Chapter 17 Abdominal Pain
ETIOLOGY
What Causes Abdominal Pain?
Pain identified as “abdominal” may originate from the bowel or from neighboring structures within the abdominal wall, retroperitoneum, abdomen, thorax, and pelvis. Intestinal pain is typically caused by either distention or inflammation. Distention can result from simple causes, such as constipation, or can be the consequence of obstruction or motility disturbance. Inflammation can be peptic (acid) in origin or can result from infection, allergy, injury, or autoimmunity.
How Does Age Affect the Differential Diagnosis?
Infants are more likely than older children to present with congenital lesions such as intestinal malrotation or atresia and Hirschsprung’s disease. Young children are more susceptible to certain conditions, such as spontaneous intussusception. Older children are more likely than younger ones to suffer from inflammatory bowel disease. Adolescents are more likely to have sexually transmitted diseases, mittelschmerz, or ectopic pregnancy causing their distress. Some conditions can occur at any age, including urinary tract infections, trauma, pneumonia, pancreatitis, and mesenteric adenitis. Recurrent abdominal pain (RAP) occurs in 10% to 15% of children between the ages of 4 and 14 years and presents a special challenge for the pediatrician.
What Is Recurrent Abdominal Pain?
RAP may be defined as recurring attacks of abdominal pain over at least a 3-month period in children between 4 and 14 years of age. Urgent problems such as appendicitis are seldom responsible for RAP. Many children with RAP appear healthy, are growing well, have no findings on physical examination, and have no discernible abnormalities on any test or imaging study. Such children probably have functional pain and require a different management strategy than a child with a well-defined cause such as lactose intolerance or inflammatory bowel disease.
What Is Functional Pain?
Functional abdominal pain results from the motility, or function, of the intestine. Significant discomfort can result from contractions that may be excessively intense, poorly coordinated, or perceived as painful because of elevated sensitivity or anxiety. This pain is not “psychosomatic,” in the popular sense, which implies “not real pain” or “in his head.” Functional pain is typically characterized as intermittent, colicky pain not associated with meals or bowel movements. An exception is pain associated with constipation, which is often worse after eating and is relieved by defecation.
EVALUATION
How Does Pain Location Help Determine the Likely Cause?
Visceral pain tends to be poorly localized and aching or cramping in nature. In contrast, pain from somatic structures, such as the abdominal wall musculature, is easily defined as coming from a well-circumscribed area. Sometimes, as is the case with appendicitis, the discomfort begins as ill-defined visceral pain, becoming much more intense and well localized as overlying somatic structures become involved. Pain arising from the small intestine is typically periumbilical in location. Proximal gut injury (esophagus, stomach, and duodenum) tends to cause epigastric discomfort, as does inflammation of the pancreas and gallbladder. Problems arising in the colon are typically perceived directly in the same region of the abdomen.
How Do I Evaluate Acute Abdominal Pain?
Acute abdominal pain is defined as a condition of recent onset, with characteristics that indicate an urgent need for diagnosis and management. You must obtain a precise history, examine the child carefully, and, finally, order appropriate tests. Table 17-1 summarizes the information you must gather to evaluate the child with acute abdomen. Not all of the studies listed in Table 17-1 must be performed in all patients. If your history and examination lead you directly to a particular diagnosis, such as constipation, you may treat it directly.
Table 17-1 Evaluation of the Child with Acute Abdominal Pain
| History | |
| Onset | Sudden vs. gradual, preceding injury, prior episodes |
| Associated symptoms | Fever, nausea, dysuria, diarrhea, constipation, bloody stools or emesis, cough |
| Location of pain | Periumbilical, epigastric, right lower quadrant, left lower quadrant, well-localized or vague |
| Nature of pain | Aching, cramping, dull, sharp, burning, constant vs. colicky |
| Progression | Worsening, improving, changing location |
| Physical Examination | |
| General | Hydration, appearance of toxicity, growth and weight gain |
| Chest | Crackles, rhonchi, wheezing, tenderness of musculoskeletal structures |
| Abdomen | Distention, bowel sounds, tenderness (location, severity, rebound, superficial vs. deep), mass |
| Rectal examination | Fecal impaction, occult blood, pelvic tenderness, extrinsic mass |
| Laboratory/Radiologic Evaluation | |
| CBC | Evidence of infection or inflammation |
| ESR and CRP | Evidence of inflammation or infection |
| Amylase, lipase | Pancreatitis |
| GGT | Bile duct obstruction or injury |
| ALT, AST | Hepatitis |
| Urinalysis | Urinary tract infection, hematuria (stones, obstruction) |
| Plain x-rays | Bowel gas pattern, evidence of obstruction, free peritoneal air, constipation, kidney stones, appendiceal fecalith |
| CT or ultrasound | Appendiceal abscess, intussusception, gallstones, pancreatitis, bile duct obstruction, kidney stones, renal anomalies |
| Barium enema | Intussusception, malrotation, less useful for appendicitis |
ALT, Alanine transaminase; AST, aspartate transaminase; CBC, complete blood count; CRP, C-reactive protein; CT, computed tomography; ESR, erythrocyte sedimentation rate; GGT, gamma-glutamyltransferase.
When Should I Obtain Surgical Consultation?
Acute appendicitis should be carefully considered when evaluating any patient with acute abdominal pain. Not all patients exhibit typical features, especially if the appendix is located retrocecally or in another atypical location. Perforation of the appendix usually occurs within 24 to 48 hours of symptom onset. Therefore, you must work rapidly and enlist the help of your colleagues early in the evaluation. Surgeons should also be consulted promptly when there is evidence of obstruction, peritonitis, or mass lesion.
What Causes Recurrent Abdominal Pain?
Table 17-2 lists most of the more common causes plus features on history, physical examination, and laboratory testing that may suggest the diagnosis.
What History Helps Evaluate RAP?
You will need to define accurately the nature and time course of the pain, determine what exacerbates and relieves it, identify associated symptoms, and decide whether or not indications of serious underlying illness are present. It is also important to assess whether genetic or environmental factors may be playing a role. It is not useful to approach the child with the attitude that the abdominal pain may not be “real.” A child with pain is in need of your assistance, whether the cause is a significant underlying illness or a purely functional disorder. Table 17-3 lists questions that you should ask of every patient.
Table 17-3 Historical Data for Abdominal Pain
