Due to the strong emphasis on screening procedures, CRC is often detected before any signs or symptoms occur. In other cases, however, signs can be very nonspecific, such as fatigue, cramping, constipation or weight loss. In more advanced cases, there can be abdominal tenderness or rectal bleeding. The clinical presentation can sometimes be dictated by the location of the tumor. Proximal, or right-sided, tumors can cause diarrhea and are more likely to bleed, which may result in iron-deficiency anemia. Distal, or left-sided, lesions are more often discovered later in the disease progression, and may present as a bowel obstruction.