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.

Renal Trauma: Short Notes

Genitourinary tract traumas are common in the pediatric age group consisting of injuries to the kidneys, ureter, bladder, and genitalia. 50% of genitourinary tract trauma involves the kidney. In this short notes I will talk about renal trauma. As in most solid organ traumas, it can be managed non-operatively in the majority of patients.

Epidemiology

• Injuries are classified into blunt and penetrating injuries.
• MVAs make up about 60% of the cause of renal injuries, followed by falls (20%) and sports injuries (10%).
• Sudden decelerations with flexion-extension movement in seat-belt is a known mechanism of injury
• In the USA, penetrating injuries are caused mostly by gunshot wounds (86%) followed by stab wounds.
• Associated injuries include liver, spleen and bowel injury. These injuries most be sought for and ruled out.

Kidneys in Children

Certain features and differences in the child's kidneys make them more susceptible to injury compared to adults.

• Kidneys are relative larger compared to the size of the child's body.
• Position is much lower as well in the abdomen.
• Less protected due to decreased perirenal fat.
• Renal capsule and Gerota's fascia less well-developed.
• More mobile kidneys at the pedicle make it more susceptible to deceleration injuries.
• Retainment of lobulations increase risk of parenchymal distruption.
• Weaker abdominal wall muscles and poorly ossified rib cages make renal injury more likely.
• Congenital anomalies increases risk ie. hydronephrosis, horseshoe kidney, polycystic kidneys, renal tumors.

Clinical Features

• Abdominal pain and flank pain.
• Flank echymosis
• Hematuria (absence does not exclude underlying injury)
• Associated injuries include lower ribs and lumbar vertabrae fracture.
• A lot of children are also asymptomatic

Investigations

• FBC, Renal function
• Urinalysis (controversy in further radiological imaging if microscopic hematuria is present. Request for imaging must be correlated with the whole clinical picture).

Imaging

• Contrasted abdominal CT-scan is standard for evaluation.
• Intravenous pyelography useful in unstable patient prior to op to determine functioning of 2 kidneys, extent of urinary extravasation, pedicle injuries.
• Ultrasound not sensitive in detecting parenchymal injuries. Useful for follow-ups to exclude urinomas, expanding hematomas, abscess, pseudoaneurysm.

Grading of Injury

From: Simple Medicine website, http://simple-med.blogspot.com/

 American Association for the Surgery of Trauma (AAST) Grading for Renal Injury

Grade I: Subcapsular, nonexpanding hematoma. Microscopic or gross hematuria with normal urologic studies in contusions.

Grade II: < 1 cm parenchymal depth of cortex laceration without urinary extravasation. Non-expanding hematoma confined to renal retroperitoneum.

Grade III: > 1 cm parenchymal depth of cortex laceration without urinary extravasation.

Grade IV: Laceration extending up to cortex, medulla and collecting system. Renal artery or vein injury with contained hemorrhage.

Grade V: Complete shattered kidney. Avulsion of renal hilum that devascularizes the kidney.

*Grading to standardize description for research and collection purposes.

**Generally the lower the grade I - III, the less likely need for operative intevention provided patient is stable.

***This grading is developed for adults that although may apply for children, but management should be based on case to case basis.

The following pictures are not only from pediatric cases.

Grade III renal injury. Hypoechoic lesion in the left kidney after an MVA.

Grade V renal injury. Note the lacerations through and through the left kidney with surrounding hematoma.

Management

• As mentioned, most (~98%) require only bed rest and observation in stable patients, even in grade IV and V injuries.
• However, falling blood counts (Hb), persistent gross hematuria, hemodynamic instability and multiple transfusion requirements may indicate ongoing bleeding.
• Arteriography and embolization to be considered in selective cases. 
• Unstable patients may need explorative laparotomy.
• Nephrectomy to be considered in extensive unsalvagable injuries, especially in hemodynamically unstable patients. 
• Preservation of vessels attempted in cases of solitary kidneys or bilateral non-functioning kidneys.

Complications of Non-operative Management

• Ongoing bleeding.
• Urinary extravasation, may present as ileus, abdominal flank mass or discomfort. Urinomas, most resolve spontaneously.
• Perinephric abscess.
• Hydronephrosis
• Arterio-venous fistula
• Pseudoaneurysm
• Pyelonephritis
• Renal calculi
• Hypertension, may be delayed.

Follow-up

• Most have normal renal function and without hypertension.
• The above complications need to be sought out.
• Further imaging (ultrasonography to reduce radiation exposure) may be required if complications develops. 

Challenge:

Describe the images:

References:

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


Other future related topics to write on:

• Management of trauma in children.
• Ureter, bladder and urethral injuries.
• Operative management.
• Wilm's tumor.
• Management Congenital anomalies.

Congenital Diaphragmatic Hernia: Short Notes

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Incidence

1 in 2000 - 5000 live births (unknown Malaysian figures)

Bochdalek hernia most common, left sided (80%)

Morgagni hernia (2%) usually in older children

Embryology

-       Diaphragm fusion involves 4 layers:

o   Septum transversum anteriorly

o   Pleuroperitoneal membrane dorsolaterally

o   Esophageal mesentry

o   Muscular portion from intercostal muscles

-       Starts at 4^th week of gestation

-       Completes at 8^th week of gestation

-       Lungs develope as a derivative from foregut and forms a diverticulum. Two lung buds form at around 4th week of gestation.

-     Airway differentiation developes up to 24 weeks of gestation. This is followed by appearance of pneumocyte I and II, the later responsible for secreting surfactant.

-     Vascular deveopement occur concurrently with lung growth. 

Pathology:

-       Gut herniates through the yolk sac and returns into the abdominal cavity at 8 – 9^th week of gestation.

-       Failure of closire of diaphragm results in hernia

-       May cause obstruction to the esophagus (resulting in polyhydroamnios)

-       Circulation maintained as fetus is dependant on utero-placental-fetal circulation

-       After birth, adult type of circulation unable to be achieved due to persistent raised pulmonary pressure and reduction in pulmonary blood flow.

-       This results in right to left shunt resulting in deoxygenated blood circulating in the system and results in increase in pulmonary pressure.

Diagnosis

Antenatal:

Ultrasound

-       Stomach or other abdominal organ in the fetal thorax

-       Polyhydromnios (80%)

At birth:

-       Respiratory distress

-       Scaphoid abdomen (need high index of suspicion)

-       Asymmetrical distended chest wall

-       Shifted heart sounds (‘Dextrocardia’ is CDH until proven otherwise)

-       Absent breath sounds

-       Hypotension and peripheral hypoperfusion (reduced venous return from caval compression)

-       Chest X-ray: Loops of intestine or stomach in chest wall. Clearer if NG tube inserted.

-       Contrast studies might be indicated in certain cases but usually not necessary.

Some late presentations present with chronic lung disease, recurrent coughs, pneumonia.

Notice the heart on the right side and the nasogastric tube tip ending in the thorax.

 

Associated Anomalies

High incidence of lethal congenital anomalies asociated with CDH

-       Skeletal defects (32%)

-       Cardiac anomalies (24%)

-       Tracheobronchial anomalies (18%)

-       Neural tube defects

Differential Diagnosis:

Eventration of the diaphragm (weakness of the diaphragm ie. Phrenic nerve injury)

Management

Antenatal:

-       Tertiary center delivery with well equiped NICU and pediatric surgery support.

-       Transport to be made in-utero.

-       Parent counselling

-       Amnicentesis for karyotyping if suspected congenital anomaly

-       Delivery as indicated, not necessary for Caesarian section

-       In-utero intervention remains experimental

Delivery:

-       NBM

-       Ryles tube insertion

-       Prompt intubation, avoid bagging as may distend stomach and worsen condition. Difficulty to ventilate in unknown cases should have high index of suspicion.

-       Avoid excessive bagging as high risk of barotrauma and pneumothorax.

-       Adequate ventilation, pulmonary hypertension and pulmonary hypoplasia is the main complication of CDH and requires aggressive ventilatory support.

-       Adequate fluid resuscitation as hypotension may develop due to pulmonary hypertension.

-       Prompt surgical intervention not needed. Stabilization of patient and delayed surgery is preferred but lacking of controlled studies.

-       Extracorporeal membrane oxygenation (ECMO) in certain selected cases.

Surgery:

-       Approach: Subcostal or thoracotomy

-       Reduction of herniated organs

-       Primary repair

-       Placement of prosthesis over repaired diaphragm

-       Muscular and fascial flaps may be used to close repaired diaphragmatic defects.

-       Closure of abdominal incision might need to be done in two phases as there might not be enough ‘space’ for the returned abdominal organs. Silo might be necessary while awaiting for abdominal wall to expand for closure later.

-       ECMO support if necessary during surgery, but high risk of mortality from bleeding.

-       Chest tube not routine and only if indicated (pneumothorax)