Nursing care
Pyloric Stenosis nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Pyloric stenosis nursing care centres on recognising forceful, non-bilious projectile vomiting in a three- to six-week-old infant who remains hungry immediately after vomiting. Priorities are correcting the resulting dehydration and hypochloraemic, hypokalaemic metabolic alkalosis before surgery, since pyloromyotomy is never an emergency operation — fluid and electrolyte correction always comes first.
What it is and why it happens
Pyloric stenosis is hypertrophy of the circular muscle of the pylorus, the gastric outlet narrowing until feeds can no longer pass into the duodenum. The exact cause is not established, but it is more common in first-born male infants and there is a familial pattern. It typically becomes symptomatic between three and six weeks of age, rarely before two weeks or after twelve.
The muscle thickening is progressive, so early feeds may pass with some difficulty before the obstruction becomes complete. As gastric outlet obstruction worsens, the stomach empties only by forceful contraction against a fixed narrowing, which is what produces the projectile character of the vomiting rather than simple regurgitation. Understanding this mechanical, progressive course explains why the infant's presentation changes over days to weeks rather than appearing all at once.
How it presents — what you will actually see
The defining picture is projectile vomiting in a hungry infant. Vomiting occurs shortly after a feed, is forceful enough to travel some distance, and is non-bilious because the obstruction sits proximal to the duodenum. Critically, the infant remains hungry and feeds eagerly again straight after vomiting — this hunger-after-vomiting pattern is the discriminator that separates pyloric stenosis from reflux or gastroenteritis, where infants are typically less interested in refeeding.
On examination, a firm, mobile, olive-shaped mass is often palpable in the right upper quadrant or epigastrium, best felt after the infant has vomited and the stomach is empty. Visible gastric peristaltic waves may be seen crossing the abdomen left to right during or just before a feed. Weight loss, poor weight gain, and signs of dehydration accumulate over days as intake fails to keep pace with losses.
Nursing assessment priorities
Weigh the infant on admission and track weight at least daily, since trends guide both rehydration and readiness for surgery. Assess hydration status directly: fontanelle, skin turgor, mucous membranes, urine output, and capillary refill. Document the character of every vomit — timing relative to feeds, force, and whether it is bile-stained — because bilious vomiting points away from pyloric stenosis and should prompt reassessment of the diagnosis.
Monitor electrolytes closely. Repeated vomiting of gastric contents rich in hydrochloric acid and potassium produces a hypochloraemic, hypokalaemic metabolic alkalosis, and this laboratory picture is expected and should be anticipated rather than treated as an incidental finding. Palpate for the olive-shaped mass during a calm, unhurried abdominal examination, ideally right after a vomiting episode. Confirm ultrasound findings are on the chart before surgery is scheduled, since ultrasound is the diagnostic standard.
Interventions and what to do first
The first intervention is not surgery — it is correction of dehydration and the metabolic alkalosis. Establish IV access and begin isotonic fluid replacement with potassium added once urine output is confirmed, following the prescribed rehydration regimen. Keep the infant nil by mouth once the diagnosis is suspected, and insert a nasogastric tube if ordered to decompress the stomach and reduce further vomiting and aspiration risk.
Reassess hydration and electrolyte values against the ordered targets before the infant goes to theatre; pyloromyotomy is corrective, not urgent, and proceeding with an alkalotic, hypokalaemic infant risks post-anaesthetic apnoea. Post-operatively, resume feeds gradually per unit protocol, starting with small volumes of clear fluids and advancing as tolerated, and continue to monitor for vomiting, wound integrity, and pain. Position the infant with the head slightly elevated after feeds to reduce reflux risk during the early post-operative period.
Complications to watch for
Untreated or delayed presentation carries the risk of severe dehydration, hypovolaemic shock, and profound electrolyte derangement, so ongoing vigilance for deterioration is essential while awaiting surgery. Aspiration is a real risk given repeated forceful vomiting, particularly if the infant is fed orally before the stomach is adequately decompressed.
Post-operatively, watch for wound infection, dehiscence, and persistent vomiting, which can indicate an incomplete pyloromyotomy or duodenal perforation during the procedure. Apnoea in the immediate post-anaesthetic period is more likely if metabolic alkalosis was not fully corrected beforehand, which is why continuous cardiorespiratory monitoring is standard practice for several hours after surgery in this age group.
Patient teaching before discharge
Teach parents the expected post-operative feeding progression and reassure them that occasional small vomits in the first day or two after surgery are common and not necessarily a sign of recurrence. Advise them to feed slowly, burp frequently, and avoid overfeeding, since a stretched stomach that has been obstructed for weeks needs a graded return to full volumes.
Review wound care: keep the incision clean and dry, and explain the signs of infection to report — redness, discharge, swelling, or fever. Confirm parents know when to seek urgent review: bilious vomiting, forceful vomiting that resumes and persists, poor feeding, lethargy, or reduced wet nappies. Arrange the routine surgical follow-up appointment and confirm parents have contact details for concerns in the interim.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pediatrics practice questions are the closest set to what this page covers.
Common questions
What is the classic sign that distinguishes pyloric stenosis from reflux?
The infant remains hungry and feeds eagerly again immediately after a forceful, projectile vomit. In reflux, infants are typically less keen to refeed straight away, which makes this hunger-after-vomiting pattern the key discriminator.
Why is surgery delayed until fluids and electrolytes are corrected?
Pyloric stenosis causes a hypochloraemic, hypokalaemic metabolic alkalosis from repeated vomiting of gastric acid and potassium. Operating on an uncorrected infant increases the risk of post-anaesthetic apnoea, so pyloromyotomy is always treated as corrective rather than emergency surgery.
Where would I expect to palpate the olive-shaped mass?
In the right upper quadrant or epigastrium, and it is usually easiest to feel right after the infant has vomited, when the stomach is empty and the abdominal wall is relaxed.
Is bilious vomiting consistent with pyloric stenosis?
No. The pyloric obstruction sits proximal to the duodenum, so vomiting is non-bilious. Bile-stained vomiting should prompt reconsideration of the diagnosis, such as malrotation with volvulus.
What electrolyte pattern should I anticipate on the metabolic panel?
Expect low chloride, low potassium, and a metabolic alkalosis from the ongoing loss of hydrochloric acid and potassium in vomitus. This pattern is anticipated in pyloric stenosis and guides the IV fluid and potassium replacement plan before surgery.