I appreciate your request, but I must clarify an important limitation: The evidence provided does not contain content from Harrison's Internal Medicine textbook, and therefore I cannot provide a chapter-by-chapter summary of that specific resource.

The studies and guidelines you've provided focus on specific gastrointestinal conditions (IBS, diabetic neuropathy, cancer-related GI complications, eosinophilic disorders, and GERD) rather than comprehensive textbook chapters.

However, I can offer you a structured review of gastrointestinal disorders based on the available evidence, organized by organ system with emphasis on signs/symptoms, diagnostics, and treatment—which may serve your RITE review purposes:

Esophageal Disorders

Eosinophilic Esophagitis

Symptoms: Dysphagia and food impaction in adults; heartburn, abdominal pain, and vomiting in children 1, 2
Diagnosis: Endoscopy revealing esophageal rings, texture changes, or nonspecific mucosal appearances; biopsy showing eosinophilic infiltration 1
Treatment: Proton pump inhibitor therapy or swallowed topical corticosteroids; esophageal dilation as needed 1

Infectious Esophagitis

Candida Esophagitis: White nummular lesions on endoscopy; diagnosed via cytobrush or biopsy showing fungal forms; more common in immunosuppressed patients but can occur in immunocompetent hosts 1
HSV/CMV: Multiple ulcers with diarrhea or bleeding; diagnose via immunocytochemistry and PCR of biopsy samples from ulcerated areas (blood PCR for CMV is insensitive) 1

GERD and Erosive Esophagitis

Treatment: PPIs remain the medical treatment of choice 3, 4
Omeprazole indications: Short-term treatment (4-8 weeks) of erosive esophagitis in patients ≥2 years; maintenance healing in patients ≥2 years 3

Gastric and Duodenal Disorders

Peptic Ulcer Disease

H. pylori Eradication: Triple therapy (omeprazole + clarithromycin + amoxicillin) is indicated for active duodenal ulcer or 1-year history to eradicate H. pylori 3
Treatment Duration: Most duodenal ulcers heal within 4 weeks; some require additional 4 weeks 3
Gastric Ulcer: Short-term treatment (4-8 weeks) with omeprazole 3

Gastroparesis

Suspect in: Erratic glucose control or upper GI symptoms without identified cause 1
Exclude first: Medications, gastric outlet obstruction, peptic ulcer disease via esophagogastroduodenoscopy or barium study 1
Diagnostic gold standard: Gastric emptying scintigraphy with digestible solids at 15-minute intervals for 4 hours; 13C octanoic acid breath test is approved alternative 1

Small Intestine Disorders

Dumping Syndrome (Post-Surgical)

Early dumping: Cramp-like contractions, bloating, diarrhea within 1 hour of eating 1
Late dumping: Hypoglycemia 1-3 hours postprandially 1
Diagnosis: OGTT showing hypoglycemia with symptoms; gastric emptying scintigraphy (though low sensitivity/specificity) 1
Treatment: Dietary modifications first-line; somatostatin analogues for both early and late dumping; acarbose specifically for late dumping 1

Small Bowel Bacterial Overgrowth (SIBO)

Consider in: "Wet wind" with faecal incontinence; assess dietary fiber intake 1
Role in constipation: May contribute, especially with methane-producing organisms 1

Large Intestine Disorders

Irritable Bowel Syndrome

Diagnosis

Rome IV criteria-based: Recurrent abdominal pain, bloating, altered bowel habits without structural pathology 1, 5
Exclude organic disease: Colonoscopy if alarm features (rectal bleeding, iron deficiency anemia, age >50, family history) 1

Treatment Algorithm

For Predominantly GI Symptoms 1:

First-line medical therapy:
- Diarrhea-predominant: Loperamide or codeine 1
- Constipation-predominant: Increase dietary fiber (ispaghula better tolerated than wheat bran); laxatives as needed 1
- Abdominal pain: Antispasmodics with anticholinergic effect most effective 1
Second-line: Low-dose tricyclic antidepressants for abdominal pain and global symptoms 1

For IBS with Mental Health Comorbidity 1:

SSRIs at therapeutic doses are better initial choice than low-dose TCAs when depression/anxiety suspected, as low-dose TCAs inadequate for mood disorders 1
SNRIs: Beneficial in chronic painful disorders and useful for GI symptoms with psychological comorbidity 1

Dietary Management 1:

Mild symptoms: Standard dietary advice
Moderate-severe GI symptoms: Low FODMAP diet 1
Substantial psychological symptoms: Mediterranean diet; can be modified for FODMAP content if needed 1

Psychological Treatment 1:

Low severity: Self-management via education and lifestyle
Moderate-severe: Brain-gut behavior therapy (CBT, hypnotherapy) 1
Significant psychiatric disease: Traditional psychological treatment; psychiatric referral if warranted 1

Functional Constipation

Post-cancer treatment: Rule out opioid-induced constipation; consider PAMORAs (peripherally acting mu-opioid receptor antagonists) or conventional laxatives first-line 1
Faecal impaction: Managed with suppositories or enemas initially 1

Faecal Incontinence

Investigations: Assess anal tone; flexible sigmoidoscopy to rule out structural pathology 1
"Wet wind": Assess dietary fiber intake (too little or too much); exclude SIBO 1
Treatment: Transanal irrigation effective when other treatments fail, especially with passive incontinence, severe constipation, anterior resection syndrome 1

Gastrointestinal Neuropathies (Diabetic)

Screening and Diagnosis

Annual screening: All type 2 diabetes patients and type 1 diabetes ≥5 years duration using 10-g monofilament 1
Clinical tests: Pinprick (small fiber), vibration with 128-Hz tuning fork (large fiber), 10-g monofilament (protective sensation), ankle reflexes 1

Specific Manifestations

Gastroparesis: Suspect with erratic glucose control or upper GI symptoms; solid-phase gastric emptying via double-isotope scintigraphy (though test results correlate poorly with symptoms) 1
Lower GI: Constipation most common; can alternate with diarrhea episodes 1
Esophageal: Dysmotility, enteropathy 1

Treatment

Prevention: Tight glycemic control only strategy convincingly shown to prevent/delay DPN and cardiovascular autonomic neuropathy in type 1 diabetes; slows progression in type 2 diabetes 1
Pain management: Gabapentinoids, SNRIs, tricyclic antidepressants, sodium channel blockers as initial pharmacologic treatments 1
Referral: To neurologist or pain specialist when pain control not achieved 1

Post-Cancer Treatment GI Complications

Diarrhea and Urgency

Bacterial infection: Loperamide safe before microbiology results available; theoretical risk of toxic dilatation with high-dose loperamide in neutropenic patients with C. difficile 1
C. difficile in neutropenic patients: Pseudomembrane formation requires neutrophils (may not be seen); endoscopic biopsy can diagnose 1

Obstruction

Subacute obstruction: Low-fiber diets prescribed by dietitian, time-limited with clinical benefit review; additional laxatives may be required 1
Complete obstruction: Surgical emergency; requires CT imaging to understand anatomy and exclude cancer recurrence 1
Recurrent cancer obstruction: Self-expanding metal stents preferred over surgery when possible; expert medical management with opioids, antispasmodics (hyoscine butyl bromide), antiemetics, antisecretory agents (octreotide), corticosteroids 1

Key Clinical Pitfalls

IBS diagnosis: Symptoms unreliable at identifying underlying cause; one-third of symptoms attributed to cancer therapy are unrelated after investigation 1
Gastroparesis testing: Gastric emptying studies have low sensitivity/specificity because rapid emptying occurs early (not adequately assessed); 4-hour study integrated into single value may neutralize rapid initial emptying effect 1
Post-surgical dumping vs. other complications: Internal herniation causes colicky pain without vegetative symptoms; stenosis causes dysphagia; marginal ulcer causes pain during meals with acid reflux—all can mimic dumping 1, 6
Diabetic neuropathy: Electrophysiological testing rarely needed except when features atypical; consider alternative causes (neurotoxic medications, heavy metals, alcohol, B12 deficiency, renal disease, vasculitis) in severe/atypical cases 1
Eosinophilic disorders: When hypereosinophilia present (AEC >1500), consider non-EoE eosinophilic GI disease, hypereosinophilic syndrome, EGPA; consult allergy/immunology 1

What are the signs, symptoms, diagnostics, and treatments for gastrointestinal disorders, including esophageal, gastric, small intestine, large intestine, liver, and pancreatic diseases?

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