Omphalocoele & Gastrochisis

Both are quite common abdominal wall defects afflicting neonates. Omphalocoele and gastrochisis were once thought to be the same entity until quite recently. Gastrochisis was once thought to be a ruptured omphalocoele. Now it is well known that this is not the case.

Other disease of abdominal wall defect includes cloacal exstrophy (epispadias), pentology of Cantrell and cordis extrophy but will not be covered in this article.

Definitions

Omphalocoele
This is a large defect in the anterior abdominal wall when amniotic membrane covers protruding midgut components which may include the liver, gonads and spleen.



Gastrochisis
This is usually a smaller defect with protrusion of midgut components without membrane covering. The defect is usually to the right of the umbilicus.

In both defects, the rectus abdominis muscles are intact.



Umbilical hernia differs from omphalocoele in the it is covered by skin instead of amniotic membrane. It also usually appears not at birth but much later after.



Prevelance

Gastrochisis is more common than omphalocoele. Incidence is about 2 - 4.9 per 10000 live births.

Omphalocoele has an incidence of about 1 - 2.5 per 10000 live births.

Embryology

The body cavities are enclosed by folding of the embronic disc, anteriorly, caudally, and right and left laterally. This will leave the yolk sac in the middle. This occurs at 3 weeks of gestation.

At 5 weeks, the gut 'herniate' into the yolk sac and develop within.

At 10 weeks, the gut retracts back into the peritoneal cavity.

At least this is whats supposed to happen. When there's a failure of the lateral fold to complete, omphalocoele develops with failure of retraction of the midgut.

Gastrochisis supposedly occur due to failure of developement of the yolk sac. The gut has no space to expands and ruptures out of the abdominal wall. This usually occur on the right side of the umbilicus, probably due to weakness at that side due to involution of the right umbilical vein at 4 weeks of gestation.

Associated Anomalies

Omphalocoele

• Chromosomal ~20%

1. Trisomy 18, 13, Triploidy, 45 X (Turner's)
2. Aneuploidy
3. Beckwith-Wiedemann syndrome

• Cardiac ~ 7 - 50%
• Central nervous system ~ 4 - 30%
• Musculoskeletal ~ 4 - 25%
• Genitourinary ~ 6 - 20%
• Gastrointestinal ~ 3 - 20% (Less compared to gastrochisis, probably due to protective effect of covering sac.

Gastrochisis

More associated with midgut anomalies

• Intestinal atresia ~ 7 - 30% (due to mesentric ischemia, likely due to compression by small abdominal defect)
• GERD ~ 16%
• Undescended testis ~ 15%

Antenatal Diagnosis

Sensitivity for detection with ultrasonography: 75% for omphalocoele, 83% for gastrochisis.

Omphalocoele
Centrally located, at base of umbilical cord insertion.
Presence of membrane.
Presence of liver (extracorporeal liver) carries poorer prognosis.
Associated with polyhydromnios (poorer prognosis)

Gastrochisis
Abdominal wall defect noted at right of umbilicus.
Variable amount of bowel protrusion.
Bowels usually thickened and edematous.
Assoicated with oligohydromnios
Associated with IUGR

Other anomalies should be sought out, especially for omphalocoeles.

Both have elevated serum and amniotic aFP and amniotic fluid acetylcholine (AChE) but more in gastrochisis (~80 more).

Amniocentesis may also help to rule out chromosomal abnormalities that may predict prognosis.

All above information combined may provide useful information to convey to parents and provide counseling as well as for discussion of prognosis.


Mode of Delivery

Controversial. No good RCT studies.

For gastrochisis, some reports less GIT complications with elective Caesarian section. Caesarian section recommended for large omphalocoele to prevent rupture of sac.

No benefit in earlier delivery unless if obstetrically indicated. Preterm delivery is associated with more complications associated with prematurity that may make management of the infant more difficult postnatally.

Termination of pregnancy should be considered and discussed with chromosomal abnormalities.

Delivery should ideally be done in a center with pediatric surgery expertise. Conditions of the bowels post-delivery is related to duration of time it takes between delivery and repair.

Management

Initial Care

• Keep NBM
• Keep warm
• Intestinal decompression with nasogastric tube and meconium evacuation
• Adequate hydration
• Prevent heat loss (especially important in gastrochisis where the bowels without sac are exposed, wrap with plastic or kitchen wrap).
• Respiratory support, ventilator readily available.
• Other anomalies excluded, especially cardiac lesions with omphalocoele.

Surgical Care



Omphalocoele

• The sac is cleaned with antiseptic.
• Attempt be made at manual reduction. May not succeed wholly at first. Incision around the defect is made and then the sac excised.
• Abdominal wall may be stretched posterior-to-anterior and bowel be replaced first followed by the liver to wedge the bowel in.
• The anterior abdominal wall is closed with sutures applied on all layers of the rectus including the muscle. After the closure is done without tying off the knot, an attempt is made to ventilate the patient. Closure is safe if patient is able to be ventilated with peak inspiratory pressure of less than cm H2O. 
• If unable to reduce without closing the abdominal wall too tightly, a prosthetic silo is applied and the bowel reduced weekly.
• Any atresia or other bowel anomalies found may be operated 6 weeks after initial surgery.

Gastrochisis

• Similar principle to omphalocoele.
• Bowels are reduced and primary closure.
• While waiting, the bowel may be kept in a prosthetic silo. Some centers attempt to reduce bowel bedside.

Post-operative Care

• Continued ventilation.
• Continued hydration with urine output monitoring.
• Antibiotics.
• Bowel function may be delayed for up to 3 weeks. Any longer a contrast study may be indicated.
• Monitoring of complications related to respiratory difficulties. Sutures may need to be released and gradual reduction be made.

Complications

Short Term

• Associated anomalies (especially in omphalocoele).
• Associated with prematurity (especially in gastrochisis; hypoglycemia, respiratory distress syndrome, electrolyte imbalance, heat loss).
• Associated with tight closure causing respiratory distress.

Long Term

Small bowel obstruction.
*Absence of umbilicus (social distress).
Poor weight gain
Low IQ

Most of these complications vary in frequency depending on where the study is conducted.

References:

1. Coran, Arnold G., et al., Pediatric Surgery, 7th Ed., Elsevier. 

2. Hutson, John M., et al., Jones' Clinical Pediatric Surgery Diagnosis and Management, 6th ed., Blackwell Publishing (2008).

3. Nyberg, David A., et al., Diagnostic Imaging of Fetal Anomalies, Lippincott Williams & Wilkins, 2003.

Future Topics:

Surgical management
Bladder extrophy
Pentalogy of Cantrell
Cordis ectopia

Twin-Twin Transfusion Syndrome: Clinical Features

Twin to twin transfusion syndrome (TTTS) is a condition where there is an over-perfusion in one twin and under-perfusion in the other. Although more common in monochorionic twins, it has been reported to occur in diamniotic twins.

Clinical Features and Diagnosis:

Most important is the discrepancy in amniotic fluid volume.
1 twin would be oligohydramnios ( < 2cm deep vertical pool )
1 twin would be polyhydramnios ( > 8cm deep vertical pool)

WEIGHT DISCREPANCY IS NOT THE MAIN CRITERIA FOR DIAGNOSIS!
In some cases, there are no significant weight discrepancies.
If there are, the discordance should be > 15-20%

"Stuck twin appearance"



Anhydromnios fetus appear as if there are no separating membrane.

Discrepancies in size of umbilical cords.

Presence of hydrops or cardiac dysfunction in recipient twin.

Abnormal umbilical artery doppler in donor fetus.

Other features of monochorionic twins:

• Single placenta
• Gender concordance

Fetal Blood Sampling:
- Lower hematocrit level in donors
- Difference in hemoglobin levels.

Staging:

Quintero staging uses simple concept of staging involving presence/absence of oligo or polyhydromnios, bladder, abnormal dopple, hydrops fetalis, or fetal death.

A table can be seen in this Emedicine website.

References:

Creasy, Robert K., et al., Maternal-Fetal Medicine, Principles and Practice, 5th Ed.

Other Topics To Discuss:

- Management of TTTS
- Monochorionic twins
- Conjoint twins.

Hydrops Fetalis: Workup

Historically, hydrops were first associated with fetal anemia caused by destruction of fetal red blood cells by antibodies produced by Rh negative mothers in response to antigenic exposure of a Rh positive fetus, usually from the first pregnancy. What result is a severely edematous fetus which characterizes this condition. In today's era where blood group is screened and Rh alloimmunization is prevented with anti Rh(D) immunoglobulin, the majority of causes of hydrops are non-immune related (~90%).

There is a whole list to the causes of hydrops. Typing every single condition would not be beneficial. I feel that work-up to the cause of hydrops should be aimed to detect maternal conditions that may lead to hydrops as well as anomalies that may recur. This is to prevent recurrence, if possible, in future pregnancies as mortality of neonates with hydrops is at 50% depending on the cause of hydrops. 

DIAGNOSIS

Diagnosis are usually made antenatally with detection of the following:

• Skin edema
• Scalp edema
• Ascites
• Pleural effusion
• Pericardial effusion (most difficult to see)

CAUSES

I will not list all the possibilities but most of the common and important ones:

Immune-mediated:
Rhesus alloimmunization

Nonimmune causes:

Congenital anomalies
- Cystic hygroma
- Turner's (XO monosomy)
- Trisomies (21 most common)

Hematological
- Alpha thalassaemia
- Massive fetomaternal hemorrhage

Cardiac anomalies (all sorts)

Thoracic anomalies
- Congenital cystadenomatoid malformation (CCAM)
- Any mass/lesions that may cause increase thoracic pressure

Infections
- TORCHES (Toxoplasmosis, rubella, cytomegalovirus, Herpes simplex, syphilis [most common])
- Parvovirus B19

Metabolic Disorders
ie. Gaucher's disease, Tay-Sach's disease, sialidosis, generalized (GM1) gangliosidosis

Twinning
- Twin-twin transfusion syndrome

Others
- Skeletal dysplasias


WORK-UP

Antenatal

As usual, history from the mother should be obtained when hydrops is first detected. Family history of genetic anomalies, consanguineous marriage should be obtained. Recurrence are more likely in families with such histories ie. Alpha thalassaemia, metabolic disorders (which most are autosomal recessive), congenital anomalies.

History of exposure to infections may also be beneficial.

Rhesus negative mothers should always be ruled out.

Other associated anomalies may be looked for and detected during the initial ultrasound or repeated in more expert hands later. Amniocentesis for fetal karyotyping may be obtained after counselling. If infection is suspected, amniotic fluid may be sent for cultures or PCR if facilities are available. 

Postnatal

Evaluation of the neonate post-delivery should always be after initial resuscitation as these fetus tends to have turbulent births.

Relevant physical examination:

• Cyanosis - may indicate underlying structural heart anomaly
• Hepatosplenomegaly - metabolic disease, congenital infections
• Features of Turner's, Down's and other features of chromosomal anomalies
• Congenital anomalies - cystic hygroma, dysplasia
• Hypotonia - metabolic disorders, dystrophies
• Placenta - in case of TTTS

Investigations:

• FBC - To rule out anemia or determine severity of anemia
• PBF - To look for hemolysis
• Kleihauer-Betke test - if fetomaternal hemorrhage suspected
• ECG - to rule out arrythmias
• Echocardiography - to rule out cardiac anomalies
• Chest x-ray (Pleural effusion, CCAM)
• Infection screen (TORCHES)
• Karyotyping (if not yet done antenatally and if suspicious of chromosomal anomalies)
• Metabolic screen (for metabolic diseases)

Management are then commenced according to cause and prognosis.

Postmortem:

If the fetus delivers as a stillbirth or had an early neonatal death, postmortem may be important to determine underlying anomalies or condition.


Determining the cause of hydrops is important to rule out causes that are potentially preventable or predictable, especially those associated with chromosomal anomalies. Future pregnancies may be followed-up more carefully with anticipation of treatment better. Mothers should always be counselled for possibilities for recurrence and next pregnancy planned well.

As mentioned this article only covers some of the causes and work-up for the hydrops patient. Mode of delivery, management of the fetus is not discussed in details here but both depends on the cause of hydrops and after further discussions with the parents.


References:
Creasy, Robert K., et al., Maternal Fetal Medicine, Principles and Practice, 6th Ed.
Speer, Micheal E., Postnatal Care of Hydrops Fetalis, Up-to-Date Article, 2012.

Neonatal Resuscitation: The Basics

Fortunately most term babies are born without complications or needing help for resuscitation. About 10% do and that's a significant number. Basic knowledge of neonatal resuscitation must be available to all medical staffs (doctors and nurses) working in the labour room or the emergency department for that matter as mothers in advanced labour may just pop-up in the emergency department in the middle of the night.

The algorithm above pretty much sums up the steps of neonatal resuscitation covering even babies whom are delivered 'normal' without complications. There are many other variations but this is the one that I'm most used to.

Most times, the outcome of delivery can be roughly predicted even before birth itself. Knowledge of the patient's history helps a lot in anticipating outcome of delivery.

The initial step as in the box above emphasize the recognition of a baby in need of resuscitation. Four basic questions must be answered:

• Is the baby term?
• Is the liqour clear?
• Is the baby crying or breathing?
• Is the muscle tone good?

If any of the above is NO, then the next step of resuscitation is required. 

Even the first two questions above can be answered before delivery and can be anticipated. With anticipation comes preparation and with good preparation hopefully better outcome may be borne out of the delivery.

If all those answered above are YES, then the baby maybe passed on to the mother unless otherwise contraindicated, for skin to skin contact and initiation of breast feeding and routine care.

Another interesting note is that delayed cord-clamping should be practiced (as late as 1 minute after delivery) as there is evidence of reduced incidence of transfusion and increased iron storage in babies with delayed cord-clamping.

INITIAL STEPS TO RESUSCITATION

Below are the basic initial steps for resuscitation. All these steps are to be done ideally within 30 minutes and the baby reevaluated afterwards to assess success of resuscitation and need to proceed with the next step.

Provide warmth and Dry
- Baby is to be placed under radiant warmers.
- If baby is preterm, best to be wrapped in plastic wrappings as preterms are more likely to lose heat more easily

Position and maintain airway
- Positioned in sniffing position.

Stimulate
- Only back stimulation is necessary up to 2 to 3 times.
- Slapping the feet of babies should not be in practice today.

*Clear airway
- Latest guidelines from WHO states that babies whom are breathing on their own should not have regular suctioning, even if meconium was present.
- Suctioning should only be done if there are evidence of excessive secretions.
- There is no evidence in improved outcomes in babies suctioned intrapartum (after delivery of head, before delivery of shoulder) when meconium is present.
- If meconium is present and baby is not *vigorous, direct-suctioning with the meconium aspirator should be initiated straight away, even before positive pressure ventilation is performed.
- Direct suctioning is done until airway produces clear returns or baby becomes bradycardic.

*vigorous = not breathing, limp, heat rate <60 bpm.


POSITIVE PRESSURE VENTILATION (PPV)

- If the baby is still apneic or heart rate is less than 60 bpm after the initial steps, positive pressure ventilation should be initiated.
- 40 to 60 cycles of breath should be given per minute.
- Ensure there is chest rise. If not, reposition in sniffing position.
- Intubation is to be considered if unable to ventilate.
- Excessive pressure or 'bagging' must be avoided for risk of pneumothorax.
- Heart rate is to be evaluated after 60 seconds of PPV with target > 100 bpm.
- SpO2 monitoring may be attached during the resuscitation, best SpO2 probe to be placed at pre-ductal areas ie. right hand. One must be aware that oxygen saturation is not maximal in the newborn till at least 10 minutes after delivery.

Preductal SpO2 According to Duration after Birth

• 1 minute - 60-65%
• 2 minutes - 65-70%
• 3 minutes - 70-75%
• 4 minutes - 75-80%
• 5 minutes - 80-85%
• 10 minutes - 85-95%

CHEST COMPRESSIONS

- PPV and adequate ventilation should be done before initiation of chest compressions.
- Chest compressions done if heart rate < 60 bpm.
- Best to be done with 2 thumbs on the sternum with the other fingers around the baby for better control of pressure.
- Depth of compression should be 1/3rd of the AP diameter of the baby.
- Ratio of breath to compressions should be 1:3.
- 2 finger technique done if space is needed for procedures ie. insertion of umbilical catheters.
- Intubation must be considered at this stage if not earlier.

MEDICATIONS

- Rarely are medications need in neonatal resuscitation (as compared to adult resuscitation),
- If compressions are ineffective, IV adrenaline 0.01 - 0.03 mg/kg is to be given via intraumbilical venous catheter. If not, adrenaline 0.05 - 0.1 mg/kg may be administered through an endotracheal tube.
- Adrenaline should be diluted in 1:10000 (0.1 mg/mL)
- Adrenaline may be repeated every 3 to 5 minutes if heart rate remains < 60 bpm.
- IV bolus of N/S or HM 10 mL/kg may be given in suspected hypovolemia or anemic babies.
- Naloxone should not be given routinely.


Other Points: 
- Remember that resuscitation of the neonate should NOT be done alone.
- Always call for help of someone more experienced.
- Know what is available ie. laryngeal mask airway may be beneficial
- Know when to quit (Perhaps I'll write about this in other articles)
- And always inform the mother or parents of what was done and why and the outcome.
- Remember documentation.



That's it for now. This is just a 'short-note' of mine that I hope will be beneficial for me and to whoever that reads this. It's definitely incomplete but I hope will cover more of the basic stuff. Future related articles that I'll be posting may be on intubations, UVC insertions, other methods of ventilations, and withdrawing treatment, all important aspects of neonatal resuscitation. Let's hope that I've obtained at least a certificate for NRP by then :D


References:
- Neonatal resuscitation Textbook 5th Edition.
- Special Report - Neonatal Resuscitation, 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, PEDIATRICS, Journal of American Academy of Pediatrics
- WHO Guidelines on Basic Newborn Resuscitation 2012.