What are the next steps for managing long-term diarrhea, vomiting, and weight loss?

Management of Chronic Diarrhea, Vomiting, and Weight Loss

The immediate priority is assessing hydration status and initiating oral rehydration solution (ORS) if the patient can tolerate oral intake, while simultaneously investigating the underlying cause of these chronic symptoms, as weight loss signals significant pathology requiring diagnostic workup rather than symptomatic management alone. 1

Immediate Assessment and Stabilization

Hydration Status Evaluation

• Assess for severe dehydration signs: altered mental status, poor perfusion, abnormal pulse, or shock—these require immediate intravenous isotonic crystalloid (lactated Ringer's or normal saline) until vital signs normalize 1
• For mild-to-moderate dehydration with intact mental status: initiate reduced osmolarity ORS at 50-100 mL/kg over 3-4 hours for rehydration 1
• If vomiting prevents oral intake: administer small, frequent volumes of ORS (5 mL every 1-2 minutes) via spoon or syringe; consider nasogastric administration if oral route fails but mental status remains normal 1

Critical Red Flags Requiring Urgent Intervention

• Bilious vomiting: requires immediate nasogastric decompression and urgent CT scan to exclude intestinal obstruction or enterocolitis 1
• Bloody diarrhea with fever: suggests inflammatory or infectious etiology requiring stool studies and possible antimicrobial therapy 1
• Severe abdominal pain, distention, or signs of peritonitis: necessitates surgical evaluation 1

Diagnostic Workup for Chronic Symptoms

Essential History Elements

The combination of chronic diarrhea, vomiting, and weight loss demands investigation for:

Medication-induced causes (most common and reversible):

• Angiotensin II receptor antagonists (olmesartan) can cause severe enteropathy mimicking celiac disease 1
• Mycophenolate mofetil, chemotherapy agents (capecitabine, 5-FU), and other immunosuppressants 1
• Action: Obtain complete medication history and consider discontinuation of suspect agents 1

Infectious etiologies:

• Parasitic infections (Giardia): obtain stool PCR or specific immunoassay 1
• HIV enteropathy: HIV antibody testing if risk factors present 1
• Tropical sprue: relevant if travel to endemic areas 1

Malabsorptive/inflammatory conditions:

• Celiac disease (even if seronegative): duodenal biopsy showing villous atrophy 1
• Crohn's disease: elevated inflammatory markers (ESR, CRP), imaging showing skip lesions 1
• Small intestinal bacterial overgrowth (SIBO): hydrogen-glucose breath test or duodenal aspirate 1
• Pancreatic exocrine insufficiency: consider in context of weight loss 1

Immune-mediated disorders:

• Common variable immunodeficiency (CVID): check immunoglobulin levels (IgG <5 g/L with low IgA or IgM) 1
• Autoimmune enteropathy: anti-enterocyte antibodies 1

Initial Laboratory and Imaging Studies

• Complete blood count, comprehensive metabolic panel, inflammatory markers (ESR, CRP) 1
• Stool studies: culture, ova and parasites, Giardia antigen, C. difficile if recent antibiotics 1
• Celiac serologies (tissue transglutaminase IgA with total IgA) 1
• Consider CT abdomen/pelvis if alarm features present or to evaluate for structural abnormalities 1

Symptomatic Management During Workup

Rehydration and Nutritional Support

• Continue ORS replacement: 10 mL/kg for each watery stool, 2 mL/kg for each vomiting episode 1
• Resume age-appropriate diet immediately after rehydration; do not withhold food 1
• If breastfeeding: continue throughout illness 1
• Avoid lactose-containing products temporarily if lactose intolerance suspected 1

Antiemetic Therapy

• Ondansetron (0.15-0.2 mg/kg, maximum 4 mg) may facilitate oral rehydration in patients >4 years with persistent vomiting 1, 2
• Use cautiously and only after adequate hydration assessment 1

Antimotility Agents: Critical Cautions

• Loperamide is CONTRAINDICATED in children <18 years with acute diarrhea 1, 3
• In adults: may use loperamide (4 mg initially, then 2 mg after each loose stool, maximum 16 mg/day) ONLY if:
  • No fever present 1, 3
  • No bloody diarrhea 1, 3
  • Adequately hydrated 1, 3
  • No suspected inflammatory or infectious colitis 1, 3
• Avoid entirely if taking CYP3A4 inhibitors, CYP2C8 inhibitors, or P-glycoprotein inhibitors due to risk of cardiac arrhythmias 3

Common Pitfalls to Avoid

1. Treating symptomatically without investigating weight loss: Weight loss indicates significant underlying pathology requiring diagnosis, not just symptom control 1

2. Missing medication-induced enteropathy: Always review medications, particularly olmesartan and chemotherapy agents, as discontinuation may resolve symptoms entirely 1

3. Using antimotility agents inappropriately: Never use in children, never use with fever/bloody stools, and recognize cardiac risks with drug interactions 1, 3

4. Delaying evaluation for seronegative enteropathy: Negative celiac serologies do not exclude celiac disease or other causes of villous atrophy—duodenal biopsy may still be indicated 1

5. Overlooking SIBO and pancreatic insufficiency: These are under-recognized causes of chronic diarrhea with weight loss, particularly post-chemotherapy or in patients with anatomical abnormalities 1

When to Escalate Care

• Symptoms persisting >14 days without identified cause warrant endoscopy and comprehensive stool testing 1
• Development of severe dehydration, altered mental status, or inability to maintain oral intake requires hospitalization 1
• Suspected enterocolitis (particularly with chemotherapy history) requires urgent CT imaging and intensive intervention 1