Prashant Mahajan, MD, MPH, MBA

Sixteen-year-old with a recurrent, painful, pruritic rash on right cheek and right eyelid. Current outbreak started 2 days earlier. The rash always appears in the same fashion and in the same location; it typically lasts a few days and resolves spontaneously.

No eye pain or discomfort. No prodromal symptoms (eg, tingling, numbness, or pain) before rash onset. Patient believes that rash is related to being outdoors during the warm months. Complains of feeling feverish.

Patient has eczema and asthma and had chickenpox when he was 6 years old.

Well-appearing afebrile adolescent in no apparent distress. The only positive physical finding: a 3 3 1-cm area of multiple, coalescing vesicles on the right cheek tender to palpation. A second area with 5 to 6 vesicles present over the right upper eyelid.

The diagnosis, based on the history and clinical presentation, was reactivated herpes zoster (shingles).

Herpes zoster is the reactivation of the varicella virus (chickenpox). It appears as painful crops of cutaneous vesicles that are distributed along specific dermatomes that correspond to the dorsal root ganglia where the virus is latent (between recurrences). The causative agent is the human herpesvirus 3 (HH3), which occurs worldwide. HH3 can cause both the primary form of varicella (chickenpox) and the reactivated form (shingles).

The incidence and complications of both varicella and zoster are much higher in immunocompromised patients.

 The incidenceof herpes zoster also increases with age. Herpes zoster is relatively rare in children, but the earlier primary varicella develops, the greater is the likelihood that herpes zoster will develop in childhood or early adulthood.

Typically, a prodromal or pre-eruptive phase is noted before the eruption of vesicles. In the prodromal phase, cutaneous symptoms include paresthesias, pain, and tingling, which may last up to 72 hours. Following this phase, vesicles erupt in a dermatomal fashion and undergo stages of vesicular rupture, crusting, and possible scarring. The last phase is resolution, but reactivation can occur at any time.

Sequelae of herpes zoster include herpes ophthalmicus, CNS complications, and otic zoster (Ramsay Hunt syndrome).

Management of zoster in children is controversial.

 Zoster lesions contain the HH3 virus; viral shedding and spread to susceptible hosts (pregnant patients, immunocompromised patients) is therefore possible. Transmission can result in either primary disseminated varicella or reactivation dermatomal zoster. Consequently, patients with zoster need to be isolated from susceptible persons.

The need for post-exposure prophylaxis depends on the setting. The American Academy of Pediatrics (AAP) recommends administration of varicella immu- noglobulin (VZIG) within 96 hours of exposure in a patient who is at risk for developing the disease and its complications.

Treatment depends on a patient's immune status. The AAP currently does not recommend the routine use of antivirals such as acyclovir in an otherwise healthy, immunocompetent person who does not have a complicated form of the disease.

 The AAP also suggests that patients with a history of eczema, who may be prone to secondary bacterial infection, may benefit from oral acyclovir if given early in the course of the illness.

 One reason for this recommendation is that disseminated zoster infection (eczema herpeticum) may develop in patients with underlying eczema and in those who are immunocompromised.

Antiviral agents decrease viral shedding but do not affect the resolution of symptoms such as neuralgia. Corticosteroids are not of proven benefit.

Common complications of herpes zoster include secondary bacterial infections, depigmentation of the affected area, and scarring.

 Herpes zoster ophthalmicus is a serious ocular form of zoster infection and is characterized by serpiginous (dendritic) corneal ulcers. These ulcers may become chronic and result in loss of vision. Optic keratitis and uveitis are among the more chronic complications of zoster infection. Oral acyclovir treatment is thought to be of some value in patients with ocular herpes zoster.

 Leung AK, Rafaat M. Photo quiz. Vesicular rash on the flank and buttock. 

 American Academy of Pediatrics. Varicella-zoster infections. In: Pickering LK, ed. 

Red Book: 2003 Report of the Committee on Infectious Diseases.

 26th ed. Elk Grove Village, Ill: American Academy of Pediatrics; 2003:672-686.


 Lancaster T, Silagy C, Gray S. Primary care management of acute herpes zoster: systematic review of evidence from randomized controlled trials. 

 Stankus SJ, Dlugopolski M, Packer D. Management of herpes zoster (shingles) and postherpetic neuralgia. 

Articles

Herpes Zoster (Shingles) in a Teenager

A 17-year-old Asian male with no significant medical history presented to the emergency department (ED) with acute shortness of breath and associated left-sided chest pain. Symptoms began while the patient was at rest: the pain was sharp and worsened with inspiration. He denied a history of fever, trauma, cough, or any other constitutional complaints.

In the ED, the patient's temperature was 37.8°C (100°F); heart rate was 100 beats per minute; respiratory rate, 28 breaths per minute; and blood pressure, 124/96 mm Hg. Oxygen saturation was 100% on room air. He had no nasal flaring but used accessory respiratory muscles. The trachea was in midline. Breath sounds were markedly diminished on the left side, with good air entry on the right. No crepitus, wheezing, stridor, or crackles were appreciated. Cardiac examination revealed a normal S

, without any murmurs, rubs, or gallops. Mediastinal shift could not be detected clinically. Chest films showed a left-sided tension pneumothorax (

A chest tube was placed, and symptoms resolved (

). The patient underwent surgery to resect an apical pleural bleb.

A spontaneous pneumothorax (SP) is a collection of air or gas between the visceral and parietal pleura that causes the lung to collapse in the absence of a traumatic injury to the chest or lung. Primary spontaneous pneumothorax (PSP) occurs in persons with no previously known lung disease. Typically, the cause of this type of pneumothorax is the rupture of a subpleural bleb or cyst in the lung.

A secondary spontaneous pneumothorax (SSP) occurs in persons with known lung disease--most often chronic obstructive pulmonary disease in adults. In pediatric patients, cystic fibrosis, pneumonia, and asthma are the most common causes of SSP. Other conditions less commonly associated with SSP are tuberculosis, cystic adenomatoid malformation, Marfan syndrome, and certain types of interstitial lung disease.

SSP is generally more severe than PSP--and is often life threatening. Mortality associated with SSP is about 15%.

Smoking greatly increases the risk of SP.

 Men who smoke a pack a day or less have a 20-fold increased risk of SP; in women, the risk rises by 10-fold. In men who smoke more than a pack per day, the risk of SP increases more than 80-fold; in women, the risk increases more than 40-fold.

SP also can be an inherited disorder, although this is not common. One literature review described 61 cases of familial SP in 22 families.

The major symptom is sudden-onset chest pain with breathlessness. This pain may be dull, sharp, or stabbing; it typically begins suddenly while the patient is at rest. Pain can be associated with dyspnea, tachypnea, and hypoxia; typically, it is exacerbated by breathing deeply or by coughing.

Patients with SSP may also experience dyspnea disproportional to the size of the pneumothorax as well as tachycardia, hypotension, and cyanosis.

The diagnosis usually can be made after a detailed history and physical examination. Chest radiographs can confirm the diagnosis and determine the size of the pneumothorax. A recent randomized controlled trial found no advantage for inspiratory/expiratory films.

The objectives of management are to eliminate the intrapleural air collection, to facilitate pleural healing, and to prevent recurrence. The treatment of SP is multifactorial and depends on its size, course, and classification. A small pneumotho-rax may resolve spontaneously. Needle decompression or chest tube placement may be needed to facilitate reexpansion when air accumulation is relatively large. Strong- ly consider therapeutic interventions for patients with recurrent pneumo- thorax.

While the treatment options for PSP and SSP are the same, the conditions are managed differently. In asymptomatic patients with PSP who have less than 15% air accumulation, simple observation and administration of 100% oxygen have been successfully used as a treatment option.

 Oxygen increases the resorption rate of the pneumothorax 3-fold to 4-fold; the greatest increases occur in patients with larger pneumothoraces. The application of oxygen creates a gas pressure gradient between the pleural space and the tissue capillaries that surround the pleural space. This enhances the absorption of nitrogen and other gases within this space.

If the pneumothorax is smaller than 15% and if the patient is symptomatic but hemodynamically stable, needle aspiration is considered the treatment of choice. Advantages include its relative simplicity and lack of invasiveness.

SSP, on the other hand, can be life-threatening. Most patients are treated with a chest tube. Tube thoracostomy has been advocated for patients with PSP in whom simple aspiration fails--and for most patients with SSP.

 Other more invasive management options include pleural sclerosis (pleurodesis) and video-assisted thoracic surgery (VATS).

Recurrence rates can be high, espeically if SP is untreated. Recurrence rates as high as 30% at 6 months and 50% at 2 years have been reported.

 More specifically, recurrence rates have been reported at 28% for PSP and 53% for SSP.

 There is a 15% rate of recurrence on the contralateral side in patients with PSP. Recurrence is more likely in patients who are tall and thin and who smoke; however, there is no relationship with the number or size of apical blebs on CT. Once a recurrence has occurred, the risk for repeated pneumothoraces exceeds 50%.

Chest tube insertion helps relieve the pneumothorax and improve symptoms. However, it does not reduce the risk of recurrence as significantly as VATS or pleurodesis. One randomized trial compared simple needle aspiration with tube thoracostomy in the management of first-time PSP.

 Recurrence rates were measured at 1 week (11% vs 12%), at 3 months (15% vs 8%), at 1 year (22% vs 42%), and at 2 years (31% vs 25%). There were no statistically significant differences between the 2 treatment modalities.

Patients who have had SP need to stop smoking and to avoid high altitudes, scuba diving, or flying in an unpressurized aircraft in attempt to limit the risk of a recurrent pneumothorax.

Cardiac causes of pediatric chest pain are uncommon. If the pain is associated with shortness of breath, especially in a thin adolescent who smokes, consider spontaneous pneumothorax (SP). When SP is diagnosed, it is important to differentiate between a primary and secondary cause because management differs.	

 
1.  Light RW. Pneumothorax. In: Murray JF, Nadel JA, eds. 

 Philadelphia: WB Saunders; 1994:2193-2210.
2. Melton LJ 3rd, Hepper NG, Offord KP. Incidence of spontaneous pneumothorax in Olmsted County, Minnesota: 1950-1974. 

 1979;20: 1379-1382.
3. Wilson WG, Aylsworth AS. Familial spontaneous pneumothorax. 

 1979,64:172-175.
4. Seow A, Kazerooni EA, Pernicano PG, Neary M. Comparison of upright inspiratory and expiratory chest radiographs for detecting pneumothoraces. 

 1996;166:313-316.
5. Chada TS, Cohn MA. Noninvasive treatment of pneumothorax with oxygen inhalation. 

1983;44:147-152.
6. Light RW. Spontaneous Pneumothorax. In: 

 3rd ed. Baltimore: Williams & Wilkins; 1995;24.
7. Mason RJ.Pneumothorax, chylothorax, hemothorax, and fibrothorax. In: 

Murray and Nadel's Textbook of Respiratory Medicine.

3rd ed. Philadelphia: Elsevier; 2005:1964.
8.  Ayed AK, Chandrasekaran C, Sukumar M. Aspiration versus tube drainage in primary spontaneous pneumothorax: a randomized study. 

Case In Point: Spontaneous Pneumothorax in a Teenage Boy

Chest pain in children evokes anxiety in patients and their parents--and prompts frequent visits to the pediatrician's office, urgent care facility, or emergency department (ED). In a prospective study, Selbst and colleagues

 reported that chest pain accounted for 6 in 1000 visits to an urban pediatric ED.

Pediatric chest pain is often benign. Studies have shown that without a specific indication, routine tests--including echocardiography and exercise stress testing--are of no benefit in determining the cause of chest pain.

 Nevertheless, chest pain is one of the leading reasons for referral to a cardiologist.

Here we provide a comprehensive review of the causes of chest pain in children. We also suggest a clinical approach to the evaluation, diagnosis, and management of pediatric chest pain (

). Such an approach will help ensure that unnecessary investigations are avoided and rare but potentially life-threatening disorders are identified.

Chest pain in children is rarely the result of cardiac abnormalities or life-threatening conditions.

 Chest pain may be associated with pathology of any of the pain-sensitive structures in the chest, neck, and abdomen. It may arise from the chest wall, lungs (pleura), heart, mediastinum, esophagus, or trachea, and it has no sex predilection.

 Structures in the chest wall are the most common source of chest pain in children.

 Muscle injuries or strain in the pectoral, shoulder, or back muscles secondary to trauma or physical activity are frequent causes of chest pain. Repeated use of chest wall muscles during protracted coughing leads to muscle discomfort from strain.

Costochondritis usually presents as chronic sharp pain in the anterior chest wall that may radiate to the back or abdomen. The pain is exacerbated by deep breathing and physical activity and may be preceded by upper respiratory infections or exercise. Pain related to costochondritis may last for months; typically, it is reproducible by the application of pressure at the costochondral junction. Infections from coxsackie virus may also cause chest pain (pleurodynia). Herpes zoster (shingles) causes pain in the chest wall that may precede the typical vesicular rash eruption.

 Patients with pleuritis have sharp chest pain that makes them catch their breath. Deep breathing and coughing usually exacerbate the pain. Pleuritic pain is sometimes referred to the abdomen and shoulder because of the common sensory nerve supply.

 A rub may or may not be audible on chest auscultation.

Pneumothorax, another cause of chest pain of acute onset, may be spontaneous or secondary to lung pathology or trauma. The patient usually presents with breathlessness and pain of variable severity. Spontaneous pneumothorax is more common in children and adolescents who have marfanoid features (tall, thin build and arachnodactyly).

 Acute asthma exacerbations may also cause chest pain.

 Inflammation of the upper GI tract (gastritis, esophagitis) accounts for 5% to 10% of pediatric chest pain.

 The pain typically is located retrosternally and is aggravated when the child eats or leans forward. Gastritis often coexists with esophagitis and is a more likely diagnosis if the child is taking oral cortico- steroids or NSAIDs. Also consider the possibility of foreign-body impaction in the esophagus, especially in younger children or in children with developmental delays.

Cholecystitis and choledocholithiasis may be seen in obese adolescents and patients with hematologic disorders such as sickle cell disease and hereditary spherocytosis. This pain is often localized to the epigastrium, lower right rib cage, back, or right shoulder.

Hepatitis is often associated with pain in the right upper quadrant of the abdomen. Reproducible tenderness may be noticed in the intercostal spaces of the overlying chest wall.

Chest pain attributable to cardiovascular lesions occurs in only about 4% to 6% of children with chest pain

 but is the scenario that is most feared by the patient, family, and pediatrician. Although such lesions are potentially life-threatening, early identification can prevent morbidity and mortality. Be especially vigilant with children who have a history of such disorders as Kawasaki disease and aortic valve stenosis. These conditions may present with symptoms and laboratory and ECG findings that suggest myocardial infarction.

 causes a stabbing, sharp pain that may worsen when the patient is supine and improve with sitting. The presence of a frictionrub is a useful but variable sign in acute pericarditis. Larger fluid collections in the pericardium may lead to absence of a rub, and muffled and distant heart sounds may be the only auscultatory findings. Still larger collections may lead to cardiac tamponade with neck vein distention, narrow pulses, tachypnea, and tachycardia. Pulsus paradoxus can be elicited in patients with cardiac tamponade.

Typical ECG findings include generalized low voltage from the damping effect of fluid. Generalized ST-segment elevation may result from fluid pressure on the myocardium. Electrical alternans, characterized by variable QRS amplitude, may be observed. 

Chest radiographic findings vary according to the volume of pericardial fluid. Larger collections typically cause the heart to appear globular or assume the classic "money bag" shape. Emergency pericardiocentesis can be a life-saving procedure in cardiac tamponade. Biochemical and microbiologic evaluation of the tapped pericardial fluid often reveals the underlying cause of pericardial effusion.

Myocarditis, either alone or in association with pericarditis, may cause chest pain. Depending on the area of myocardium involved, the ECG may show arrhythmias or ST- segment changes.

 a familial condition, can present with syncope and angina-like chest pain in children and adolescents and is a known cause of sudden cardiac death.

 Suspicion of this disorder usually emergesduring the evaluation of a cardiac murmur or an assessment of fatigue, dyspnea on exertion, palpitations, syncope, or angina-like symptoms. There may be a family history of sudden, unexplained death.

The examination findings include hyperdynamic precordium, double apical impulse, and ejection systolic murmur. Immediate postexercise evaluation may show increased murmur intensity. ECG findings generally include left ventricular hypertrophy with or without ST-segment changes and Q wave changes consistent with a left ventricular strain pattern. Chest radiography typically shows a slight left ventricular cardiac enlargement. Echocardiography usually reveals asymmetric interventricular septal hypertrophy.

 Electrocardiography is warranted in a patient who has syncope with a suspected cardiac cause. If the age-corrected QT interval is prolonged--whether or not there is a family history of sudden death--consider a diagnosis of long QT syndrome.

Premature coronary artery diseases are rarely seen in adolescents with hypercholesterolemia and uncontrolled diabetes, although there may be a family history of sudden death from premature coronary artery disease. Case reports of lymphocytic myocarditis in adolescents with angina-like clinical and laboratory findings have also been published.

 The incidence of pediatric chest pain that has a psychogenic or psychiatric cause is 5% to 17%.

 Although these causes represent a diagnosis of exclusion, a trusting relationship between the family and the pediatrician is essential to help elucidate the underlying problems. A variety of psychosocial causes may contribute to psychogenic chest pain; these include a death in the family, familial discord, poor school performance, and social isolation. Psychogenic chest pain is generally seen in children older than 12 years and is more prevalent in girls.

 A thorough history taking and physical examination can help rule out organic and psychiatric causes of chest pain. Nevertheless, a precise cause cannot be identified in many children. The pain typically has a chronic course and often resolves spontaneously.

 Patients with sickle cell disease frequently present with chest pain as a manifestation of vaso-occlusive episodes.

 Cocaine abuse is a known cause of angina-like pain, especially in adolescents.

 Pubertal breast changes and diseases such as mastalgia and fibrocystic disease may cause chest pain in teenagers.

 Male breast enlargement (gynecomastia) sometimes produces pain and tenderness.

 Mediastinal and chest wall tumors are a rare cause of chest pain in children.

Taking a thorough history is important for an accurate diagnosis (

). The mnemonic "PQRST" is helpful in describing pain: 

It is also important to elicit factors that aggravate and relieve pain, as well as associated symptoms.

A history of exertional chest pain associated with palpitations and syncope may indicate a cardiac origin. A family history of sudden premature death, heart disease, hypertension, or hypercholesterolemia may also suggest possible cardiac risk factors.

Pain that is associated with eating may point to a gastric or duodenal source. Typically, eating tends to relieve pain that is of duodenal origin, but it can also aggravate gastritic pain. GI pathology is suggested by a history of melena, hematochezia, or hematemesis.

Chest pain that is aggravated or relieved when the patient changes position may offer helpful clues. For example, a patient with pericarditis experiences relief when sitting or leaning forward and exacerbation when lying down.

A history of the use of medication (prescription and nonprescription) and drugs of abuse is important, especially because cocaine use is known to cause angina-like pain.

 A history of fever, cough, hemoptysis, or dyspnea points to a likely respiratory source. Pain that worsens with deep inspiration may suggest pleuritis or occult rib fracture. Children who participate in contact sports should also be asked about a history of injuries that may cause chest pain, such as overt or occult rib fracture.

A detailed social history that focuses on the child's relationship with peers, school performance, family dynamics, and potential life stressors should be elicited. A family or personal history of psychiatric disorder is often helpful in determining the cause of chest pain in patients in whom a psychogenic cause is suspected.

A thorough physical examination can often reveal the cause of chest pain. Examine the vital signs for indications of fever, tachycardia, tachypnea, or age-corrected abnormalities in blood pressure. Whenever possible, have the patient score the pain using a standard pain scale.

Physical examination should include identification of marfanoid features, such an atypically long arm span. Reproducibility of chest pain on application of pressure suggests a musculoskeletal origin. Palpate the breasts for tenderness. Bruises or point tenderness may indicate accidental or nonaccidental trauma.

The respiratory evaluation should include assessment of retractions, air entry, and abnormal lung sounds (crepitations and wheezes). Evaluate the heart rate and rhythm and check for the presence of murmurs. Hypotension, hypertension, or gallop rhythm may indicate a potential cardiac cause of chest pain. Vasculitic or photosensitive rashes may indicate an autoimmune cause.

SUGGESTED LABORATORY EVALUATION AND WORKUP

A careful history taking and physical examination usually reveals the cause of chest pain and helps guide subsequent evaluation. A focused workup, rather than exhaustive laboratory evaluation, should be the first step. For example, chest radiography is reasonable if one suspects a fracture or respiratory cause. Chest radiography can detect air-space disease, pneumothorax (

), soft tissue swelling, and fractures and identify cardiac size and silhouette abnormalities. Performing a complete blood cell count and blood cultures is reasonable in patients with suspected lung infections. Elevated erythrocyte sedimentation rate is a nonspecific marker of inflammation.

If the history and physical examination suggest a likely cardiac cause, an ECG and pediatric cardiology referral may be indicated. Psychological evaluation and counseling are warranted if psychosomatic causes are likely. A urine drug screen may be useful if cocaine use is suspected.

Identification of the cause of chest pain will determine appropriate treatment. Costochondritis and other musculoskeletal conditions are usually managed with analgesics, especially NSAIDs. Patients with pneumonia are treated with antibiotics and supportive care.Gastritis, peptic ulcers, and gastroesophageal reflux may require pharmacologic treatment; dietary modification may help in uncomplicated cases. In rare cases of potentially life-threatening cardiac causes, inpatient hospitalization with cardiorespiratory monitoring and evaluation by a pediatric cardiologist may be required. Antiarrhythmic medications may be indicated in rare cases that involve arrhythmias or long QT syndrome. Psychological or psychiatric evaluation is sometimes necessary.

Occasionally, even after frequent reassurance and after an organic cause has been ruled out, patients continue to experience symptoms. Analgesics may offer relief during exacerbations. Many children with chest pain experience spontaneous resolution.

  Selbst SM, Ruddy RM, Clark BJ, et al. Pediatric chest pain: a prospective study. 

  Fyfe DA, Moodie DS. Chest pain in pediatric pa-tients presenting to cardiac clinic. 

  Pantell RH, Goodman BW Jr. Adolescent chest pain: a prospective study. 

  Evangelista JA, Parsons M, Renneburg AK. Chest pain in children: diagnosis through history and physical examination. 

  Coleman WL. Recurrent chest pain in children. 

Gray's Anatomy: The Anatomical Basis of Clinical Practice.

 39th ed. New York: Elsevier Churchill Livingstone; 2005:1664.
 

  Hall JR, Pyeritz RE, Dudgeon DL, Haller JA Jr. Pneumothorax in the Marfan syndrome: prevalence and therapy. 

  Wiens L, Sabath R, Ewing L, et al. Chest pain in otherwise healthy children and adolescents is frequently caused by exercise-induced asthma. 

  David DG, Benjamin H. Nontraumatic musculoskeletal disorders: shoulder pain. In: Tintinalli JE, ed. 

Emergency Medicine: A Comprehensive Study Guide.

 6th ed. New York: McGraw-Hill; 2004:283.
 

  Walsh CA. Syncope and sudden death in the adolescent. 

  Azzano O, Bozio A, Sassolas F, et al. Natural history of hypertrophic obstructive cardiomyopathy in young patients: apropos of 40 cases [in French]. 

Chest pain in children evokes anxiety in patients and their parents--and prompts frequent visits to the pediatrician's office, urgent care facility, or emergency department (ED). In a prospective study, Selbst and colleagues reported that chest pain accounted for 6 in 1000 visits to an urban pediatric ED.

Pediatric Chest Pain: Keys to the Diagnosis

A 7-week-old white boy presented to the emergency department (ED) with vomiting and weight loss. His parents brought him to the ED 3 weeks earlier after he had vomited for several days. Possible milk protein allergy was diagnosed at that visit, and a change from cow milk formula to an elemental formula was recommended. Vomiting subsequently increased in frequency. Nonbilious but forceful vomiting occurred with each feeding. The patient lost nearly 2 lb during the 3 weeks that followed the first ED visit.

The patient was born at term by spontaneous vaginal delivery. The perinatal course had been unremarkable. Birth weight was 7 lb 10 oz. The baby weighed 9 lb 8 oz at 3 weeks and 8 lb at 7 weeks.

The patient was active and alert but had lost a significant amount of subcutaneous tissue. His abdomen was soft and nondistended. There were no masses in the upper quadrant and no organomegaly. Other physical examination findings were unremarkable.

The patient's white blood cell count was 12,400/µL, with 24% neutrophils and 74% lymphocytes. The hematocrit was 41.4%, and the platelet count was 685,000/µL. The serum sodium level was 129 mEq/L; serum potassium, 2.7 mEq/L; serum chloride, 72 mEq/L; serum bicarbonate, 37 mEq/L; blood urea nitrogen, 24 mg/dL; and serum creatinine, 0.5 mg/dL (44.2 µmol/L). Capillary blood gas pH was 7.56; partial pressure of alveolar carbon dioxide, 52.8 mm Hg; partial pressure of alveolar oxygen, 59.2 mm Hg; and bicarbonate level, 46.2 mEq/L.

The persistent vomiting with hypochloremic metabolic alkalosis prompted the performance of abdominal ultrasonography. The test showed the length of the pyloric channel to be 19.5 mm and the muscle width itself to be more than 6.9 mm (

). These findings were diagnostic of pyloric stenosis. The patient's electrolyte abnormalities were corrected, and a pyloromyotomy was scheduled.

INFANTILE HYPERTROPHIC PYLORIC STENOSIS (IHPS)

IHPS classically presents with the gradual onset of nonbilious projectile vomiting at about the third week of life. However, 20% of infants are symptomatic from birth, and most are symptomatic within 2 months after birth.

 IHPS is the most common cause of nonbilious vomiting and metabolic alkalosis in infants.

 It is the most common reason for abdominal surgery in the first 6 months of life.

The incidence of IHPS varies from 1 in 200 to 1 in 750 live births. The disorder is 4 to 6 times more common in boys than in girls. The overall average is 3 in 1000 live births.

 Although believed to be more common in first-born boys, pyloric stenosis recently has been shown to be associated with smaller family size and higher socioeconomic class, rather than with birth order. The incidence is 2- to 3-fold higher in African Americans than in whites, and it is rare in Asians.

 The disorder has a familial tendency: 7% of children with this disorder have an affected parent. Among infants with IHPS, the incidence of recurrence is 10% in subsequent male siblings and 2% in subsequent female siblings.

Multiple theories have been proposed to explain the development of pyloric stenosis. Postnatal infusion of gastrin produces an identical lesion in newborn puppies; it has therefore been suggested that hypergastrinemia may play an important etiologic role in IHPS.

 infusion--used to maintain a patent ductus arteriosus in certain cardiac anomalies--has been linked to a higher incidence of IHPS.

 Recent studies show a relative lack of nitric oxide synthase (a smooth muscle relaxant) innervation in the hypertrophied muscles.

 Recent studies suggest that erythromycin therapy may be associated with development of pyloric stenosis in infants younger than 30 days.

Patients who have IHPS typically present with hypochloremic metabolic alkalosis. Although the serum potassium level may be normal or low, there often is total-body potassium depletion. The observed metabolic alkalosis is a result of 2 related but independent processes: loss of acid and retention of bicarbonate.

Initially, vomiting of gastric contents results in excessive loss of hydrogen chloride and potassium chloride, which leads to a metabolic alkalosis. Under normal circumstances, carbonic acid in the villi of the stomach dissociates into hydrogen and bicarbonate. The hydrogen ions cross the luminal membrane of the enterocyte and enter the stomach, from where they are transported to the duodenum. The entry of acid into the duodenum stimulates the secretion of an equal amount of pancreatic bicarbonate. This normal stimulus is absent in pyloric stenosis because of the mechanical obstruction: the diminished secretion of pancreatic bicarbonate into the GI tract contributes further to the metabolic alkalosis created by stomach acid lost through vomiting.

Moreover, as intravascular volume decreases with dehydration, the concentration of bicarbonate in the plasma increases, resulting in a "contraction alkalosis." The loss of potassium during vomiting also may contribute to the development of metabolic alkalosis. As the plasma potassium concentration falls, potassium moves out of the cells to replenish extracellular stores and electroneutrality is maintained by hydrogen moving into the cells. This shift causes paradoxical extracellular alkalosis with intracellular acidosis.

The kidneys also play a role in the metabolic alkalosis seen with pyloric stenosis. To maintain volume in the face of fluid losses from vomiting, the kidneys reabsorb bicarbonate in the distal tubules despite alkalosis. If the excess bicarbonate is excreted in the urine, it obligates sodium loss to maintain electroneutrality. Because water loss follows sodium excretion, further volume is lost. In addition, decreased chloride delivery to the macula densa of the kidneys results in renin release and secondary hyperaldosteronism. This, in turn, leads to increased distal hydrogen secretion and the paradoxical finding of acid urine in the presence of alkalemia. Finally, in response to hypokalemia, the distal tubules of the kidneys reabsorb potassium in exchange for hydrogen, resulting in further loss of acid.

Nonbilious vomiting is the initial symptom of IHPS. The vomiting may or may not be projectile, but it is usually progressive and occurs during or shortly after each feeding. The full-terminfant usually has an avid appetite after vomiting. In contrast, the preterm infant usually does not display exaggerated peristalsis: although the child may appear hungry, he or she does not have the avid appetite seen in the full-term infant. The frequent preexistence of gastroesophageal reflux in the preterm infant may confound the diagnosis.

 Typically, the infant is malnourished. He will have a palpable, firm, movable mass ("olive") in the right upper quadrant of the abdomen and visible intestinal peristalsis. To enhance the sensitivity of the physical examination, it may be helpful to empty the child's stomach with a nasogastric or orogastric tube and to palpate the abdomen while the child is held in a prone position. Comforting the infant to prevent crying also helps.

When palpable, a pyloric mass is pathognomonic of hypertrophic pyloric stenosis. As noted, patients classically have a hypochloremic metabolic alkalosis, occasionally with severe deficits of potassium and sodium. Hyperbilirubinemia is present in about 5% of patients with pyloric stenosis.

Barium swallow shows a narrowed and elongated pyloric canal. Ultrasonography is the current diagnostic study of choice.

 Test results may be more accurate than clinical examination in detecting IHPS at an early stage, when the typical "olive" is not yet palpable and the peristaltic waves of the stomach are not yet visible.

 Ultrasonographic findings of a pyloric muscle thickness of more than 4 mm and a pyloric length of more than 14 mm have a diagnostic sensitivity and specificity of 95% and 100%, respectively.

Management of IHPS includes meticulous correction of fluids and electrolytes, followed by corrective surgery. Appropriate medical management reverses the volume contraction and metabolic derangements. All metabolic derangements--including hypokalemia and alkalosis, along with dehydration--must be corrected before surgical repair is undertaken.

Pyloromyotomy is curative for gastric outlet obstruction. The prognosis following surgery is excellent.

The diagnosis of pyloric stenosis is frequently delayed. Consider pyloric stenosis as a cause of emesis in infants. Remember that the presence of gastroesophageal reflux does not rule out pyloric stenosis. And keep in mind that even though hypochloremic metabolic alkalosis strongly suggests pyloric stenosis as the underlying problem, normal electrolyte levels do not exclude the diagnosis.

 Rudolph CD. Infantile hypertrophic pyloric stenosis. In: Rudolph CD, Rudolph AM, eds. 

 21st ed. New York: McGraw-Hill; 2002: 1402-1403.
 

 Wylie R. Pyloric stenosis and congenital anomalies of the stomach. In: Behrman RE, Kliegman RM, Jenson HB, eds. 

 17th ed. Philadelphia: WB Saunders Co; 2004:1229-1231.
 

 Mahon BE, Rosenman MB, Kleiman MB. Maternal and infant use of erythromycin and other macrolide antibiotics as risk factors for infantile hypertrophic pyloric stenosis. 

 Honein MA, Paulozzi LJ, Himelright IM, et al. Infantile hypertrophic pyloric stenosis after pertussis prophylaxis with erythromycin: a case review and cohort study. 

 Broderick KB. Pyloric stenosis. In: Schaider J, Hayden SR, Wolfe R, et al, eds. 

Rosen and Barkin's 5 Minute Emergency Medicine Consult.

 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 2003:926-927.
 

 Dinkevich E, Ozuah PO. Pyloric stenosis. 

 Breaux CW Jr, Georgeson KE, Royal SA, Curnow AJ. Changing patterns in the diagnosis of hypertrophic pyloric stenosis. 

 Chen EA, Luks FI, Gilchrist BF, et al. Pyloric stenosis in the age of ultrasonography: fading skills, better patients? 

 Hernanz-Schulman M, Sells LL, Ambrosino MM, et al. Hypertrophic pyloric stenosis in the infant without a palpable olive: accuracy of sonographic diagnosis. 

 Touloukian RJ, Higgins E. The spectrum of serum electrolytes in hypertrophic pyloric stenosis. 

Prashant Mahajan, MD, MPH, MBA

Articles

Herpes Zoster (Shingles) in a Teenager

Case In Point: Spontaneous Pneumothorax in a Teenage Boy

Pediatric Chest Pain: Keys to the Diagnosis

Case In Point: Infantile Hypertrophic Pyloric Stenosis