5 The Acute Abdomen
Abdominal pain is a chief complaint frequently encountered in the pediatric office, urgent care, and emergency department settings. Although typically minor and self-limited, acute abdominal pain may also signify a medical or surgical process requiring immediate treatment. The clinician’s role is to identify patients who have serious or potentially life-threatening conditions, such as acute appendicitis, bowel obstruction, or peritonitis. The most difficult challenge lies in making a timely diagnosis so treatment can be initiated and potential morbidity prevented.
In this chapter, a clinical guideline is presented for the evaluation and management of children with acute abdominal pain. Appendicitis is the most common surgical emergency in children and adolescents and deserves special mention. Key features of its pathophysiology, clinical presentation, evaluation, and management are highlighted throughout this chapter.
Etiology and Pathogenesis
Abdominal pain falls into three clinical categories: visceral, parietal (somatic), and referred pain. A general understanding of these is helpful in determining the cause of abdominal pain.
Visceral pain is poorly localized and is often described as dull and aching. It is caused by stretching, distension, or ischemia of the viscera. Parietal (somatic) pain is well localized, discrete, and often described as sharp and intense in character. Pain is stimulated by stretching, inflammation, or ischemia of the parietal peritoneum. The pattern of pain in appendicitis has features of both visceral and parietal pain. Initially, the pain is visceral in nature: vague, poorly localized, and periumbilical. As the peritoneum becomes inflamed over the ensuing 12 to 48 hours, the pain migrates to and localizes in the right lower quadrant (RLQ).
Referred pain is often perceived at sites distant from the affected organ and may be described either as sharp and localized or as a vague aching sensation (Figure 5-1). Examples include irritation of the parietal pleura of the lung perceived as abdominal wall pain and inflammation of the gallbladder perceived as scapular pain.
It is helpful to classify the cause of acute abdominal pain by age (Table 5-1). There are many potential causes of abdominal pain, including infectious, anatomic, traumatic, inflammatory, functional, and oncologic.
Clinical Presentation
Differential Diagnosis
The differential diagnosis for abdominal pain in children is very broad, and it can be approached in different ways (Figure 5-2). Certain conditions occur more commonly at specific ages and therefore it may be useful to classify causes of acute abdominal pain based on age. Pain may also be classified as surgical or medical (Table 5-1).
Across all ages, gastroenteritis and appendicitis are the most common medical and surgical causes of acute abdominal pain, respectively. Malrotation with midgut volvulus is the single most devastating abdominal surgical emergency of childhood (see Chapter 109).
Abdominal pain can also be classified based on the location of the pain. A classic approach is by dividing the abdomen into four quadrants (Figure 5-3). This can help the practitioner direct the workup to rule in or out the most common diagnoses based on the location of symptoms. For example, hepatic and gallbladder disease usually present with right upper quadrant pain (see Chapter 115). Appendicitis classically presents with migration of pain to the RLQ. Gastritis or peptic ulcer disease may present with left upper quadrant pain (see Chapter 108).
History
The initial evaluation of acute abdominal pain is particularly challenging in pediatrics because children often cannot describe, articulate, or localize their symptoms. This is often exacerbated by anxiety, making it harder for the clinician to examine and identify positive findings.
Pain Character
Acute abdominal pain caused by a medical or surgical emergency typically increases in intensity over time, may awaken the child at night, and likely interferes with activity. In addition to the age of patient and the location of the pain, other important features of the history include the onset, frequency and duration, pattern, associated symptoms, and pertinent medical history.
Infants and young children can seldom localize their pain, and parents often describe an inconsolable child who lies with his or her legs drawn up to the chest. Asking the parents if they think the child is in pain can be helpful to distinguish pain from fussiness or irritability. Pain that is intermittent, with paroxysms of cramping inconsolable pain alternating with return to normal state, is characteristic of intussusception (Figure 5-4). Peritoneal irritation is suggested by pain that is worse with movements that change the tension of the abdominal wall, such as a bumpy car ride or walking. Pain that improves after vomiting or a bowel movement reflects a small bowel or large bowel cause, respectively.
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