A 2-month-old infant is brought to the emergency department by parents who report projectile vomiting after every feeding for the past week. Which assessment finding would be most indicative of hypertrophic pyloric stenosis?
1Bilious vomiting immediately after feeding
2Abdominal distension with visible bowel loops
3Bloody stools with mucus
4Palpable olive-shaped mass in the right upper quadrant✓ 정답
해설
The palpable olive-shaped mass in the RUQ is the classic diagnostic finding for pyloric stenosis. Other findings like bilious vomiting, abdominal distension, or bloody stools are not typical and suggest different conditions.
Core Nursing ExplanationKey Concept Analysis: This question assesses the classic clinical presentation and physical assessment finding for Hypertrophic Pyloric Stenosis (HPS). HPS is a condition where the muscle of the pylorus (the valve between the stomach and duodenum) thickens, causing a functional obstruction. This prevents the passage of stomach contents into the small intestine. The pathophysiology is straightforward: Muscle hypertrophy → Gastric outlet obstruction → Forceful, non-bilious vomiting → Metabolic alkalosis.
Answer Rationale: Key Point! The palpable olive-shaped mass in the right upper quadrant (RUQ) is the pathognomonic (definitive) physical finding for HPS. It represents the hypertrophied pyloric muscle. This finding is most reliably detected during or right after a feeding when the infant is calm, and the abdominal muscles are relaxed. The nurse or provider feels deep in the epigastrium/RUQ for a small, firm, movable mass about the size of an olive. This finding, combined with the history of projectile, non-bilious vomiting, strongly confirms the diagnosis.
Distractor Analysis:
Watch out for confusion! Option ①, "Bilious vomiting immediately after feeding," is a hallmark of a surgical emergency like malrotation with midgut volvulus. In HPS, the obstruction is before the ampulla of Vater (where bile enters), so the vomitus is non-bilious and often contains curdled milk.
Option ②, "Abdominal distension with visible bowel loops," is more characteristic of a distal intestinal obstruction (e.g., ileal atresia, Hirschsprung's disease). In HPS, the obstruction is high (gastric outlet), so the abdomen is typically scaphoid (sunken) or soft because nothing gets past the stomach to distend the intestines.
Option ③, "Bloody stools with mucus," describes "currant jelly stools," which are classic for intussusception, a different pediatric surgical emergency. This is not associated with HPS.
Related Concepts: The metabolic consequence of persistent vomiting in HPS is a hypochloremic, hypokalemic metabolic alkalosis. The infant loses hydrogen ions (H+) and chloride (Cl-) in gastric fluid. Potassium (K+) is lost in vomitus and also exchanged for H+ in the kidneys in an attempt to correct the alkalosis. Pre-operative management focuses on correcting this fluid and electrolyte imbalance with IV fluids (typically Normal Saline with potassium chloride) before the definitive surgical treatment, a pyloromyotomy.
Concept Summary
Component
Key Points for Hypertrophic Pyloric Stenosis
Pathophysiology
Hypertrophy of pyloric muscle → Gastric outlet obstruction.
Typical Patient
First-born male infants, 2-8 weeks old. "First-born male" is a classic association.
Effortless, often with positioning, "happy spitter"
Non-bilious, small amounts
Malrotation with Volvulus (Surgical Emergency)
Any age, often infant
Bilious vomiting, acute pain
Bilious emesis is a RED FLAG. May have abdominal distension.
Bilious (green)
Intussusception (Surgical Emergency)
3 months - 3 years
Paroxysmal pain, lethargy
"Currant jelly" stools, sausage-shaped abdominal mass
May occur late, non-bilious initially
Anatomy, Physiology & Pharmacology PointsAnatomy: The pylorus is the muscular sphincter connecting the stomach's antrum to the duodenum. In HPS, the circular muscle fibers hypertrophy.
Physiology: Persistent loss of gastric contents (HCl, KCl) leads to a contraction alkalosis. The body's compensatory mechanism involves the kidneys excreting bicarbonate (HCO3-) and retaining H+, but this is overwhelmed. Potassium is wasted in urine as the kidney attempts to conserve H+.
Pharmacology: Pre-op IV fluids are critical. 0.9% Normal Saline (NS) with added Potassium Chloride (KCl) is standard to replace chloride and potassium deficits and correct the alkalosis.
Memory TipsMnemonics:
HPS Findings: "Projectile, Palpable olive, Peristaltic waves, Persistent hunger" (The 4 P's).
Age: Think "2" - often starts around 2 weeks, peaks at 2 months.
Vomitus: "NO BILE in the PYLORIC profile" (Non-bilious vomiting is key).
Labs: Remember the alkalosis: "Vomiting HCl causes pH to go High, Chloride and Potassium go Low."
High-Frequency NCLEX Topics
HPS is a classic NCLEX-RN topic. You must know:
1. The classic triad: Projectile non-bilious vomiting + Olive-shaped mass + Visible peristalsis.
2. The metabolic imbalance (Hypochloremic, hypokalemic metabolic alkalosis) and its nursing priority (correct fluid/electrolyte imbalance BEFORE surgery).
3. How to differentiate HPS from other causes of infant vomiting (especially bilious vomiting = emergency!).
4. Post-op care after pyloromyotomy: Small, frequent feedings (e.g., start with clear fluids, advance to formula), monitor for vomiting (some post-op edema is common).
Watch Out for Question Variations!
* Instead of asking for the assessment finding, the question might ask: "Which lab result would the nurse anticipate?" (Answer: Metabolic alkalosis with hypokalemia and hypochloremia).
* Or: "What is the priority nursing intervention pre-operatively?" (Answer: Administer IV fluids to correct dehydration and electrolyte imbalance).
* Or: "The parent reports the infant's vomit is green. What is the nurse's best action?" (Answer: Notify the provider immediately, as bilious vomiting suggests a different, potentially emergent diagnosis).
Nursing Clinical Practice GuideClinical Scenario: You are the triage nurse in the Pediatric ED. Parents bring in their 6-week-old son, stating he has been vomiting forcefully "across the room" after every bottle for 4 days. He acts very hungry right after vomiting. You note he appears slightly lethargic, has dry mucous membranes, and a sunken fontanelle.
Nursing Intervention Strategy:
1Assessment* History: Detail the vomiting (timing, force, content - is it curdled? Is it ever green?). Ask about urine output (number of wet diapers).
* Physical Exam: With the infant calm and supine, flex the hips and knees to relax the abdomen. Use warm hands. Feel deep in the right upper quadrant/epigastrium for a small, firm, mobile mass. Observe the abdomen for left-to-right peristaltic waves. Assess for signs of dehydration.
* Diagnostics: Assist with or prepare for an abdominal ultrasound. Obtain IV access for lab draws (electrolytes, BUN/Cr, blood gas) and fluid resuscitation.
2Nursing Diagnosis & PlanningPrimary diagnoses are Deficient Fluid Volume and Imbalanced Nutrition: Less Than Body Requirements. The plan is to stabilize the infant metabolically before surgery.
3Implementation* NPO Status: The infant will be made NPO (nothing by mouth).
* IV Therapy: Administer ordered IV fluids (e.g., D5 0.45% NS or 0.9% NS with KCl) at the calculated maintenance + replacement rate. Key Point! Potassium is NEVER given as a IV push and is infused cautiously, especially in dehydrated patients with potential renal issues.
* Pre-op Care: Provide parent education, ensure consents are signed.
4EvaluationMonitor for improved hydration (increased urine output, moist mucous membranes, normal fontanelle), normalization of electrolyte levels, and readiness for surgery.
Patient Safety and Precautions:
* Never attempt to palpate the olive mass if the infant is crying—the abdominal muscles will be tense. Soothe the infant first.
* Bilious vomiting is an emergency. If you see green vomit, stop thinking about HPS and think about malrotation/volvulus. Notify the provider STAT.
* Post-pyloromyotomy, vomiting a few times in the first 24-48 hours is common due to edema. However, persistent projectile vomiting must be reported as it may indicate an incomplete myotomy.
2PlanningCalculate fluid requirements: Maintenance (e.g., 100 mL/kg/day for a 4kg infant = ~17 mL/hr) PLUS deficit replacement (based on % dehydration).
3Implementation* Start IV infusion with the prescribed solution (commonly 0.9% NS with 20 mEq KCl/L).
* Potassium Administration Caution: Infuse via an IV pump. Ensure adequate urine output before adding KCl to the bag. Never administer IV push. Monitor for signs of hyperkalemia (peaked T-waves on ECG, muscle weakness).
* Re-check electrolytes in 6-12 hours.
4EvaluationThe goal is a well-hydrated infant with normal electrolyte levels and acid-base balance prior to surgery.
A Word from Your Senior Nurse
"Trust your assessment skills! That 'olive' can be tricky to feel, especially in a chubby baby. Take your time, warm your hands, and get the baby relaxed. Remember, in pediatrics, parents are your best historians. Listen carefully to their description of the vomiting—'projectile' is a very specific term they often use accurately. Your role in stabilizing this baby with fluids is just as critical as the surgeon's role in fixing the problem. Mastering the pre-op management of HPS teaches you fundamental principles of fluid, electrolyte, and acid-base balance that apply to countless other conditions. You've got this!"
Hypertrophic Pyloric Stenosis — A condition in infants where the pyloric muscle thickens, causing a gastric outlet obstruction, leading to projectile, non-bilious vomiting.
Pyloromyotomy — The definitive surgical procedure for HPS, where the surgeon cuts the hypertrophied pyloric muscle lengthwise to relieve the obstruction (Ramstedt procedure).
Hypochloremic Hypokalemic Metabolic Alkalosis — The classic electrolyte and acid-base imbalance in HPS due to loss of gastric acid (HCl) and potassium in vomitus.
Projectile Vomiting — Forceful vomiting where stomach contents are ejected several feet away; a hallmark symptom of HPS.
Olive-Shaped Mass — The palpable, firm, movable mass in the right upper quadrant representing the hypertrophied pylorus; the pathognomonic physical finding for HPS.