What Causes Loose Stool?

Loose stool, also known as loose bowel movements or diarrhea, is caused by infectious agents, inflammatory bowel diseases, intake of various medications, and systemic disorders. When a person has loose stool for less than two weeks, the condition is said to be acute. If it occurs for two to four weeks, it is said to be persistent, while if it goes beyond four weeks, it is said to be chronic. The duration of the condition is often a clue of what is causing the problem.

Most cases of acute diarrhea are due to viral, bacterial, or helminthic infections. In acute diarrhea, the passage of frequent stools is often accompanied by symptoms of vomiting, fever, and abdominal pain. Infectious agents are generally introduced to the fecal-oral route if contaminated water or food is consumed.

The five groups most at risk for infectious diarrhea are travelers, those who consume undercooked meat, children in day care (and their families), people who are institutionalized, and those with suppressed immune systems or who are taking steroid therapy, such as patients with HIV/AIDS. The specific infections that cause the condition vary among the five groups. Although the infectious causes may be different, the pathophysiology of acute diarrhea is basically the hypersecretion of the small bowel as a response to bacterial toxins or the adherence of the pathogens to the intestinal mucosa.

Other causes of this condition include lactose intolerance and stress. When stress is the cause of loose stool, the condition is termed psychogenic or emotional diarrhea and is caused by the overstimulation of the parasympathetic nervous system. Chronic loose stool may be due to an inflammatory bowel disease called ulcerative colitis, wherein the colon becomes inflamed and ulcerated. In ulcerative colitis, the ulcerated large bowel has increased motility and increased secretions, leading to frequent loose bowel movements.

A person suffering from frequent passage of loose stool is treated depending on the cause. For instance, most cases of infectious diarrhea are given supportive treatment through fluid and electrolyte replacement. Antibiotics or antiprotozoal drugs are rarely used. For lactose intolerance and stress, the key is to avoid dairy products or situations that precipitate stress. Treatment for chronic inflammatory bowel diseases involves medical control of the inflammation and/or surgical removal of the defective part of the intestine.