Abdominal Pain

A two-year old male presents to the ED with abdominal pain. The parents are concerned because the child has been vomiting and is complaining of pain in his abdomen. On exam, the patient is writhing in pain and is unable to get comfortable on the bed.

The patient's lung examination is clear to auscultation, bilaterally. The heart examination is notable for tachycardia, but no murmurs, gallops, or rubs. The abdominal examination demonstrates no abdominal tenderness to palpation.

The student asks the attending what she thinks is going on...

As with any patient who presents to the emergency department (ED), the first priority is Airway, Breathing, Circulation, and initial stabilization as needed. An approach focusing on the ABC’s in a child with abdominal pain and vomiting is necessary to rule out an acute cardiorespiratory process. Abdominal pain and vomiting can be the presenting symptoms of significant cardiorespiratory disease, and many etiologies of abdominal pain can cause clinical deterioration and sepsis if not addressed promptly.

Initially, a targeted history and physical followed by a detailed directed history and physical should be performed. Many patients with complaints of abdominal pain and vomiting will have self-limited conditions and will be stable on presentation. However, some require rapid diagnosis and stabilization/resuscitation.

Key Points to Identify

• Is the patient septic? If the patient is septic, rapid interventions such as fluid resuscitation, having the patient placed on cardiopulmonary monitoring, rapid acquisition of labs, and prompt initiation of appropriate broad-spectrum antibiotic coverage can have a significant impact on patient outcomes.
• Is the patient dehydrated? Fluid resuscitation may be all that is needed to improve perfusion in the dehydrated child. This initially consists of giving normal saline in 20 cc/kg bolus three times before considering vasopressors.
• Is this presentation an acute abdomen? Rapidly identify the need for emergent or surgical intervention such as appendicitis, bowel ischemia, gonadal torsion, etc. If identified, these conditions require prompt referral to surgeons or subspecialists skilled in their specific management either within the hospital associated with the ED or via transfer to another center.

Abdominal Pain Types: Somatic, Visceral, and Referred

• Somatic pain is typically well-localized and sharp in character. The pain signal travels via somatic nerves unilaterally. Somatic pain may originate from a somatically-enervated organ experiencing inflammation or from inflammation in a nearby structure. The classic example of this is late appendicitis causing a localized peritonitis in the right lower quadrant.
• Visceral pain is typically dull or achy and usually located in the epigastric, middle, and lower abdomen. Visceral pain results from distension of a viscus or hollow organ. The pain signal is transmitted through autonomics that overlap with nerves from the contralateral side on their path to the CNS and results in a poorly localized pain. When asked to localize the pain, a patient may use an open hand to indicate a general region as the location for visceral pain. The classic example of this is early appendicitis causing periumbilical pain from inflammation of the appendix.
• Referred pain is felt remotely from the disease site and can vary in character. This pain signal is in fact created by transmission through shared afferent nerve pathways. A classic example of this is testicular pain that is experienced as abdominal pain by the child.

These varied mechanisms for pain can be used to further understand abdominal pain and shed light on a diagnosis. For example, appendicitis classically presents as a vague pain that then localizes to the right lower quadrant. This is a transition from visceral to somatic pain as the infection/inflammation worsens and spreads from viscus to affect the abdominal wall.

Vomiting is often coupled with abdominal pain. It is a forceful, coordinated expulsion of gastric contents from the mouth. The control and induction of vomiting is regulated in the medulla, with signals coming from a variety of areas throughout the body including chemoreceptors, nociceptors, and mechanoreceptors in the GI track, GU track, middle ear, heart, and brain. Serotonin plays a key role in these signals and has been targeted for antiemetic therapies. Emesis should be considered as having different probable etiologies by age groups, particularly dividing infants and very young children from school-aged children and adolescents.

Infants

• Spitting up: This is typically smaller volume and post feeds. It is one of the most common causes of emesis in infants and is a benign condition if there is appropriate weight gain. This exists on a spectrum with gastroesophageal reflux. Most are "happy spitters." Some infants may appear to be in pain and may benefit from acid suppression, although this is by no means emergent. Some infants with gastroesophageal reflux will have paroxysmal episodes of generalized stiffening and opisthotonic posturing (Sandifer Syndrome).
• Anatomic defects: Vomiting may be a presenting symptom of malrotation, volvulus, intussusception, pyloric stenosis, or other anatomic problems and require the attention of a surgeon.
• Necrotizing enterocolitis: This is typically seen in preterm or very ill infants, however it can occur in healthy term neonates as well. This is less likely as children grow older.
• Non-GI infection: Fever with vomiting can be the presenting symptoms in children with serious infections (e.g. meningitis). Fever and vomiting may also be presenting symptoms in more commonly seen febrile illness such as otitis media or upper respiratory infections. Gastroenteritis is a common cause of fever, vomiting, and diarrhea, but should be a diagnosis of exclusion in infants less than six months. Young children with urinary tract infections (pyelonephritis) will also present with fever, vomiting, and diarrhea.
• Post-tussive: Triggers to cough may be potent enough that coughing results in gagging and emesis. This can be seen in any condition causing cough although it has been classically described in pertussis.
• Chemical: Inborn errors of metabolism may present with emesis and have variable ages of onset although generally shortly after birth. Some can take time for metabolites to build up before symptoms appear. Additionally, many ingested substances may induce emesis and should be considered.
• Intussusception: Occurs when one part of the intestine telescopes into an adjacent portion. Often presents as a colicky abdominal pain, with bloody stools being a later presentation.
• Pyloric stenosis: Commonly occurs between three- and six-weeks of age. The vomiting is classically described as "projectile."

Older Child and Adolescent

• Gastroenteritis: The most common cause of emesis in older children and adolescents. Gastroenteritis may also present with diarrhea. Evaluate hydration status carefully.
• Obstruction: This may be secondary to incarcerated hernia, intussusception, or post-surgical adhesions. Suspicion of this should be dictated by history and physical examination.
• Infection: Serious infections of GI origin such as appendicitis or cholecystitis may present with emesis and require surgical referral. CNS infections may also present with emesis and clinicians should look for nuchal rigidity and other signs.
• GU: Urologic processes such as nephrolithiasis, particularly with obstruction, as well as UTI, frequently present with emesis.
• Diabetic ketoacidosis: Due to metabolic disturbances, emesis is often present.
• Toxins/drugs/ingestions: Ingestions of certain types of substances, such as opiates and cholinergics, can cause emesis.
• OB/GYN: Pregnancy or pelvic inflammatory disease can present with abdominal discomfort and vomiting.

• Abdominal Imaging: Abdominal x-rays may be used to help with the diagnosis of intestinal obstruction or to show evidence of perforation such as free air within the peritoneum. It is usually not sensitive enough to rule the aforementioned diagnoses.
• Ultrasound: Ultrasound is an invaluable tool in the practice of pediatric emergency medicine and even more so in patients with abdominal pain. Ultrasound with doppler may be used to rule out torsion of either an ovary or testis.  It can also provide a view of the kidneys and demonstrate hydronephrosis suggestive of obstruction secondary to renal stone. In younger patients, it can be used to look for intussusception, and in some centers, it is used in the workup of appendicitis. RUQ ultrasound is invaluable in the evaluation of patients with concern for liver and gallbladder disease. It can be used to screen for tubo-ovarian abscess or pyosalpinx. Furthermore, it can assist in determining if there is a viable intrauterine pregnancy.
• Abdominal MRI: This is used in some centers as first line in the diagnosis of pediatric appendicitis.
• Abdominal CT: This has many advantages. It is a test that can often be performed rapidly and is readily available in essentially every emergency department. It carries the risk of a high dosage radiation exposure and should be reserved for cases where other imaging will not be effective or is unable to be performed.
• Labs: Several different labs can be used to assess hydration status, organ function, and immune activity to investigate systemic causes or effects of abdominal pain. Common labs ordered in abdominal pain work up include complete blood cell counts with differentiation, complete metabolic panel, lipase, urinalysis, and beta hcG (in adolescent patients).
• Physical Exam: See below.

Key Aspects of History

History should be appropriately detailed and obtained from all available sources. An older child may provide better insight to the events leading up to their seeking care than an adult in many cases, whereas younger children are often unreliable historians and parents must be relied upon to relate events. Healthcare records, EMS, and other providers can also provide valuable information. History and physical exam can provide enough information to make the diagnosis in many cases, differentiating emergent from non-emergent interventions. Some causes of abdominal pain and vomiting are due to pathology outside of the GI tract (e.g. streptococcal pharyngitis).

• Duration of Symptoms: Acute vs. chronic, constant vs. intermittent.
• Pain: Location, character, radiation, and severity.
• Exacerbating or Alleviating Factors for Pain: Oral intake vs. NPO.
• Presence/Frequency of Associated Symptoms: emesis, diarrhea, cough, etc. If the patient has emesis or diarrhea, ask whether it is bloody, green, dark, or pale. Ask about changes with defecation, eating, urination, and position.
• Oral Intake: Degree of enteral nutrition and hydration; recent ingestion of food or medications, especially new foods or medications.
• Past medical history and surgical history.
• Family History: e.g. IBD or celiac disease.

Key Aspects of Physical Examination

• Inspection of the Abdomen: This should be done first as palpation may change findings.
• Auscultation: This should also be done prior to palpation as findings may be altered. Listen in all four quadrants of the abdomen. Decreased or absent bowel sounds in a specific area may suggest pathology in this area.
• Palpation: This is the main focus of examining an abdomen. Evaluate for tenderness in specific regions of the abdomen. Initial palpation should be superficial and progress to deeper palpation. Rebound tenderness indicates a degree of peritonitis.
• Percussion: Dullness or resonance may help direct towards specific disease processes.
• Specific Signs: Signs such as Murphy's, psoas, obturator, and tenderness at McBurney's point in conjunction with the remainder of H&P can have a high degree of specificity for particular disease processes.
• Determining Hydration Status: In an infant or toddler - activity level/overall appearance, eyes (sunken or not), anterior fontanels (sunken flat or bulging when age appropriate), capillary refill time, and mucous membranes. In a child or adolescent - general appearance, capillary refill time, and mucous membranes.

Physical Examination Clues as to the Potential Cause of Abdominal Pain (Non-Abdominal)

• HEENT: Tonsillar hypertrophy, exudates, and erythema can indicate pharyngitis, a well-known but poorly explained cause of abdominal pain and vomiting.
• Lung Exam: Auscultation of the chest may reveal a pneumonia, which can refer pain to the abdomen.
• Back Exam: Costovertebral angle tenderness may indicate pyelonephritis or GU obstruction. This physical finding is less likely to be seen in infants and young children.
• GU Exam: A pelvic exam is necessary in female patients if there is suspicion of a gynecologic process. Particular attention must be paid to evaluating cervical motion tenderness, as a sign of pelvic inflammatory disease, and adnexal tenderness, which may help localize ovarian pathology. A GU exam is needed in male patients to check for hernia and testicular torsion. Testicular pathology may present with pain referred to the abdomen.

Differential Diagnosis

The differential diagnosis for abdominal pain and vomiting in a pediatric patient can be broad, but here are some key diagnoses to consider in any patient with these symptoms.

• Gastrointestinal: Gastroenteritis, constipation, appendicitis, GERD, gastritis, diverticulitis, IBD, hernia, intussusception, volvulus, post-surgical adhesions, neoplasm, sickle cell disease, abdominal migraine, celiac disease, cholecystitis, cholelithiasis, hepatitis, liver abscess, pancreatitis, pyloric stenosis, colic, dehydration.
• Genitourinary: UTI, nephrolithiasis, pelvic inflammatory disease, ovarian torsion, testicular torsion, epididymitis, menstruation, Mittelschmerz, ovarian cyst, pregnancy.
• Referred: Pneumonia, asthma, pharyngitis.
• Other: Diabetic ketoacidosis, functional, irritable bowel syndrome.

Treatment for abdominal pain is based on etiology, which can vary depending on the patient's age. Some of the most common causes of abdominal pain and their treatments are listed below, organized by age group.

Infants

• UTI: UTIs in infants can be managed with antibiotics. Typical courses last 7-14 days. Trimethoprim-sulfamethoxazole is a common choice as it is inexpensive, well-tolerated, and administered twice per day. First-generation cephalosporins, such as cephalexin, are also effective but they must be administered at least three times per day, which can be less convenient than TMP-SMX. It is important to consult your local antibiogram as susceptibilities vary with location.
• Intussusception: Typically, intussusception is not immediately life-threatening, however, it can lead to bowel obstruction, ischemia, perforation, and peritonitis if not addressed in a timely manner. In clinically stable patients, most intussusceptions can be reduced using a barium, water-soluble, or air-contrast enema, with an efficacy rate of 80%. If an enema is unsuccessful, or the patient shows signs of sepsis, the intussusception can be reduced surgically.

School-Aged Children

• Constipation: Constipation in children is often classified as functional constipation, for which there is no apparent organic cause. Less commonly, constipation occurs secondary to medical conditions such as cystic fibrosis, Down syndrome, and neuromuscular disorders. Polyethylene glycol (Miralax) is the first-line treatment for acute constipation or impacted stool. It is more effective at reducing impactions than other stool softeners and is generally well-tolerated. Treatments for chronic constipation include increasing dietary sorbitol through apple, pear, or prune juice, as well as behavioral therapy.
• UTI: Like infants, UTIs in children are managed with antibiotics. TMP-SMX is the first-line choice, but cephalosporins or amoxicilin-clavulanate (Augmentin) may also be used. Uncomplicated lower UTIs can be treated with 2-4 days of oral antibiotics, whereas pyelonephritis may require 10-14 days. It is important to note that recurrent UTIs in children should be investigated for underlying causes, such as obstruction or vesicoureteral reflux.
• Appendicitis: Uncomplicated appendicitis in children can be managed non-operatively with antibiotics, however in cases with complications like appendicoliths, surgery is recommended. In contrast, acute appendicitis with perforation is a medical emergency that should be treated surgically.

Adolescents (General)

• Diabetic Ketoacidosis: DKA results from a depletion of insulin and subsequent uncontrolled hyperglycemia, resulting in polyuria, dehydration, and ketoacidosis. Patients can deteriorate rapidly, so treatment of DKA involves timely replacement of insulin, fluids, and electrolytes. If a DKA episode in an adolescent patient is the first presenting sign of type I diabetes, patients should be counseled about starting insulin and how to manage their condition.
• Irritable Bowel Syndrome: The symptoms and severity of IBS can vary greatly depending on the patient, so treatment of IBS focuses primarily on managing the symptoms that are present. Patients with constipation may benefit from fiber supplements and laxatives, whereas probiotics and medications such as loperamide can be helpful for patients with diarrhea. Patients can also try to identify and avoid foods that exacerbate their symptoms. Additionally, rifaximin, a non-absorbable antibiotic, has been shown in some studies to reduce abdominal pain and diarrhea in IBS patients.
• Functional Abdominal Pain Syndrome: Functional abdominal pain syndrome has many biopsychosocial elements, thus treatment for it must be tailored to meet the specific needs of the patient. IBS and functional dyspepsia are common components that can be addressed with diet changes and medications, including laxatives and antidiarrheals for IBS and H1 receptor antagonists like cyproheptadine for dyspepsia. Robust management of functional abdominal pain syndrome also involves psychological therapies, such as cognitive behavioral therapy.

Adolescents (Biological Females)

• Ovarian Torsion: Although most common in women of reproductive age, approximately 15% of ovarian torsion cases occur in pediatric patients, so it is an important differential diagnosis in biological females with abdominal pain, including adolescents. Conservative management with laparoscopic detorsion is the preferred method of treatment, as detorsion preserves ovarian function in 90% of cases. Ultrasound can be used for follow-up examination to assess for follicular development after the torsion is reversed and blood flow to the ovary is restored.
• Ovarian Cyst Rupture: Unlike ovarian torsion, ovarian cyst ruptures are not usually medical emergencies and can be managed expectantly with analgesics and observation. Cyst ruptures can happen idiopathically, however, work up for hemorrhagic cyst ruptures should include testing for predisposing factors, such as thrombophilia A.
• Pelvic Inflammatory Disease: Untreated PID can have severe impacts on future health and fertility, so treatment should be started early and promptly based on clinical suspicion. Several antibiotic combinations can be used to treat PID, however, all regimens should cover both Nisseria gonorrhea and Chlamydia trachomatis, the two organisms most often implicated in PID. Antibiotics used to treat PID in the inpatient setting include an IV second-generation cephalosporin + oral doxycycline + metronidazole, or IV clindamycin + gentamicin. First-line treatment regimens for outpatient management include one IM dose of a third-generation cephalosporin (usually ceftriaxone) + oral doxycycline and metronidazole for two weeks.
• Ectopic Pregnancy: Unruptured ectopic pregnancies that are detected early can be managed expectantly, medically with methotrexate, or with minimally invasive surgery. In contrast, ruptured ectopic pregnancies can threaten both life and future fertility and are thus considered medical emergencies. Clinical signs of a ruptured ectopic pregnancy include acute abdominal pain and hemodynamic instability. Patients with these symptoms should be treated surgically to remove the ectopic pregnancy.

Adolescents (Biological Males)

• Testicular Torsion: Testicular torsion can lead to ischemia, necrosis, and permanent loss of testicular function, so diagnosis and treatment must be prompt. Ideally, the torsion should be reduced within 4-8 hours after the onset of symptoms. Ultrasound with Doppler can be used to confirm testicular torsion, however in patients with severe symptoms, a clinical diagnosis is sufficient to seek surgical consultation to reduce the torsion. It is within the scope of practice for an emergency medicine physician to attempt detorsion.
• Epididymitis: Treatment for epididymitis in adolescent males is similar to treatment for PID in females. Antibiotic regimens should cover the most common causative organisms, N. gonorrhea and C. trachomatis. The most common regimen consists of a single dose of IM ceftriaxone + oral doxycycline and metronidazole for 14 days. In patients who practice anal intercourse, co-infection with an enteric organism is also likely, so a single dose of IM ceftriaxone + oral levofloxacin or ofloxacin and metronidazole for 10 days is recommended.

Some pearls are listed below:

• Monitor vital signs for impending hemodynamic collapse.
• A detailed history and physical can identify many conditions prior to any diagnostic testing.
• Patients with significant intra-abdominal conditions tend to have exams that evolve over time. Frequent re-examinations will help with both diagnosis and early treatment.
• Manage and treat pain when appropriate.
• Patients with a peritoneal examination warrant early surgical consult.
• When in doubt, arrange close follow-up.

Some important pitfalls to be mindful of in cases of ingestion are described below:

• Failure to investigate acute pathologies (such as bowel obstruction, appendicitis, or intussusception) that could lead to morbidity and mortality if not addressed in time.
• Failure to do a genitourinary exam in children with abdominal pain.
• Failure to evaluate for cardiac and pulmonary etiologies, especially in cases of upper abdominal pain.
  

Abdominal pain in pediatric patients ranges widely in level of acuity, necessitating ED practitioners to have a solid foundation in its evaluation. The need to prioritize A, B, C's as the basis of initial assessment remains essential, as with all patients seen on an urgent or emergent basis. Goals of care should include early recognition of conditions that require immediate emergent intervention, or else those conditions can progress to a more critically ill level. Particular attention should be focused on fluid status, as many children with abdominal pain may present dehydrated.

Abdominal pain in children requires a DETAILED history and physical as many conditions can be determined prior to any diagnostic testing. Be cautious with radiation in children and "image gently" using MRI and ultrasound when appropriate and available over CT or X-ray.

The attending completes a testicular exam on the child. She notes an absence of cremasteric reflex on the right that is high-riding with an abnormal lie. A bedside color doppler of the testicle is performed, which does not show any flow. Urology is consulted, who takes the patient stat to the OR. The attending then goes on to discuss with the student the importance of a GU exam in the patient with abdominal pain.

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