Does delaying pyeloplasty affect renal function in children with a prenatal diagnosis of pelvi-ureteric junction obstruction?
Objective To evaluate retrospectively children with an antenatal diagnosis of pelvi-ureteric junction (PUJ) obstruction who required pyeloplasty for deteriorating renal function during the follow-up, specifically assessing the recovery of function after surgery.
Patients and methods Between 1988 and 2000, 44 consecutive patients with a prenatal diagnosis of PUJ obstruction who were initially treated by observation underwent pyeloplasty because their renal function deteriorated during the follow-up. Patients with bilateral disease, a single kidney or vesico-ureteric reflux were excluded from the study. The mean ( sd ) age of the patients was 13.3 (4.5) months and their mean (range) initial renal function 39.7 (30.4–45)%. In all patients the diagnostic criteria and indications for surgery were identical. The main indication for surgery was deteriorating renal function of >5%, confirmed by renal scintigraphy. Of 44 patients, 35 (77%) had severe dilatation of the renal pelvis by >3 cm. The mean ( sd ) deterioration in renal function during the follow-up, just before surgery, was 8.2 (2.4)%, and the mean time between the last acceptable renogram and the study showing deterioration was 8.3 (1.3) months; the mean follow-up was 5.1 (1.6) years. The results were assessed statistically using the unpaired nonparametric Mann–Whitney U -test.
Results An improvement in hydronephrosis was confirmed in all patients, with renal function returning to the initial levels in 36 of 44 (81%) patients 6–12 months after surgery, although in two patients renal function did not improve after surgery. There was no significant difference between the preoperative characteristics and the degree of hydronephrosis, renal function or patient age with the level of renal functional improvement after surgery.
Conclusion In patients with an antenatal diagnosis of PUJ obstruction, expectant management is recommended and spares the children unnecessary surgery. Even if renal function deteriorates, delayed pyeloplasty recovers the initial functional level.
The advent of routine antenatal ultrasonography enables urinary tract abnormalities to be identified as early as 12–14 weeks of gestation [1,2]. Maternal ultrasonography detects fetal hydronephrosis, leading to the diagnosis of PUJ obstruction postnatally in 0.2–0.4% of cases [1–5]; PUJ obstruction requires surgery in 15–30% of affected children [6–14]. Controversy continues on the optimal timing of the surgical correction in these children with antenatally detected hydronephrosis [7,8,14–17]. Children with an antenatal diagnosis of PUJ obstruction reportedly show a significant improvement in renal function after surgery compared with those who are diagnosed and operated much later because of their clinical symptoms . In early published series, King et al. encouraged immediate pyeloplasty, regardless of renal function, after obstruction was detected by diuretic renography. In recent years, Koff et al.[7,9,15] suggested that unilateral antenatal hydronephrosis caused by PUJ obstruction is a relatively benign condition requiring surgery only in highly selected cases. Despite numerous studies it remains unclear what improvement in renal function can be expected after pyeloplasty, and which patients will benefit from expectant management; this paper addresses these issues.
Patients and methods
Between 1988 and 2000, 272 children with PUJ obstruction were evaluated at our institutions; we retrospectively evaluated 44 consecutive patients (34 boys and 10 girls; mean age 13.3 months, sd 4.5) with a prenatal diagnosis of unilateral PUJ obstruction who were initially managed expectantly but underwent pyeloplasty for renal functional deterioration. Patients with bilateral disease, a single kidney, clinical symptoms or VUR were excluded from the study. The same diagnostic criteria were used in all patients from both institutions. The regimen of conservative follow-up was described elsewhere . Ultrasonography was used in the first week of life in those children with an antenatal diagnosis of hydronephrosis, with the examination repeated and radionuclide studies undertaken at 6–8 weeks old. Further examinations were tailored according to the findings of the initial studies. DTPA and recently MAG3 studies were used to assess perfusion during the initial 2 min, according to the absolute counts. The isotope washout curve was recorded after a bolus of 1 mg/kg frusemide was injected 10 min after administering the radionuclide . DTPA is excreted almost exclusively by filtration and provides accurate information about glomerular filtration in undilated kidneys. As the accuracy of this measurement in the presence of hydronephrosis and with kidney immaturity during the first 2 years of life is controversial, we now routinely use MAG3 in patients with hydronephrosis and deteriorated renal function; this agent is excreted mostly by the renal tubules and yields better images in infants with compromised renal function. DMSA scans were taken to assess the relative renal function, using background-corrected regions of interest of each kidney in the posterior view and calculating the resultant percentage uptake. The repeat ultrasonography was used to evaluate the degree of hydronephrosis, which was graded according to the Society for Fetal Urology (SFU) guidelines . The mean (range) initial renal function was 39.7 (30.4–45)%; in 35 of the 44 patients (77%), renal pelvis was dilated by >3 cm, with thinned parenchyma in a few (grade 3 and 4 SFU hydronephrosis). The indications for surgery were identical in all the patients; the main indication was deterioration of renal function by >5% during the follow-up, as determined by repeat DTPA or MAG3 and DMSA renal scans. The mean (sd) renal functional deterioration just before surgery was 8.2 (2.4)%. The mean (range) time between the last acceptable renogram and the study showing deterioration and indicating surgery was 8.3 (1.3) months. The clinical data are summarized in Table 1. Dismembered pyeloplasty was undertaken using the same technique by senior surgeons (P.P. and A.F.) or under their supervision. The mean (sd) follow-up was 5.1 (1.6) years. Changes in renal function and their correlation with preoperative variables were assessed statistically using the unpaired nonparametric Mann–Whitney U-test.
Table 1. The mean age, renal function and SFU grading of hydronephrosis
|No. (%) of patients|| 9 (20)||31 (70)|| 4 (10)|
|Mean age, months||17.2||13.6|| 9.5|
|Initial renal function, %||41.5||38.3||33.6|
|Renal function, %|
| before surgery||32.7||29.8||26.1|
| after surgery||41.1||38.8||31.9|
There were no major complications after pyeloplasty; all the patients had a significant improvement in kidney drainage on washout curves from radionuclide studies. Repeat ultrasonography showed a significant improvement in hydronephrosis in all 44 patients. At 6–12 months after surgery the radionuclide studies showed that 36 (81%) patients had a regained their initial level of renal function. The remaining six patients showed an improvement in renal function over 2 years after surgery. Thus, overall 42 of 44 (95%) patients had either stabilized (at the initial level) or even slightly improved renal function after surgery. In two patients the renal function remained poor after pyeloplasty. There was no correlation between the recovery of renal function and preoperative variables, e.g. patient age, SFU hydronephrosis grade and initial renal function.
The postnatal treatment of children with prenatally diagnosed hydronephrosis remains controversial in terms of the optimal timing of surgery, the ability to define which kidney will benefit from surgical intervention and which children will have a deterioration in renal function under surveillance [3–10]. The recovery of kidney function after either surgery or conservative management is the main issue in the treatment of patients with PUJ obstruction [6–9,15,16]. Recently there has been a trend away from aggressive surgery to a more conservative approach [14,15]. As a result of these reports, surgery is reserved for children who become symptomatic or who have deteriorating renal function during the follow-up. Recently Ulman et al. reported results of the initial conservative treatment of patients with severe hydronephrosis, indicating that in no patients was pyeloplasty undertaken for subjective reasons or for potential obstruction. All patients in the present study were initially treated expectantly, regardless not only of the degree of hydronephrosis but also of renal function. The mean renal function of all kidneys requiring pyeloplasty was 31% and renal function returned to their initial levels in all. The present findings strongly suggest that newborns with severe hydronephrosis can be safely treated conservatively. Renal function and hydronephrosis might improve during the first few years of life. If there is obstructive injury those who are followed closely can be identified easily and then treated with pyeloplasty. In contrast to the present study, others found no improvement in renal function after pyeloplasty. McAleer and Kaplan  noted that a third of patients with a prenatal diagnosis of PUJ obstruction and followed conservatively ultimately required pyeloplasty; the authors detected no recovery in renal function after surgery and suggested more aggressive treatment for patients with a prenatal diagnosis of PUJ obstruction. Cornford and Rickwood  reported no recovery of renal function among children initially followed expectantly and emphasized that loss of function could be avoided by early surgery. A crucial problem, reported by Dhillon , is distinguishing between children in whom function will be maintained and those in whom it will deteriorate. Dhillon indicated that measuring the degree of hydronephrosis by ultrasonography is most useful for identifying those requiring a close follow-up, and therefore recommended pyeloplasty at 6 months old in those children who have hydronephrosis of >50 mm diameter, while those with 20–50 mm of hydronephrosis and good renal function required only a close follow-up. Most authors acknowledge the importance of close surveillance, with a maximum interval between diagnostic tests of 3 months for the first 2 years of life, so that any obstruction can be relieved promptly and kidney damage avoided.
The present patients were divided into three groups by initial renal function: those with <30% relative renal function seem unlikely to benefit from expectant management and should undergo early surgery; those with moderate (30–40%) and good renal function (>40%) may be spared unnecessary surgery. Most of the present patients who required pyeloplasty initially had moderate renal function, but only 30% of all patients with PUJ obstruction in both institutions required pyeloplasty during the follow-up. Unfortunately the diagnostic tests are inaccurate in infancy and are invalid for predicting which kidney will deteriorate . Many diuretic renograms are false-positive and show tubular immaturity in the first 2 years of life. The surgical decisions in the present patients were based only on the results of repeated and reproducible diagnostic studies. All patients considered for expectant management should be assessed by ultrasonography and radionuclide studies every 3–6 months during first 2 years of life; as in almost all there will be either deterioration or stabilization of renal function during the first 2 years, these patients require only an annual examination afterwards. To avoid a subjective criterion we defined a deterioration in renal function as 5% on repeated studies to indicate pyeloplasty in these patients.
The duration of follow-up after surgery is also important; six of the 44 patients had improved renal function 2 years after surgery. We are aware that any improvement might also be related to kidney maturation rather than surgery, but the patients from all studies underwent surgery because renal function deteriorated rather than increased age. Also, it is important to determine for how long patients with asymptomatic hydronephrosis should be followed. Capolicchio et al. discussed the effect of a prenatal diagnosis of hydronephrosis on renal function after pyeloplasty, indicating that a median follow-up of 6 years was valid. In contrast others showed that most obstruction becomes reactivated during the first 2 years of life ; these hypotheses require further evaluation.
The preoperative assessment of which kidney with PUJ obstruction will be benefit from surgery remains unreliable. Zaccara et al. concluded that there was no correlation between currently adopted diagnostic tests, e.g. age at surgery, anteroposterior diameter of the pelvis and parenchymal thickness on ultrasonography, renal function and which kidney would benefit from surgery. Similarly, there was no statistical correlation between these variables and renal functional improvement in the present series. Further studies are needed to clarify which patients with antenatal hydronephrosis from PUJ obstruction will benefit from conservative management and which need early surgery. Appropriate selection is required to avoid any loss of renal function during expectant management.
In conclusion, the expectant management of patients with an antenatal diagnosis of PUJ obstruction is safe and avoids unnecessary surgery in most patients. Where renal function deteriorates during the follow-up, delayed pyeloplasty allows renal function to return to the initial level.
P. Puri, Children's Research Centre, Our Lady's Hospital for Sick Children, Crumlin, Dublin 12, Ireland.