Transcript Infectyion & infertility
Ultrasound in obstetrics
By
Dr. Khattab KAEO
Assis. Prof. of Obstetrics and Gynaecology Faculty of Medicine, Al-Azhar University, Damietta
Introduction
– Ultrasound has a frequency >20 000 Hz (20kHz). However, ultrasound machines have frequencies of 2-10 mega Hz (MHz). – Higher frequencies give better resolution, but decreased tissue penetration; thus, used to examine near structures. Conversely, lower frequency probes are used to examine deep structures. For instance, abdominal probes give 3-5 MHz, while vaginal probes give 5-7.5 MHz. – It is best to reduce 'depth' as much as possible. – Increasing the 'gain' increases the echoes, and thus, may improve the image where obesity is csausing attenuation.
Early pregnancy scanning
Aim: To determine location of
pregnancy (intra- or extra uterine), viability, gestational age and fetal number, in addition to adnexal pathology (an ovarian cyst mostly). Uterine abnormalities may be seen as an empty cavity adjoining the pregnancy sac.
Gestational sac:
It could be detected by TAS from 6 weeks ’ amenorrhoea, while TVS may detect it from 4.5 weeks (2-4mm). Normal sac growth is 0.7-1 mm/day. It is considered abnormal if its tro phoblastic reaction is <2 mm. Shape of the sac may be affected by uterine contraction or bladder fullness.
The embryo:
•Yolk sac (10mm) is the first structure to
be seen within the sac. It should be detec ted within an intrauterine gestational sac of a 20 mm diameter using TAS, or 8 mm using TVS. It is first seen at 5 weeks that the pregnancy is intrauterine.
length). weeks (sac diameter of 15-20 mm).
’ gestation on TVS and at 6 weeks on TAS. It has no predictive value but confirms
•Embryo is first visible with heart pulsa-
tion on TVS at 5 weeks (2-4mm embryonic
• Heart tone is first visible on TVS at 6.5
Early pregnancy assessment clinic (EPAC) Aim:
avoidance of admission or reduced hospital stay (& cost).
Ultrasonography results:
# Viable intrauterine pregnancy: Most women are suitable for immediate discharge and GP follow-up.
# Fetal pole, no cardiac activity: Some are viable, while others represent delayed miscarriage. Early embryos typically appear adjacent to the yolk sac in the periphery of the gesta tional sac. CRL is the key for management.
CRL 6mm = home & re-scan in 7-10d CRL >6 mm = termination.
A dead embryo of CRL >6mm and no cardiac activity as seen by M mode ultrasonography.
# Empty gestational sac: Some are viable, while others represent blighted ovum. The mean sac diameter (MSD = the mean of 3 perpendicular measurements), rather than volume, is the key for management. MSD 20mm = home & re-scan in 7-10 d. MSD >20 mm = termination of pregnancy. You should look for a second opinion.
Empty gestational sacs (absent embryo, even if amniotic sac is seen [arrow]). Arrow heads point to thin decidual reaction. The lowermost sonogram shows an abnormally large yolk sac, presented for comparison with the first one sonogram.
# Retained products of conception: Mixed echogenicity with irregular echo-bright areas (it is difficult to differentiate blood clots from retained tissues). Mostly the tissue is of <30 mm maximum diameter with light blood loss and no signs of infection, and so, management is conservative. Large volume of tissue or heavy blood loss = evacuation.
# Empty uterus: Differential diagnosis: 1- very early pregnancy; 2- complete miscarriage; or 3- ectopic pre gnancy. Consider: 1- history for risk factors for ectopic pregnancy, 2 examination findings and 3 TVS (5000 iu/l for TAS). -hCG level as well as its rate of disappearance. If tissues have been passed, this should be examined microscopically for chorionic villi. When management. -hCG level is the key for -hCG level exceeds 1000 iu/l, intrauterine pregnancy would be visible by A -hCG <1000 iu/l: All the 3 possibilities are probable. If there are no risk factors for ectopic pregnancy and no peritonism, review after 48 hours by TVS and -hCG. The absolute level of -hCG (1000IU/L) should be relied upon rather than the rate of rise in -hCG level. Some ectopic pregnancies (13%) show normal rate of -hCG rise. Some normal pregnancies (15%) show slow rate of -hCG rise. (Between the 2nd & 4th post ovulation weeks the level of -hCG doubles every 48 hours; ectopic pregnancy and abortion shows <66% rise). B -hCG 1000 IU/L, only ectopic pregnancy or complete abortion are possible. Laparoscopy can be considered or selectively with review in 48 hours. Complete abortion can be confirmed by a -hCG fall to 20% by 48 hours. History may assist decision-making. Regarding the disappearance rate of hCG: if it is less than 1.4 days, the most likely diagnosis is miscarriage. If it is greater than 7 days, the case is almost always ectopic pregnancy.
# Suspected trophoblastic disease.