Fever with Abdominal Pain in Children

A. SURGICAL EMERGENCIES

1. Acute Appendicitis

• WBC >10,000 with neutrophilia
• US: non-compressible tubular structure >6mm
• CRP >10mg/L
• Alvarado score >7
• CT: wall thickening, fat stranding

2. Intussusception

• US: target/doughnut sign
• Age 6mo-3yr typical
• Sausage-shaped mass RUQ/epigastric
• Currant jelly stools (late)
• Plain film: absence of cecal gas

3. Malrotation with Volvulus

• UGI: corkscrew sign/abnormal duodenal position
• US: whirlpool sign of SMA
• X-ray: double bubble sign
• Elevated lactate
• Metabolic acidosis

B. INFECTIOUS/INFLAMMATORY CONDITIONS

1. Acute Gastroenteritis

• Stool WBC >5-10/hpf (bacterial)
• Stool culture/PCR panel
• Na+ <135 or >145 mEq/L
• BUN/Cr ratio >20:1 (dehydration)
• Rotavirus/adenovirus antigen test

2. Mesenteric Adenitis

• US: cluster of ≥3 nodes >8mm
• Elevated throat swab/viral PCR
• Normal appendix on imaging
• CRP may be elevated
• Associated URI symptoms

3. UTI/Pyelonephritis

• UA: WBC >5/hpf, positive nitrite/LE
• Urine culture >100K CFU/mL
• US: hydronephrosis/perinephric stranding
• DMSA: cortical defects
• PCT >0.5 ng/mL suggests pyelonephritis

C. HEPATOBILIARY/PANCREATIC DISORDERS

1. Acute Pancreatitis

• Lipase >3x upper limit normal
• US: pancreatic edema/fluid
• ALT/AST may be elevated
• Ca2+ <8.5 mg/dL
• CT severity score if needed

2. Cholecystitis

• US: wall >3mm, pericholecystic fluid
• Murphy sign positive
• ALT/AST/GGT elevation
• Direct bilirubin elevation
• HIDA scan: non-filling GB

D. SYSTEMIC/MISCELLANEOUS

1. HSP (IgA Vasculitis)

• Elevated IgA levels
• Skin biopsy: leukocytoclastic vasculitis
• Urinalysis: proteinuria/hematuria
• Normal platelets (vs ITP)
• Positive stool guaiac (GI involvement)

2. Kawasaki Disease

• ↑ESR/CRP
• Thrombocytosis >450K after day 7
• Sterile pyuria
• ALT >50
• Echo: coronary changes

E. RESPIRATORY CONDITIONS

1. Lower Lobe Pneumonia

• CXR: infiltrate/consolidation
• ↓breath sounds lower zones
• SpO2 <95%
• PCT >0.5 ng/mL (bacterial)
• Positive respiratory PCR panel

2. Pleural Effusion/Empyema

• CXR: fluid level/blunting
• US: septations/loculations
• Pleural fluid: pH <7.2 (empyema)
• Pleural glucose <60 mg/dL
• Positive pleural culture

F. HEMATOLOGIC/ONCOLOGIC CONDITIONS

1. Acute Leukemia

• CBC: blasts, cytopenias
• LDH >500
• Uric acid elevation
• Flow cytometry: blast markers
• Bone marrow: >20% blasts

2. Lymphoma

• CT: lymphadenopathy/masses
• ↑LDH, ↑uric acid
• ESR >50
• Node biopsy: diagnostic
• PET scan: staging

3. Sickle Cell Crisis

• Hemoglobin SS on electrophoresis
• ↓Hb from baseline
• ↑Reticulocyte count
• ↑Bilirubin, ↑LDH
• US: splenic infarction

G. GENITOURINARY CONDITIONS

1. Ovarian Torsion

• US: enlarged ovary >4cm
• Doppler: reduced/absent flow
• Elevated WBC common
• ↑β-hCG if pregnant
• CT: whirlpool sign

2. Testicular Torsion

• US Doppler: absent flow
• High-riding testis
• Loss of cremasteric reflex
• Nuclear scan: photopenic area
• Urinalysis normal

3. Nephrolithiasis

• CT: stone(s) >3mm
• US: hydronephrosis, stone
• UA: hematuria, crystals
• ↑Ca, ↑uric acid, ↑oxalate
• XR: radio-opaque stones

H. RHEUMATOLOGIC CONDITIONS

1. Systemic JIA

• Ferritin >1000
• ESR/CRP markedly elevated
• Quotidian fever pattern
• ANA often negative
• ↑IL-6, ↑IL-1β

2. PAN (Polyarteritis Nodosa)

• ↑ESR/CRP
• ANCA typically negative
• Angiography: microaneurysms
• Tissue biopsy: vasculitis
• Hepatitis B serology

I. METABOLIC/ENDOCRINE CONDITIONS

1. Diabetic Ketoacidosis

• Glucose >250 mg/dL
• pH <7.3, bicarb <15
• Ketones in blood/urine
• Anion gap >12
• Corrected Na+ for calculation

2. Adrenal Crisis

• Na+ <135, K+ >5.0
• Morning cortisol <3 µg/dL
• ACTH >100 pg/mL
• Glucose <60 mg/dL
• Failed ACTH stim test

3. Acute Intermittent Porphyria

• ↑Urinary PBG
• ↑Urinary ALA
• Na+ often <135
• Dark/red urine with light
• Genetic testing: HMBS gene

J. TOXICOLOGIC/INGESTIONS

1. Iron Toxicity

• Serum iron >350 µg/dL
• Abdominal XR: radio-opaque tablets
• Anion gap metabolic acidosis
• ↑AST/ALT after 24hrs
• Transferrin saturation >45%

2. Lead Poisoning

• Blood lead >5 µg/dL
• Basophilic stippling RBCs
• XR: lead lines
• ↓Hemoglobin/anemia
• ZPP >35 µg/dL

K. RARE BUT IMPORTANT CONDITIONS

1. Mediterranean Fever

• MEFV gene mutation
• Periodic fever pattern
• ↑ESR/CRP during attacks
• Family history positive
• Colchicine response

2. Hemolytic Uremic Syndrome

• Schistocytes on smear
• ↓Haptoglobin, ↑LDH
• ↑Creatinine, BUN
• Thrombocytopenia
• Stool STEC if diarrheal

CLINICAL PEARLS

Important Red Flags

• Bilious vomiting → surgical emergency until proven otherwise
• Fever >5 days with abdominal pain → consider Kawasaki
• Night sweats + weight loss → malignancy workup
• Periodic fever + serositis → autoinflammatory disorder
• Travel history crucial for tropical infections

Key Laboratory Studies

• CBC, CMP, CRP essential baseline
• Urinalysis before antibiotics
• Blood culture if T >39°C
• Lipase if epigastric/radiation
• LDH/uric acid if malignancy suspected

Imaging Guidelines

• US first-line for RLQ pain
• CXR for respiratory symptoms
• CT with contrast if US inconclusive
• MRI for chronic/complex cases
• Nuclear studies for specific indications

Disclaimer

The notes provided on Pediatime are generated from online resources and AI sources and have been carefully checked for accuracy. However, these notes are not intended to replace standard textbooks. They are designed to serve as a quick review and revision tool for medical students and professionals, and to aid in theory exam preparation. For comprehensive learning, please refer to recommended textbooks and guidelines.