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How long should an anomaly scan take?
by
Dr John Parks
Consultant
Obstetrician Gynecologist
Pietermaritzburg
KZN
Many
ultrasound departments experience heavy scanning loads on a
daily basis which they are expected to complete without
missing any abnormalities.
It is not
unusual for an ultrasound department in a busy hospital to get
50 to 100 cases in a morning. If there are limited numbers of
ultrasonographers, they could individually scan up to 40 cases
in the morning. Where this scenario exists, what is the risk
of missing significant pathology due to inadequate
visualization of all anatomic structures? Obviously this will
depend on the expertise of the ultrasonographer.
In a survey
from
San Diego
, * V Catanzarite and co-workers attempted to answer this
question. They conducted 100 ultrasound examinations at 16 –
22 weeks gestational age. The scans performed attempted to
complete a comprehensive survey of the fetus. If the scan
lasted only 10 minutes, only 8% of all structures were
visualized, 15 minute scans visualized 31%, 20 minutes –
53%, 25 minutes – 72% and 30 minutes – 81% of structures
were visualized. Rates of completed anatomic surveys increased
with advanced fetal age.
Obviously
there are factors such as maternal weight, fetal position,
abdominal wall scarring, amniotic fluid volume, gestational
age and the quality of the ultrasound machine which, among
others, will influence the time of scanning. The authors felt
that 25 minutes is adequate in a normal patient. They also
feel that 15 minutes is the minimum time that should be set
for a scan.
In a
litigation-dominated era of medical practice, it seems logical
therefore to suggest that an attempt be made to allow
sufficient time for our ultrasonographers to do their scanning
properly.
*
V Catanzarite et al. Ultrasound Obstet Gynecol 2005; 26:
521-526
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