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You join a new neonatal unit. On your routine baby check you find a newborn with an isolated preauricular tag/pit. The baby has no other malformation or dysmorphic feature on detailed examination. You know that this baby needs to have their hearing tested but you are not sure whether it needs an ultrasonogram as part of routine evaluation to rule out urinary tract anomalies. The unit where you worked previously had a policy of performing routine scans, but your registrar tells you that this is not the policy here. You decide to search for the evidence behind this.
Structured clinical question
In newborns with isolated preauricular tags/pits [patients] is an ultrasonogram of the renal tract [test] required to rule out urinary tract malformations [outcome]?
Search strategy and outcome
Pubmed—(((“Kidney/abnormalities”[MeSH] OR “Kidney/ultrasonography”[MeSH]) OR (“Urinary Tract/abnormalities”[MeSH] OR “Urinary Tract/ultrasonography”[MeSH])) AND “Ear/abnormalities”[MeSH]). Field: title/abstract. Limits: all infant: birth–23 months.
Sixty five results found and then each abstract read for relevant articles.
Embase—same search strategy. No additional papers.
Six relevant papers found. See table 2.
The association between external ear abnormalities and renal malformation has been reported previously. There is a general consensus on the need to rule out a urinary tract malformation in a child with a gross ear malformation or when the isolated preauricular tag/pit is accompanied with other dysmorphic features.7 Some experts have recommended that there is no need for renal ultrasound if isolated tags/pits are not associated with other malformation or dysmorphic feature.8 However, the studies above give mixed results. The three older studies did not find any increase in number of renal malformations in those with isolated preauricular tags/pits, but they are all limited by small sample size and absence of controls. The other three studies have controls but are underpowered. The fact that the two largest studies which are from the same country with comparable sociodemographic population give opposite results, underlines the need for a larger sample size. This is not easy when you consider the fact that the incidence of preauricular tags and sinuses is around 5–10/1000 live births, and the prevalence of mild renal pelvis dilatation in general population by postnatal screening is 4.6% compared to a reported prevalence of renal malformations ranging from 2.2% to 8.6% in those with tage/pits. So to achieve a significant sample size, the study would have to be done over multiple centres for a considerable period of time.
At this stage what seems a sensible practice is that the presence of a preauricular tag or pit should lead to a careful search for other malformations or dysmorphic features, the presence of which will tilt the balance in favour of doing a renal ultrasonogram.
CLINICAL BOTTOM LINE
There is not enough evidence to derive a firm conclusion on the need for renal ultrasonogram in newborns with isolated preauricular tags/pits.
The presence of a preauricular tag or pit should lead to a careful search for other malformations or dysmorphic features, the presence of which will tilt the balance in favour of doing a renal ultrasonogram.