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.

Role of urinary biomarkers for diagnosis and prognosis of kidney stone disease.

PURPOSE OF REVIEW: Urinary biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1) and N-acetyl-B-D-glucosamindase (NAG) are recognised as being useful for the detection of kidney tubular damage but their role in the diagnosis and prognosis of kidney stone disease (KSD) is still unknown. To clarify this, we performed a systematic review of literature in accordance with Cochrane methodology from inception to September 2020. RECENT FINDINGS: Twelve studies were included and a variety of urinary biomarkers (KIM-1, NGAL, NAG, proteins/peptides, cytokines, CA19-9) were measured in a total of 998 patients with KSD. Despite some contradicting studies, majority of the biomarkers studied showed a significant rise in patients with KSD compared to healthy controls, with levels decreasing after their surgical management, noticed as early as 4 h postprocedure. There was limited evidence of correlation with stone burden and elevated levels were also associated with hydronephrosis and superimposed infections. SUMMARY: Urinary biomarkers could be used in the diagnosis, prognosis and stone-treatment response in patients with KSD. However, as novel indicators, they may not be reliable as the sole diagnostic or prognostic tool for KSD as they are readily confounded by other causes of kidney injury. Further studies are needed to determine their ability to separate KSD from other causes of obstructive uropathy and acute renal injury.

Contrast-enhanced ultrasound in the evaluation of focal testicular complications secondary to epididymitis.

OBJECTIVE: The purpose of this study is to determine the effectiveness of contrast-enhanced ultrasound in evaluating incidental focal testicular lesions in epididymitis. MATERIALS AND METHODS: Intratesticular lesions ipsilateral to epididymitis were subject to B-mode color Doppler ultrasound and contrast-enhanced ultrasound, with their appearances reviewed in consensus. Final interpretation was by histologic analysis or follow-up ultrasound. RESULTS: Over 28 months, 16 focal testicular lesions (median lesion size, 24 mm; range, 14-48 mm) in 14 patients (median age, 49 years; range, 18-81 years) were examined. Lesions were oval (n = 14), wedge shaped (n = 1), or involved the entire testis (n = 1). Lesions were isoechoic (n = 1), hypoechoic (n = 4), or of mixed echogenicity (n = 11). Color Doppler ultrasound flow was not clearly depicted in 13 lesions but was present in three lesions, with contrast-enhanced ultrasound concordant with color Doppler ultrasound, showing unequivocal absence of vascularity and increased flow, respectively. In the avascular lesions, rim enhancement (n = 6), vascular projections (n = 4), and irregular (n = 10) and smooth (n = 2) borders were documented. The observers identified infarction (n = 9), abscess (n = 4), orchitis (n = 1), and tumor (n = 2). Histologic examination (seven lesions in five patients) confirmed infarction, abscess formation, and seminoma; follow-up ultrasound confirmed resolution for eight patients. CONCLUSION: Contrast-enhanced ultrasound is a useful adjuvant to color Doppler ultrasound examination of a focal lesion in the testis ipsilateral to epididymitis to improve the characterization of nonvascularized tissue.