The Utility of Radiologic and Symptomatic Surveillance After Minimally-invasive Adult Pyeloplasty

OBJECTIVE

To evaluate different types of failure after minimally-invasive pyeloplasty (MIP) when stratified by initial radiologic study and symptoms after ureteral stent removal.

METHODS

We retrospectively reviewed adults who underwent MIP (1996-2019) at a single academic center. Patients with at least 11 months of follow-up and patients who had a Mag3 scan as their initial postoperative imaging were included. Postprocedure, patients were categorized as having normal, equivocal, or obstructed imaging based on their initial radiologic test. Patients who were obstructed were excluded. Primary outcome was procedural failure, defined as the need for a procedure to treat recurrent obstruction. Secondary outcomes were radiologic failure and symptomatic failure. Groups were compared to assess for statistical significance (P <.05).

RESULTS

Overall, 122 patients met inclusion criteria. On initial postoperative imaging, 108 (89%) patients had no obstruction and 14 (11%) had equivocal findings. The procedural failure rate was 6.5% in the unobstructed group and 28.6% in the equivocal group (P = .023). Seven unobstructed patients (6.5%) and 2 equivocal patients (14.3%) eventually experienced radiologic failure (P = .275). Among patients who had no obstruction on initial imaging and remained asymptomatic, only one (0.9%) required a salvage procedure.

CONCLUSION

Recurrent obstruction after pyeloplasty varied based on the outcome of the initial radiologic study. These rates can be used to counsel patients and guide physicians' choice of surveillance schedules. The risk of future failure is very low in asymptomatic patients with normal initial imaging. The utility of routine radiologic surveillance in these patients may be limited.

The Use of Neutrophil Gelatinase-Associated Lipocalin (NGAL) as a Diagnostic and Prognostic Biomarker in Urinary Tract Obstruction: a Systematic Review

PURPOSE OF REVIEW

The early recognition of urinary tract obstruction (UTO) is vital in order to prevent mortality and morbidity associated with an acute kidney injury (AKI) and progression to irreversible kidney damage. Urinary biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) have been recognised as an accurate tool in the timely diagnosis of AKI, but its role in the detection, prognosis and subsequent monitoring of a variety of obstructive uropathies has not yet been explored. We performed a systematic review of literature in accordance with Cochrane methodology from inception to August 2021.

RECENT FINDINGS

Eleven studies were included in which urine and serum NGAL were measured (616 patients) presenting with multiple UTO aetiologies. Four investigated kidney stone disease (KSD) exclusively, whilst other studies identified other causes of UTO including pelviureteric junction obstruction (PUJO), retroperitoneal fibrosis (RPF) and ureteric strictures. Six studies monitored NGAL levels after surgical intervention to relieve the obstruction. Nine studies demonstrated a significant increase in both urine and serum NGAL levels in UTO, often in a more sensitive and timely manner than serum creatinine. Subclinical unilateral UTO could be recognised by urinary NGAL levels even in the absence of changes in serum creatinine. Following surgical intervention, a reduction in urinary and serum NGAL was seen in all but two studies. NGAL levels decreased acutely by 14% in 2 h and showed a long-term reduction of 78% in 6 months. Readily available but not yet widely accepted, NGAL has the potential to be a less invasive, low-cost diagnostic test for urinary tract obstructions as a whole. Not only can it be used as a marker of treatment success but also to monitor for obstruction recurrence or progression. Further research is required to acknowledge urinary biomarkers such as NGAL as a potential replacement to standard renal function monitoring tests in the context of obstructive uropathy.