Chapter 40 Hypertrophic Pyloric Stenosis
PATHOPHYSIOLOGY
Hypertrophic pyloric stenosis is one of the more frequently occurring conditions requiring surgery within the first 6 months of life. Hypertrophy (increased size) and hyperplasia (increased mass) of the circular muscle of the pylorus cause obstruction at the pyloric sphincter. The circular muscle increases to as much as twice the normal thickness, and the pylorus lengthens, which results in severe narrowing of the lumen. In addition, the stomach dilates, and hypertrophy of the gastric antrum occurs. The cause is unknown, but multiple factors have been implicated, and evidence suggests that local innervation is involved. Immaturity of function and the absence of pyloric ganglion cells has been suggested. Hypertrophic pyloric stenosis may be associated with intestinal malrotation, esophageal or duodenal atresias, and anorectal anomalies. In addition, there is a genetic predisposition. In 1999, the Centers for Disease Control and Prevention (CDC) reported a possible link between the use of oral erythromycin in infants and hypertrophic pyloric stenosis. The CDC does not recommend that physicians stop prescribing erythromycin, just that they be aware of the possible risk. A study done in Denmark determined that the maternal use of macrolides such as erythromycin during breast feeding increased the risk of infantile hypertrophic pyloric stenosis.
INCIDENCE
1. Hypertrophic pyloric stenosis occurs in 1 to 4 cases per 1000 live births, usually 2 to 8 weeks after birth, with peak incidence within the first 3 to 5 weeks of life.
2. Hypertrophic pyloric stenosis is less common in African Americans and is rare in Asian individuals. It is most commonly seen in white children.
3. Male/female ratio is 5:1. This ratio is not observed as much in children of low birth weight (<2500 g) as in children of birth weight over 2500 g.
CLINICAL MANIFESTATIONS
1. Nonbilious vomitus; may be blood-streaked (initial symptom)
2. Vomiting, usually occurring 30 to 60 minutes after feeding
3. Vomiting that becomes progressively more projectile, projecting up to 3 feet from the infant
4. Appears hungry; eagerness to be fed after vomiting
5. Vomiting of retained feeding with current feeding
6. Signs of dehydration (decreased tears, poor skin turgor, dark circles under eyes, sunken fontanelle)
8. Failure to gain weight or weight loss
10. Distended upper abdomen after feeding
12. Visible left-to-right gastric peristaltic waves
13. Palpable firm, movable, olive-shaped mass in right upper quadrant
LABORATORY AND DIAGNOSTIC TESTS
Refer to Appendix D for normal values and/or ranges of laboratory and diagnostic tests.
1. Complete blood count—elevated hemoglobin and hematocrit, due to hemoconcentration—used to determine fluid balance, specifically dehydration status
2. Serum electrolyte levels—hypochloremia, hypernatremia, hypokalemia (may be masked by hemoconcentration from extracellular fluid depletion)—used to determine electrolyte levels, which may be imbalanced as a result of vomiting
3. Arterial blood gas values—used to determine acid/base balance, specifically metabolic alkalosis related to vomiting
4. Upper gastrointestinal barium studies—diagnostic; show delayed gastric emptying and narrowing of the pyloric channel (barium is aspirated through a nasogastric tube after the procedure to decrease risk of aspiration)
5. Abdominal ultrasonography—first-line diagnostic study. Used to visualize hypertrophy and hyperplagia of pyloric sphincter
6. Urine specific gravity—used to determine hydration status
7. Blood urea nitrogen (BUN)—elevated BUN can indicate dehydration from vomiting and inadequate fluid intake
MEDICAL AND SURGICAL MANAGEMENT
Before surgery, fluid and electrolyte abnormalities and acid-base imbalances are corrected with intravenous (IV) fluids and electrolyte replacement. Antibiotics may be administered prophylactically. If emesis is excessive, a nasogastric tube may be inserted for gastric decompression. An open pyloromyotomy, involving a small transverse abdominal incision or a periumbilical incision, down to the mucosa and fully across the pyloric length, is the standard surgical treatment for this disorder. Laparoscopic pyloromyotomy has also been found to be safe and successful for the correction of hypertrophic pyloric stenosis, resulting in shorter surgical time, more rapid postoperative feeding, and quicker discharge. General anesthesia is usually used; however, studies have demonstrated the advantages of spinal anesthesia over general anesthesia in infants undergoing pyloromyotomy, especially to decrease the risks of apnea and aspiration of stomach contents. Overall surgery is well tolerated with few complications.
NURSING ASSESSMENT
NURSING INTERVENTIONS
Preoperative Care
1. Promote and maintain fluid and electrolyte balance.
2. Monitor and report laboratory results.
3. Monitor for signs of fluid and electrolyte imbalances.
4. Prepare parents preoperatively for child’s upcoming surgery (see the Preparation for Procedures or Surgery section in Appendix F).
Postoperative Care
1. Promote and maintain fluid and electrolyte balance.
2. Monitor child’s response to oral intake. (Traditionally, feedings have been reintroduced slowly, but recent studies indicate that ad lib feedings postoperatively are beneficial and result in earlier discharge from the hospital.)
3. Provide nonpharmacologic and pharmacologic pain relief measures as indicated (see Appendix I).
4. Monitor and maintain integrity of incisional site.
5. Provide psychosocial support (see the Supportive Care section in Appendix F).
Discharge Planning and Home Care
CLIENT OUTCOMES
1. Child will retain feedings.
2. Child will be adequately hydrated and have normal electrolyte balance.
3. Child will have appropriate weight gain.
4. Child will experience no complications, such as infection.
5. Child will obtain pain relief.
6. Parents will demonstrate understanding of infant’s or child’s condition, possible complications, and home care requirements.
Ball JW, Bindler RC. Child health nursing: Partnering with children and families. Upper Saddle River, NJ: Pearson Prentice-Hall, 2006.
Bianca S, et al. Sex ratio imbalance and birth weight in newborns with isolated hypertrophic pyloric stenosis. J Obstet Gynaecol. 2003;23(1):43.
Morash D. An interdisciplinary project that changed practice in feeding methods after pyloromyotomy. Pediatr Nurs. 2002;28(2):113.
Morbidity and Mortality Weekly Report. Hypertrophic Pyloric Stenosis in Infants Following Pertussis Prophylaxis with Erythromycin–Knoxville, Tennessee, 1999. MMWR Weekly, January 23, 2007. (serial online) www.cdc.gov/mmwr/preview/mmwrhtml/mm4849a1.htm Accessed January 23, 2007
Somri M, et al. The effectiveness and safety of spinal anaesthesia in the pyloromyotomy procedure. Paediatr Anaesth. 2003;13(1):32.
Sorenson H, et al. Risk of infantile hypertrophic pyloric stenosis after maternal postnatal use of macrolides. Scand J Infect Dis. 2003;35(2):104.
