8.1 Acute Surgical Conditions: Pyloric Stenosis, Intussusception & Appendicitis

Acute Surgical Conditions: Pyloric Stenosis, Intussusception & Appendicitis

Quick Overview: Acute abdominal emergencies in pediatric patients demand rapid clinical discrimination between mechanical obstructions, vascular strangulation, and invasive inflammatory processes. Hypertrophic pyloric stenosis, intussusception, and acute appendicitis represent the three most common surgical abdominal disorders encountered from infancy through adolescence. Certified pediatric nurses must master their distinctive pathophysiological trajectories, fluid and electrolyte derangements, and evidence-based preoperative and postoperative nursing priorities.

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1. Hypertrophic Pyloric Stenosis (HPS)

Hypertrophic pyloric stenosis (HPS) is a condition characterized by progressive hypertrophy and hyperplasia of the circular smooth muscle fibers of the pyloric sphincter, resulting in severe luminal narrowing and mechanical obstruction of the gastric outlet.

Epidemiology & Risk Factors

• Peak Age of Onset: Typically manifests between 2 and 8 weeks of age (peak presentation occurs at 3 to 5 weeks). It rarely develops in infants older than 12 weeks.
• Demographic Distribution: Significant male predominance with a male-to-female ratio of approximately 4:1 to 5:1. First-born males and infants with a positive family history (especially an affected mother) face the highest statistical risk.
• Pharmacological Association: Exposure to oral macrolide antibiotics—specifically erythromycin and azithromycin—either directly administered to neonates in the first 2 to 4 weeks of life (e.g., for pertussis prophylaxis) or through maternal ingestion during late pregnancy and lactation, is strongly linked to the development of HPS.

Pathophysiological Cascade & Metabolic Derangements

1. Mechanical Obstruction: Progressive circular pyloric muscle hypertrophy leads to elongation, thickening, and narrowing of the pyloric canal, creating a tight functional stricture. Ingested formula or breast milk cannot exit the stomach into the duodenum.
2. Gastric Dilation & Hyperperistalsis: The stomach becomes massively distended. Vigorous compensatory gastric contractions generate visible peristaltic waves that travel from left to right across the epigastrium.
3. Projectile Non-Bilious Emesis: Intragastric pressure overcomes the resistance of the lower esophageal sphincter, resulting in explosive, projectile vomiting that characteristically ejects several feet from the infant. Because the anatomical obstruction is proximal to the ampulla of Vater (where bile empties into the second portion of the duodenum), the emesis is strictly non-bilious (containing only curdled milk and clear gastric secretions).
4. Persistent Hunger ('Hungry Vomiter'): Unlike infants with systemic infectious gastroenteritis who exhibit anorexia, infants with HPS are ravenously hungry immediately following vomiting and will eagerly accept another bottle.
5. Fluid and Electrolyte Depletion: Persistent vomiting causes massive losses of water, hydrochloric acid (HCl), sodium, and potassium, precipitating the classic metabolic triad:
   • Hypochloremic, Hypokalemic Metabolic Alkalosis: Gastric juice contains high concentrations of hydrogen (H+) and chloride (Cl-). Loss of gastric acid leaves unbuffered bicarbonate (HCO3-) in the extracellular space, elevating serum pH and HCO3-. Hypovolemia activates the renin-angiotensin-aldosterone system (RAAS), stimulating renal aldosterone secretion to retain sodium. Aldosterone promotes distal renal tubular excretion of potassium and hydrogen ions in exchange for sodium reabsorption, worsening systemic hypokalemia and alkalosis.
   • Paradoxical Aciduria: As hypokalemia becomes profound, renal tubular cells have insufficient intracellular potassium to exchange for filtered sodium. Consequently, the kidneys are forced to secrete hydrogen ions (H+) into the urine to conserve sodium, resulting in acidic urine despite severe systemic metabolic alkalosis.

+-------------------------------------------------------------------------+
|          METABOLIC CASCADE IN HYPERTROPHIC PYLORIC STENOSIS            |
+-------------------------------------------------------------------------+
| Persistent Non-Bilious Vomiting                                         |
|   --> Loss of Gastric H+, Cl-, K+, and H2O                              |
|   --> Severe Dehydration & Hypovolemia                                  |
|   --> Renin-Angiotensin-Aldosterone System (RAAS) Activation             |
|   --> Renal Aldosterone promotes Na+ retention, wasting K+ and H+       |
|   --> Intracellular K+ depletion forces distal renal tubules to dump H+ |
|   --> Hypochloremic, Hypokalemic Metabolic Alkalosis                    |
|   --> Paradoxical Aciduria (Acidic urine in the setting of alkalemia)   |
+-------------------------------------------------------------------------+

Clinical Presentation & Diagnostic Assessment

• Hallmark Vomiting Pattern: Regurgitation progresses over days to forceful, projectile non-bilious emesis occurring within 30 to 60 minutes after every feed.
• The 'Pyloric Olive': On physical examination, a firm, non-tender, mobile, olive-shaped mass approximately 1 to 2 cm in diameter is palpable in the epigastrium or right upper quadrant just to the right of the umbilicus. Palpation is easiest when the infant's stomach is emptied following emesis or while the infant is soothed with a pacifier or sucrose.
• Visible Peristalsis: Visible left-to-right gastric peristaltic waves can frequently be observed rippling across the epigastrium immediately prior to an emetic episode.
• Dehydration Indicators: Sunken anterior fontanelle, dry mucous membranes, delayed capillary refill (>3 seconds), decreased skin turgor, oliguria or anuria, and significant weight loss.
• Diagnostic Ultrasound: Abdominal ultrasonography is the diagnostic gold standard, with sensitivity and specificity approaching 100%. Diagnostic criteria include:
  • Pyloric muscle wall thickness >= 3 mm (or >= 4 mm in older infants).
  • Pyloric canal length >= 14 to 16 mm.
  • Failure of the pyloric channel to relax or open during real-time scanning.
• Upper Gastrointestinal (UGI) Contrast Series: Reserved for cases where ultrasound is equivocal. Demonstrates an elongated, string-like pyloric canal known as the 'string sign' or 'double-track sign'.

Preoperative Nursing Priorities & Anesthetic Safety

CRITICAL CLINICAL PRINCIPLE: Pyloromyotomy is NEVER an emergency surgical procedure; it is a planned, elective procedure that must be delayed until metabolic stabilization is achieved. Operating on an infant with uncorrected metabolic alkalosis carries a catastrophic risk of severe intraoperative and postoperative central hypoventilation and prolonged central apnea, because metabolic alkalosis suppresses central chemoreceptor respiratory drive.

1. Strict NPO Status & Gastric Decompression: Place the infant on strict NPO. Insert a wide-bore orogastric or nasogastric tube (8 to 10 Fr) to low intermittent suction to evacuate retained milk curds, prevent gastric distension, and eliminate the risk of pulmonary aspiration.
2. Aggressive Fluid Resuscitation:
   • Initial phase: Administer an isotonic crystalloid fluid bolus (Normal Saline 0.9% at 10 to 20 mL/kg IV over 30 to 60 minutes) to restore effective circulating intravascular volume.
   • Maintenance and deficit replacement: Administer Dextrose 5% with 0.45% Normal Saline (or 0.9% Normal Saline) at 1.5 to 2 times the maintenance rate.
   • Potassium Chloride Addition: Add potassium chloride (20 to 30 mEq/L KCl) to IV maintenance fluids ONLY AFTER adequate renal function and spontaneous urine output (at least 1 to 2 mL/kg/hour) are confirmed, to prevent lethal hyperkalemia.
3. Target Laboratory Criteria Before Surgery:
   • Serum Chloride: > 100 mEq/L (ideally > 102 mEq/L).
   • Serum Potassium: > 3.5 mEq/L.
   • Serum Bicarbonate (Total CO2): < 30 mEq/L (ideally < 28 mEq/L).
   • Urine output >= 1 to 2 mL/kg/hour with normal specific gravity.

Surgical Correction & Postoperative Nursing Care

• Pyloromyotomy (Ramstedt Procedure): The surgeon performs a longitudinal incision through the hypertrophied circular pyloric muscle down to, but not through, the submucosa and mucosal layer, allowing the underlying mucosa to bulge outward and relieving the luminal obstruction. It can be performed via open laparotomy or laparoscopically.
• Postoperative Feeding Advancement:
  • Feedings are typically initiated within 4 to 6 hours postoperatively once the infant is fully recovered from anesthesia.
  • Begin with small volumes of clear oral rehydration solution (Pedialyte), such as 15 mL every 2 to 3 hours.
  • If tolerated without vomiting, advance to half-strength formula or breast milk, progressing to full-strength feedings within 24 to 48 hours.
  • Postoperative Emesis Anticipation: Reassure parents that mild, non-projectile vomiting occurs in up to 50% of infants during the first 24 to 48 hours due to transient local surgical edema and impaired gastric motility. However, persistent projectile vomiting indicates incomplete muscle division or mucosal perforation and requires urgent surgical re-evaluation.

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2. Intussusception

Intussusception is the invagination or 'telescoping' of a proximal segment of the intestine (the intussusceptum) into an immediately adjacent, distal segment of bowel (the intussuscipiens). It is the leading cause of intestinal obstruction in children between 3 months and 6 years of age.

Anatomical Location & Pathophysiology

• Most Common Site: Ileocolic intussusception accounts for approximately 85% to 90% of cases, occurring where the terminal ileum telescopes through the ileocecal valve into the cecum and ascending colon.
• Mesenteric Strangulation Cascade: As the proximal bowel is propelled forward by peristalsis into the distal segment, it pulls its mesentery and mesenteric blood vessels along with it.
  • Mesenteric venous and lymphatic compression occurs first, producing rapid mucosal congestion, massive mural edema, and venous stasis.
  • Increased tissue pressure eventually exceeds arterial perfusion pressure, resulting in arterial insufficiency, localized bowel ischemia, transmural necrosis, and full-thickness bowel perforation with subsequent bacterial peritonitis and septic shock.
  • Mucosal sloughing combined with capillary bleeding and mucus hypersecretion produces the classic bloody, gelatinous stool.

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|                    INTUSSUSCEPTION PATHOLOGY CASCADE                    |
+-------------------------------------------------------------------------+
| Telescoping of Proximal Bowel (Intussusceptum) into Distal Bowel         |
|   --> Mesenteric vessels dragged into lumen                             |
|   --> Venous and lymphatic compression                                 |
|   --> Intestinal wall edema, mucosal engorgement & ischemia             |
|   --> Sloughing of necrotic mucosa mixed with blood and mucus           |
|   --> 'Currant Jelly' Stools                                            |
|   --> Arterial occlusion --> Transmural Gangrene --> Perforation        |
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Etiology & Lead Points

• Idiopathic Form (90% of cases): Predominates in infants aged 3 months to 3 years (peak incidence 5 to 9 months). Strongly correlated with hypertrophy of Peyer patches (submucosal lymphoid follicles in the terminal ileum) provoked by viral infections (adenovirus, enterovirus, rotavirus, human herpesvirus 6, or upper respiratory infections).
• Pathological Lead Points (10% of cases): Far more common in children older than 2 to 3 years or younger than 3 months. Pathological triggers include:
  • Meckel diverticulum (most common anatomical lead point).
  • Intestinal polyps (e.g., Peutz-Jeghers syndrome).
  • Intestinal duplication cysts.
  • Intramural hematomas secondary to Henoch-Schönlein purpura (IgA vasculitis).
  • Intestinal lymphomas or benign tumors.
  • Cystic fibrosis (thick, inspissated fecal concretions).

Clinical Presentation: The Classic Triad

Although the 'classic triad' occurs simultaneously in fewer than 30% to 50% of presentations, its clinical components remain fundamental for board examination mastery:

1. Severe, Paroxysmal Colicky Abdominal Pain: Sudden, intermittent episodes of severe abdominal cramping during which a previously healthy, thriving infant screams inconsolably, pulls their knees up to their chest, and turns pale. Episodes last 15 to 20 minutes, followed by intervals of calm or exhaustion. Over time, the pain-free intervals become shorter as bowel ischemia worsens.
2. Palpable Abdominal Mass with 'Dance Sign': A firm, tubular, sausage-shaped mass is typically palpable in the right upper quadrant or epigastrium, oriented horizontally. Concurrently, palpation of the right lower quadrant reveals an empty, retracted feeling because the cecum and terminal ileum have invaginated upward into the transverse colon—known as Dance sign.
3. 'Currant Jelly' Stools: Passage of dark red, gelatinous stool composed of blood, sloughed intestinal epithelial tissue, and thick mucus. This is a late sign indicating advanced mucosal ischemia and strangulation.

• Atypical / Neurological Presentation: In young infants, intussusception may manifest primarily as profound lethargy, altered consciousness, glassy-eyed staring, or shock-like hypotonia without overt initial screaming, easily misleading clinicians toward sepsis or meningitis.

Diagnostic Modalities

• Abdominal Ultrasonography: The first-line imaging modality of choice (sensitivity >98%). Characteristic findings include:
  • Transverse view: 'Target sign', 'doughnut sign', or 'bullseye sign', created by concentric rings of hypoechoic edematous bowel wall alternating with hyperechoic mesenteric fat.
  • Longitudinal view: 'Pseudokidney sign' or 'sandwich sign', reflecting the elongated overlapping layers of bowel resembling renal architecture.
• Abdominal Plain Radiographs: Often normal early; may reveal non-specific paucity of right lower quadrant gas, soft-tissue mass in RUQ, or signs of bowel obstruction (multiple air-fluid levels) and pneumoperitoneum (free air under diaphragm) if perforation has occurred.

Non-Operative Reduction: Procedures & Nursing Management

+-------------------------------------------------------------------------+
|               EVIDENCE-BASED INTUSSUSCEPTION REDUCTION                  |
+-------------------------------------------------------------------------+
|  PNEUMATIC (AIR) ENEMA (Preferred) or HYDROSTATIC (SALINE/CONTRAST)     |
|  - Diagnostic and therapeutic in 80% to 90% of uncomplicated cases       |
|  - Performed under fluoroscopic or real-time sonographic guidance        |
|  - Maximum pneumatic pressure: 80 to 120 mmHg                            |
|  - Strict Contraindications: Peritonitis, free peritoneal air, shock    |
+-------------------------------------------------------------------------+

1. Pneumatic (Air) Enema: Considered the treatment of choice worldwide. A small catheter is inserted into the rectum, an airtight seal is established, and air is insufflated under controlled pressure (not exceeding 80 to 120 mmHg) under continuous fluoroscopic observation. The column of air forces the telescoped bowel backward through the ileocecal valve into its anatomical position.
2. Hydrostatic (Saline or Barium) Enema: Saline or water-soluble contrast is infused into the rectum from a height of approximately 3 feet (1 meter) above the table, utilizing hydrostatic gravity pressure to reduce the intussusception under ultrasound or fluoroscopic control.
3. Success Rate & Recurrence: Non-operative reduction succeeds in 80% to 90% of uncomplicated cases. Recurrence occurs in approximately 5% to 10% of patients, with the vast majority recurring within the first 24 to 48 hours post-reduction.

CRITICAL NURSING ALERT: If an infant scheduled for pneumatic/hydrostatic reduction or emergency surgical exploration passes a normal, brown formed stool, the nurse must IMMEDIATELY NOTIFY THE SURGEON AND RADIOLOGIST. Passage of normal brown stool indicates spontaneous reduction of the intussusception. The procedure must be held, the patient re-examined, and imaging repeated before subjecting the infant to an unnecessary procedure or laparotomy.

Surgical Indications & Postoperative Care

• Indications for Surgery:
  • Incomplete non-operative reduction after 2 to 3 well-performed attempts.
  • Clinical signs of peritonitis, bowel gangrene, or hemodynamic shock.
  • Evidence of free peritoneal perforation (pneumoperitoneum on radiograph).
  • Identified pathological lead point requiring resection.
• Operative Approach: Laparoscopic or open laparotomy. Manual reduction is attempted by gently milking the distal bowel backward (never pulling the proximal bowel, which causes tearing). If bowel is necrotic, perforated, or irreducible, segmental bowel resection with end-to-end anastomosis is performed.
• Postoperative Care: Keep NPO with NG tube decompression until bowel sounds return and flatus is passed. Monitor for recurrence (sudden colicky crying, bilious vomiting), surgical site infection, and anastomotic leaks.

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3. Acute Appendicitis

Acute appendicitis is an acute inflammation of the vermiform appendix resulting from luminal obstruction. It is the most common condition requiring emergent abdominal surgery in the pediatric population.

Pathophysiological Cascade to Perforation

1. Luminal Obstruction: The appendiceal lumen becomes mechanically obstructed. Primary causes in children include:
   • Lymphoid Hyperplasia (60%): Submucosal lymphoid tissue proliferation triggered by viral gastrointestinal or respiratory infections; predominant cause in children and adolescents.
   • Fecalith / Appendicolith (35%): Inspissated calcified fecal stone; associated with higher rates of rapid gangrene and perforation.
   • Foreign Bodies / Parasites (5%): Pinworms (Enterobius vermicularis), vegetable seeds, or ingested foreign items.
2. Intraluminal Hypertension & Mucosal Ischemia: Mucosal secretions continue behind the obstruction, causing rapid intraluminal pressure elevation (>85 mmHg). Increased pressure compresses intramural venules and lymphatic channels, leading to mucosal ischemia, loss of epithelial barrier integrity, and transmural edema.
3. Bacterial Infiltration & Gangrene: Normal intestinal flora (Escherichia coli, Bacteroides fragilis, Pseudomonas aeruginosa, Peptostreptococcus) rapidly invade the ischemic appendiceal wall. Arterial thrombosis ensues, causing transmural tissue gangrene.
4. Perforation & Peritonitis: Continued pressure elevation leads to full-thickness wall rupture. Appendiceal rupture typically occurs within 24 to 72 hours of symptom onset. Peritoneal contamination results in localized periappendiceal phlegmon/abscess or diffuse generalized chemical and bacterial peritonitis.

Age-Specific Presentation & High Perforation Risk in Young Children

• School-Age Children & Adolescents: Present with classic historical and physical findings.
• Toddlers and Preschoolers (< 4 years of age): Present with non-specific, atypical symptoms—diffuse irritability, lethargy, poor feeding, fever, and diarrhea. Because young children cannot verbalize pain location, possess a thin appendiceal wall, and have an underdeveloped greater omentum incapable of walling off localized infection, perforation rates exceed 70% to 80% in children under 3 years of age.

Clinical Manifestations & Diagnostic Signs

• Abdominal Pain Progression:
  • Early Visceral Phase: Dull, diffuse, poorly localized periumbilical or epigastric cramping pain mediated by visceral afferent C-fibers (T10 dermatome).
  • Somatic Peritoneal Phase: Over 12 to 24 hours, the inflammatory process breaches the appendiceal serosa to irritate the parietal peritoneum. Pain sharpens, intensifies, and migrates definitively to the right lower quadrant (RLQ), specifically localizing to McBurney's point (located two-thirds of the distance along an imaginary line drawn from the umbilicus to the right anterior superior iliac spine).
• Associated Cardinal Symptoms:
  • Anorexia: Cardinal historical sign; a child who willingly eats their favorite meal rarely has acute appendicitis ('hamburger sign').
  • Nausea and Vomiting: Vomiting characteristically occurs after the onset of pain (a critical clinical discriminator: in gastroenteritis, vomiting precedes abdominal pain).
  • Low-Grade Fever: Typically 38.0°C to 38.5°C (100.4°F to 101.3°F) early, rising significantly (>39°C) following perforation.

Specialized Physical Examination Maneuvers

OMINOUS RED FLAG — ABRUPT PAIN RELIEF: If a pediatric patient with suspected appendicitis who has been crying with severe, worsening right lower quadrant pain suddenly reports that the pain has completely disappeared, the nurse must recognize this as an ominous emergency indicating appendiceal perforation. The sudden decompression of the tense, obstructed appendiceal lumen provides transient pain relief. However, within several hours, spilled bacterial contents provoke diffuse peritonitis, characterized by high-spiking fever (>39°C), board-like abdominal rigidity, diffuse guarding, tachycardia, and rapid progression to septic shock.

Diagnostic Workup

• Laboratory Evaluation: Moderate leukocytosis (WBC 11,000 to 18,000/mcL) with a 'left shift' (neutrophilia >75% and elevated immature bands). C-reactive protein (CRP) >10 mg/L (CRP and WBC elevation together have >90% sensitivity). Urinalysis is performed to rule out urinary tract infection (though mild pyuria without bacteriuria can occur from bladder irritation by an inflamed pelvic appendix). A beta-hCG pregnancy test is mandatory in all post-menarchal females to rule out ectopic pregnancy.
• Graded Compression Ultrasonography: The first-line imaging modality in children to avoid ionizing radiation. Diagnostic ultrasound criteria:
  • Non-compressible, blind-ending tubular structure in the RLQ.
  • Outer appendiceal diameter > 6 mm.
  • Wall thickness > 2 mm with hyperemic blood flow ('target' or 'halo' sign on color Doppler).
  • Presence of an echogenic fecalith casting an acoustic shadow.
• Contrast-Enhanced Abdominal Computed Tomography (CT): Highest diagnostic accuracy (sensitivity and specificity >95%), reserved for equivocal ultrasound findings, obese patients, or suspected deep pelvic/retrocecal abscesses.

Preoperative Nursing Priorities & Absolute Contraindications

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*           STRICT PREOPERATIVE CONTRAINDICATIONS IN APPENDICITIS             *
*                                                                             *
*  1. NEVER APPLY HEATING PADS OR HEAT PACKS TO THE ABDOMEN!                  *
*     Heat induces local vasodilation, increases intraluminal pressure,       *
*     accelerates tissue gangrene, and precipitates IMMEDIATE PERFORATION!     *
*                                                                             *
*  2. NEVER ADMINISTER ENEMAS, LAXATIVES, OR CATHARTICS!                      *
*     Stimulating intestinal motility and increasing colonic intraluminal     *
*     pressure forces mechanical rupture of the inflamed appendix!           *
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• Preoperative Protocol:
  • Strict NPO status.
  • Intravenous fluid resuscitation with isotonic crystalloids (Normal Saline or Lactated Ringer's) to correct dehydration and restore renal perfusion.
  • Administer broad-spectrum intravenous antibiotics targeting enteric aerobes and anaerobes (e.g., Ceftriaxone plus Metronidazole, or Piperacillin-Tazobactam, or Ampicillin-Sulbactam).
  • Analgesia Administration: Contrary to historical misconceptions, evidence-based pediatric practice dictates that providing judicious IV analgesia (e.g., morphine or fentanyl) does not mask physical examination signs or impair diagnostic accuracy. Relieving excruciating pain facilitates cooperative examination.

Postoperative Nursing Management: Non-Perforated vs. Perforated

• Laparoscopic Appendectomy (Simple / Non-Perforated):
  • Short postoperative antibiotic course (single preoperative dose or <24 hours post-op).
  • Early oral intake: Clear liquids initiated once alert, advancing to regular diet as tolerated.
  • Early ambulation within 6 to 12 hours.
  • Hospital discharge typically within 12 to 24 hours.
• Complicated / Perforated Appendicitis:
  • Extensive peritoneal irrigation during surgery; intra-abdominal closed-suction drain (Jackson-Pratt) may be placed.
  • Nasogastric tube to low intermittent suction until flatus and spontaneous bowel sounds return.
  • Prolonged IV antibiotic therapy (minimum 3 to 7 days, continued until child is afebrile for 24 hours, tolerating regular diet, with normalizing WBC count).
  • Position patient in semi-Fowler position (head of bed elevated 30 to 45 degrees) to facilitate dependent drainage of infected peritoneal fluid downward into the pelvic cavity, preventing subdiaphragmatic abscess formation.
  • Monitor for postoperative complications: Pelvic or intra-abdominal abscess (manifesting as spiking fevers, persistent anorexia, leukocytosis, and pelvic diarrhea around post-op days 5 to 7), wound infections, and mechanical bowel obstruction secondary to adhesions.

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4. Comparative Synthesis of Pediatric Acute GI Conditions

Interpretation safeguard: Sudden pain relief does not independently prove appendiceal perforation, and passage of normal stool does not independently prove intussusception has reduced. Reassess and notify the responsible team; do not cancel an indicated procedure without clinical confirmation. Avoid repeated provocative abdominal examination when it adds distress without changing the plan.