What is the treatment approach for a 10-year-old patient with distal colitis and a three-week history of diarrhea?

Treatment of Distal Colitis in a 10-Year-Old with 3 Weeks of Diarrhea

Start with combination therapy of topical mesalazine 1g daily (suppository or enema depending on disease extent) plus oral mesalazine 2-4g daily as first-line treatment. 1, 2

Initial Assessment Before Treatment

Before initiating therapy, several critical steps must be completed:

• Confirm the diagnosis through stool culture to exclude infectious causes (particularly C. difficile), followed by endoscopy with biopsy to establish the diagnosis and extent of disease 3
• Assess disease extent via sigmoidoscopy to determine whether disease is limited to the rectosigmoid junction (requiring suppositories) or extends more proximally (requiring foam or liquid enemas) 1
• Check for proximal constipation with an abdominal X-ray, as abnormal intestinal motility can cause proximal colonic stasis in distal colitis, which impairs drug delivery to the inflamed mucosa 3, 4
• Evaluate for dehydration and ensure adequate hydration to minimize thromboembolism risk 1

First-Line Treatment Protocol

The cornerstone of therapy combines topical and oral aminosalicylates:

• Topical mesalazine 1g daily delivered as suppositories for rectosigmoid disease or enemas for more proximal left-sided disease 1, 2
• Oral mesalazine 2-4g daily given concurrently with topical therapy 1, 2
• This combination approach is superior to either agent alone and has fewer adverse effects than topical corticosteroids 5

If proximal constipation is identified on X-ray, treat with polyethylene glycol (PEG) 17g daily as the preferred laxative, as this improves drug delivery to the inflamed distal colon 4. Avoid mineral oil-based products in pediatric colitis patients due to risks of rectal mucosa irritation and potential bacterial translocation 4.

Second-Line Treatment for Inadequate Response

If the patient fails to improve after 2-4 weeks on combination mesalazine therapy:

• Add oral prednisolone 40mg daily (approximately 1mg/kg for a typical 10-year-old) with gradual taper over 8 weeks 1, 2
• Continue both topical and oral mesalazine during corticosteroid therapy 3
• Reassess adherence to prescribed therapy, as poor compliance is a common cause of apparent treatment failure 3

Topical corticosteroids can be considered as an alternative second-line option for patients intolerant of topical mesalazine, though they have lower efficacy 1.

Management of Refractory Disease

For patients with endoscopically documented active distal colitis who fail oral corticosteroids combined with oral and rectal mesalazine:

• Consider hospital admission for IV corticosteroid therapy, which induces remission in a high proportion of patients with refractory distal colitis 3
• Alternative salvage therapies include infliximab 5mg/kg IV at weeks 0,2, and 6, followed by maintenance dosing every 8 weeks 6
• In pediatric ulcerative colitis trials, 45% of patients aged 6-17 years achieved clinical response at week 8 with infliximab, and 40% achieved clinical remission 6

Critical warning: Infliximab carries significant risks in pediatric patients, including increased risk of lymphoma and hepatosplenic T-cell lymphoma (particularly when combined with azathioprine or 6-mercaptopurine), serious infections including tuberculosis, and fungal infections 6. These risks must be carefully weighed against benefits in refractory disease.

Maintenance Therapy

Once remission is achieved:

• Continue lifelong maintenance therapy with oral mesalazine, as patients with distal colitis who relapse more than once yearly require ongoing treatment 1, 2
• Topical mesalazine can be continued for maintenance of remission, as rectal delivery is effective for preventing relapse 5
• Discontinuation may only be considered after 2 years of sustained remission in patients strongly averse to medication 1

Common Pitfalls to Avoid

• Do not use bulk-forming laxatives like psyllium for constipation in colitis patients, as these are not recommended 4
• Do not overlook proximal constipation, which affects drug delivery and can mimic treatment failure 3, 4
• Do not continue ineffective therapy beyond 2-4 weeks without reassessing the diagnosis and considering treatment escalation 3
• Do not assume treatment failure without first confirming medication adherence and ruling out infectious complications 3