, Jacobsson B, and Riha M: A computerized system for handling renal size measurements for urograms. Pediatr Radio1 17: 459462, 1987. 14. Zderic S, et al: The extraction factor renal scan and GFR measurements in solitary kidneys. Unpublished data.
619
WHEN TO OPERATE ON NEONATAL HYDRONEPHROSIS JOHN W. DUCKETT, JR., M.D. From the Division of Urology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
Prenatal ultrasound detects hydronephrosis in as many as 1.4 percent of fetuses, with it persisting postnatally in half.’ As this is a serendipitous finding, when to intervene surgically remains one of the most controversial issues in pediatric urology. Since surgical correction carries a high success rate with minimal morbidity in the neonate, it is very tempting to take an aggressive position of “conserving” all renal function that might be compromised by achieving optimum drainage early Admittedly, since our diagnostic techniques are not as precise as we would like, it is difficult to find a “comfort” level for the urologist when observing urinary dilatation in the neonate and hoping for its improvement.
Evaluation Our current recommendation is to use ultrasound on the baby at two days of life. If it is a male with hydronephrosis and a thick-walled bladder, urethral valves should be suspected; a voiding cystourethrogram and immediate attention are required. With persistent renal dilatation without bladder involvement, we wait for four to six weeks while transitional renal function improves dramatically and then perform a diethylenetriaminepenta-acetic acid (DTPA) scan usually with furosemide (Lasix) washout. At the same time, a conventional voiding cystourethrogram is done to detect and grade reflux. The babies are maintained on antibacterial prophylaxis prior to this six-week evaluation. In the case of unilateral hydronephrosis, a pyeloplasty is performed if the function is less than 35 percent. A repeat DTPA scan at three to six months compared with the neonatal scan in the babies operated on usually confirms anticipated improvement and confirms that the observational course was a good choice. At The Children’s Hospital of Philadelphia, the early uptake of technetium DTPA by each kidney is measured at three minutes and used to estimate individual renal function. The percent of the total
UROLOGY
/ DECEMBER1993 I VOLUME42, NUMBER6
isotope injected which is taken up by each kidney at three minutes, prior to any accumulation of isotope in the collecting system, is expressed as the “extraction factor.“2 For instance, in a two-week old baby, the total extraction factor for 9gTC DTPA should be greater than 2.5 percent, or 1.25 percent per kidney. For a one-year-old baby, it should be 2.5 percent for each or 5 percent total. Since we have accumulated thirteen years of data using 9gTC DTPA, we are reluctant to switch to MAG 3, a newer radionuclide used for renograms. In unilateral hydronephrosis, this is not as important as with bilateral hydronephrosis. If bilateral dilatations are present, a total extraction factor below the expected norm for that infant with a delayed furosemide washout will prompt us to perform bilateral pyeloplasties. The extraction factor study is particularly helpful in evaluating bilateral megaureters also. Excretory urography (IVU) has limitations in the neonate, but still has a role in demonstrating caliceal anatomy and the kinks and folds of the ureter in the older infant. Koff et a1.3 showed that pressure flow measurements, as with the Whitaker test, often reflect mainly the response of the renal pelvis to distention and that the test may be positive in the absence of obstruction. This is a convincing reason to avoid this invasive test in the evaluation of the neonate. Pathophysiology of the high incidence of transient dilatations in the neonate detected antenatally is explained well in the embryology section of our recent review article.4 We believe that the natural kinks and folds in the ureters that were described by Ostling in 19425 explain why hydronephrosis improves with time. “Hydronephrosis and hydroureters in the fetus are manifestations of a disturbance in normal growth and in differentiation and caliber. The boundary lines between physiological and pathological variations in the ureters and renal pelvis in the fetus are ureteral folds comvague. “5 These transverse monly seen at the ureteropelvic junction and
617
ureterovesical junction may disappear with time, and the dilatation may improve dramatically Indications for surgery when unilateral hydronephrosis presents with a percent function of less than 35 percent is our relative cutoff point for early intervention. It is nevertheless arbitrary. Ransley et aI have chosen 40 percent as a cutoff point. Koff,7 on the other hand, has demonstrated in a group of patients with an average of 25 percent of total renal function in the dilated kidney that there was improvement to better than 40 percent of total function in all cases without surgery In our series, 85 percent of the patients we followed improved their extraction factor while 15 percent (6 patients) required surgical intervention for decreasing function, urinary tract infection, or otherwise unexplained colic.* The eventual differential renal function improvement in these patients was no different than a group of 12 patients who were agematched with greater than 35 percent function but who had undergone pyeloplasty at an earlier date. Bilateral hydronephrosis, however, is a different entity Differential functions (EF) will indicate if both kidneys are depressed and with furosemide washout delay will guide us to bilateral pyeloplasty T-‘/2 for Lasix This is usually done simultaneously washout has not been a reliable marker for surgical intervention in the neonate. The accumulation of isotope in the dilated collecting system is quite variable so that the timing of the Lasix stimulus may easily be premature or delayed in regard to maximum isotope excretion. Thus, the standard T’/2 greater than twenty-minute cutoff for “obstruction” is often misleading. When function is very poor, we have not felt that percutaneous drainage of a kidney preoperatively to determine the return of function is warranted. In these cases, we proceed with a pyeloplasty, taking a biopsy of the kidney at the beginning of the case. While the pathologist is processing the biopsy, the pyeloplasty is completed. The histology determines whether we do a nephrectomy or leave the kidney. If a poorly functioning kidney is left, we place a drainage tube for assessment of the anatomy with contrast media in follow-up. A recent review of our experience with ureteropelvic junction obstruction at Children’s Hospital of Philadelphia over ten years (1982-1993) showed that 43 percent of neonates (70 of 163) with antenatally diagnosed hydronephrosis had surgical correction.9 All had good results with improved function with no complications. Only one was treated by nephrectomy. In the postnatally diagnosed group (139), 85 percent (119) had surgi-
618
cal correction. Three cases (2.6%) came to reoperation, but only 1 had renal deterioration. These overall excellent results, however, do not justify an operation for prophylactic indications. If we look at the last five years’ experience compared with the previous five years, we see that our “comfort level” has changed. The pyeloplasty rate in the neonates was only 40 percent in the last five years while it was 60 percent before.9 The early pyeloplasty advocates argue that early relief of obstruction will lessen the stimulus for contralateral compensatory hypertrophy. However, the clinical support for this theoretical consideration is still lacking.4J0 King et al. in 198411 reported on 11 patients less than three months old who underwent pyeloplasty and compared the relative increase in renal function with that of older patients undergoing pyeloplasty. The mean increase in relative function was 19 percent in the younger patients compared with only 4.6 percent in the older group. However, the final relative function values were 36.5 and 32.5, respectively; not a significant difference. The larger increase noted in the younger group only reflects the expected maturation in renal function with age, not that early surgical intervention is better. For infants with hydronephrosis secondary to ureterovesical junction narrowing, or possible primary obstructed megaureter, similar recommendations are presently made. In these cases, impressive dilatation of the ureters have resolved. In our series of 34 renal units, only 6 percent required operation for diminishing renal function.12 Early surgical intervention, however, is clearly indicated in other obstructive causes of neonatal hydronephrosis such as ureterocele, ectopic ureter, or urethral valves. The debate concerning early surgical correction of neonatal hydronephrosis is less of an issue today than it was ten years ago. This is due to our current extensive experience with observation of significant dilatation of the pelvis and calices in the presence of reasonable renal function detected by 9gTC DTPA scans or MAG 3. Since our “comfort” level is now based on more experience, we are on firmer ground in opposing those who wish to make the x-ray film look better, preserve every possible nephron from deterioration, and avoid the theoretical consequences of renal compensatory hypertrophy by subjecting a lot of neonates with dilated kidneys to surgery that might not be necessary As Frank Hinman, Sr., showed years ago with the counterbalance theory of the two-kidney model, when one side is “hurting,” its function
UROLOGY
/ DECEMBER 1993 I VOLUME42, NUMBER6
will be taken over by its mate; the hurting side will recover once the obstruction is corrected. Claesson et ~1.‘~ have shown with the reflux nephropathy model that the “good” kidney will demonstrate hypotrophy when the scarred kidney begins to grow. We believe the same process is occurring in the hydronephrosis model with two kidneys. On the other hand, when a spot check of renal function is made in a patient with a solitary kidney with partial obstruction, its moment-bymoment measure of function is quite variable.14 Our renal function studies today are not valid in this setting and may give us a false sense of confidence. There is, therefore, still more of an indication to repair a solitary kidney with a partial UPJ obstruction. John
W. Duckett,
Jr., M.D.
Division of Urology Children’s Hospital
of Philadelphia Philadelphia,
Pennsylvania
REFERENCES 1. Livera LN, Brookfield DS, Egginton JA, and Hawnaur JM: Antenatal ultrasonography to detect fetal renal abnormalities: a prospective screening programme. BMJ 298: 1421-1423,1989. 2. Heyman S, and Duckett JW: The extraction factor: an estimate of single kidney function in children during routine radionuclide renography with 99’” technetium-diethylenetriaminepenta-acetic acid. J Urol 140: 780-783, 1988.
UROLOGY
/ DECEMBER1993 / VOLUME42, NUMBER6
3. Koff SA, Hayden LJ, Cirulli C, and Shore R: Pathophysiology of ureteropelvic junction obstruction: experimental and clinical observations. J Urol 136: 336-338, 1986. 4. Blyth B, Snyder HM, and Duckett JW: Antenatal diagnosis and subsequent management of hydronephrosis. J Urol 149: 693-698,1993. 5. &tling K: The genesis of hydronephrosis particularly with regard to the changes at the ureteropelvic junction. Acta Chir Stand (Suppl72) 86: 1, 1942. 6. Ransley PG, Dhillon HK, Gordon I, Duffy PG, Dillon MJ, and Barratt TM: The postnatal management of hydronephrosis diagnosed by prenatal ultrasound. J Ural 144: 584-587,199O. 7. Koff SA: The case for nonoperative management of apparent UPJ obstruction. Dial Pediatr Urol 14: l-8, 1991. 8. Cartwright PC, Duckett JW, Keating MA, Snyder HM, Escala J, Blyth B, and Heyman S: Managing apparent ureteropelvic junction obstruction in the newborn. J Urol 148: 122+1228,1992. 9. Canning D, et al: Unpublished data. 10. Chevalier RL, and El Dahr S: The case for early relief of obstruction in young infants, in King LR (Ed): Urologic Surgery in the Neonates and Young Infants, Philadelphia, WB Saunders Co, chap 6, pp 95-l 18,1988. 11. King LR, Couglin PW, Bloch EC, Bowie JD, Ansong K, and Hanna MK: The case for immediate pyeloplasty in the neonate with ureteropelvic junction obstruction. J Urol 132: 725-728,1984. 12. Keating MA, Escala J, Snyder HM 3rd, Heyman S, and Duckett JW: Changing concepts in management of primary obstructive megaureter. J Ural 142: 636-640, 1989. 13. Claesson 1, Jacobsson B, and Riha M: A computerized system for handling renal size measurements for urograms. Pediatr Radio1 17: 459462, 1987. 14. Zderic S, et al: The extraction factor renal scan and GFR measurements in solitary kidneys. Unpublished data.
619