Acute urinary retention, is a relatively rare entity in children, associated with multifactorial etiology, necessitate bladder decompression to relieve discomfort. Role of early urinary tract ultrasound (US) in the workup of these patients is controversial and no clear indication and patients selection is available in literature to manage pediatric patients with urinary retention in an emergency setting. We tested the hypothesis that early US provides important information.

Retrospective study of pediatric patients admitted to the emergency unit for acute urinary retention between 01/2010 and 12/2020. Neonates, and patients with post-operative acute urinary retention or known (urological, neurological, or mental) disorders were excluded. Palpable bladder was identified in all patients after physical examination and, transabdominal ultrasound (US) was performed us a diagnostic toll of acute urinary retention.
Bladder hyperdistention alone was not considered an abnormal US finding.

193 patients presenting with acute urinary retention were identified. Median (range) age was 3 (2-16) year-old. US evaluation was performed in 129/193 (66.8%) patients, more commonly <5-year-old (73.6%vs 26.4, p<0.01). US detected urinary tract abnormalities in 16 patients including upper urinary tract dilatation in 10 [eventually diagnosed with vescico-ureteral reflux (n=6), tethered cord (n=1) and posterior urethral valves (n=3)]; bladder wall thickened in 2 patients, eventually diagnosed with neurogenic nonneurogenic bladder]; urinary stones in 2; and bladder suspended echoes in 2 patients with urinary tract infections only. In 13 additional patients, US showed a distended rectum consistent with fecal impaction or constipation. In the remaining 100/129 (78%) patients the US was normal. 
Children with history of previous emergency access for Acute urinary retention, had less probability to underwent US evaluation. No variable, including gender and associated symptoms, was able to predict the risk of an abnormal US.

In our experience, US provided relevant urological information in less than 15% of patients with acute urinary retention, but allowed detecting clinically relevant conditions. We were unable to identify possible factors to select patients warranting US evaluation probably related to different bias such us, presence or the absence of others urological symptoms and conditions,  or, the experience of the pediatrician managing patients with urinary tract retention in the emergency. 
No clear indication for US in an emergency setting was identified. In our opinion history taken is good complimentary evaluation for the decision-making.

Urinary tract ultrasound is un import diagnostic tool in the management of patients with urinary tract retention, useful to urological pathologies identification and better patients management. Standardization is needed to define the steps and indication to ultrasound evaluation managing children with acute urinary retention

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Acute Urinary retention in children Ana-Marija Schmidt , Karin Hirsch, Michael Schroth, Maximilian Stehr, Frank-Mattias Schäfer                     J Pediatr Urol 2020 Dec;16(6):842.e1-842.
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Continence 2S2 (2022) 100440
DOI: 10.1016/j.cont.2022.100440