Approach to the acute abdomen (pediatrics): Clinical sciences

Acute abdomen refers to sudden, severe abdominal pain characterized by extreme abdominal tenderness, rebound, or guarding. These signs suggest the presence of peritoneal inflammation or peritonitis, and an underlying cause that requires urgent surgical intervention.

Evaluation of a child with an acute abdomen depends on their age, the presence of an inguinal mass or bilious emesis, and the location of maximum abdominal tenderness.

Here’s a high yield fact! The acute abdomen is often referred to as a “surgical abdomen,” but some non-surgical conditions can mimic peritoneal signs. Examples include acute bacterial peritonitis, diabetic ketoacidosis, pancreatitis, sickle cell crisis, familial Mediterranean fever, and lead poisoning.

When a pediatric patient presents with a chief concern suggesting an acute abdomen, your first step is to perform an ABCDE assessment to determine if the patient is stable or unstable. Most patients with an acute abdomen are unstable, so be sure to stabilize their airway, breathing and circulation. Obtain IV access and start fluid resuscitation; continuous vital sign monitoring; and provide supplemental oxygen if needed. Additionally, make your patient NPO in anticipation of surgical intervention, and consider placing a nasogastric tube. Finally, obtain an emergent surgical consultation and start broad spectrum IV antibiotics.

Now that you’ve stabilized your patient, perform a focused history and physical examination. Patients typically describe severe, acute abdominal pain with a sudden onset. If the physical examination demonstrates abdominal tenderness with rebound and guarding; and possibly abdominal distension, or even a rigid abdomen; consider an acute abdomen.

Here’s a clinical pearl! It can be tricky to interpret exam findings when a child is experiencing pain or anxiety, but certain techniques can help you obtain a more reliable exam.

For instance, you might begin the exam by auscultating the heart and lungs, and then move your stethoscope to the abdomen to perform both auscultation and palpation using the stethoscope’s diaphragm. Since most children don’t associate a stethoscope with discomfort, this method can reduce your patient’s anxiety and reveal signs like tenderness, rebound, or guarding!

Next, consider ordering a complete blood count or a complete metabolic panel, since patients with an acute abdomen may have leukocytosis, anemia, or electrolyte abnormalities. Now, before you proceed with the evaluation, consider your patient’s age.

First, let’s discuss patients under two months of age. In this case, you should also assess the gestational age at birth.

If your patient was born premature, consider necrotizing enterocolitis. Infants with this condition typically have feeding intolerance, lethargy, apnea and bradycardia, temperature instability, and in some cases, bilious vomiting. The exam may reveal abdominal distension and bloody stools.

Next, obtain an abdominal X-ray. If it reveals pneumatosis intestinalis, which is visible air inside the bowel wall, diagnose necrotizing enterocolitis.

Now let’s discuss patients who were born full term. In this case, your next step is to assess for passage of meconium within 48 hours of birth.

If your patient failed to pass meconium within this time frame, consider Hirschsprung disease. These infants demonstrate poor feeding and vomiting that is often bilious. Physical examination will reveal abdominal distension, and if you perform a rectal exam, you will find no stool in the rectal vault. Next, obtain a contrast enema and consider a rectal suction biopsy.

Imaging may demonstrate a funnel-shaped transitional zone between the dilated proximal colon and a narrow distal segment. The biopsy will reveal an absence of ganglion cells in the colonic submucosa, which confirms Hirschsprung disease.

Now, if your patient did pass meconium within 48 hours of birth, consider pyloric stenosis. These patients have immediate postprandial, non-bilious projectile vomiting, and appear perpetually hungry. Caregivers may report a sibling with a history of pyloric stenosis. The physical exam might demonstrate a palpable olive-shaped mass in the epigastrium or right upper quadrant, and lab findings classically reveal hypochloremic, hypokalemic metabolic alkalosis. Next, order an abdominal ultrasound, and if it reveals a hypertrophic pylorus, diagnose pyloric stenosis.

Okay, now let’s go back and discuss children two months of age and older. In this case, assess for an inguinal mass. If you identify a mass, consider an incarcerated hernia. These patients are usually diagnosed during infancy and present with vomiting, as well as abdominal and groin pain. If the physical exam demonstrates a non-reducible groin mass, diagnose incarcerated hernia. Generally, this can be diagnosed clinically based on exam findings, if you’re uncertain, you can order an ultrasound or CT scan to confirm the presence of bowel within a hernia defect, and to look for signs of bowel obstruction.

On the flip side, if you don’t find an inguinal mass, your next step is to assess for bilious emesis. The presence of bilious emesis should make you consider the possibility of intestinal obstruction, which is often caused by intestinal malrotation with volvulus, or intussusception.

First up is intestinal malrotation with volvulus. These infants typically present during infancy with bilious vomiting, and bright red blood per rectum; the exam will reveal abdominal distension and tenderness. Now, bilious vomiting in an infant is a warning sign that should immediately make you consider intestinal malrotation with volvulus!

This can’t-miss condition results from defective embryonic rotation of the gut, which causes the intestines to twist around their mesenteric root. Consequently, these infants can quickly develop vascular compromise and bowel ischemia, so order an emergent upper GI contrast study. Imaging will show a spiral appearance of the duodenum and jejunum called the “corkscrew sign,” confirming the diagnosis of intestinal malrotation with volvulus.