Warning Signs of Colon Cancer Adults Over 45 Should Never Ignore
Adults over 45 should watch for warning signs of colorectal cancer, including gradual bloating, constipation, and cramping that worsen over time, as tumors in different colon sections cause distinct symptoms ranging from fatigue and weight
Dr. Jetsada Bunyavongvirooj, deputy director of primary care at Maha Sarakham Hospital, warns adults over 45 about large intestine obstruction symptoms that could signal colorectal cancer and should never be overlooked. Many people believe bowel obstruction causes severe pain preventing movement, but many patients—especially those with cancer-related obstruction—experience gradually worsening symptoms beginning with bloating, constipation, and intermittent cramping that they mistake for stomach disease or indigestion. By the time symptoms worsen and patients reach the hospital, some require emergency surgery due to severe intestinal distension.
The characteristic pain of large intestine obstruction is surgical-specific: intermittent cramping (colicky abdominal pain) caused by the colon contracting to push stool and gas through narrowed points. Each contraction causes wave-like pain, sometimes every 5-15 minutes before gradually subsiding, then recurring. After hours or days, internal pressure rises, the intestine expands, blood circulation to the intestinal wall decreases, and pain transitions from intermittent to constant—a dangerous sign indicating the intestine may be losing blood supply or perforating.
Symptoms vary depending on the obstruction's location in the colon. Right colon tumors (cecum and ascending colon) often develop gradually since this section has a wider diameter and stool is still relatively liquid, allowing passage past the cancer mass. Patients typically present with fatigue, weakness, pale appearance from chronic blood loss, weight loss, or a palpable lump in the right abdomen, rather than sudden obstruction. Many never experience clear abdominal pain until the mass becomes very large.
Transverse colon tumors cause symptoms between right and left colon presentations: patients may experience intermittent cramping around the navel or upper abdomen, bloating after eating, abdominal distension, reduced appetite, and weight loss. Large masses may cause intermittent obstruction before complete obstruction develops later.
Left colon tumors (descending and sigmoid colon) typically produce the clearest symptoms because stool in this section becomes firmer and the intestinal opening narrower, allowing cancer masses to obstruct more easily. Patients usually develop chronic constipation alternating with diarrhea, difficult bowel movements, increased straining, pencil-thin or ribbon-like stools, intermittent cramping especially in the lower left abdomen, increasing bloating, decreased gas passage, and eventually complete inability to defecate or pass gas—characteristic of full bowel obstruction.
The sigmoid colon is the most common obstruction site from colorectal cancer because it is the narrowest part of the large intestine. Many patients experience intermittent cramping in the lower left abdomen combined with bloating and distension. Some feel constant urge to defecate but cannot, or pass only mucus and small amounts of blood. When symptoms worsen, the abdomen becomes severely distended, especially the lower portion, and vomiting may occur in late disease stages.
