Paediatric Abdominal Pain

Introduction

• Up to 5% of presentations
• Surgery required in only 1-7% of children who present with abdominal pain
• Up to 15% of children will be discharged without a diagnosis
• Providing adequate analgesia improves reliability of examination and DOES NOT mask peritoneal findings
• Close observation with serial examination remains useful in indeterminate cases

Warning signs for surgical cause

• Reproducible localised tenderness
• Constant pain over hours
• Opiate analgesia requirement
• Inconsolability
• Remains motionless despite severe pain
• Pallor or shock
• Guarding
• Rebound
• Abdominal distension
• Rigidity
• Bilious vomiting
• Re-presentation

Differential diagnosis

Inflammatory gastrointestinal causes

• Appendicitis
• Meckel’s diverticulum
• Mesenteric adenitis
• Gastroenteritis
• Peritonitis
• Peptic ulcer/gastritis
• Hepatitis
• Pancreatitis
• Inflammatory bowel disease

Non-gastrointestinal inflammatory causes

• Tonsillitis/pharyngitis
• Pneumonia
• Pericarditis
• Serositis
• Pyelonephritis/cystitis
• Pelvic inflammatory disease
• Intra-abdominal abscess
• Epididymitis

Generalised causes

• Infectious mononucleosis
• Acute rheumatic fever
• Herpes zoster

Intestinal obstruction causes

• Intussusception
• Volvulus
• Adhesions
• Incarcerated hernia

Other ddx

• Cholecystitis/cholelithiasis
• Leukaemia/lymphoma
• Haemolytic crisis
• Sickle cell crisis
• Neuroblastoma/Wilm’s tumour

• Metabolic – DKA, Adrenal insufficiency, Hyperparathyroidism, hypokalaemia, acute intermittent porphyria
• Vasculitis – HSP, Polyarteritis nodosa, Kawasaki
• Renal – Renal colic, hydronephrosis, nephrotic syndrome
• Miscellaneous – Constipation, colic, toxic ingestion (iron, lead), gonad torsion, ectopic pregnancy, dysmenorrhoea, Mittelschmerz, Familial mediterranean fever, abdominal migraine, psychosomatic

The age of the child

• Neonates and infants (most common causes)
  • Surgical – Testicular torsion, appendicitis, peritonitis, necrotising enterocolitis, volvulus, Intussusception, Hirschprung’s disease and incarcerated hernia
  • Medical causes – DKA, toxic (e.g. iron), sepsis, haemolytic uraemic syndrome, pyelonephritis/cystitis
• Preschool
  • Acute gastroenteritis, UTI, appendicitis, mesenteric adenitis, pneumonia, constipation, intussusception and trauma
  • Constipation most common but diagnosis of exclusion

• School-age
  • As above + DKA, HSP, abdominal migraine, testicular torsion, psychosomatic, inflammatory bowel and gynaecological causes
  • Constipation most common but diagnosis of exclusion
• Adolescents
  • As above + pregnancy, ectopic pregnancy, cholecystitis/cholelithiasis, pancreatitis, PID, renal calculi, testicular torsion and other gynaecological disorders

History

Associated symptoms

• Vomiting – Bilious or blood, timing, projectile
• Stools – Blood/mucous, timing, diarrhoeal, painful defecation
• Anorexia or hunger – unusual for children with appendicitis to be hungry
• Recent viral symptoms suggests mesenteric adenitis
• Urinary symptoms
• Rash or sore joints suggests vasculitis

PMHx

• CF – Hirschprung’s disease
• Primary bacterial peritonitis can be seen in liver disease, nephrotic syndrome, ascites and those with VP shunts
• Pancreatitis – Seen in patients on chemotherapy or immunotherapy
• IBD – Toxic megacolon

Timing of symptoms

• Acute onset – Intussception, torsion, perforated viscous
• Episodic – Intussuception, mesenteric adenitis, gastroenteritis, constipation, testicular torsion

Examination

• Toddlers on parents lap
• Painful quadrant last
• Repeated with distraction to ascertain true peritonism and reproducibility
• Signs consistent with peritonitis
  • Lying still, refusal to walk, slow or stooped walking, increased pain with cough/movement
  • Inability to suck in tummy and push it out
• The younger the child, the more difficult to reliably find localising signs
  • Threshold for surgical review must be lower
• Always palpate testes and check for herniae

Other systems exam

• Respiratory – Check for basal pneumonia
• ENT – URTI, tonsillitis, adenopathy
• Neurological – Meningitis
• Endocrine – BSL
• Haematological – Pallor, lymphadenopathy, splenomegaly
• Dermatological – Rash, specifically HSP/zoster
• Renal – Haematuria, hypertension or oliguria

Investigations

• Blood tests
  • WCC not particularly useful in ruling appendicitis in or out
  • Renal function if dehydrated or other suggestion of renal disease
  • LFT if RUQ tenderness
  • Lipase if epigastric/upper abdominal pain
  • BSL excludes DKA
• Females of reproductive age should have beta-hCG tested
• Urine MCS

• Imaging
  • AXR – If obstruction, ingested foreign body, renal stones suspected
  • Erect CXR if perforation or basal pneumonia suspected
  • USS – Liver, gallbladder, kidney, intussusception, appendicitis or palpable mass
  • CT in selected cases

Disposition

• Significant abdominal findings – surgical review
• Severe pain with minimal examination findings – Surgical review or admission for observation
• Moderate pain and no examination findings often discharged home depending on local doctor, social setting and parents

Appendicitis

• Slightly more common in males
• Uncommon under 2yo and very rare in neonates
• Peaks age 9-12
• 50% of adults have periumbilical to RIF transition. Less common in children
• Some children will suffer diarrhoea or dysuria due to irritation by inflamed appendix – red herring
• Fever generally <39.5 unless perforated
• Asking child to hop may be useful in indeterminate cases to reveal peritoneal irritation

• Under 2yo:
  • Vomiting (85-90%)
  • Pain (35-77%)
  • Diarrhoea (18-46%) – less common and may be misleading
  • Fever (40-60%) – less common
  • Grunting respirations (8-23%) – may be misleading
  • Cough or rhinitis (40%) – may be misleading
  • Right hip symptoms (3-23%) – may be misleading
  • RIF tenderness in only 50% so Dx often delayed
  • Perforation rates of 82-92%

• Older children
  • RIF tenderness
    • Age 2-5 (58-85%)
    • School-age group (almost 100%)
    • 15% have generalised tenderness without perforation
  • Age 6-12
    • Vomiting (68-95%)
    • Anorexia (47-75%)
    • Diarrhoea (9-16%)
    • Constipation (5-28%)
    • Dysuria (4-20%)

Investigations

• CRP >10
  • Sensitivity 48-75%
  • Specificity 57-82%
• Normal CRP does not exclude appendicitis in children
• Urinalysis
  • WCC >5/HPF and red cells found in 7-25% of appendicitis cases
• Active observation
  • PPV of 97.9% in one series and normal appendicectomy rate of 2.6%

• USS in equivocal cases ONLY or young females
  • Sensitivity 71-92%
  • Specificity 86-98%
  • Up to 10% of cases, appendix cannot be visualised therefore, high positive likelihood ratio and moderate negative likelihood ratio makes ruling in possible but NOT ruling out
• CT scan
  • Sensitivity 87-100%
  • Specificity 83-97%
  • Cost-effective to perform USS then CT if remains equivocal vs. negative appendicectomy rate of 23%
• MRI
  • Limited usefulness due to pragmatics
  • In pregnant adolescents with ? Appendicitis, may play a role

Meckel’s diverticulum

• Vestige of omphalomesenteric duct, seen in 2% of population, with 2% of these manifesting symptoms
• Usually 2ft proximal from terminal ileum
• 45% of symptomatic patients are under 2
• Can present at any age
• Majority contain gastric mucosa and secrete acid
• Presentation
  • Abdo pain, bowel obstruction (lead point for intussusception or intraperitoneal band formation), GI haemorrhage or perforation
  • Most common cause of significant lower GI bleeding in children (usually from peptic ulceration)
    • Classically painless bleeding

• Investigations
  • Meckel’s scan using 99m-technetium
    • 75-85% sensitive and 95% specific in demonstrating ectopic gastric tissue, when bleeding is present
• Management
  • Supportive, urgent surgical consult and excision

Intussusception

• Most commonly ileum through ileo-caecal valve (90% of cases)
• Commonly 2 months to 2 years of age
• Peaks at 5-9 months
• Presentation
  • Intermittent pain, colicky, severe (2-3 times/hour increasing over 12-24 hours)
  • Often draw up legs and appear pale (vs. flushed in most other causes)
  • Pallor and lethargy may be primary presentation and out of proportion to dehydration
  • Vomiting usually prominent (bile-stained is late sign)
  • Red current jelly stool is classical (seen in 50%)
  • Diarrhoea is quite common and may be misleading
  • May be preceding diarrhoeal or respiratory illness

• Examination
  • Abdominal sausage-shaped mass RUQ or crossing midline in epigastrium palpable in 2/3 of children
  • Empty RLQ (caecum not in usual position) and absent/paucity of bowel sounds in RLQ (Dance’s sign)
  • PR only if no mass and no PR bleeding (one time only by surgeon)
• Investigation
  • AXR: To exclude perforation or obstruction. Normal AXR does not exclude intus.
    • Signs on AXR include target sign (RUQ) and crescent sign (LUQ)
  • USS: Useful if suspected but no palpable mass or sign on AXR
    • 98-100% sensitive and 88% specific
  • Air enema: Also therapeutic if strong clinical suspicion
  • Blood tests: FBC, U&E if looks unwell
• Consider IV antibiotics before theatre (d/w surgeon)

Midgut volvulus

• Malrotation refers to incomplete intestinal rotation in embryonic development
• Midgut volvulus occurs when small bowel rotates around  its pedicle causing mechanical obstruction and arterial occlusion
  • Midgut volvulus without malrotation is rare and seen in preterm infants
• During embryology GI tract rotates around SMA. With malrotation, get failure of duodenum and caecum to fully rotate and end up next to one another with short pedicle of mesentery that can easily rotate on itself, obstruct the bowel and impair SMA flow
• Ladd’s bands (that fix duodenum and caecum in position) are also in incorrect place and can cross over causing duodenal obstruction when twisting occurs (hence bilious vomiting)

• Presentation
  • Most cases occur in 1^st year
  • 1/500 live births
  • 40% in first week of life and 80% in first month
  • Presents with sudden onset bilious vomiting in over 80% (CLASSICAL!!)
• Investigations
  • AXR: May be normal. Otherwise small bowel obstruction
  • GI contrast X-ray with small bowel follow through
  • USS: Upper GI spiral sign: Spiralling of small bowel around SMA
• Mortality rate 3-15%

Sickle cell crisis

• Aka vaso-occlusive disease in SCD
• Sudden onset, painful episodes
• First presentation for 25% of patients
• Typically after age 1 (HbF protective)
• Leads to tissue ischaemia, hypoxia and sickling of RBC’s
• Triggers: Infection, dehydration, asthma, stress, cold temperature and high altitude

• Presentation
  • MSK: AVN of femoral head (10% of pt’s)
  • Acute abdominal pain
  • Bone infarction (long bones most commonly)
  • Priapism
  • Paediatric stroke
  • Acute chest syndrome: Fever, cough and new pulmonary infiltrates
  • Hyperhaemolytic crisis can occur, often with vaso-occlusive crisis

Neuroblastoma

• Sympathetic neural crest cell tumour in adrenal medulla/paraspinal ganglia
• Most common intra-abdominal malignancy in infants
• Most common extracranial solid tumour in children
• 90% under 5 years old
• 2/3 in the abdomen
• 50-66% already metastasized at diagnosis
• Typically presents with painless abdo mass with constitutional symptoms

• Presentation
  • Catecholamines: Fevers, sweating, flushing, palpitations, failure to thrive, HTN
  • Abdo distension/mass/pain
  • VIP release: Constipation, diarrhoea, urinary retention
  • Painless neck mass: Horner’s, SVC syndrome
  • Opsoclonus-myoclonus syndrome = Dancing eyes/dancing feet seen in 2-3% of patients
  • Blueberry muffin rash due to extramedullary haematopoiesis
  • Periorbital metastases are classical with ecchymoses and proptosis

Nephroblastoma (Wilm’s)

• Most common kidney cancer in children
• Most common age 1-3
• Typical presentation
  • Well child with mass deep in flank
  • 50% have pain
  • Haematuria in 20-30%
  • HTN
  • 15-20% present with haematogenous metastasis to lung/liver
  • 5-10% bilateral

Lower abdominal pain in adolescent female

• If severe, acute N&V – Consider ovarian torsion
• Amenorrhoea or abnormal bleeding – Consider ectopic or threatened abortion
• Vaginal discharge +- fever – Consider PID
• Recurrent pain
  • Mid-cycle: Mittelschmerz – NSAID, outpatients
  • With menses: Dysmenorrhoea – NSAID, outpatients
  • No menses: Consider imperforate hymen – Gynae referral

Non-specific abdominal pain

• Recurrent non-specific abdominal pain
• Usually termed functional
• 10-15% of children suffer this
• Constipation sometimes a contributing factor, but tends to be overdiagnosed
• Psychogenic factors must be considered
• Non-pharmacological measures are key (i.e. reassurance, relaxation, heat packs)
• Follow-up with GP +- General paediatrics is warranted

Signs suggestive of organic disease in chronic abdo pain

• Persistent fever
• Poor weight gain
• Child wakes from sleep
• Pain away from umbilicus
• Radiation to back/shoulder/legs
• Persistent vomiting/regurgitation/dysphagia
• Bloody vomitus or stools
• Altered bowel pattern
• Perianal disease
• Sleepiness following attacks
• Positive FHx of peptic ulcer or IBD

DDx of chronic abdo pain

• GI – Functional, peptic ulcer, IBD, IBS, pancreatitis, biliary colic, appendiceal colic, constipation, parasitic infection
• Endocrine – Hyperparathyroid, Addison’s, DM
• CVS – Superior mesenteric artery syndrome, coarctation of the aorta
• Neurological – Abdominal migraine
• Haematological – Sickle cell crises, porphyrias
• Gynaecological – Cystic teratoma of ovary, endometriosis, Mittelschmerz, haematocolpos
• MSK – Discitis, linea alba hernia, painful rib syndrome, muscle wall sprain

Last Updated on November 20, 2021 by Andrew Crofton