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Abstract

Objective:

Micturating cystourethrogram (MCUG) has traditionally been recommended as part of the preoperative evaluation of all cases of hydronephrosis. Several studies have shown that the majority of cases with pelviureteric junction obstruction (PUJO) and concomitant vesicoureteral reflux (VUR) were of low-grade and generally resolved spontaneously. We therefore retrospectively evaluated the need for routine MCUG in all cases of PUJO.

Methods:

We conducted a retrospective review of clinical records of all patients who underwent pyeloplasty in our institution between 2003 and 2015. Data collected included patient demographics, clinical presentation, radiological procedures performed, operative details as well as postoperative outcomes.

Results:

A total of 119 patients underwent pyeloplasty for PUJO during this study period. MCUG was performed in 88 patients (74%), of whom eight patients had VUR. All eight patients had unilateral PUJO and two patients had bilateral VUR. Only two patients had high-grade VUR (grade 4). These two patients also had hydroureter detected on ultrasound scan (US). All patients with VUR had spontaneous resolution of reflux. While comparing outcomes for patients with and without VUR, there was no statistically significant difference in terms of the need for redo surgery and improvement in differential renal function post-pyeloplasty.

Conclusion:

The outcome of pyeloplasty appears to be independent of the presence of concomitant VUR. Therefore, we conclude that MCUG does not need to be performed routinely for all PUJO patients. However, patients with history of recurrent urinary tract infection or findings of hydroureter on US should still be investigated with MCUG.

Keywords

Pelviureteric junction obstruction micturating cystourethrogram vesicoureteric reflux pyeloplasty

Introduction

Approximately 11%–14% of patients with pelviureteric junction obstruction (PUJO) have concomitant vesicoureteral reflux (VUR), and it has been reported that the successful management of PUJO may be compromised by concomitant VUR.^1,2 Therefore, micturating cystourethrogram (MCUG) has traditionally been recommended as part of the preoperative evaluation of all cases of hydronephrosis.^1,3 However, MCUG is not without its own inherent problems. Besides radiation exposure, MCUG is an invasive procedure that can cause pain or discomfort, trigger fear and anxiety in the patient, as well as cause urinary tract infection (UTI). Furthermore, several studies have shown that the majority of cases of PUJO with concomitant VUR were of low grade^1,2 and generally resolve spontaneously and hence have no clinical impact on management. We therefore retrospectively evaluated the need for routine MCUG in all cases of hydronephrosis secondary to PUJO in our population.

Methods

Clinical records of all patients with PUJO who had undergone pyeloplasty in our institution between 2003 and 2015 were retrospectively reviewed. Data collected included patient demographics, clinical presentation, radiological procedures performed, operative details as well as postoperative outcomes.

Hydronephrosis was graded according to the Society for Fetal Urology (SFU) grading system.⁴ VUR was graded using the International Reflux Study Committee classification.⁵ Indications for pyeloplasty in our institution include one or more of the following: worsening hydronephrosis, a drop in differential renal function (DRF) or a Technetium-99m mercaptoacetyltriglycine scan (MAG3) confirming complete blockage at the level of the pelviureteric junction (PUJ). All patients underwent ultrasound (US) and MAG3 at 6–12 weeks of age when hydronephrosis was antenatally diagnosed. As part of routine follow-up, a MAG3 scan was performed six to nine months post-pyeloplasty. At our institution, the patient with PUJO presenting in the neonatal period is typically managed by the Neonatologist or Renal physician and are subsequently referred to the Paediatric Urologist only when the PUJO becomes significant. The choice of imaging depends on physician and surgeon preference, which may or may not include an MCUG.

Anderson-Hynes dismembered pyeloplasty was performed in all patients either through a flank incision or laparoscopically. An indwelling urethral catheter (IDC) and a double-J (DJ) stent were inserted in all cases. The IDC was removed once close monitoring of urine output in the setting of postobstructive diuresis was no longer required. The DJ stent was removed under general anaesthesia six to eight weeks post-pyeloplasty. All male children were circumcised at the time of pyeloplasty.

Successful pyeloplasty was defined as resolution of urinary flow obstruction at the PUJ on postoperative MAG3. Failure of pyeloplasty was defined as the need for a redo procedure based on the persistence or recurrence of obstruction at the level of the PUJ as demonstrated on MAG3.

All patients with concomitant VUR on MCUG were analysed in relation to clinical presentation, postoperative outcome, presence of UTI or the need for redo pyeloplasty. UTI was defined as a positive urine culture, with or without accompanying symptoms. Patients with complex urological abnormalities such as duplex systems, and pyeloplasty operated for causes other than PUJO such as proximal ureteral obstruction (stenosis, ureteral polyp) were excluded from this study.

Statistical analysis was performed using SPSS 19.0 software. Data are reported as mean ± standard deviation (SD). Chi square test was used for detecting statistical difference for categorical variables and unpaired student t test was used for continuous variables. A p value of < 0.05 was considered statistically significant.

Institutional review board approval was obtained and all study procedures were conducted in accordance to the stipulated ethical standards.

Results

A total of 119 patients underwent pyeloplasty for the preoperative diagnosis of PUJO in our institution during the study period. The median age at surgery was 12.5 months (range 2–192 months). Patient demographics and characteristics are detailed in Table 1. MCUG was performed in 88 patients (74%), of whom eight patients had VUR. The mean follow-up was 82 months (20–167 months). The final outcome of all the patients (with and without VUR) is summarised in Figure 1.

Table 1.

Comparison of patients with PUJO who had MCUG to those who did not have MCUG done.

	MCUGn = 88	No MCUGn = 31	p value
Age at pyeloplasty (months)^a	15 (2–192)	12 (2–182)	NS
Gender (male:female)	72:16 (82%:18%)	23:8 (74%:26%)	NS
Disease involvement (unilateral:bilateral)	84:4 (95%:5%)	29:2 (94%:6%)	NS
Laterality of disease (left:right:bilateral)	65:19:4 (74%:21%:5%)	20:11:0 (65%:35%:0%)	NS
Antenatal presentation	67 (76%)	17 (55%)	NS
History of urinary tract infection	35 (40%)	12 (39%)	NS
Redo pyeloplasty	3 (3%)	3 (10%)	NS

Data: median (range).

Figure 1.

Outcomes of patients with PUJO.

VUR

Of the patients that had a preoperative MCUG, concomitant VUR (on the same side as the PUJO) was diagnosed in eight patients (6.7%). All eight patients had unilateral PUJO but two of them had bilateral VUR (Table 2). Only two patients had high-grade VUR (defined as grade 4 and above), and both had hydroureter on US. All other patients (grade 3 and below) had normal ureters on US.

Table 2.

Characteristics of patients with PUJO and VUR.

Patient	Age at diagnosis of VUR (months)	Laterality	Grade of VUR	Interval to resolution of VUR (months)	Age at diagnosis of PUJO (months)
1	2	Left	III	40	44
2	2	Left	I^a	NA	8
3	52	Left	II	2	54
4	1	Left	II	12	119
5	3	Left	III	21	47
6	2	Left^b Right	IV III	32	36
7	2	Right	I^a	NA	22
8	2	Left^b Right	IV III	48	57

MCUG: micturating cystourethrogram; PUJO: pelviureteric junction obstruction; VUR: vesicoureteral reflux.

NA: no repeat MCUG performed for Grade 1 VUR.

PUJO side.

Despite concomitant VUR, six out of eight patients had spontaneous resolution of the reflux within 48 months from diagnosis of VUR as demonstrated on repeat MCUG, which was also prior to pyeloplasty surgery (Table 3). Two of these eight patients (Patient 2 and 7) had only grade 1 VUR and no repeat MCUG. Both patients did not subsequently develop complications secondary to VUR and were assumed to have had spontaneous resolution.

Table 3.

Comparison of patients with and without VUR on MCUG.

	VUR(n = 8)	No VUR(n = 84)	p value
Antenatal presentation	5 (62.5%)	66 (78.5%)	NS
History of urinary tract infection	5 (62.5%)	33 (39.3%)	NS
Preoperative DRF (%)^a	31.9 (20.9)^b	43.6 (12.9)^b	NS
Improvement of DRF post-pyeloplasty (%)^a	7.7 (68.5)^b	8.4 (44.7)^b	NS
Redo pyeloplasty	0	3 (3.6%)	NS

DRF: differential renal function; VUR: vesicoureteral reflux.

One patient with a single kidney was excluded from analysis, leaving eight patients with VUR.

Data: mean (standard error of mean).

History of UTI was noted in 62.5% of patients with VUR but only in 39.3% of patients without VUR (Table 3). However, this did not reach statistical significance. All cases had successful pyeloplasty, and no documented episodes of UTI post-pyeloplasty.

Redo pyeloplasty

Of the 123 kidneys, there were six (4.8%) failed pyeloplasties. Of these six failures, MCUG was performed in three, and were negative for VUR. The causes of these failures were re-stenosis in two cases, a ‘twisted’ PUJ in one case, extramural adhesions in two cases, and redundant renal pelvis with poor drainage in one case.

DRF

At last follow-up, the mean improvement in DRF post-pyeloplasty was 8.3%. When comparing PUJO patients with and without VUR, we found that there was no statistical significant difference in baseline preoperative DRF and improvement in DRF post-pyeloplasaty between these groups (Table 3). Patients who had no MCUG performed and one patient with a solitary kidney were excluded from this subgroup analysis.

We also compared patients with no MCUG with patients with MCUG and no VUR, and we found that there was no statistical significant difference in baseline preoperative DRF and improvement in DRF post-pyeloplasty between these groups (Table 4).

Table 4.

Comparison of patients without MCUG with patients with MCUG and no VUR.

	No MCUG(n = 31)	MCUG and no VUR(n = 84)	p value
Preoperative DRF (%)	42.65 (14.7)^a	43.63 (12.7)^a	0.762
Improvement of DRF post-pyeloplasty (%)	3.76 (18.0)^a	9.78(46.4)^a	0.563

DRF: differential renal function; MCUG: micturating cystourethrogram; VUR: vesicoureteral reflux.

Data: mean (standard deviation).

Discussion

Previous studies have reported that the successful management of PUJO may be compromised by the co-existence of VUR.¹ High-grade VUR may compromise the healing of PUJ anastomosis which may lead to stricture and impaired drainage across the anastomosis. Surgeons have traditionally advocated an MCUG be performed to detect VUR as an integral part of the preoperative evaluation for all patients with PUJO undergoing pyeloplasty. However, MCUG is not without its own inherent problems. Incidence of post-MCUG UTI varies widely in literature; it was reported to be 7%–42% without antibiotic prophylaxis,^6–8 and 0%–13% with antibiotic prophylaxis.^6,7,9,10 Other problems with performing MCUG include pain and discomfort from urethral catheterisation, as well as cost of the procedure. The dose of radiation in MCUG, especially the risk of high gonadal exposure during fluoroscopy, is of concern. Although there have been aggressive modifications in the design and technique of fluoroscopy to reduce radiation exposure, the risk is still 10 times that of radionuclide cystography.^11,12 This translates to one year of annual background radiation at sea level in the United States for a newborn. This further strengthens the argument against performing routine MCUG.

Hollowell et al. divided patients with PUJO and concomitant VUR into three clinical categories with different clinical and management implications.¹ Group 1 - primary PUJO with incidental low-grade reflux; Group 2 - secondary PUJO with high-grade reflux into ureters that are dilated, tortuous and have a fixed kink at the PUJ, which leads to true obstruction, and Group 3 - pseudo-PUJO defined as reflux into a distended pelvis with a kink at the PUJ radiographically mimicking the upper tract seen in PUJO.

There have been varying recommendations for the initial surgical procedure of choice for patients described in Group 2. According to Hollowell et al. and Lebowitz and Blickman,¹³ the appearance of a dilated pelvis in PUJO that is associated with VUR may indicate the presence of a ‘secondary PUJO’, in which the dilated and tortuous ureter in high-grade VUR causes a kink at the PUJ. They recommended that these patients should first undergo pyeloplasty followed by ureteral reimplantation, and the pelviureteric anastomosis should be protected from the refluxing urine by postoperative bladder drainage with an IDC. Conversely, Williams reported treating similar cases with ureteral reimplantation.¹⁴ They reasoned that since the PUJO is secondary to an overdistended pelvis kinking the PUJ, the establishment of urinary flow downstream at the vesicoureteric junction would relieve the pseudo-proximal obstruction. To complicate things further, Johnston and Farkas have further divided pseudo-PUJO secondary to VUR as those with ‘severe, fixed kinks’ and those with ‘tortuosities’ not amounting to obstruction.¹⁵

In a study of 41 patients, Bomalaski et al. reported a five-fold increase in the risk of secondary obstruction in the presence of high-grade VUR.¹⁶ There was however no increase in the risk of obstruction with low or intermediate grades of VUR. In cases of PUJO with concomitant VUR, the majority of VUR detected was low grade and resolved spontaneously on follow-up.

All our patients except two had low-grade reflux (Table 2). All of them had spontaneous resolution of the reflux over a mean interval of 24 months (range 2–48). None of our patients required treatment of VUR. Furthermore, as all our patients routinely had at least two postoperative days of bladder decompression via IDC for the purpose of monitoring postobstructive diuresis, an undetected low-grade reflux would not have compromised the healing of our anastomosis during the early postoperative phase.

With regards to DRF, Schuster et al. reported that among 85 cases, impaired preoperative DRF and absence of improvement post-pyeloplasty in PUJO was associated with coexisting VUR with renal dysplasia.¹⁷ In our study, there was no statistically significant difference in the preoperative DRF and improvement of DFR post-pyeloplasty between the two groups (Table 3).

One-quarter of the children with PUJO did not have MCUG in our study. The diagnosis of concomitant VUR may have been missed in some patients in this group. It is possible that this was due to a selection bias, i.e. children who did not have a history of UTI did not undergo MCUG. However, when we compared the two groups (with or without MCUG), there was no difference in clinical symptoms and postoperative outcomes, suggesting that even if the diagnosis of VUR was missed, there was no detrimental impact on the patients (Table 1). Our findings are consistent with outcomes reported by ElSheemy et al.¹⁸

The incidence of PUJO associated with VUR in our study population is 6.7% compared to 11%–14% as reported in other studies.^1,2 It has emerged in recent years that the incidence and severity of VUR is not uniform across all ethnic groups. In a study by Park, Caucasian children have a higher rate of VUR compared to children of African and Asian ancestry in the ratio of 3.4 to 1.¹⁹ Given an overall lower population risk for VUR, it may be postulated that the risk of PUJO with concomitant VUR may be lower as well in the Asian population.

During the study period spanning over 13 years, the US technology and accuracy has improved remarkably. From reporting dilatation of the renal pelvis, ureter and parenchyma thickness, the reporting has evolved to SFU grading and currently to urinary tract dilatation (UTD) grading.²⁰ The current system of monitoring with UTD grade may be able to replace the need for MCUG in PUJO effectively. In our study, all patients with concomitant PUJO and VUR had spontaneous resolution of VUR and uncomplicated pyeloplasty surgery. We did not have any secondary PUJO in our study cohort. However, in cases of secondary PUJO due to high-grade reflux, the presence of US-detectable hydroureter is expected to be high. As the management for this group of patients would be different, it is important to confirm the diagnosis. Therefore, we propose that only if PUJO is associated with hydroureter or other congenital anomalies of the genitourinary tract, then MCUG should be performed to exclude concomitant high-grade reflux.

Our study is limited by its small size and retrospective nature. However, this was a similar limitation to other studies in published literature. The evidence that preoperative MCUG adds benefit to patient management is very thin if at all and is more based on expert opinions and driven by defensive practice of surgery. Randomised studies with multicentres are needed to conclusively prove the need for routine MCUG in PUJO patients. In an institution with a low volume of index cases like ours, a collaborative regional registry to include other Asian populations may be useful to collate disease pattern information to fine-tune clinical practice guidelines. Furthermore, management guidelines formulated in a particular population setting may not be directly applicable to another population of different ethnic demographics.

Conclusion

Traditionally MCUG was performed as part of routine work-up for hydronephrosis, but it is not without risk. There is a lower incidence of concomitant VUR with PUJO and also of lesser severity in our population as compared to previously published data. The outcome of pyeloplasty appears to be independent of the presence of concomitant VUR. Therefore, we propose that an MCUG should be reserved for those cases with both hydronephrosis and hydroureter on US or history of recurrent UTI.

Footnotes

Acknowledgements

None.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Availability of data and materials

The datasets generated and analysed during the current study are not publicly available due to CIRB guidelines but are available from the corresponding author on reasonable request.

Authors’ contributions

SW Sim: study design, data collection, data analysis, manuscript preparation and review; FX Li: data analysis, manuscript preparation and review; MM Oo: data collection, data analysis, manuscript preparation and review; KL Narashimhan: study design, preparation of manuscript and review; AS Jacobsen: study design, preparation of manuscript and review; TL Yap: study design, preparation of manuscript and review.

Conflict of interest

The authors declare that there is no conflict of interest.

Informed consent

The study has been approved by Singhealth CIRB (Ref: 2017/3016). It was not required to obtain informed consent from the individual study subjects.

Ethical approval

Institutional review board approval was obtained and all study procedures were conducted in accordance to the stipulated ethical standards.

ORCID iD

Siam Wee Sim

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