Diverticulitis: Given the patient's age and symptoms of bloody stool and bloating, diverticulitis is a strong consideration. The fact that a similar episode resolved spontaneously a year ago supports this diagnosis, as diverticulitis can have recurrent episodes.

Colorectal Cancer: Although less likely than diverticulitis given the spontaneous resolution of the previous episode, colorectal cancer is a possibility, especially in a 61-year-old patient. Bloody stool is a common symptom.
Angiodysplasia: This condition, characterized by vascular malformations in the colon, can cause recurrent episodes of bloody stool, especially in older adults.
Inflammatory Bowel Disease (IBD): Conditions like ulcerative colitis or Crohn's disease could present with bloody stool and bloating, although the age of onset might be slightly older than typical for IBD.

Ischemic Colitis: This condition can present with sudden onset of bloody stool and abdominal pain. It's crucial to diagnose promptly as it can lead to significant morbidity if not treated.
Infectious Colitis: Certain infections (e.g., Clostridioides difficile, Salmonella, Shigella) can cause bloody diarrhea and are important to identify due to the need for specific antimicrobial therapy.
Lower Gastrointestinal Bleed from Other Sources: Bleeding from the small intestine or other sources could present similarly and requires prompt identification and management to prevent severe outcomes.

Intussusception: Although more common in children, intussusception can occur in adults and may present with bloody stool and abdominal symptoms.
Meckel's Diverticulum: A congenital anomaly of the small intestine that can cause bleeding, though it's more commonly diagnosed in younger patients.
Colonic Varices: These are dilated submucosal veins in the colon that can bleed, often associated with liver disease and portal hypertension.