Abdominal pain accounts for approximately 10% of visits, and elicits a broad differential. Serious etiologies often present similarly to processes that are benign and self-limited.¹ The most frequently encountered surgical and medical causes of abdominal pain are addressed in this chapter.

Abdominal pain can be visceral or somatic. Visceral pain is poorly localized and difficult to describe, even in older children; somatic pain is intense and readily localized. Referred pain syndromes manifested as abdominal pain may be characteristic of a variety of clinical problems. An effective relationship with the caregiver and careful observation can provide important information about a child’s diagnosis. Overall, questions should be posed that are appropriate for the child’s level of development. Open-ended inquiries over “yes or no” questions are more helpful. With older children, the presence of a caregiver may hinder communication, particularly when needing an accurate sexual history.

A preliminary differential diagnosis, including abdominal conditions, systemic illnesses, and referred pain syndromes, should be formulated. Afferent nerves from distant organs can share central pathways that allow pain from one organ to be interpreted as if the stimulus is affecting another organ. A classic example is a right lower lobe pneumonia that refers pain to the abdomen, mimicking appendicitis. Conversely, some conditions that are intra-abdominal in origin may produce pain syndromes that are manifested in other locations; for example, shoulder pain due to hepatic irritation (right), or splenic rupture (left), and groin pain from renal stones. Table 70-1 lists extra-abdominal and systemic conditions that can present with abdominal pain.²

When considering possible etiologies of abdominal pain, the provider must consider entities that are more common in specific age groups (Table 70-2). A traditional bedside examination may be limited in frightened infants and small children and should therefore begin with observation. While the child is in the parent’s lap, carefully observe, auscultate, palpate, and percuss the child’s abdomen. Include an examination of the genitalia and perineum, considering diagnoses such as an incarcerated inguinal hernia, or a testicular torsion. In cases of severe stranger anxiety, further assess the abdomen while the child sleeps, or alternatively, request that the parent palpate the child’s abdomen while observing the child’s reaction.

Although a broad differential for abdominal pain is important, it is just as imperative to remember that the patient’s chief complaint is in fact “pain.” The use of analgesics will not mask potentially serious causes of abdominal pain; however, not treating pain will negatively impact patient and family satisfaction. In infants, delaying pain medication may have lifelong consequences by altering future pain processing.³

Clinical suspicion should direct focused laboratory testing and diagnostic imaging. Table 70-3 reviews ancillary laboratory tests that are helpful in identifying causes of abdominal pain.

Ultrasonography, plain radiography, and computed tomography (CT) represent the most common imaging performed for assessment of abdominal pain. Recognize potential effects of ionizing radiation; young infants and children are particularly vulnerable to the long-term effects. It is estimated that the lifetime risk of developing cancer after a single abdominal CT is 1/1000, with abdominal CT having higher radiation risks than other CT imaging such as head CT.⁴ Plain films are often the primary step during a sequence of imaging modalities. Appropriate images can demonstrate the presence of extraluminal air or a mass effect that may direct further imaging. Contrast CT scans should be used judiciously due to the risk of contrast-induced nephropathy, particularly in those with an elevated creatinine. Ultrasound has the advantage of portability as well as lack of ionizing radiation. Table 70-4 lists conditions that can be diagnosed by ultrasonography.

Abdominal obstruction presents with colicky, cramping abdominal pain, usually associated with vomiting that is often bilious in nature. Irritability and inconsolable crying in the young child may be due to obstruction.