MCQs in Neonatology - II

Q 1:

You are discussing with a medical student the criteria for screening infants in the neonatal intensive care unit for retinopathy of prematurity.

Of the following, the MOST accurate statement is that:

A. all infants exposed to prolonged supplemental oxygen should be screened independent of gestational age

B. all infants whose gestational age is less than 29 weeks should be screened independent of oxygen   

      exposure

C. optimal frequency for serial examination is at 2-week intervals for zone I or stage 3 disease

D. optimal time for final retinal examination is at 40 weeks’ postmenstrual age

E.  optimal time for initial retinal examination is within 2 weeks of birth

Answer

B

All infants whose gestational age is less than 29 weeks should be screened for retinopathy of prematurity (ROP) independent of oxygen exposure. Prematurity is the principal predisposing factor for the occurrence of ROP; the risk of ROP varies inversely with gestational age. 

ROP is classified according to location and extent of disease, severity of abnormal vascularization, and the presence or absence of dilatation of the posterior retinal vessels (referred to as plus disease). The location of the disease is described by zones I to III and the extent by comparing the retina with a clock face marked off by hours 1 to 12. The severity of abnormal vascularization is described by stages 1 to 3. Prethreshold ROP is defined as zone I, any stage; zone II, stage 2 with plus disease; or zone II, stage 3. Threshold ROP is defined as stage 3 disease extending to five contiguous or eight cumulative hours in zone I or II with plus disease. Prethreshold ROP carries a poor prognosis for visual function and warrants weekly monitoring by eye examination for progression. Threshold ROP is an indication for cryotherapy or laser photocoagulation.

            The optimal time for initial retinal examination is between 4 and 6 weeks’ chronologic age or 31 and 33 weeks’ postmenstrual age, whichever occurs earlier. Retinal vascularization typically starts near the optic nerve at approximately 20 weeks’ gestational age. Progression of the retinal vessels toward the periphery of the retina occurs steadily thereafter. Abnormalities of retinal vessels become evident at approximately 4 weeks’ chronologic age or 31 weeks’ postmenstrual age. Earlier eye examinations, therefore, will have a minimal yield.

            The optimal time for final retinal examination in ROP is at 44 weeks’ postmenstrual age. Normally, the retina is fully vascularized at that age. Any progression or new occurrence of ROP is extremely unlikely thereafter

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Q 2

A newborn who weighs 1,250 g and whose estimated gestational age is 32 weeks is receiving mechanical ventilation at 12 hours after birth. His ventilator settings are: ventilator rate, 18 breaths/min; fraction of inspired oxygen, 0.4; peak inspiratory pressure, 23 cm H2O; and positive end expiratory pressure, 4 cm H2O. Physical examination reveals good chest excursion and equal breath sounds, with heart sounds heard best to the left of the sternum on the midclavicular line. Measurements of arterial gases include: pH, 7.20; Po2, 68 mm Hg; Pco2, 60 mm Hg; and Hco3, 24 mEq/L.

Of the following, the MOST appropriate next step in management is to:

A.  administer sodium bicarbonate

B.  increase ambient oxygen

C.  increase peak inspiratory pressure

D.  increase ventilator rate

E.   rule out pneumothorax

Answer 

D

The infant described in the vignette has blood gas evidence of respiratory acidosis, as indicated by a low pH (normal, 7.35 to 7.45) and a high Pco2 (normal, 35 to 45 mm Hg). The acidosis does not have a metabolic component, as evidenced by a normal Hco3 measurement (24 mEq/L). The appropriate course of action is to increase ventilation by increasing the ventilator rate, which should improve minute ventilation and gas exchange.

            Administration of sodium bicarbonate is not indicated because the infant does not have metabolic acidosis. In the presence of uncorrected respiratory acidosis, sodium bicarbonate can raise the Pco2 further and worsen the pH.

            The infant’s oxygenation is normal, as indicated by the arterial Po2 (normal, 60 to 80 mm Hg), so increasing the ambient oxygen concentration is unnecessary.

            The good chest excursions exhibited by the infant obviates the need to increase the peak inspiratory pressure. Although an improvement in ventilation can be achieved by increasing the peak inspiratory pressure, such an action carries a potential risk of lung injury associated with high ventilator pressures.

            The good chest excursions, equal breath sounds, and a lack of evidence of a mediastinal shift based on the normal location of the heart sounds makes pneumothorax unlikely. However, it is prudent to suspect pneumothorax in any infant undergoing mechanical ventilation who has respiratory acidosis and/or hypoxemia.

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Q 3

During a health supervision visit, the parents of a 3-week-old female infant express their concern about a pink vaginal discharge noted with each diaper change.

You explain to the parents that the MOST likely reason for this finding is:

A. diaper dermatitis

B.  estrogen withdrawal

C.  urinary tract infection

D.  vaginitis

E.   vitamin K deficiency

Answer

B

Estrogen withdrawal is the most common cause of uterine bleeding in the newborn. The fetus is exposed to maternal estrogens in utero and becomes accustomed to certain hormone levels. Postnatally, infant estrogen levels decrease to prepubertal amounts, prompting uterine withdrawal bleeding. The bleeding may be preceded by a physiologic clear or whitish vaginal discharge (similar to leukorrhea) that later becomes pink or blood-tinged. This usually occurs during the second or third week of life and does not last for more than a few days. The amount of blood loss is negligible. Maternal estrogen exposure also can cause breast tissue enlargement in both male and female neonates.

            Diaper dermatitis, a common entity in infants, usually is not associated with bleeding. Minimal skin bleeding can be seen with severely macerated rashes, but this can be distinguished readily from vaginal bleeding on the physical examination.

            Vitamin K deficiency can cause bleeding, but the intramuscular administration of vitamin K immediately after birth is a universal practice. In addition, other signs of bleeding, such as petechiae, probably would accompany the uterine bleeding.

            A urinary tract infection in the neonate generally manifests as poor feeding, irritability, fever, or lethargy. In addition, the infant may have poor weight gain. Vaginal bleeding does not occur with urinary tract infections, and rarely is the urine grossly bloody.

            Vaginitis is unusual in the neonate unless there is a congenital anomaly (eg, ectopic urethra).

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Q 4

The pregnant mother of a 3-year-old girl in your practice is concerned because her obstetrician just told her that her serum alpha-fetoprotein value is markedly increased.

Of the following, the MOST appropriate advice to give to this woman is that she should:

A.have an ultrasonographic examination to date her pregnancy and to search for fetal anomalies

B.have another blood sample drawn to repeat the test

C.have chorionic villus sampling as soon as possible to determine the chromosome complement of the fetus

D. obtain further testing only if she older than age 35

E. only be concerned if there is a history of open neural tube defects in her family


Answer

A

Alpha-fetoprotein (AFP) is produced by the fetal liver and crosses the placenta to enter the maternal circulation. Any defect that causes a breech in fetal skin can result in increased levels of AFP in the maternal circulation due to leaking of the protein. These fetal defects include open neural tube defects, anencephaly, and omphalocele. Maternal serum AFP (MSAFP) levels also can be increased in twin pregnancies, with fetal demise, and in pregnancies in which the fetus has congenital nephrosis. Because the measurement of MSAFP is simple and inexpensive, the American College of Obstetricians and Gynecologists, the American Society of Human Genetics, and the American Academy of Pediatrics recommend offering MSAFP screening to all pregnant women at 16 to 18 weeks of gestation. However, such screening should be undertaken only if there is adequate counseling, access to high-quality laboratory services, and appropriate facilities for follow-up testing (ie, qualified diagnostic centers that offer conventional and high-resolution ultrasonography and amniocentesis). More recently, additional biochemical markers have been added to this screening test to permit the identification of pregnancies at increased risk for chromosomal abnormalities, most notably trisomy 21.

Because elevated MSAFP levels are associated primarily with open neural tube defects, which usually do not result from chromosome abnormalities, chorionic villus sampling, which is used to determine fetal karyotype, would not be indicated for the woman in the vignette. In addition, AFP cannot be measured in chorionic villi. 

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Q 5

A newborn male develops bilious vomiting shortly after birth. Abdominal radiography shows distended loops of small intestine that have a ground-glass appearance. No calcifications are seen. Barium enema reveals a normally positioned but contracted microcolon.

Of the following, these findings are MOST characteristic of:

A. Hirschsprung disease

B.  malrotation

C.  meconium ileus

D.  meconium peritonitis

E.  volvulus


Answer

C

Meconium ileus is the third most common etiology of neonatal small bowel obstruction, accounting for 9% to 33% of cases. In most patients, meconium ileus is associated with cystic fibrosis; it is the presenting symptom of this disease in 10% to 25% of cases. The obstruction is caused by the thick, tenacious meconium that cannot be passed beyond the terminal ileum, resulting in the ground-glass appearance on radiography and dilation of the proximal small intestine. The meconium contains high concentrations of protein and mucoproteins and appears to be related to exocrine pancreatic insufficiency and abnormal intestinal secretions. In some instances, the inspissated meconium may serve as a fulcrum for volvulus of the bowel, leading to ischemia, necrosis, and perforation of the affected intestinal segment in approximately 50% of cases.   The differential diagnosis of meconium ileus is meconium plug syndrome, ileal atresia, colonic atresia, intestinal pseudo-obstruction, and Hirschsprung disease. Often the family history of cystic fibrosis suggests the diagnosis.

            Within the first few days of life, infants who have meconium ileus develop abdominal distension. They fail to pass meconium and vomit bilious material. Due either to the pulmonary complications of cystic fibrosis or the abdominal distension, infants often develop respiratory distress. Peristalsis of the intestine is increased, and the rectal vault is empty.

            Radiographic examination is diagnostic of meconium ileus in most patients, revealing minimal air-fluid levels and a sentinel loop of small intestine in approximately 50%. Intraluminal calcifications are noted in a small number of patients. The ground-glass appearance is due to air bubbles trapped in the meconium. Barium enema shows microcolon of the unused large intestine and may outline the obstructing mass of meconium.

            Gastrografin or N-acetyl-cysteine enemas are the treatments of choice for meconium ileus. Surgical intervention, though rarely needed, can be necessary when enema therapy is unsuccessful or in a sicker child in whom the enema cannot be performed or who develops bowel ischemia.

            Hirschsprung disease results from the abnormal innervation of the bowel beginning at the anus and extending proximally. Affected infants often fail to pass meconium within the first 48 hours of life, but rarely do they develop symptoms of small intestinal obstruction during this period. The disorder can usually be diagnosed by barium enema if a “transition zone” in which a funnel-shaped area of intestine has a proximal dilation and distal narrowing is visualized. Often the rectum is larger than the sigmoid colon. Failure to pass the barium on a delayed film 24 hours later is suggestive of Hirschsprung disease, even in the absence of a transition zone.

            Malrotation can present with signs and symptoms in the neonatal period, and it accounts for 10% of the obstructions occurring in this age group. Contrast radiography reveals an abnormal position of the ligament of Treitz and the presence of small bowel loops in the right upper quadrant. A normal position of the colon does not exclude the possibility of a malrotation.

            Meconium peritonitis may complicate meconium ileus, but it is associated most often with a volvulus of the small intestine, intestinal atresias, gastroschises, and congenital peritoneal bands. Abdominal calcifications are found on the abdominal flat plate. As stated previously, volvulus can be found in patients who have meconium ileus, but it also may develop as an independent disorder. Unless associated with inspissated meconium, there is no ground-glass appearance on radiography.

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Q 6:

A newborn who weighs 3,200 g and whose estimated gestational age is 40 weeks is receiving mechanical ventilation at 12 hours after birth. Her clinical course and laboratory findings are consistent with group B streptococcal sepsis and pneumonia. Ventilator settings are: ventilator rate, 60 breaths/min; fraction of inspired oxygen, 1.0; peak inspiratory pressure, 34 cm H2O; positive end expiratory pressure, 4 cm H2O; and mean airway pressure, 13 cm H2O. Clinical examination reveals good chest excursion in synchrony with the ventilator and equal breath sounds. The blood pressure is 68/44 mm Hg, with a mean of 52 mm Hg. Arterial blood gas measurements are: pH, 7.45; Po2, 48 mm Hg; Pco2, 35 mm Hg; and Hco3, 22 mEq/L.

Of the following, the MOST appropriate next step in management is:

A. bicarbonate administration

B. extracorporeal membrane oxygenation

C. high-frequency oscillation

D. inhaled nitric oxide administration

E. vasopressor therapy

Answer:

The infant described in the vignette has blood gas evidence of hypoxemia refractory to high ventilatory support. This clinical course is compatible with the diagnosis of persistent pulmonary hypertension of the newborn (PPHN) resulting from group B streptococcal sepsis. Echocardiography should be performed to confirm the diagnosis and rule out congenital heart disease. The most appropriate next step in the management of this infant is to initiate inhaled nitric oxide (NO) administration. NO is a selective pulmonary vasodilator that improves oxygenation by enhancing blood flow through the pulmonary vascular bed. 

            Bicarbonate administration to induce metabolic alkalosis has been used both in the treatment of PPHN before the advent of inhaled NO therapy and as an adjunct to NO administration. Alkalosis, whether metabolic or respiratory, attenuates hypoxic pulmonary vasoconstriction and improves oxygenation by enhancing blood flow through the pulmonary vascular bed. This effect is largely mediated by the increased pH, independent of the Pco2. The optimal pH required for reversing hypoxic pulmonary vasoconstriction is not known. The drawbacks to this therapeutic approach are systemic hypotension, decreased cerebral blood flow, reduced cardiac output, and lung injury.

            Extracorporeal membrane oxygenation (ECMO) is warranted if the infant fails to respond to maximal ventilatory support, inhaled NO therapy, and other supportive measures. ECMO is invasive, expensive, and can cause a host of potential complications. Appropriate and earlier use of inhaled NO should result in fewer infants requiring ECMO.

            High-frequency oscillation (HFO) is a mode of ventilation designed to minimize the lung injury that can accompany broad fluctuations in pressures associated with conventional ventilation. HFO is indicated if conventional ventilation fails to promote adequate gas exchange. The infant described in the vignette has blood gas evidence of adequate ventilation, as indicated by the normal Pco2. HFO may be useful if the peak inspiratory pressure needed to ventilate the infant is excessive, and it may be beneficial for the infant in the vignette if the requirement for high peak inspiratory pressure persists. HFO is used in conjunction with inhaled NO therapy in some centers. This approach, however, remains investigational.

            Vasopressor therapy is an important adjunct, but not a replacement, for inhaled NO therapy. Inotropic agents, such as dopamine and dobutamine, are indicated in appropriate doses to support cardiac function, blood pressure, and tissue perfusion. Other supportive measures for the treatment of PPHN include sedation, muscle paralysis, blood replacement, and maintenance of fluid-electrolyte balance.

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Q 7:

A newborn male has excess abdominal skin, deficiency of the abdominal musculature, and cryptorchidism.

Of the following, the MOST likely etiology of these findings is:

A.  chronic amniotic fluid leakage during pregnancy

B.   early urethral obstruction

C.   extrophy of the bladder

D.   polycystic kidneys

E.   renal agenesis

Answer

B

Early urethral obstruction sequence results most commonly from urethral valve formation, but it can be due to urethral atresia or more distal urethral obstructions. It causes accumulation of urine in the fetal bladder and urinary system beginning at about 8 weeks of gestation, when urine formation begins. Because the most common etiology of the disorder is malformed development of the penile urethra, it is most common in males, who also typically have cryptorchidism due to failure of the testes to descend because of pressure from the enlarged bladder. The bladder distension also causes hydroureter and renal dysplasia. In some cases, compression of the abdominal contents by the bladder can lead to malrotation of the colon, and rarely compression of the iliac vessels can disrupt blood flow to the lower extremities, leading to limb deficiency. The abdominal distension results in an excess of abdominal skin and a deficiency of abdominal musculature, as described for the infant in the vignette. 

This condition has been called prune belly syndrome because of the flaccid, wrinkled appearance of the abdominal skin. Affected infants also display the features of oligohydramnios deformation complex, including hypoplastic lungs, breech presentation, altered facial features, and abnormal positioning of the hands and feet.

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Q 8

    A newborn female has loose neck skin and nonpitting edema of the lower extremities.

Of the following, the MOST appropriate evaluation for this infant is:

A. blood chromosome analysis

B.  magnetic resonance imaging of the brain

C. slitlamp ophthalmologic examination

D. ultrasonography of the liver

E.  voiding cystourethrography


Answer:

A

The finding of loose neck skin, which is suggestive of the presence of a cystic hygroma in fetal life, and nonpitting edema of the lower extremities in a newborn female should raise the suspicion of Turner syndrome . Congenital lymphedema, which occurs in up to 80% of affected females, typically disappears during infancy, leaving only a puffy appearance to the hands and feet, although in some patients it reappears when estrogen therapy is initiated. The posterior neck skin can persist as the pterygium colli, or webbed neck. The clinical diagnosis of Turner syndrome should be confirmed by peripheral blood chromosome analysis, which will reveal monosomy X, mosaic monosomy X, or the presence of an abnormal X chromosome that contains a deletion.

            Affected girls also have short stature, ovarian dysgenesis, broad chest with wide-spaced nipples, ear anomalies, cubitus valgus, and renal and cardiac defects. Intelligence is normal. Estrogen replacement therapy at the expected time of puberty is required in most cases, and treatment with growth hormone also should be offered.

            Magnetic resonance imaging of the brain, slitlamp ophthalmologic examination, and ultrasonography of the liver are not indicated because central nervous system and ophthalmologic findings are not features of Turner syndrome, and liver size and function is normal. Although renal defects may be present, the most common abnormality is horseshoe kidney, which can be detected by ultrasonography and usually has no clinical effects that would prompt the need for voiding cystourethrography.

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Q 9:

A prenatal ultrasonographic examination of a male fetus at 32 weeks' gestation reveals bilateral renal aplasia.

When the infant is delivered several weeks later, the condition MOST likely to be evident is:

A.  bladder wall hypertrophy

B.   cryptorchidism

C.   incomplete development of the sacrum

D.   prune belly (wrinkled abdominal skin)

E.    pulmonary hypoplasia

Answer

E

Bilateral renal aplasia is one etiology of the oligohydramnios sequence, which results in pulmonary hypoplasia, fetal compression, and growth deficiency. The lack of adequate amniotic fluid due to failure of the fetus to produce urine has an adverse effect on lung development, partly because of compression of the developing lung. Affected infants die from respiratory insufficiency and have the typical Potter faciescharacterized by a flat nose, micrognathia, and wrinkled skin. The lack of amniotic fluid also results in fetal compression of the limbs and positioning defects.

            The oligohydramnios sequence also can be caused by chronic leakage of amniotic fluid or obstructive uropathies. The latter conditions, which are due to abnormal formation of the penile urethra, therefore, are most common in males. They can result in bladder distension that leads to bladder wall hypertrophy and cryptorchidism due to the compressive effects of the bladder on the fetal abdomen that results in failure of the testes to descend. 

The development of prune belly, which reflects lack of abdominal musculature and wrinkling of the skin, also is a feature of obstructive uropathies. Incomplete development of the sacrum (the caudal dysplasia sequence) leads to disruption of the distal spinal cord and associated neurologic deficit. Oligohydramnios is not a usual feature.

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Q 10

A resident who is rotating with you in the newborn nursery asks for advice on the management of a 4.1-kg, 1-day-old male newborn whose heel stick specimen revealed an initial glucose value of 45 mg/dL (2.5 mmol/L). Results from repeat testing after the infant was fed revealed a blood glucose concentration of 82 mg/dL (4.6 mmol/L). A third glucose test performed 24 hours after birth revealed a blood glucose concentration of 95 mg/dL (5.3 mmol/L). The resident reports that on physical examination the infant is sleepy but easily aroused and in no acute distress. The remainder of the results of his physical examination are normal except that his penis appears to be less than 2 cm in length.

Of the following, the MOST appropriate next step in the management of this infant is to

             A.  begin an intravenous glucose infusion

             B. measure gonadotropin and growth hormone concentrations

             C. obtain a complete blood cell count and blood and urine culture

             D. obtain a stretched penile length measurement

             E. obtain head magnetic resonance imaging

Answer:

D

The infant described in the vignette has hypoglycemia and a penis that appears to be less than 2 cm in length. These findings should suggest the possibility of panhypopituitarism (eg, growth hormone, gonadotropin, and corticotropin deficiency). Infants who have panhypopituitarism may present with both hypoglycemia due to lack of insulin counterregulatory hormones (growth hormone and cortisol) and micropenis due to inadequate exposure in utero to growth hormone and gonadotropins (luteinizing hormone and follicle-stimulating hormone).

With the immediate concern for hypoglycemia alleviated, the most appropriate next step in this boy’s evaluation is to determine whether he has micropenis. Many children who are slightly large for gestational age will have a generous suprapubic fat pad anterior to the pubic symphysis. This fat pad can give the false impression that the child’s penis is inappropriately small. Thus, inspection is not an adequate technique for assessing penile size. Instead, a stretched penile length (SPL) measurement should be obtained. SPL is performed by placing a tongue blade at the dorsal base of the penis and gently pushing down to the pubic symphysis while extending the penis along the length of the blade. The length of the penis can be accurately assessed by drawing a horizontal line on the tongue blade just above the glans of the stretched penis and subsequently measuring the distance from the end of the blade to the marked line. Children who have an SPL less than 1.8 cm (2.5 standard deviations less than normal) are considered to have micropenis and would require additional workup to determine the cause.

Although head magnetic resonance imaging and gonadotropin and growth hormone measurements would be indicated if the infant was confirmed to have micropenis and persistent hypoglycemia, these tests are not indicated for the infant described in the vignette.