Intestinal failure (IF) is a physiological state where the gut is incapable of absorbing the necessary fluids, electrolytes, and macronutrients required to sustain life. When the intestine cannot maintain the body’s nutritional and hydration needs, a person becomes dependent on intravenous feeding, known as parenteral nutrition (PN). This support bypasses the digestive tract, delivering a liquid formula of nutrients directly into the bloodstream. IF is a severe complication arising from various underlying conditions that impair the gut’s ability to function.
Failure Due to Loss of Intestinal Length
The most common cause of long-term intestinal failure is a reduction in the physical length of the small intestine, known as Short Bowel Syndrome (SBS). Extensive surgical removal of the small intestine, or massive resection, leaves an insufficient surface area for adequate absorption. The severity of the failure is directly related to the amount of intestine remaining after surgery.
A frequent cause for this massive loss is a vascular event, such as mesenteric ischemia or infarction, where the blood supply to a large segment of the bowel is cut off, leading to tissue death. In adults, this often results from blood clots or low blood flow states. Trauma or surgical complications can also necessitate the removal of a portion of the gut. In infants, conditions like Necrotizing Enterocolitis (NEC) or intestinal volvulus (twisting of the intestine) are leading causes that demand extensive surgical resection.
The presence of the colon plays a role in determining the level of nutritional dependency for a patient with a shortened gut. If the colon remains, it can partially adapt to absorb fluid and short-chain fatty acids, which helps reduce the need for intravenous fluids. However, when both the small intestine and the colon are removed, the loss of absorptive capacity is more profound, leading to a higher reliance on parenteral nutrition.
Failure Due to Mucosal and Structural Destruction
Intestinal failure can occur even when the physical length of the intestine is intact, but the integrity of the absorptive lining, or mucosa, is severely damaged. In these cases, the issue is not the quantity of the gut but the quality and function of the intestinal surface. The delicate villi that extend into the lumen to absorb nutrients become flattened, inflamed, or scarred, compromising their function.
Chronic, widespread inflammatory conditions, such as extensive and refractory Crohn’s disease, can lead to this type of failure. The persistent inflammation and subsequent scarring can severely reduce the absorptive capability of the remaining intestinal segments. Another significant cause is radiation enteritis, which results from damage to the small intestine following radiation therapy for abdominal or pelvic cancers. Radiation can cause strictures, scarring, and persistent inflammation that inhibits nutrient uptake.
Furthermore, some conditions create non-resectable structural problems that compromise function, such as extensive enterocutaneous fistulas. These abnormal connections allow intestinal contents to bypass the absorptive surface and leak out of the body, leading to massive losses of fluid and nutrients. In all these scenarios, the failure stems from the inability of the enterocytes to perform their primary function of absorption.
Failure Due to Severe Motility Disorders
This category of intestinal failure involves functional failure where the bowel is structurally sound but cannot move its contents along effectively. This is due to severe motility disorders, where the muscles or the nerves controlling the intestine are damaged or dysfunctional. The coordinated wave-like contractions, known as peristalsis, are lost or become disorganized.
One example is Chronic Intestinal Pseudo-Obstruction (CIPO), a condition where the gut behaves as if it is blocked, even though no physical obstruction is present. This disorder can be caused by damage to the muscle layer (visceral myopathy) or the nerves (visceral neuropathy) that regulate gut movement. Systemic diseases like scleroderma can also cause intestinal failure by leading to the progressive degeneration of the intestinal muscle.
The lack of peristalsis causes intestinal stasis, meaning food and fluids sit for extended periods. This stagnation leads to severe symptoms like bloating, pain, and vomiting, and promotes the overgrowth of bacteria in the small intestine. This bacterial overgrowth further interferes with digestion and absorption, culminating in severe malabsorption and the requirement for intravenous nutritional support.