ISS vs IBS

Quick reference clinical tool

Etiology and Risk Factors
  • Genetics: Polymorphisms in NOD2/CARD15 (especially in Crohn's Disease). First-degree family history increases the risk significantly.
  • Microbiome: Intestinal dysbiosis with reduction in microbial diversity.
  • Immunology: Inappropriate mucosal immune response to normal intestinal flora.
  • Environmental: Passive smoking, early use of antibiotics, diet rich in ultra-processed foods, Vitamin D deficiency.
Clinical tip: An initial outbreak is usually triggered by a gastrointestinal infection (eg. Campylobacter o Salmonella) that alters the mucosal barrier in a genetically predisposed patient.
Clinical Findings

Crohn's disease (CD)

  • Insidious abdominal pain, weight loss, weight stagnation.
  • Pubertal delay (can precede digestive symptoms by years).
  • Perianal disease (fistulas, atypical fissures, plicomas).

Ulcerative Colitis (UC)

  • Chronic bloody diarrhea (>4 weeks), urgency of defecation, tenesmus.
  • Crampy abdominal pain that is relieved with defecation.

⚠️ Warning Signs (Red Flags)

Heavy rectal bleeding, persistent fever of unknown origin, palpable abdominal mass (right iliac fossa), severe recurrent oral thrush, associated arthritis/uveitis.
Laboratory Findings
  • Blood: Anemia (iron deficiency or chronic disorder), thrombocytosis, elevated ESR and CRP, hypoalbuminemia.
  • Stool: Negative stool culture. Elevated fecal calprotectin (>250 µg/g is highly suggestive of active inflammation).
  • Serology (support): ASCA+ (Crohn's), pANCA+ (Ulcerative Colitis). Not diagnostics alone.
Management and Drugs

The current objective is the mucosal healing, not just symptomatic control.

Drug (Trade Name ES) Pediatric Dosage Main Indication
Mesalazine
(Pentasa®, Claversal®)		 30-80 mg/kg/day (max. 4.8g/day) in 1-2 doses. Induction/maintenance in mild UC-mod.
Prednisone
(Dacortin®)		 1 mg/kg/day (max. 40-60 mg). Gradual decline. Rapid induction in moderate-severe outbreaks.
Azathioprine
(Imurel®)		 2 - 2.5 mg/kg/day (once a day). Maintenance (corticosteroid saver).
Infliximab
(Remicade®, Inflectra®)		 5 mg/kg IV (weeks 0, 2, 6, then every 8 weeks). CD and moderate-severe UC, refractory or fistulas.
Monitoring and Guidelines

✅ What to do

  • Monitor growth speed semi-annually.
  • Optimize vitamin D and ferric/IV iron.
  • Emphasize adherence in adolescents.

❌ What Not to Do

  • Do not use NSAIDs to control pain (risk of exacerbation of the flare). Use paracetamol.
  • Do not restrict diets on your own.
Etiology, Clinic and Labs (Rome IV)
  • Brain-Gut Axis: Bidirectional alteration, resulting in visceral hypersensitivity.
  • Clinic: Abdominal pain at least 4 days a month associated with defecation or changes in frequency/shape of stool.
  • Gold Labs: If there are no warning signs, they are normal (Calprotectin <50 µg/g is key to differentiate from IBD). Ask for Celiac Serology if there is diarrhea.

⚠️ Warning Signs (Exclude IBS)

Unintentional weight loss, rectal bleeding, nocturnal diarrhea, fever, history of IBD.
Management and Drugs
Drug (Commercial ES) Pediatric Dosage Indication
Macrogol 3350/4000
(Movicol Pediátric®)		 0.4 - 0.8 g/kg/day. Adjust according to response. IBS subtype Constipation (IBS-C).
Trimebutin
(Polibutin®)		 <5a: 4.8 mg/kg/day.
>5a: 100-200 mg/day in 2-3 doses.		 Antispasmodic for cramping pain.
Monitoring and Guidelines

✅ What to do

  • Demedicalize: ensure that the intestine is "healthy but sensitive."
  • Maintain mandatory school routines.

❌ What Not to Do

  • Do not prescribe routine loperamide in children.
  • Do not repeat invasive tests if there are no new warning signs.
Quick Emergency Calculator

Enter the patient's weight to calculate usual doses in the management of IBD exacerbations or IBS pain crises.

Immunization in IBD (Immunosuppression)

It is essential to adapt the vaccination schedule in patients with IBD who are starting or undergoing immunosuppressive treatment (high-dose corticosteroids >2mg/kg/day, Azathioprine, or Biologics such as Anti-TNF).

🚫 ABSOLUTE CONTRAINDICATIONS

Live attenuated viral or bacterial vaccines are formally contraindicated during treatment and up to 1-3 months post-suspension:

  • MMR (Measles, Rubella, Parotitis)
  • Chickenpox (Priority to vaccinate before starting immunosuppressants if seronegative)
  • Rotavirus
  • yellow fever (Travel medicine care)
  • intranasal flu (Injectable yes you can)

✅ RECOMMENDED VACCINES (Inactivated)

Inactivated vaccines are safe. They must be administered to avoid morbidity and mortality:

  • Flu: Recommendation annual universal with intramuscular inactivated vaccine.
  • Pneumococcus: Increased risk of invasive disease. Administer conjugate (VNC13/15) followed by polysaccharide (VNP23) at 8 weeks according to the Spanish regional protocol.
  • HPV: Recommended for both sexes; immunosuppressant may increase the risk of dysplastic lesions.
  • Hepatitis B: Request serology (Anti-HBs) before starting biological therapy. If titers <10 mIU/mL, administer a booster dose or complete regimen.

💡 Anti-vaccine Tip

In consultation, if the parents of a patient with IBD doubt inactivated vaccines, emphasize that "The treatment that keeps your child's intestine healthy temporarily weakens his defenses against common germs. The vaccine is an indispensable artificial shield that prevents admission to the ICU for diseases that we can avoid today, such as severe pneumonia."

Literature
  • Rome IV Criteria for Functional Gastrointestinal Disorders:
    Hyams JS, et al. Childhood Functional Gastrointestinal Disorders: Child/Adolescent. Gastroenterology. 2016;150(6):1456-1468.
  • ECCO/ESPGHAN Guidelines on Crohn's Disease and Vaccination:
    van Rheenen PF, et al. The Medical Management of Pediatric Crohn's Disease. J Crohns Colitis. 2020;15(2):171-194.
  • Vaccine Advisory Committee (CAV-AEP): AEP online vaccine manual. Vaccination in immunosuppressed children (2025).