Congenital Abdominal Wall Defects and Umbilical Hernias Flashcards
A 1-month-old neonate has an umbilical hernia with a palpable 1-cm defect. Which of the following statements is true?
A. The likelihood of spontaneous closure is low, and the hernia should be repaired.
B. Indications for the early repair of an umbilical hernia include a history of incarceration, a large skin proboscis, and the presence of a ventriculoperitoneal shunt.
C. Repair of the hernia defect should include the placement of a mesh.
D. Complete closure of the umbilical ring may be expected in 30% of children by the age of 4 to 6 years.
E. All of the above.
ANSWER:
B
COMMENTS: Umbilical hernias occur as a result of persistence of the umbilical ring. By the age of 4 to 6 years, the closure of this ring can be expected in 80% of children.
In patients with umbilical hernias with greater than a 2-cm defect, spontaneous closure is less likely. Umbilical hernias are usually repaired early if the defect is greater than 2 cm, there is a history of incarceration, or a large skin proboscis or a ventriculoperitoneal shunt is present.
Repair of an umbilical hernia involves an infraumbilical semicircular incision, separation of the hernia sac from the overlying skin, repair of the fascial defect, fixation of the base of the umbilicus to the fascia, and closure of the skin.
The fascial closure is rarely under tension and does not require a prosthetic mesh.
With regard to neonatal defects of the abdominal wall, which statement is correct?
A. In gastroschisis, the herniated bowel contents are covered by a membrane.
B. Gastroschisis is frequently associated with cardiac malformations.
C. Chromosomal abnormalities are often present with omphalocele.
D. Treatment of abdominal wall defects is the immediate surgical closure of the fascial defect.
E. In omphalocele, a silo bag is placed to cover the exposed intestine.
ANSWER: C
COMMENTS: Both omphalocele and gastroschisis are neonatal abdominal wall defects. In omphalocele, the defect is a failure of abdominal wall formation and contraction of the umbilical sac. The extraabdominal contents are covered by layers of peritoneum and amnion. In contrast, in gastroschisis, the abdominal wall is complete, but there is a hernial defect to the right of the umbilical ring with external herniation of the intestines. Approximately 50% of infants born with omphalocele have other malformations, including cardiac and chromosomal abnormalities. Anomalies associated with gastroschisis are rare, with the major exception being intestinal atresia.
The initial management of patients with abdominal wall defects consists of nasogastric decompression, intravenous fluids, broadspectrum antibiotics, and protection of the protruding abdominal contents. In omphalocele, the sac is covered with a sterile occlusive dressing, and a workup for associated anomalies is initiated. In gastroschisis, a silo bag is placed to cover the exposed intestines. A complete medical evaluation and resuscitation of the infant with the protection of the abdominal contents take precedence over a surgical closure. A surgical repair of omphalocele depends on the size. Small omphaloceles may be treated with serial attempts to reduce the intestinal contents into the abdominal cavity. Once the cavity is large enough to accept the contents, a definitive fascial closure can be performed. Surgical management of large omphaloceles is difficult and not standardized. Options include painting the sac with an antiseptic to encourage epithelialization, skin grafting, use of Gore-Tex or other meshes, or wound vacs.
Definite closure of gastroschisis also depends on the size of the abdominal cavity and the extent of herniation. Early closure after birth with primary reduction and fascial repair is performed when possible. If not, a silo bag is placed to cover the intestines and serially reduce them into the abdominal cavity over time.
What 5 structures are present in the umbilicus?
The umbilical vein, 2 umbilical arteries, the omphalomesenteric (or vitelline duct), and the urachus (or allantois).
How long does it take for the umbilical cord stump to fall off?
On average, about 10–14 days but it can vary widely.
What is omphalitis?
A newborn infection of the umbilical tissues and surrounding skin.
How is omphalitis managed?
If severe, it requires parenteral antibiotics and possibly debridement. Most cases however, will respond to oral antibiotics and careful hygiene measures. Topical alcohol can be used to dry out the tissue.
What is an umbilical granuloma?
A small fleshy appearing nodule of granulation tissue in the umbilicus after the
umbilical cord stump has fallen off.
How are umbilical granulumas treated?
Classically, they are treated with topical silver nitrate over the course of several applications. Care must be taken not to burn the surrounding skin. Silver nitrate can stain the skin and clothing. Topical steroids may also be an effective therapy [1].
What if there is bilious drainage from the umbilicus?
There would be concern for a patent omphalomesenteric duct or an omphalomes- enteric cyst. Further workup is not typically necessary if the physical exam confirms the diagnosis. If it is unclear a contrast study or an ultrasound might be helpful.
How is an omphalomesenteric duct remnant treated?
These require operative exploration and excision. If there is a connection to the bowel, it should be closed in a fashion so as not to narrow the bowel lumen. Often, this can be done just through an umbilical incision without needing a larger laparotomy.
What if the drainage is more consistent with urine?
This is highly suspicious for a patent urachus. Similarly, a contrast study or an ultrasound could be helpful. Some advocate obtaining a voiding cystourethrogram to evaluate for a distal urinary obstruction prior to surgery, however this may not be necessary. The operation to remove the patent urachus can be done through an open umbilical incision or via a laparoscopic approach where excision and ligation are done down to the level of the dome of the bladder [2].
Can urachal anomalies present later?
There can be urachal sinuses or cysts that manifest later with infectious com- plications. If so, they can be treated with antibiotics and then excised electively. Although exceptionally rare, there can be malignant degeneration into urachal cancer [3].
What causes an umbilical hernia and how common are they?
After the umbilical cord stump falls off, the ring is supposed to close spontaneously. Umbilical hernias occur when the umbilical ring doesn’t close. They are extremely common, affecting up to 23% of newborns in the US each year [4].
Are umbilical hernias more common in certain types of patients?
Premature infants have a very high incidence of umbilical hernia at birth. Also, African Americans have a higher incidence than other races.
Do all umbilical hernias require urgent repair?
No, many will close spontaneously. Unless there are symptoms of incarceration or strangulation, watchful waiting is appropriate. Furthermore, there is some data to suggest that early repair is associated with a higher rate of complications [5].
What is the right time to repair an asymptomatic umbilical hernia?
There is no consensus regarding optimal timing for repair of an asymptomatic umbilical hernia. However, the risk of complications such as incarceration or strangulation is quite low, so waiting until age 4–5 years is a reasonable approach and is not affected by the size of the hernia [4, 5].
How do you repair an umbilical hernia?
Classically, a curved infra-umbilical incision is used. The apex of the hernia sac is separated from the umbilical dermis and the sac excised down to healthy fascia. The fascia is closed with absorbable suture and then the umbilical dermis tacked down to the fascia. The skin is closed and a compressive dressing is applied.
What is the incidence of gastroschisis and omphalocele?
The incidence of gastroschisis is 1 in 4,000 live births, the incidence of omphalocele is 1 in 4–6,000 live births.
The incidence of gastroschisis has been increasing in all maternal age groups over the last two decades without a known etiology.
The incidence of omphalocele has remained stable over time [1].
What are risk factors for gastroschisis and omphalocele?
Known risk factors for gastroschisis include young maternal age, lower socioeconomic status, vasoactive recreational drug use, aspirin use, low body mass index, prematurity, gestational diabetes, use of antidepressants and cigarette smoking.
Risk factors for omphalocele include numerous syndromes and chromosomal abnormalities that will be outlined below.
What is the pathophysiology of gastroschisis and omphalocele?
The exact etiology remains unknown for abdominal wall defects.
The most widely accepted theory for the etiology of gastroschisis is the lateral ventral body folds theory, which suggests the condition stems from failure of migration of the lateral folds.
Omphalocele is thought to arise from failure of the viscera to return to the abdomen during development due to a developmental arrest at that time.
In both instances, there is an accompanying loss of abdominal domain which substantially impacts management [1].
Presentation of gastroschisis and omphalocele?
Gastroschisis presents as eviscerated bowel without a covering membrane, usually to the right of umbilicus [2].
Omphalocele presents as a membrane covered bowel and liver in the midline.
Care must be taken not to mistake ruptured omphalocele for gastroschisis [3].
What anomalies are associated with gastroschisis and omphalocele?
Gastroschisis is associated with other intestinal atresia in 10–15% cases.
Omphalocele is more frequently associated with other anomalies, including chromosomal (trisomy 13, 18, 21, and 45X), syndromic (Beckwith-Weideman, pentalogy of Cantrell) and non-syndromic organ system abnormalities (cardiac defects) [1–3].
How are gastroschisis and omphalocele diagnosed prenatally?
In most cases AWD are detected prenatally. They are both associated with elevated maternal serum alpha-fetoprotein levels and are diagnosed on ultrasonography.
Gastroschisis has intestinal loops floating in amniotic fluid and growth retardation.
Omphaloceles have a variable size and contents, with potential anomalies in other organ systems.
How are patients with abdominal wall defects followed prenatally?
For gastroschisis, factors to watch for on prenatal imaging include intra-abdominal bowel dilation, bowel wall thickening, gastric dilation, IUGR, polyhydramnios, liver or urinary bladder herniation, and changes in bowel dilation during the ges- tation.
For omphalocele, karyotyping via amniocentesis and prenatal ultrasound, particularly looking for cardiac and central nervous system anomalies that may affect survival and whether termination of the pregnancy is considered [1–3].
What timing/mode of delivery is optimal for gastroschisis and omphalocele?
Vaginal delivery has been shown to be both safe and beneficial to the mother and baby.
Cesarean should be reserved for specific obstetric or fetal indications.
Term or close to term delivery is recommended for both.
Initial management of a patient with gastroschisis?
The intestines need to be covered with a ‘bowel bag’, and intravenous fluid resuscitation should be started.
Babies should be positioned laterally to reduce mesen- teric kinking.
The defect should be enlarged at the fascial level if it is too tight.
Initial management of a patient with omphalocele?
Care should be taken to prevent damage to the sac, and cover with a moist gauze.
Intravenous fluid resuscitation should be started at the same time that a cardiac evaluation is performed and examination for other syndromes and defects is carried out [3].
How is the decision made to use a silo versus primary closure in gastroschisis?
Regardless of which approach is used, maintaining adequate bowel perfusion by avoiding kinking of the mesenteric vessels and high intra-abdominal pressures is key to maintaining bowel viability.
Overall, outcomes are equivalent for simple gastroschisis that is closed primarily versus being placed in a silo.
Definitive closure can be obtained in a variety of ways, ranging from sutured closure of the skin and fascia, to sutureless closure using the umbilical stalk as a patch to close the skin defect and allowing the defect to close spontaneously.
How should the fascial opening be enlarged in a patient with gastroschisis if the bowel appears to be ischemic in the silo?
If the fascial defect appears to be causing bowel compromise the fascia can opened.
The facial opening is generally extended to the patient’s right (opposite the umbilical cord) to avoid injury to the umbilical vein medially. The skin does not need to be opened in most cases.
What is closing or vanishing gastroschisis?
Closing or vanishing gastroschisis refers to when the fascial defect decreases in size or closes completely prior to birth. This can result in bowel compromise with an atresia and potential for short bowel syndrome [2].
What defines complex gastroschisis?
Complex gastroschisis is defined as those patients with intestinal complications including atresia, ischemia, or perforation at birth. Development of NEC was con- sidered to be complex, however that is not present at birth and has been excluded [1, 2].
What is a ruptured omphalocele?
The amniotic sac can rupture prenatally in patients with omphalocele.
While the basic principles of the bowel requiring coverage to prevent dehydration and infection still apply, recognition of this is critical as it affects the workup that the patient requires and the comorbidities that will affect the patient’s course.
In general, these patients will not have adequate abdominal domain to be able to place a spring-loaded silo and will require a silo or mesh to be sewn to the fascia and skin for placement.
These are difficult conditions to manage [3].
What are the key points of postoperative care for patients with abdominal wall defects?
Following abdominal closure, patients should be closely monitored for signs of abdominal compartment syndrome, including respiratory compromise, hypotension, and impaired renal function. Nutritional support with parenteral nutrition will be required until bowel function returns.
Why do patients with gastroschisis have difficulties with feeding, even after reduction?
Impaired bowel motility and ability to absorb nutrients both lead to feeding difficulties in neonates with gastroschisis.
This bowel dysfunction is thought to be related to the inflammatory peel that occurs as a result of contact of the bowel with amniotic fluid, as well as to decreased numbers of interstitial cells of Cajal seen on pathologic analysis.
Use of prokinetic agents has not been shown to improve time to goal feeds.
It takes 2–4 weeks in cases of simple GS for the dysmotility to resolve [2].
What are the surgical options for closure of omphaloceles?
A variety of options exist that are used based on the size of defect and the ability of the patient to undergo surgical interventions.
Primary repair can be performed in some patients with small defects (with those <1.5 cm commonly called hernias of the cord) when the patient has adequate abdominal domain and the associated anomalies do not preclude surgical intervention.
Other methods include staged closure, in which the amniotic sac is inverted to serially reduce the abdominal content until the abdomen can be closed primarily or with mesh.
Delayed closure involves excising the amniotic sac and sewing a mesh to the abdominal wall fascia or skin that can be used for reduction prior to closure.
Scarification involves the use of topical agents to promote formation of an eschar over the amniotic sac that will gradually epithelialize over time.
If closure of the abdomen does not involve closure of fascia, the resulting ventral hernia is generally closed primarily or in stages when the child is several years old [1, 3].
What are the long-term outcomes for patients with abdominal wall defects?
Overall outcomes for patients with gastroschisis are largely based on whether it is a simple or complex defect.
Those with complex GS have longer length of stay and are far more likely to develop intestinal failure and liver disease.
Gastroschisis remains the leading cause of intestinal failure requiring intestinal transplant.
It is also associated with cryptorchidism, which is generally addressed at one year of age.
Malrotation is part of the defect, but rarely leads to volvulus.
Intestinal obstruction may occur and present with bilious emesis and should be promptly assessed [1, 2].
For patients with omphalocele, outcomes are likely related to several factors, most notably associated cardiac and neurologic anomalies.
Additionally, pulmonary hypoplasia is common in omphalocele patients with large defects and can lead to long term respiratory failure requiring tracheostomy.
Several risk stratification categories have been created, but none is commonly used [1, 3].
What are the neurodevelopmental outcomes for patients with abdominal wall defects?
Neurodevelopmental outcomes among patients with gastroschisis have not been well studied and are largely unknown to date.
Patients with omphalocele overall have decreased motor and language score for age, with 35% having severe neu- rodevelopmental delay, which may reflect the multiple congenital issues.
Simple gastroschisis patients are not considered to have any long-term neurodevelopmental issues [1–3].
Components of the Pentalogy of Cantrell?
Sternal cleft Ectopia cordis Cardiac structural defects Epigastric omphalocoele Morgagni hernia
How do you resuscitate a neonate with gastroschisis?
Neonates with gastroschisis have significant evaporative water losses from the open abdominal cavity and exposed bowel.
Appropriate intravenous access should be obtained and fluid resuscitation initiated after birth.
Nasogastric (NG) decompression is important to prevent further gastric and intestinal distention.
Routine endotracheal intubation is not necessary.
The bowel should be wrapped in warm saline-soaked gauze and placed in a central position on the abdominal wall.
The neonate should be positioned on the right side to prevent kinking of the mesentery with resultant bowel ischemia.
Viscera are covered by a plastic wrap or the infant is placed partially in a plastic bag (“bowel bag”) to reduce evaporative losses and improve temperature homeostasis.
Although gastroschisis most often is an isolated anomaly, thorough examination of the neonate is important.
Concomitant bowel atresia is the most common associated anomaly in patients with gastroschisis, with rates ranging from 7–28% in several series.
A review of the literature noted rare occurrences of associated anomalies in the cardiac, pulmonary, nervous, musculoskeletal, and genitourinary systems, as well as chromosomal abnormalities in babies with gastroschisis.
Additional evidence suggests that excess fluid resuscitation is detrimental and results in edema, an increase in time to closure, and an increased risk of abdominal compartment syndrome.
How do you manage closing gastroschisis?
An intestinal atresia should be differentiated from “vanishing bowel” in infants with gastroschisis.
A “closing gastroschisis” is when the defect size decreases prior to delivery.
As the hole gets smaller, the blood supply to the viscera progressively diminishes and can result in an atresia.
In extreme cases, the intestine outside the abdominal cavity completely disappears and results in congenital short bowel syndrome.
There is no prenatal US finding that can reliably distinguish this condition. However, intra-abdominal bowel distention or dilation can occur, which can help in deciding to deliver early in some patients.
Although this is a rare finding, it usually results in short bowel syndrome.
[H&A]
—
A particularly devastating form of complex gastroschisis, closing gastroschisis, is increasingly being reported. This is essentially a strangulated gastroschisis due to in utero closure of the defect.
The anomaly also presents with a wide spectrum of findings, but typically results in bowel atresia proximally and distally with severe ischemia or necrosis of the eviscerated bowel. Short bowel syndrome is common.
Closing gastroschisis may be suspected if intra-abdominal bowel dilatation is seen on ultrasound, in combination with a stable, dilating, or possibly shrinking extra-abdominal bowel mass. This may be an indication for early delivery, affording an opportunity to salvage the bowel from an impending catastrophe.
Ultrasound findings showing progressive intra-abdominal and extra-abdominal dilatation, raises the suspicion of closing gastroschisis.
[Sherif]
How do you differentiate gastroschisis from omphalocoele?
What are surgical approaches for managing omphalocoele?
There are a large variety of repairs described, as a one-sizefits-all option does not exist.
In a recent survey, authors of reports from 1967–2009 discussing closure of giant omphaloceles were asked to see if they were still using the same approach or whether they had modified their techniques.
Interestingly, 42% of the authors no longer use the approach they favored in the original article.
They concluded that there is currently no completely accepted technique to treat giant omphaloceles and two methods are used the most: staged closure and delayed closure.
Bauman et al. reported a systematic review of the literature for repair of a giant omphalocele, with the data favoring initial nonoperative scarification.
The definition of a giant defect is variable as some surgeons use size alone, others consider the presence or absence of liver herniation, others use an estimate of the amount of intestinal contents, and still others have used a combination of the amount of liver and intestine in the sac as well as size.
This lack of an accepted definition is part of the reason for an inability to arrive at a consensus for management.
[H&A]
—
First, is the omphalocele small or large? A defect resulting in only bowel herniation is usually small and can be closed primarily without tension or increased intra-abdominal pressure. This is the case even if the entire bowel mass is herniated.
If the omphalocele is large and contains solid organs, this should prompt the second question: Are there significant cardiorespiratory comorbidities that are resulting in oxygen dependence, respiratory insufficiency, or hemodynamic instability?
If the answer to this question is affirmative, the baby is best served by omitting any surgical procedure and applying local treatment to produce an eschar of the sac.
The most common agent used currently is silver sulfadiazine which is applied to the sac once or twice daily.
A controlled ventral hernia results and can be closed in one or more procedures later in life after the cardiorespiratory morbidities have been addressed.
A component separation technique may be required in these patients to avoid mesh placement, but the overwhelming majority can be closed primarily.
If the baby does not appear to have any significant cardiorespiratory comorbidity after 24–48 hours of observation, the goal should be to obtain complete fascial closure during the first few weeks of life in a primary or staged manner.
Primary closure should be attempted and has proved successful in many cases of large defects containing all or most of the liver, such as seen in the index case. The surgeon can get an impression of abdominal domain by examining the abdomen. In some patients, the abdomen will appear “empty” despite a large omphalocele.
In giant omphaloceles, the rectus muscles are always far apart. Transverse closure may be easier.
Interrupted figure of eight or Smead-Jones sutures placed along the defect and then tied sequentially is my preferred technique.
If the contents cannot be reduced due to lack of abdominal domain, or if the closure results in increased mean airway pressure over 25cm H2O or hemodynamic compromise, the surgeon can either use a biologic mesh to close the abdomen or convert to a staged closure by installing a spring-loaded or sutured silo, with or without an abdominal expander.
In selected patients, the redundant omphalocele sac can be used as a silo.
Vacuum-assisted closure (VAC) has also proved useful in these difficult cases.
[Sherif]
How should umbilical hernias be managed?
For many years, it has been known that umbilical hernias will close spontaneously.
It is very safe to observe the hernia until ages 4–5 years to allow closure to occur.
Pressure dressings and other devices to keep the hernia reduced are not suggested and do not enhance the closure process. Instead they may result in skin irritation and breakdown.
A number of studies have demonstrated spontaneous resolution rates of >90% of hernias by 1 year of age.
One study found that 50% of hernias still present at age 4–5 years will close by age 11 years.
Another study suggests that hernias with fascial defects greater than 1.5 cm are unlikely to close by age 6 years, whereas other series conclude that even large defects may spontaneously resolve without an operation.
The primary danger associated with observation is the possibility of incarceration or strangulation.
Studies have shown these complications to be quite rare, with an incidence less than 1%.
Patients with small fascial defects (0.5–1.5 cm in diameter) appear more prone to incarceration.
Operative closure of an umbilical hernia is generally straightforward and usually can be completed as an outpatient procedure.
A small transverse infraumbilical incision is made, usually placed in the redundant skin, which is inverted at the conclusion of the procedure, thereby hiding the incision.
The hernia sac is identified and dissected free from the dermis underlying the umbilical cicatrix.
The authors’ preference is excision of the sac to the fascial edges, although other surgeons prefer a more limited excision of the sac or inversion of the sac through the fascial opening.
Interrupted sutures with 0 or 2-0 nonabsorbable or longlasting absorbable sutures are placed and tied, closing the fascial defect in a transverse direction.
Using 3-0 absorbable suture, the dermis of the umbilicus is tacked in two places to the fascial closure.
Inversion of the umbilical skin may be impaired in the setting of a fascial remnant of the umbilical stalk or a thickened dermis.
To improve skin inversion, radial partial-thickness incisions on the undersurface of the umbilicus in the fascia and dermis can be performed.
The skin incision is closed with an absorbable subcuticular suture, and a dressing is applied.
Many surgeons use a pressure dressing to help prevent the development of a hematoma and keep the umbilical skin inverted, but it is not clear if this type of dressing is necessary.
Methods used commonly in the adult, such as prosthetic placement, are almost never needed in the child.
Excision of the redundant skin is usually not needed because the umbilicus tends to return to a normal appearance after the hernia is repaired. This can take up to 12 months to occur, and the family should be reassured appropriately.
If the umbilicus fails to return to an acceptable appearance after 1–2 years, there are a number of techniques described to restore it to a more normal configuration.
Complications of umbilical hernia repair are infrequent and include seroma or hematoma formation. These are usually self-limited and resolve spontaneously.
Wound infections generally can be managed with local care and antibiotics, whereas a recurrent hernia, occurring in less than 1%, requires reoperation.
A male infant is precipitously delivered after a placental abruption at 30 weeks gestation. The infant shows clear signs of distress and is taken to the neonatal intensive care unit (NICU) for further monitoring, with umbilical catheters being placed. Which of the following organs is most likely supplied by the remaining patent portion of the umbilical artery?
Choices:
1. Liver
2. Stomach
3. Spleen
4. Bladder
Answer: 4 - Bladder
Explanations:
• The pelvic portion of the umbilical artery remains patent and becomes the superior vesical artery. The superior vesical artery supplies the superior portion of the bladder.
• The remainder of the umbilical vessel is converted into the medial umbilical ligament, which extends from the pelvis to the umbilicus.
• The umbilical artery originates from the internal iliac artery and travels within the umbilical cord to the placenta in utero.
• The distal part of the superior vesical artery converts to the medial umbilical ligament, which courses superiorly along the abdominal wall to the umbilicus.
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