Chapter 69: Abdominal Pain

• If a patient complains of abdominal pain, an examination of the external genitalia should be a part of a routine examination.

• Ovarian and testicular torsions are important causes of abdominal pain that should not be overlooked.

• Intussusception should always be considered in infants/children with intermittent abdominal pain associated with vomiting.

Abdominal pain accounts for approximately 10% visits and elicits a broad differential, with more serious etiologies often presenting similar to processes that are benign and self-limited.¹ The most frequently encountered surgical and medical causes of abdominal pain are addressed herein, including causes of abdominal pain that are unique to the female and male reproductive tracts.

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 abundant information about a child's diagnosis. With older patients, the presence of a caregiver may hinder communication, particularly when needing an accurate sexual history. Overall, formulate questions appropriate for the child's level of development, regardless of the patient's age. Use open-ended inquiries over “yes or no” questions.

Create a preliminary differential diagnosis, including abdominal conditions, systemic illnesses, and referred pain syndromes. 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 69-1 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 69-2). A traditional bedside examination may be limited in frightened infants and small children and should 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; although 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 69-3 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 when compared to 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 69-4 lists conditions that can be diagnosed by ultrasonography. See Chapter 20 for more details on imaging modalities.

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.

Malrotation

Malrotation occurs in utero when the midgut fails to rotate counterclockwise, preventing the normal abdominal orientation of the intestine where the cecum rotates into the right lower quadrant; predisposing the bowels to twisting, a volvulus, and subsequent bowel ischemia. The majority of cases of midgut malrotation present in the first week of life, 80% in neonates. Males have a 2:1 higher incidence of malrotation than females. Neonatal bilious emesis should always be considered a potential surgical emergency; however, even without bilious emesis, the diagnosis must be considered in infants with poor feeding, recurrent emesis, abdominal distention, or failure to thrive. Although 20% of infants with malrotation will have normal abdominal radiographs, some will demonstrate findings of obstruction with a markedly dilated stomach and duodenal bulb (the double bubble sign). Ultrasound has also been shown to be an effective screening tool by identifying the correct orientation of the superior mesenteric artery and vein, but an upper GI study is considered the gold standard for definitive diagnosis.¹ Once the diagnosis is made, place a nasogastric tube and initiate an emergent surgical consult.

Intussusception

The most common cause of bowel obstruction in children younger than 2 years is intussusception, which occurs when a portion of bowel prolapses into another section of bowel. This telescoping is most common in the ileocolic region. As the bowel prolapses, the associated mesentery is pulled along and blood flow to the bowel is compromised. Classically, the resultant ischemia can be recognized as intermittent colicky pain that may be associated with lethargy or somnolence; other signs and symptoms include an abdominal mass, rectal bleeding, and vomiting. Some patients will draw their legs up toward the abdomen when experiencing peristaltic episodes of pain. Intussusception is associated with lead points such as the appendix, a lipoma, an intestinal polyp, Henoch–Schonlein purpura-associated submucosal hematoma, an enlarged peyer's patch, and a Meckel diverticulum. Special consideration should be given to older patients who develop intussusception, as those beyond the age of 2 to 5 years have an increased incidence of pathologic lead points.

Although normal radiographs do not exclude the diagnosis of intussusception, they may demonstrate a right-sided abdominal mass outlined by a lucency of peritoneal fat called a “target sign,” or a crescent of gas within the colonic lumen that outlines the apex of the intussusception—the “meniscus sign.” Ultrasound is the preferred method for initial imaging, showing a cross-sectional 3- to 5-cm mass in the shape of a target or donut.¹ Air contrast enemas are the therapy of choice, but surgical intervention is required for patients whose intussusceptions fail to reduce. If air enema reduction is successful and symptome are reliered, immediately feed the child and discharge if tolerating oral feeds.⁵

Incarcerated Hernias

An incarcerated hernia most often occurs when bowel prolapses through a patent inguinal canal; infants may not present with abdominal pain, but rather irritability or refusal to feed. The incidence of pediatric incarcerated hernias is between 6% and 18%, with most presenting within the first 2 months of life. Prompt diagnosis and reduction may obviate the need for emergent surgical intervention. Ultrasound is the modality of choice in differentiating inguinal hernias from other masses such as abscesses, tumors or hydroceles. For hernias not reducible through traditional means (cold packs, Trendelenburg positioning, or massage), obtain surgical consultation due to risk of bowel ischemia and perforation.¹ For patients with hernias that are successfully reduced in the ED, discharge the child if asymptomatic and able to feed normally, with a referral for elective surgical repair.

Pyloric Stenosis

Hypertrophic pyloric stenosis (HPS) has an estimated prevalence of 1.5 to 4 per 1000 live births. It is four to six times more common in males with 30% of cases occurring in firstborn children. Although the etiology of HPS is unclear, some studies have shown that exposure to macrolides may be a risk factor. Patients typically present between 3 and 6 weeks of age with projectile, nonbilious emesis. Some infants may have diarrhea known as “starvation stools” which can lead to a misdiagnosis of gastroenteritis. The classic “olive” is best palpated near the right upper quadrant along the edge of the liver, a third of the distance between the xiphoid and the umbilicus. Hypokalemic, hypochloremic alkalosis may be found on a basic metabolic panel. Diagnostic ultrasound will show a thickened pyloric muscle (3.5–4 mm) and a pyloric channel of ≥16 mm. If ultrasound is equivocal, an upper GI will show a narrowing known as a “string sign.” Once the diagnosis of HPS is made, administer intravenous fluids followed by maintenance fluids, and obtain surgical consultation. A nasogastric tube is not required and may worsen the infant's metabolic alkalosis.

Appendicitis

Acute appendicitis classically produces vomiting, anorexia, and fever associated with vague periumbilical pain which localizes over time to the right lower quadrant. Table 69-5 reviews the clinical signs of appendicitis and peritoneal irritation. Appendicitis in infants is difficult to diagnose, but represents less than 2% of all pediatric appendectomies, with a 0.4% incidence in those younger than 12 months.¹ Imaging typically begins with ultrasound, which although user-dependent, is very accurate in thin children and particularly useful for females if ovarian torsion is in the differential diagnosis. CT may be necessary to either confirm the diagnosis or identify associated abscess formation, more common with prolonged symptoms (See Chapter 50, Appendicitis).

Spontaneous Peritonitis

Spontaneous or primary peritonitis is a condition that is often associated with disease processes such as nephrotic syndrome, which may result from ascites in the face of a relative immunodeficiency. Antibiotic therapy should be directed at the typical causative organisms including Streptococcus species and gram-negative rods; although, other organisms must be considered in patients with an indwelling catheter for peritoneal dialysis.

Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is more common in premature infants; although primarily diagnosed in the neonatal intensive care unit (NICU), NEC can be seen after nursery discharge. Infants present with, poor feeding or vomiting, bloody stools, or irritability due to abdominal pain. Initiate resuscitation and consult surgery in the ED; admit for bowel rest and parenteral antibiotics. Some infants will require surgical resection of involved small bowel (typically, watershed areas), with risk of subsequent short-gut syndrome.

Hirschsprung Disease

Hirschsprung disease is characterized by a lack of parasympathetic ganglia to affected portion of the colon, making peristaltic efforts of the bowel ineffective at moving stool through the colon. Even though abnormal stool may occur since birth, the diagnosis of Hirschsprung disease may be delayed, with these patients at risk for developing toxic megacolon. When the distal rectum is involved, digital rectal examination may be diagnostic in revealing a lack of rectal tone. Diagnosis may include a barium enema demonstrating a “transition zone,” rectal manometry, or a suction biopsy of the rectum and colon; antibiotics and decompression of the bowel may be indicated for stabilization prior to testing.

Acute Gastroenteritis

Vomiting, with or without diarrhea, frequently accompanies the chief complaint of abdominal pain. Surgically correctable causes of abdominal pain and other medical mimickers of gastroenteritis, such as diabetic ketoacidosis (DKA), dehydration ketosis, streptococcal pharyngitis, pneumonia, and urinary tract infections (UTIs), must first be ruled out. When a diagnosis of acute gastroenteritis is made, focus on rehydration and electrolyte repletion, preferably in the form of oral fluids.⁶

Diabetic Ketoacidosis

Children younger than 5 years commonly present in DKA when first diagnosed with diabetes. DKA manifests with increased urinary frequency, abdominal pain, vomiting, lethargy, and tachypnea.⁷ Tachypnea from a compensatory respiratory alkalosis, along with abdominal pain from ketosis and dehydration, may be the only clinical clues to the diagnosis of DKA. Once the diagnosis of DKA is made, provide fluid resuscitation with electrolyte repletion and insulin therapy to correct the metabolic disturbance. Do not give insulin as a bolus, but infuse at 0.1 U/kg/h.

Dehydration/Ketosis

Dehydration in the pediatric population accounts for approximately 5% of pediatric hospital admission, and more than 300 annual deaths in United States.⁸ Dehydration and ketosis in infants and young children can cause abdominal pain and vomiting. The magnitude of volume depletion can be assessed most accurately by the percentage of body weight lost (Table 69-6).⁶ Send a basic metabolic panel for severely dehydrated children where electrolyte abnormalities are a concern; carefully correct hypernatremia to avoid iatrogenic cerebral edema.⁶

Streptococcal Pharyngitis

Streptococcal pharyngitis is most common in children 5 to 15 years of age and has the risk of postinfectious sequelae of poststreptococcal glomerulonephritis and rheumatic fever. Although the classic symptoms of pharyngitis include throat pain, fevers and malaise, common presentations in younger children are fever, abdominal pain, and vomiting. Streptococcal pharyngitis may occur with scarlet fever, manifested by a “sandpaper” erythematous rash. Treatment options include penicillins, cephalosporins, and macrolides.⁹

Urinary Tract Infections

A common source of abdominal discomfort in children is both upper and lower UTIs, manifestations which can include fever, nausea, emesis, abdominal pain, and accompanying urinary frequency, urgency, and dysuria. An oral course of antibiotics is appropriate treatment for nontoxic children who are able to tolerate oral intake. Strongly consider parenteral antibiotics and admission in infants younger than 3 months as well as those with signs of systemic disease (see Chapter 84).

Constipation

Constipation is one of the most common causes of colicky abdominal pain in children, and is associated with significant behavioral overlay. The pain may limit their everyday function and progress to cause nausea and vomiting. Some patients will present with recurrent UTIs secondary to bladder compression and incomplete emptying with voiding. Patients with long-standing constipation can derelop encopresis or liquid stools from leakage around impacted stool in the distal colon and rectum.

Bleeding and Abdominal Pain

Abdominal pain associated with bleeding is discussed in detail in Chapter 72. Infants and toddlers may present with hard stools streaked with blood from anal fissures. A more serious disease process is hemolytic uremic syndrome (HUS) that presents with anemia, thrombocytopenia, and renal failure. Abdominal pain with bloody diarrhea may precede HUS, the causative agent of which is often Escherichia coli O157:H7. Patients with HUS require aggressive fluid resuscitation and treatment of their hemolytic anemia and coagulation disorders. The characteristic rash of Henoch–Schöenlein purpura (HSP) can also present with abdominal pain, arthralgias, and blood in the stool.

Biliary Disease

With increases in childhood obesity, gallstones are becoming more frequent in the pediatric population, particularly among children of Hispanic origin, with rates estimated prevalence as high as 4%.¹⁰ Some children are at particularly high risk for gallbladder disease, including patients with ongoing hemolytic disease such as sickle cell anemia. Due to the fact that gallbladder disease remains less common in the pediatric population, there is a paucity of evidence regarding the optimal treatment, but NSAIDS and opioids are options for initial pain management (Please refer to Chapter 73).³

Pancreatitis

Although uncommon in the pediatric population, the incidence of pancreatitis appears to be increasing with escalating obesity rates. Patients may present with abdominal pain radiating to the back after high-fat meals (Please refer to Chapter 74, Pancreatitis).

Hepatitis

Jaundice and abdominal pain may be the first manifestations of hepatitis, the etiology of which can be from infection, drug exposure (especially acetaminophen), systemic disease, or intrinsic diseases of the liver and biliary tree. Please refer to Chapter 73 for a detailed hepatitis discussion.

Nephrolithiasis

Renal colic typically presents as an acute onset of severe unilateral flank pain. Although historically considered uncommon in the pediatric population, incidence in children is increasing, particularly in the southern portions of the United States known as the “stone belt.”¹¹ Hospitalizations from renal stones account for 1 in 1000 to 1 in 7600 pediatric hospital admissions. Although there is a paucity of research on the medical management of children with nephrolithiasis, NSAIDS and opioids are recommended for the ED setting.³

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a consideration for the undiagnosed patient with repeated ED visits for abdominal pain. IBD pain may be vague in nature, possibly associated with melena or frankly bloody stools (Please refer to Chapter 75, Inflammatory Bowel Disease).

The complexity of decision making about the causes of abdominal pain is increased when considering the adolescent female. Pubescent females may have abdominal pain that can cause significant morbidity if left untreated. Ovarian cysts and tumors may cause pain with or without ovarian torsion. Postpubertal females may present with pain from dysmenorrhea or endometriosis. Pelvic inflammatory disease manifests as lower abdominal pain, cervical motion tenderness, with or without associated fever. Consider normal or ectopic pregnancies in any postmenarche female with abdominal pain.

As acute scrotal or testicular pain often presents as abdominal pain, a careful evaluation of the genitalia is essential (Please refer to Chapter 85).