Approach to acute abdominal pain (pediatrics): Clinical sciences

Acute abdominal pain is a common presenting concern in pediatric patients. While severe abdominal pain combined with abdominal rigidity, rebound, or guarding suggests a condition requiring urgent surgical intervention, most underlying causes of acute abdominal pain in children are transient and non-life-threatening. Acute abdominal pain can be caused by gastrointestinal, urinary, pelvic, and neurologic or musculoskeletal conditions.

When a pediatric patient presents with acute abdominal pain, you should first perform an ABCDE assessment to determine if they’re stable or unstable. If unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access, begin fluid resuscitation, and continuously monitor vital signs. Provide supplemental oxygen if needed, ensure that the patient does not take anything by mouth, and consider placing a nasogastric tube. Finally, obtain an emergency surgical consultation and administer broad spectrum IV antibiotics.

Once you’ve initiated acute management, perform a focused history and physical examination. The history will reveal a sudden onset of severe abdominal pain, and the physical exam will often demonstrate abdominal tenderness, rebound, and guarding, possibly with abdominal distension and rigidity. These peritoneal signs indicate an acute “surgical” abdomen, which requires immediate surgical intervention.

Here’s a high-yield fact! Appendicitis is the most common cause of a surgical abdomen in childhood, but other significant causes include intussusception, intestinal malrotation with volvulus, and incarcerated inguinal hernia. Remember that blunt abdominal injury and nonaccidental trauma can cause intraperitoneal bleeding and visceral damage, both of which can present with acute abdominal pain in the absence of obvious external signs.

Now that we’ve discussed unstable patients, let’s move on to stable ones. First, perform a focused history and physical examination. The history will reveal an acute onset of pain; occasionally with nausea, vomiting, or fever; while the physical exam will demonstrate abdominal tenderness. Continue your evaluation by assessing your patient’s stooling pattern.

Let’s start with patients who report increased stooling frequency. In this case, consider acute gastroenteritis. In addition to loose, watery stools, these patients often report crampy abdominal pain, as well as nausea, vomiting, anorexia, and fever. There might also be a known sick contact or a history of recent travel. The exam often demonstrates abdominal tenderness. Keep in mind that presentation may vary by age. Some patients, especially smaller children, may show signs of dehydration like dry mucous membranes and decreased skin turgor.

While acute gastroenteritis is usually a clinical diagnosis, if the diagnosis is uncertain, you can order stool viral antigen testing or a stool culture and microscopic examination. If any of these tests are positive, you can confirm acute gastroenteritis, which can be caused by norovirus and rotavirus, as well as bacteria such as E. coli, Campylobacter, and Salmonella.

Here’s a clinical pearl! Acute abdominal pain can also be caused by non-gastrointestinal infections, such as pneumonia and group A Streptococcal pharyngitis.

Next, let's discuss cases in which stooling frequency is decreased, which should make you consider constipation. Patients will report infrequent bowel movements, straining or pain during defecation, and hard stool consistency. The exam may demonstrate mild abdominal distension, a palpable stool mass in the lower abdomen, and occasionally, anal fissures. In this case, you can diagnose acute constipation.

Here’s another clinical pearl! Acute gastroenteritis and acute constipation are the most common causes of acute abdominal pain in children.

Now, let’s talk about cases in which there’s no change in the patient’s stooling pattern. Here, you should assess for signs and symptoms suggesting urinary tract pathology. In the case of urinary tract infection or UTI, infants under 2 months of age might have foul-smelling urine and irritability, while older children may describe dysuria, urgency, and frequent urination. Physical exam might reveal an elevated temperature; as well as suprapubic or costovertebral angle tenderness.

These findings should lead you to consider a urinary tract infection and obtain a CBC, urinalysis, and urine culture. If the CBC reveals leukocytosis; the urinalysis is positive for white blood cells, as well as positive leukocyte esterase, and sometimes positive nitrites; and a urine culture grows more than 50,000 colony-forming units per milliliter of a single bacterial species, diagnose a UTI.

Here’s another clinical pearl! It can be difficult to differentiate cystitis from pyelonephritis, especially in children under 2 years of age. Because a UTI can progress quickly, you should initiate empiric antibiotics as soon as you suspect one. Be sure to select antibiotics that cover enteric bacteria like E. coli, which are the most common pathogens causing UTI in children.

Another urinary tract pathology is urolithiasis. Patients might report hematuria and severe colicky back pain radiating to the groin, while physical exam demonstrates costovertebral angle tenderness. With these findings, consider urolithiasis and order imaging. The gold standard for diagnosing urolithiasis is a CT scan, but you can often establish the diagnosis quickly and minimize radiation exposure with an ultrasound or an X-ray of the kidneys, ureter, and bladder. If imaging demonstrates calculi, possibly in combination with hydronephrosis on the affected side, diagnose urolithiasis.

Here’s another clinical pearl! Urolithiasis often occurs alongside urinary tract infection, so remember to order a urinalysis and urine culture as part of your diagnostic workup. The urinalysis will often be positive for blood, white blood cells and leukocyte esterase; and the urine culture might grow more than 50,000 colony-forming units of bacteria per milliliter. Keep in mind that a UTI in the setting of bilateral ureteral obstruction is a urological emergency that requires urgent intervention and decompression.

Now let’s discuss patients who report no urinary signs or symptoms. In this case, your next step is to assess for postprandial symptoms. If your patient’s pain worsens after eating, assess the location of the pain.