Abdominal pain in children

Abdominal pain can result from injury to the intra-abdominal organs or overlying somatic structures in the abdominal wall, or from extra-abdominal diseases. Visceral pain results when autonomic nerves within the gut detect injury, transmitting sensation by unmyelinated fibers. The pain is vague, dull, slow in onset, and poorly localised. A variety of stimuli, including normal peristalsis and various intraluminal chemical and osmotic states, activate these fibers to some degree. Regardless of the stimulus, visceral pain is perceived when a threshold of intensity or duration is crossed. Lower degrees of activation may result in perception of non painful or pheraphs vaguely uncomfortable sensations, whereas more intense stimulation of these fibers results in pain. Overactive sensation may be the basis of some kinds of abdominal pain, such as functional abdominal pain and irritable bowel syndrome.

In contrast to visceral pain, somatic pain results when overlying body structures are injured. Somatic structures include the parietal peritoneum, fascia, muscles, and skin of the abdominal wall. In contrast to pain emanating from visceral injury, somatic nociceptive fibers are myelinated and are capable of rapid transmission of well-localised painful stimuli. When intra-abdominal processes cause inflammation or injury to the parietal peritoneum or abdominal wall structures, poorly localised visceral pain becomes well-localised somatic pain. For example, in acute appendicitis, the initial activation of visceral nociceptive fibers yields poorly localised discomfort in the mid-abdomen. When the inflammatory process extends to the overlying parietal peritoneum, the pain becomes severe and localises to the right lower quadrant. This is called somatic parietal pain.

Referred pain is a painful sensation in a body region distant from the true source of pain. The location of referred pain is predictable based on the locus of visceral injury:

• Stomach pain is referred to the epigastric and retrosternal regions

• Liver and pancreas pain is referred to the epigastric region

• Gallbladder pain often is referred to the region below the right scapula

• Somatic pathways stimulated by small bowel visceral afferents affect the periumbilical area

• Colonic injury results in infraumbilical referred pain

Acute abdominal pain

Acute pain can signal the presence of a dangerous intra-abdominal process (appendicitis or bowel obstruction) or may originate from extraintestinal sources (lower lobe pneumonia or urinary tract stone). Not all episodes of acute abdominal pain require emergency intervention. Appendicitis and volvulus, for example, most be ruled out as quickly as possible. Few patients presenting with acute abdominal pain actually have a surgical emergency, but they must be separated from cases that can be managed conservatively.

Events that occur with a discrete, abrupt onset, such as passage of a stone, perforation of a viscus, or infarction, result in a sudden onset of pain. Gradual onset of pain is common with infectious or inflammatory causes, such as appendicitis and IBD. Standard bloods are performed for acute abdominal pain: FBC & CRP (evidence of infection or inflammation); LFTs (biliary or liver disease); amylase & lipase (?pancreatitis); urinalysis (UTI, bleeding due to stone, trauma, or obstruction); pregnancy test (older females - Ectopic pregnancy). An abdominal x-ray series evaluates for bowel obstruction or nephrolithiasis. Ultrasound or CT can visualise the appendix if appendicitis is suspected but the diagnosis remains in doubt. If the initial evaluation suggests intussusception, a barium or pneumatic air enema may be used to diagnose and treat this condition.

The most important thing in acute abdominal pain is to rule out surgical emergencies. Appendicitis is more common in teenagers.

Common surgical emergencies in young children

• Malrotation with volvulus

• Incarcerated hernia

• Congenital anomalies

• Intussusception

Acute surgical abdomen is characterised by:

• Peritonitis

  • Tenderness

  • Rigidity

  • Guarding

• Absent or diminished bowel sounds

Diagnosis of acute abdominal pain

History

• Onset

  • Sudden or gradual?

  • Prior episodes

  • Association with meals

  • Trauma?

• Nature

  • Sharp versus dull

  • Colickly or constant

  • Burning

• Location

  • Epigastric

  • Periumbilical

  • Generalised

  • Right or left lower quadrant

  • Change in location over time

• Associated symptoms

  • Fever

  • Vomiting - bilious?

  • Diarrhea - bloody?

  • Abdominal distention

• Extraintestinal symptoms

  • Cough

  • Dyspnea

  • Dysuria

  • Urinary frequency

  • Flank pain

Examination

• General position

  • Growth and nutrition, general appearance, hydration, degree of discomfort, body position

• Abdominal

  • Tenderness, distension, bowel sounds, rigidity, guarding mass

• Genitalia

  • Testicular torsion, hernia, pelvic inflammatory disease, ectopic pregnancy

• Surrounding structures

  • Breath sounds, rales, rhonchi, wheezing, flank tenderness, tenderness of abdominal wall structures, ribs, costochondral joints

• Rectal examination

  • Perianal lesions, stricture, tenderness, fecal impaction, blood

Bloods

• FBC, CRP + ESR

  • Evidence of infection or inflammation

• LFTs

  • Biliary or liver disease

• Amylase, lipase

  • Pancreatitis

• Urinanalysis

  • UTI, bleeding due to stone, trauma or obstruction

• Pregnancy test in older females

  • Ectopic pregnancy

Radiology/Imaging

• Plain flat and upright abdominal x-ray

  • Bowel obstruction, appendiceal fecalith, free intraperitoneal air, kidney stones

• CT scan

  • Intra-abdominal or pelvic abscess, appendicitis, Crohns/UC, pancreatitis, gallstones, kidney stones

• Barium enema

  • Intussusception, malrotation

• Ultrasound

  • Gallstones, appendicitis, intussusception, pancreatitis, kidney stones

• Endoscopy

• Upper endoscopy

  • Suspected peptic ulcer or esophagitis