Case 19.3
Discussion Part 1 – Complications from Intestinal Failure
Complications from intestinal failure can be split into those from SBS and those from long-term TPN:
- Short bowel syndrome complications – These depend on the underlying etiology and anatomy.
- The most obvious of complications are dehydration, malnutrition, and low body weight. These can lead to difficulty concentrating, confusion, somnolence, and weakness. In children and young adults, they may experience impaired growth and development.
- Small intestinal bacterial overgrowth (SIBO) is common and can lead to perturbations in carbohydrate and fatty acid metabolism. Vitamin and micronutrient deficiencies can result, and patients may be at high risk of infection and poor wound healing related to deficiencies in vitamins A and C, zinc, copper, and selenium.
- Bile salt deficiency can occur when > 100 cm of the ileum are removed, leading to deficiencies in fat soluble vitamins, increasing the risk of osteoporosis.
- Those who have a colon in continuity are at risk of D-lactic acidosis. This occurs after ingestion of a large carbohydrate load which is metabolized to D-lactic acid by colon microbiota and absorbed systemically. D-lactate can build up and cause metabolic acidosis with encephalopathy. Traditional lactate assays measure L-lactic acid, therefore lactate might be normal on labs. Note that levels of D-lactate do not always correlate with degree of clinical symptoms therefore symptoms may be related to a different substance absorbed with D-lactate.
- TPN complications –These can be related to the catheter, or to the TPN itself.
- Catheter related infections are responsible for the majority of morbidity and hospitalizations in SBS patients. Stringent catheter hygiene including ethanol or antibiotic infused locks can reduce infections. Catheter occlusion and venous thrombosis are common, leading to complete loss of vascular access. Both of these complications can be indications for intestinal transplant.
- Hepatobiliary complications are common. The incidence of abnormal liver chemistries in this population is high at 99%, however only about 4% develop severe liver dysfunction, and death due to liver complications is ~2.6%.
- Gallstones and cholestatic liver disease result from cholestasis which is more likely to occur in patients who do not take in any enteral nutrition, and in those whose TPN is continuous over 24-hours. Encouraging enteral nutrition intake and changing the TPN to cycled feeds (over 8-12 hours may help). Cholestasis can lead to parenteral nutrition associated liver disease (PNALD). If not addressed, over time, this can lead to liver fibrosis and cirrhosis. Hepatic steatosis may also contribute to PNALD.
- In addition to lack of enteral nutrition and continuous feeding, PNALD might be due to overfeeding (excess calories in TPN), excess fat and carbohydrate calories, and omega-6 fatty acids, which can promote inflammation and are found in soybean-based lipid formulations. PNALD might be addressed by cycling TPN as above, reducing total calories, altering fat and carbohydrate, and content in the TPN, and changing the lipid formulation to one derived from omega-3 fatty acids (fish oil) or one derived from a combination of sources. It is important to monitor for essential fatty acid deficiency (EFAD) particularly when reducing lipid content. This can result in dry scaly skin, and poor wound healing, and is managed by increasing the lipid content in the TPN. Essential fatty acid profiles should be checked regularly, and an elevated triene:tetraene ratio should raise suspicion for EFAD.
- Nutrient toxicities are also possible, and in particular patients are at risk of hyperoxaluria and nephroliathiasis. Those with a colon in continuity are at risk. It is recommended to limit oxalate intake and increase Ca++ in those with colon present and > 100 cm ileum resected.