Parenteral Nutrition-Related Bone Diseases

Introduction

Individuals with certain health conditions cannot eat food like normal individuals and need their food delivered to their bodies through tubes. This can be delivered directly into the stomach or one’s small intestine (enteral nutrition). However, parenteral nutrition is a process by which food and nutrition are given from outside to the individual through one’s veins and skipping the entire digestive tract.

What Are the Types of Parenteral Nutrition?

Parenteral nutrition consists mainly of carbohydrates, fats, water, protein, vitamins, and minerals in varying proportions customized to one’s requirements. Parenteral nutrition can be of two types: partial parenteral nutrition and total parenteral nutrition.

• Partial Parenteral Nutrition (PPN) - This is done as an additional nutritional supplement.

• Total Parenteral Nutrition (TPN) - This is done for individuals who are unable to utilize their digestive system for processing ingested food due to a disease or following a healing period post-injury or surgery.

Who Can Benefit From Parenteral Nutrition?

Parenteral nutrition can benefit individuals who are unable to meet the nutritional requirements of the body. Some conditions where parenteral nutrition can be beneficial are as follows:

• Gastrointestinal disorders such as inflammatory bowel syndrome (inflammation of the lining of the intestines).

• Small intestine disorders.

• Presence of fistula (abnormal connection) in the intestines.

• Individuals with cancer and who are receiving treatment for the same.

• Individuals with severe malnutrition.

What Are the Risks of Parenteral Nutrition?

Compared to other routes of nutritional administration, parenteral nutrition is considered to have a higher risk of complications. The risks involved include:

• Infection can enter the bloodstream through the catheter used for parenteral nutrition.

• Formation of blood clots at the catheter site.

• Atrophy of the gastrointestinal tract may occur if parenteral nutrition is used for a prolonged period of time.

• Imbalances in blood sugar, electrolytes, and fluids.

• Fluid retention can cause swelling (edema).

• Liver and gallbladder dysfunction.

• Bone demineralization and metabolic bone disease may occur.

What Are the Bone Diseases Caused by Parenteral Nutrition?

Bone undergoes a constant change in the human body with simultaneous bone resorption and bone formation. This process is necessary for bone health. Osteoporosis and osteomalacia are the two common metabolic bone diseases (abnormal bone formation and resorption) that can occur in individuals following prolonged parenteral nutrition. Osteoporosis is characterized by an overall reduction in bone quantity while maintaining a normal proportion between the bone mineral content and the bone matrix. Osteomalacia is characterized by inadequate calcification of the bone matrix leading to softening of the bone.

What Are the Causes of Parenteral Nutrition Bone Diseases?

The exact cause of bone diseases in these individuals is not known. However, multiple factors such as side effects of prolonged steroid (Corticosteroid) medications, the presence of underlying diseases such as cancer, liver diseases, or kidney diseases, sedentary life, or deficiencies or imbalances of essential nutrients such as vitamin D, amino acids, calcium, and phosphorus in the parenteral nutrition formula are believed to be associated with parenteral nutritional bone diseases.

What Are the Symptoms of Parental Nutrition Bone Disease?

The bone disease symptoms associated with parenteral nutrition may include:

• Persistent or recurring pain of varying intensity in the bones, joints, or muscles.

• Weak and soft bones are more susceptible to fracture.

• Reduction of up to one centimeter in height for individuals every ten years.

• Bone deformities such as curvature of the spine, bowing of the legs, or other structural deformities.

• Muscle spasms.

How to Diagnose Parenteral Nutritional Bone Disease?

Both blood tests and imaging tests can help with the diagnosis of parenteral nutritional bone diseases. The tests include:

• Blood Tests - Blood tests are done to assess the amount of vitamin D and minerals like calcium and phosphorus in the blood.

• Dual-energy X-ray Absorptiometry (DEXA) - DEXA scan is used to measure the bone’s mineral density and can help assess the fragility of bone. DEXA uses minimal radiation and minimal time and is highly accurate compared to traditional X-rays. This test measures a particular segment of the bone which is usually the hip, spine, or occasionally the forearm.

• Bone Biopsy - Bone biopsy can help determine if the bone demineralization is due to increased bone resorption activity or a decreased bone deposition activity. However, this is an expensive and invasive procedure and may not be advised unless necessary.

• Biomarkers for Bone Mineralization - The presence of certain biomarkers in the blood, such as bone-specific alkaline phosphatase (BALP), osteocalcin, procollagen type I N-terminal propeptide (PINP), serum calcium and phosphate, 25-hydroxyvitamin D, and fibroblast growth factor 23 (FGF23) help evaluate bone formation, turnover, and mineral levels.

How to Manage Parenteral Nutrition Bone Diseases?

Individuals receiving parenteral nutrition must be routinely monitored to assess any changes in the bone indicative of bone diseases. Some of the measures to follow are as follows:

• Check for any physical signs such as physical pain, loss of height, or bowing of legs indicative of bone diseases.

• Ensure appropriate amounts of minerals such as calcium, phosphorus, and magnesium are in the parenteral nutritional solution that is generally required for bone remodeling.

• Once the individual has improved nutritional status, the protein dose in the parenteral nutritional solution needs to be adjusted to a minimum of one gram per kilogram per day.

• If an individual shows signs of metabolic acidosis, then the parenteral nutritional solution needs to be adjusted with the required amount of acetate to avoid further loss of calcium from the bones.

• Monitor the blood levels of calcium, magnesium, phosphorus, and acetate at least on a monthly basis in order to adjust the parenteral nutritional solution accordingly, if needed.

• Every six or twelve months, calcium and magnesium assessment in a 24-hour urine test is recommended.

• Repeat bone density scan and DEXA scan yearly or every two years to assess any progression of the disease or effectiveness of the treatment.

• Minimize the use of steroidal medications since they are known to cause bone diseases when used for a prolonged period of time.

• Avoid smoking and alcohol consumption when on parenteral nutritional feeding.

• If possible, engage in regular exercise to keep the bones and body active.

Conclusion

As beneficial as parenteral nutrition is for individuals, using it for prolonged periods comes with long-term side effects. With proper management and monitoring, positive outcomes can be achieved in parenteral nutrition-related bone disease. Doctors need to closely monitor the individuals and make the necessary adjustments at the first sign of bone demineralization.