Irritable Bowel Syndrome (IBS): This condition is characterized by a change in bowel habits, including high frequency and small volume stools, without any visible signs of damage or disease in the digestive tract. It's common in the elderly and can be exacerbated by stress, certain foods, and other factors.

Diverticulitis: Inflammation of the diverticula in the colon can cause changes in bowel habits, including frequent small stools, especially in the elderly.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause frequent, small-volume stools due to inflammation and irritation of the bowel.
Gastroesophageal Reflux Disease (GERD) and Peptic Ulcer Disease: Though primarily associated with upper GI symptoms, these conditions can sometimes lead to changes in bowel habits.
Medication Side Effects: Certain medications, such as laxatives, diuretics, and some antidepressants, can cause changes in bowel habits.

Colorectal Cancer: A critical diagnosis to consider, as changes in bowel habits can be an early sign. The risk increases with age, making it a "do not miss" diagnosis in the elderly.
Infectious Colitis: Bacterial, viral, or parasitic infections can cause sudden changes in bowel habits, including high frequency and small volume stools.
Ischemic Colitis: Reduced blood flow to the colon can cause sudden changes in bowel habits, abdominal pain, and potentially life-threatening complications if not promptly addressed.

Microscopic Colitis: A condition characterized by inflammation of the colon that can only be seen with a microscope, leading to chronic watery diarrhea.
Bile Acid Diarrhea: Excess bile acids in the colon can cause diarrhea, which might be perceived as high frequency small volume stools.
Endocrine Disorders: Certain endocrine disorders, such as hyperthyroidism, can cause changes in bowel habits, though this would be less common and typically accompanied by other systemic symptoms.