Irritable Bowel Syndrome (IBS): Given the patient's age, symptoms of lower abdomen cramps with loose stools without blood, and a recent colonoscopy that showed only one polyp, IBS is a plausible diagnosis. The absence of fever, weight loss, and other alarming symptoms also supports this diagnosis.

Inflammatory Bowel Disease (IBD): Although less likely given the absence of blood in the stool and a recent colonoscopy, IBD (including Crohn's disease and ulcerative colitis) could still be considered, especially if the symptoms persist or worsen.
Diverticulitis: This condition is common in older adults and can cause lower abdominal pain and changes in bowel habits. However, the absence of fever and the fact that the patient is afebrile makes this less likely.
Gastroesophageal Reflux Disease (GERD) or Functional Dyspepsia: Although these conditions primarily affect the upper GI tract, they can sometimes cause lower abdominal discomfort and changes in bowel habits.

Colorectal Cancer: Despite a recent colonoscopy, the possibility of a new or missed lesion cannot be entirely ruled out, especially in a patient with a history of polyps. Any change in bowel habits or persistent symptoms warrants further investigation.
Infectious Colitis: Although the patient reports no travel or camping, infectious causes (bacterial, viral, or parasitic) could still be present, especially if the patient has been exposed to contaminated food or water.
Ischemic Colitis: This condition can present with sudden onset of abdominal pain and changes in bowel habits, and it is more common in older adults with cardiovascular risk factors, such as diabetes.

Microscopic Colitis: A condition characterized by chronic watery diarrhea, which can be difficult to diagnose and may require a colonoscopy with biopsy for confirmation.
Bile Acid Diarrhea: Can occur in patients who have had their gallbladder removed or have certain gastrointestinal conditions, leading to chronic diarrhea.
Hormone-sensitive tumors (e.g., carcinoid syndrome): Although very rare, these tumors can cause diarrhea and abdominal cramps among other symptoms, and are important to consider in the differential diagnosis of chronic diarrhea.