How useful is a complete urinary tract ultrasound in orchiepididymitis?

Orchiepididymitis (OE) is a frequent cause of pediatric emergency department attendance in boys presenting with acute scrotum. The etiology of most episodes of OE remains unclear and there is no consensus regarding the correlation between OE and underlying genitourinary malformations. Whether imaging evaluation should comprise complete urinary tract ultrasonography (US) or voiding cystography is a subject of debate. The aim of this retrospective, single-center study was to analyze i) the number/type of urinary tract malformations detected by US following a first episode of OE in boys with no previously known malformation and ii) the frequency of associated urinary tract infection (UTI). We reviewed the records of 495 boys <16 years presenting to our pediatric emergency department with acute scrotum between January 2012 and December 2017. Patients with incomplete radiological data were excluded. Of 119 boys with a radiologically-confirmed first episode of OE, 99 had a complete urinary tract US and were included in the study. No genitourinary malformation was detected (0%). Urinary cultures showed UTI in 3/98 (3.1%) patients. Mean age at presentation was 9.7 years (standard deviation, 3.9) with a three-peak incidence of OE at 10-13 years, 4-5 years, and during infancy. Conclusion: Complete urinary tract US does not appear to be useful during a first episode of OE in countries with an antenatal US screening rate similar to Switzerland. The very low UTI rate suggests that a urinalysis is sufficient to investigate a first episode of OE and antibiotics should be reserved for positive urinalysis only.