Infectious Gastroenteritis: This is the most likely diagnosis due to the combination of rectal bleeding, fever, and diarrhea, which are common symptoms of bacterial, viral, or parasitic infections of the gastrointestinal tract. Justification: The presence of fever and diarrhea alongside rectal bleeding points towards an infectious cause, and gastroenteritis is a common condition that can present with these symptoms.

Inflammatory Bowel Disease (IBD): Conditions like ulcerative colitis and Crohn's disease can cause rectal bleeding, fever, and diarrhea due to chronic inflammation of the gastrointestinal tract. Justification: IBD is a plausible diagnosis given the symptomatology, especially if the patient has a history of similar episodes or if the symptoms persist over time.
Food Poisoning: Certain types of food poisoning, especially those caused by bacteria like Salmonella, Shigella, or Campylobacter, can lead to rectal bleeding, fever, and diarrhea. Justification: The acute onset of symptoms after consuming contaminated food makes food poisoning a likely consideration.
Diverticulitis: Inflammation of a diverticulum in the colon can cause rectal bleeding, fever, and changes in bowel habits, including diarrhea. Justification: While more common in older adults, diverticulitis should be considered, especially if the patient has known diverticulosis or risk factors.

Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause bowel obstruction and ischemia, leading to rectal bleeding, fever, and diarrhea. Justification: Although rare in adults, intussusception is a surgical emergency that requires prompt diagnosis and treatment to prevent complications.
Ischemic Colitis: Reduced blood flow to the colon can cause rectal bleeding, fever, and diarrhea, and is a condition that requires immediate medical attention. Justification: Given its potential for severe outcomes, including the need for surgical intervention, ischemic colitis must not be missed.
Clostridioides difficile (C. diff) Infection: A bacterial infection that can cause severe diarrhea, fever, and potentially rectal bleeding, especially in patients who have recently used antibiotics. Justification: C. diff infection is a significant concern due to its severity and the potential for complications, making it crucial not to miss this diagnosis.

Colonic Angiodysplasia: Vascular lesions in the colon that can cause rectal bleeding, though fever and diarrhea are less common presentations. Justification: While rare, angiodysplasia should be considered in the differential diagnosis, especially in older adults or those with a history of vascular disease.
Colorectal Cancer: Although more commonly presenting with occult bleeding, advanced colorectal cancer can cause rectal bleeding, fever (if there's an associated infection), and changes in bowel habits. Justification: Given the significant implications of a cancer diagnosis, colorectal cancer must be ruled out, even though it's less likely to present with all these symptoms acutely.