13 yr male having pain in abdo vomiting -2-3 episode with fever 3 days diff diagnosis
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"abdominal pain"[MeSH Terms] AND "appendicitis"[MeSH Terms] AND child
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13-year-old boy: abdominal pain, vomiting (2-3 episodes), fever for 3 days
Fever for 3 days with pain and only a few episodes of vomiting makes an inflammatory or infective cause more likely than a purely functional one. The main concern is a surgical cause, especially appendicitis.
Differential diagnosis
Surgical or must-not-miss
- Acute appendicitis, including a perforated or complicated one. Three days of fever and pain fits delayed presentation, perforation, or an appendicular mass or abscess. Pain is typically gradual in onset and migrates to the right iliac fossa. Nausea and vomiting come after the pain starts. Schwartz's Principles of Surgery, 11e describes appendicitis as one of the hardest diagnoses to establish in children with abdominal pain.
- Mesenteric adenitis, which often follows a viral illness or tonsillitis. It is a diagnosis of exclusion and mimics appendicitis.
- Intestinal obstruction or complications such as adhesions or Meckel's diverticulitis. Intussusception is less likely at this age.
- Testicular torsion. Always examine the scrotum, because boys can present with lower abdominal pain and vomiting. It usually has sudden onset and little fever.
- Crohn's disease, for example terminal ileitis. Look for a longer history of weight loss, diarrhoea, or mouth ulcers.
- Pancreatitis, cholecystitis, or a liver abscess, which are less common.
Medical or infective
7. Gastroenteritis, the most common cause of abdominal pain in children. It is less likely here if the vomiting is mild and there is no diarrhoea. In gastroenteritis, vomiting and diarrhoea usually come first and the pain follows.
8. Urinary tract infection or pyelonephritis. Look for dysuria, frequency, or loin pain. UTI is less likely to cause vomiting than appendicitis. An obstructing ureteric stone can also cause this picture.
9. Typhoid (enteric fever). Consider it in endemic areas when fever lasts more than 3 days, with abdominal pain, relative bradycardia, and constipation or diarrhoea.
10. Hepatitis A or E. Fever, vomiting, and right upper quadrant pain may precede jaundice.
11. Malaria and dengue. Check for travel or endemic exposure, thrombocytopenia, rising haematocrit, and plasma leakage.
12. Lower lobe pneumonia, which can present as abdominal pain and fever. Check the chest.
13. Streptococcal pharyngitis can cause abdominal pain, fever, and vomiting.
14. Diabetic ketoacidosis causes abdominal pain and vomiting. It usually has no fever unless there is a trigger, so check glucose and ketones. Tintinalli's Emergency Medicine
15. Henoch-Schönlein purpura (IgA vasculitis) with abdominal pain. Look for a rash on the buttocks and legs, joint pain, and haematuria.
16. Others: tuberculosis (abdominal or ileocaecal) if the fever is prolonged, abdominal migraine (no fever), and constipation (rarely febrile).
Exam and bedside clues
- Posture: stillness suggests peritoneal irritation (appendicitis). Writhing suggests colic or obstruction. Tintinalli's
- Abdomen: check for localised tenderness, guarding, rebound, Rovsing's, psoas and obturator signs, and a mass.
- Genitals: examine the testes. Tintinalli's stresses doing this in children with abdominal pain.
- Other systems: check the throat, chest, and loins, and look for a rash, jaundice, or dehydration.
- Vital signs: a high pulse or temperature suggests perforation or sepsis.
Initial investigations
- Bloods: CBC with differential and CRP. Add a malaria smear or rapid test, dengue NS1 or IgM, and a Widal or blood culture if typhoid is suspected.
- Urine: urinalysis and culture.
- Others: blood glucose and ketones, LFTs, amylase or lipase, and renal function if he is dehydrated.
- Imaging: abdominal ultrasound is the first-line test in children (appendix, free fluid, adenitis, intussusception, ovarian or testicular pathology, hepatobiliary disease). Use CT only if ultrasound is equivocal and suspicion remains high.
- Chest X-ray if there are respiratory signs. An erect abdominal film helps only if you suspect obstruction or perforation.
Red flags that mean urgent surgical review
- Peritonitis, guarding, or rigidity
- Bilious or persistent vomiting
- Distension
- Tachycardia or hypotension
- Severe localised right iliac fossa pain
- Signs of sepsis
Note on the evidence
Recent systematic reviews (2024 to 2025) on paediatric appendicitis cover risk stratification and conservative management. See PMID 40715546 and PMID 39862589. They do not change the approach above. Antibiotic-only treatment is used for selected uncomplicated cases, but it carries a recurrence risk.
Textbook sources
- Schwartz's Principles of Surgery, 11e, Appendicitis: mimics in children.
- Tintinalli's Emergency Medicine, Abdominal pain in children (chapter 133).
Tell me his exam findings (location of the pain, bowel habit, urinary symptoms, travel or endemic exposure) and any lab results. I can then narrow this down.
Mesentric adenitis
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"mesenteric lymphadenitis"
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PMID: 39011220
Mesenteric adenitis (mesenteric lymphadenitis)
What it is: Inflammation of the mesenteric lymph nodes, mostly in the ileocaecal region because that area has the most lymphatic tissue. It is a common appendicitis mimic in children. Swollen ileocaecal nodes stretch their capsule and cause right iliac fossa pain. - Bailey and Love's Short Practice of Surgery, 28e, p. 1116-1117
Causes
- Viral: often follows an upper respiratory infection. Adenovirus is classic. SARS-CoV-2 is also reported. - Goldman-Cecil Medicine; Bailey and Love's
- Bacterial: Yersinia enterocolitica and Y. pseudotuberculosis, and Campylobacter. Y. pseudotuberculosis typically affects children and young adults and causes an appendicitis-like syndrome. At surgery the appendix looks normal but the nodes are enlarged. - Jawetz, Melnick & Adelberg's Medical Microbiology, 28e
- Tuberculosis: less common, and usually seen in an older child or adult with a more chronic course.
- Secondary to terminal ileitis, for example Crohn's disease. - Grainger & Allison's Diagnostic Radiology
How it fits your 13-year-old
| Feature | Mesenteric adenitis | Appendicitis |
|---|---|---|
| Pain | Short attacks of central colicky pain lasting 10 to 30 minutes, poorly localised | Constant pain that migrates to the right iliac fossa |
| Vomiting | Can occur, but is less frequent | More frequent, and follows the pain |
| Fever | Present in more than half, sometimes high | Usually low-grade, higher if perforated |
| Appearance | Seldom looks ill | Looks unwell, lies still |
| Tenderness | Poorly localised, shifting tenderness (moves when the patient is repositioned) | Fixed right iliac fossa tenderness, guarding, rebound |
| Other | Cervical nodes, recent sore throat | Anorexia, nausea |
| WBC | Leukocytosis on day 1, which falls by day 2 | Persistent or rising leukocytosis |
Source for the first four rows: Bailey and Love's.
A 2024 paediatric study found that nausea, vomiting, anorexia, pain migration, leukocytosis, and a higher neutrophil percentage and neutrophil-to-lymphocyte ratio all favoured appendicitis over mesenteric lymphadenitis. (Shahba et al., Cureus 2024) This is a single-centre cross-sectional study, so treat it as supportive rather than definitive.
Caution for this case: Fever lasting 3 days with persistent pain should keep appendicitis, possibly perforated, high on the list. Mesenteric adenitis is a diagnosis of exclusion.
Workup
- Exam: check for shifting tenderness, absence of peritonism, and enlarged nodes in the neck, axillae, and groins. Look at the throat and examine the testes.
- Bloods: CBC and CRP. Consider a throat swab, and stool culture or Yersinia serology if there is diarrhoea.
- Ultrasound is the first-line test. In mesenteric lymphadenitis it shows clustered, mildly enlarged right lower quadrant nodes, usually under 10 mm in short axis, with a normal, compressible appendix and no other inflammatory process. - Grainger & Allison's
- CT or diagnostic laparoscopy only if ultrasound is equivocal and suspicion of appendicitis persists. - Bailey and Love's
Management
- Treatment is supportive: fluids, antipyretics, analgesia, and observation. Viral cases resolve on their own, but may recur. - Bailey and Love's
- Bacterial cases (Yersinia, Campylobacter) can cause cramping, vomiting and diarrhoea severe enough to need admission. Give antibiotics only if the illness is severe or the patient is immunocompromised.
- Re-examine after a period of observation. Admit and arrange a surgical review if pain localises, tenderness becomes fixed, or peritonism develops.
- If the nodes are persistent or the course is prolonged, consider TB, Crohn's disease, or lymphoma.
Imaging
You can see a CT example of mesenteric lymphadenitis in Grainger & Allison's Diagnostic Radiology, Fig. 21.55, in the section on appendicitis-mimicking conditions.
I can't give a recent guideline update. My PubMed search found no systematic review or meta-analysis of mesenteric lymphadenitis in the past 5 years, only case reports and the single cross-sectional study above.
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