Stools that are very thin or pencil thin may be caused by various conditions, such as anal or colorectal cancer, fecal impaction, narrowing of the anus or rectum, and diverticulitis, according to HealthGrades. Inflammatory conditions, ulcers, surgery and trauma may also cause thin stools.
In some cases, thin stools may be caused by a life-threatening condition such as a bowel obstruction, twisting of the colon and the telescoping of the intestines into themselves, explains HealthGrades. The symptoms of potentially life-threatening conditions that may accompany thin stools include bloody stools, a high fever, the inability to pass gas, and severe abdominal or rectal pain. Anyone experiencing these symptoms should call 911. Other potential causes of thin stool include ulcerative colitis, Chron's disease, irritable bowel syndrome and infections of the gastrointestinal tract, which can result from various viruses, bacteria and parasites.
As a wide variety of conditions can cause thin stools, it's vital to seek appropriate medical attention for a proper diagnosis, explains HealthGrades. Potential complications that may occur if the condition is left untreated include dehydration and electrolyte imbalance, anemia, and the spread of cancer or infection. Other potential complications are bowel obstructions, infections of the lining in the abdomen and poor nutrition. In severe cases, doctors may recommend surgery to remove parts of the digestive tract.