In India MTP act does not allow termination of pregnancy after 20 weeks so it should be between 17 to 19 wks,
Level II usg
Level II Ultrasound How we do it RICON 2011, Lucknow
INTRODUCTION Detailed second trimester scan for assessing fetal anatomy A screening Ideal period test and a Level II 18 to 22 diagnostic test for fetal ultrasound weeks of gestation. anomalies. To predict structural normalcy of the fetus To identify severe& lethal abnormality To raise suspicion of an abnormality 2
Level II ultrasound How to start LMP Family History First and foremost History High risk/ low risk Assessment Amniotic fluid Placenta Umbilical cordGestational age by Location, appearance Number offetal biometry relation to internal os vessels 3
Fetal biometry BPD Any plane with B/L thalami and third ventricle. Maximum transverse diameter from the outer edge of near calvarial wall to the inner edge of the distal calvarial wall. 4
Head circumference Go more cephaled anteriorly for the plane which will include Image Third ventricle Thalami Cavum septum pellucidum Basal cisterns Measure outer edge 5
Femur length Transducer aligned to long axis of diaphysis Image Measure only ossified portion. To ensure full length, see the soft tissue beyond the both ends Bone should not appear merging with skin at any point. 6
Abdominal circumference AC (abdominal circumference) measures the outer perimeter of the Image abdomen At the level of stomach and intra-hepatic part of umbilical vein. 7
The intracranial anatomy Views for cerebral ventricle, Thalami and third ventricle, The cerebellum and cistern magna. For ventricles up to 20 weeks it is the same view taken for BPD. It show both anterior posterior horns and the body of the lateral ventricle. 8
Ventriculomegaly Ventricle should measured from outer to outer wall. In ventriculomegaly atrial diameter >10mm Ventricle to choroid distance >3 mm, V/H ratio > 2.8 Drooping /dangling choroid plexus. 9
Choroid plexus cyst Seen in I-6% of fetus Cystic area in choroid plexus, Typically small <10 mm Can be unilateral or bilateral Usually resolves by 26 weeks of gestation. Can be associated with trisomy I8 10
Other AnomaliesAbsence of cranial vault Anencephaly : Exencephaly:Acrania Encephalocele Holoprosencephaly Lobar Semilobar Alobar 11
Corpus callosal agenesis• Corpus callosum begins to develop at 12 wk & fully formed by 20 wk• CSP seen by 17 wk• Absence of CSP at 17-20 wk- suspect ACC Colpocephaly Too many sulci perpendicular to interhemisphere 12
For cerebellum Sub-occipito-bragmatic view It is dumb bell shaped has two lateral lobes and triangular shape connection vermis.Complete or partial absence or anterior displacement of vermis associated with spectrum of Dandy walker malformation. 13
Nuchal fold thickness, Measured from the outer border of occiput to outer border of skin Image echoes >6 mm considered to be increased strong marker of trisomy 21.(detection rate of 90% with false positive in 5%.) cystic hygroma and occipital encephalocele can be seen in this region 14
Fetal spine Screen in all three planes sagittal, transverse and coronal For three ossification centre with intact overlying skin. For sagittal place the probe just over the spine and screen the whole spine from CVJ to upsweep of the sacrum, Distance of the skin from the spine should be equal Image Image 15
Fetal spine Transverse view- Three ossification centres are seen in triangular shape Screen all the vertebra with slight curve of overlying skin especially in sacrum. In coronal view 3 parallel echoes are seen with equal distance . In this manner we can diagnose spina bifida and meningo/myelocele. 16
Spina bifida Results from incomplete closure of bony element of spine posteriorly It can be open or closed. Most common site is lumbo- sacral region. In open spina bifida we should look for secondary cranial signs like lemon sign and banana sign. 17
Fetal chest and diaphragm Most important structure is heart in the thorax. Any hypoechoic area other than heart - suspect diaphragmatic hernia 80% on the left side and stomach and bowel are the abnormal organ. Heart is often pushed to right side of the chest. In right sided hernia liver is most likely to herniated in the chest. 18
Fetal chestCongenital cysticadenomatoid malformation:•Stocker’s classification- I, II, III•Azdick’s 2 forms- macrocystic µcystic•Mediastinal shift & hydrops canoccur 19
Fetal heart Four chamber view, The aortic outflow tract, The pulmonary artery outflow tract The crossover of aorta and pulmonary artery The heart rate. 20
In four chamber view The two ventricles and ventricular walls should be of equal size. Two atria and atrial walls should be of equal size Moderator band should be seen in right ventricle Motion of the mitral and tricuspid valve should be regular Inter-ventricular septum should be complete 21
Fetal heart Aortic outflow tract this view shows continuity of inter-ventricular septum with the anterior wall of aorta. Pulmonary outflow tract shows the continuity of right ventricle wall with the pulmonary artery – abnormal in double outlet RV and pulmonary stenosis. The cross over, above two vessels crossover each other when leaving the heart. It excludes the TGA 22
3 vessel view SVC, Aorta and Pulmonaryartery.Fetal heart rate should beregular(110-150 bpm) 23
Fetal abdomen Look for normal stomach bubble, It will be seen after 16 wks. If absent rescan after 20 min. Still not seen suspect oesophageal atresia. 24
Another bubble is seen adjacent to stomach bubble other than gall bladder suspect duodenal atresia(double bubble) D/D include large choledochal cyst. Duodenal bubble is equal to or smaller than stomach bubble and shows communication with the stomach, Whereas choledochal cyst can be larger than stomach and does not show any communication . 25
Fetal abdomen Fetal liver –left lobe is larger in fetus Gall bladder –located to the right side of intra- hepatic umbilical vein Fetal spleen-not amenable to scan in second trimester. 26
Coming to the bowel Dilated bowel can be seen in abdomen indicative of obstruction. It should be >7mm in small bowel >20mmin large bowel obstruction Echogenic bowel called when it appears as echogenic as bones. It is also a soft marker of chromosomal anomaly with increased risk of trisomy of 21. 27
Anterior abdominal wall Look for intact anterior abdominal wall with cord insertion Anterior abdominal wall defect i.e. omphalocele, gastroschisis. Omphalocele develops due to failure of fusion of two lateral folds of anterior abdominal wall gut herniates into the base of umbilical cord. it is covered by protective layer of peritoneum and amnion The umbilical cord inserts into apex of the defect . 28
Gastroschiasis Body folds fused normally A small defect arise in the abdominal wall usually below the cord insertion. Cord insertion is seen normal. It is thought to be due to vascular compromise. Gut floats freely into the amniotic fluid 29
Fetal hydrops Abnormal accumulation of fluid in at least 2 body cavities/ tissues or single serous collection and anasarca• Ascites• Pleural effusion U/L or B/L• Edema- generalized/ localized/ limited-Earliest seen over fetal scalp or face 30
The urinary tract Fetal kidneys can be seen from 14 wks of gestation trans-abdominal Best located from transverse section seen in para-spinal gutters. Kidneys can be identified through the renal arteries if not clearly visible. In renal agenesis renal arteries are also absent, unilateral or bilateral. Bilateral renal agenesis is associated with oligo or anhydramnios.
MILD RENAL PELVIC DIALATION Renal pelvis AP diameter should taken inner to inner aspect of pelvis outline in transverse section. 4-5 mm is taken as upper limit in second trimester and 10mm in third trimester. mild renal pelvic dilatation constitutes a minor marker of chromosomal anomaly including trisomy 21. Re-scanned between 32-36 wks.
Cystic renal diseaseMulticystic dysplastic kidney (MCDK) Kidney- enlarged & replaced by multiple cysts with no functioning parenchyma in between A/w atretic ureter & pelvi-infundibular atresia ARPKD B/L with Numerous 1-2 mm cysts Enlarged kidneys with smooth outline, raised echogenicity & lost CMD Oligohydroamnios & small/absent UB ADPKD Cysts in kidneys & liver Small cysts B/L enlarged echogenic kidneys UB usually seen with normal AFV 33
Fetal bladder Usually visible trans-abdominally from 12 wks of gestation. Normally it empties every 30 to 45 min. Demonstration of filling of bladder implies normal function and exclude bilateral renal agenesis.
Obstructive uropathy Presents with bilateral hydro-uretero-nephrosis . Common cause posterior urethral valve. Present with over distended bladder with distended proximal urethra gives a typical key hole appearance. Other causes includes urethral atresia
Fetal limbs Confirm the three long bones in all four limbs Presence of two hands and two feet with normal carrying angle. Absent limb Complete absence-amelia Partial absence-meromelia Absence of long bone with hand and feet attach to the body called phocomelia.
Skeletal dysplasia-key features Shortening of limbs entire limb-micromelia Humerus / femur –rhizomelia Both bone forearm/leg-mesomelia Defective mineralization and/or fracture Additional features like appearance of thorax, rib and skull.
Fetal limbs All long bones should be scanned in longitudinal section. These should be straight and symmetrical. AP view of tibia and fibula- only talus should be seen. If foot print view is obtained talipus should be suspected, it is associated with trisomy of 18 and 13 38
Fetal limbslateral view of lower leg shows foot in sagittal section - exclude rocker bottom foot which is associated with trisomy 18. A planter view of foot exclude polydactyly/syndactyly exclude sandal gap ,which is associated with trisomy 21 and triploidy.
Hand Outstretched hand view - to confirm normal appearance of forefingers and thumb to exclude clinodactyly/polydactyly. Hypoplasia of proximal phalanx of fifth digit is associated with trisomy 21. Clenched fist with overlapping index finger associated with trisomy of 18
Fetal face Few views are important Nose lip view Facial profile view Axial views of orbit, maxilla and mandible Mid face coronal view.
Eyes and orbit orbits should be symmetrical separated by a distance equal to size of an orbit. Lenses should be seen with in. Intra-occular distance varies in hypotelorism and hypertelorism.
Profile view(sagittal midline) Assessment of forehead, nose and chin Anomalies can be seen are Frontal bossing, flat nose, Micrognathia-when mid part of mandible not align with maxilla macroglossia-persistent protrusion of the tongue
Cleft lip/cleft palate Two views are important Nose lip view(coronal face) Axial view of maxilla(alveolar ridge)
3D & 4D ULTRASOUND• 3D US- Acquisition of a series of 2D images over a volume f/b image display in different orientations• 2 methods – free hand acquisition & automated acquisition• 4D US- 3D US displayed over time• Especially helpful in depictingfacial anomaly, skeletal dysplasia 46
Conclusions The continuing improvement in resolution of ultrasound systems gives us ability to identify an ever-increasing range of abnormalities in the fetus Diagnosis of anomaly : opportunity for counseling, termination, or tertiary level care Benefits : Reassurance of normal pregnancy At least 20 minutes should be allocated for the examinations New advances like 3D & 4D US- can be a problem solving tools in evaluation of some anomalies. 47