Nonrespiratory aspects of cystic fibrosis

Nutrition

Gastrointestinal health

Cystic fibrosis–related diabetes (CFRD)

Sexual and reproductive health

Bone health

Kidney disease

Hearing

Mental health

Good nutrition is associated with better growth rates and respiratory outcomes.

Weight, weight percentile and BMI are used as an indication of nutritional adequacy.

Most patients with CF have pancreatic exocrine insufficiency, requiring pancreatic enzyme replacement therapy (PERT).

To maintain nutritional status, patients with CF may also require:

• specialist dietary advice
• 110 to 200% of the daily energy requirements of the general population
• supplementation with fat soluble vitamins (A, D, E and K) and salt
• other nutritional supplements or enteral feeding, if the above are insufficient
• CFTR modulator therapy to improve gastrointestinal function.

Gastrointestinal health in patients with CF is best managed by a multidisciplinary team (including dieticians and gastroenterologists with experience in CF) at a specialist CF centre.

Consider the following in patients with CF:

• general bowel problems (eg abdominal bloating and pain, diarrhoea, constipation, bowel obstruction) are common
• the risk of bowel cancer is increased; screening with colonoscopy usually begins at 40 years of age, with ongoing frequency determined by initial results
• distal intestinal obstruction syndrome (meconium ileus in infants) can occur, caused by impacted viscid faecal material in the small bowel; this requires urgent discussion with the specialist CF centre
• mild increases in liver enzymes (particularly alkaline phosphatase) are common, but advanced liver disease is uncommon
• cholelithiasis can occur; ursodeoxycholic acid can be used to rebalance the constituents of the bile salts
• infrequently, and mainly in children, biliary fibrosis results in biliary cirrhosis, portal hypertension, gastro-oesophageal varices, splenomegaly, ascites, hepatopulmonary syndrome, portopulmonary hypertension and hepatic encephalopathy; specialist treatment is required.

Occurrence of CFRD increases with age, affecting approximately 10% of adolescents and over 40% of adults older than 40 years.

Diagnosis and management of CFRD differs from Type I and Type 2 diabetes as follows:

• classic symptoms of hyperglycaemia (eg polyuria and polydipsia) are uncommon at diagnosis; patients may present only with an unexplained loss of lung function or weight
• glycated haemoglobin (HbA1c) is used to monitor patients with CFRD, but is not a sensitive screening tool to detect CFRD; screening with an annual oral glucose tolerance test is recommended
• insulin is usually the first-line therapy, rather than oral antihyperglycaemic drugs
• a high-calorie diet (including fats and carbohydrates), with maintenance of blood glucose control using insulin, is encouraged (as opposed to the dietary restrictions recommended for patients with Type 1 and Type 2 diabetes).

Good control of CFRD is essential to maintaining kidney health.

Diabetic ketoacidosis is well described but rare.

Discussions about sexual and reproductive health are as important for patients with CF as for any other person.

Give adolescents the opportunity to be seen without their parents or carers present.

Delayed puberty is more common in patients with CF; referral to an endocrinologist may be required.

For males with CF, sexual and reproductive considerations include:

• 98% of males with CF have azoospermia
• recovery of sperm from the testis to allow assisted reproduction is often possible.

For females with CF, sexual and reproductive considerations include:

• most females with CF are fertile, and around 85% are able to conceive naturally
• standard advice about contraception, including the oral contraceptive pill, applies
• management of pregnancy requires multidisciplinary specialist involvement; collaboration between the obstetric service and the specialist CF centre is essential
• pregnancy is not typically associated with a worsening of respiratory status
• the risk of premature birth is increased
• in vitro fertilisation can be considered, and allows implantation of a fertilised ovum that is not homozygous for CF.

Patients with CF have an increased risk of osteoporosis and osteopenia.

Multiple factors can contribute to low BMD, including less accrual of bone mass during childhood and adolescence.

BMD screening every 1 to 2 years (arranged by the specialist CF centre) usually begins around the age of puberty.

In addition to standard treatment of low BMD (eg nutrition, exercise, vitamin D and calcium supplementation, bisphosphonates), management of bone health in patients with CF may also include:

• limiting progression of chronic suppurative lung disease
• vitamin K supplementation
• recognising and treating delayed puberty.

The incidence of kidney dysfunction in patients with CF increases with age; the incidence is increasing with the increase in life expectancy of patients with CF.

Estimated creatinine clearance rate is not a sensitive test of kidney function in patients with CF.

Causes of kidney dysfunction in CF include antibiotics (particularly aminoglycosides and vancomycin), CFRD, renal calculi, and calcineurin drugs (used after lung transplant); less common causes include amyloid nephropathy, drug-related interstitial nephritis and renal tubular necrosis.

Strategies to reduce exposure of the kidneys to nephrotoxic antibiotics include using inhaled rather than oral antibiotics, and close monitoring of intravenous antibiotics to avoid toxic concentrations.

Good control of CFRD is essential to maintaining kidney health.

Patients with CF exposed to repeated doses of aminoglycosides are at a higher risk of hearing loss; monitoring for hearing loss is required.

CF is associated with an increased incidence of anxiety and depression in both patients, and parents or carers.

Be alert to signs and symptoms of anxiety and depression in patients with CF and their parents or carers; see Anxiety and Depression for more information.

Treatment is usually guided by the multidisciplinary specialist CF centre, which includes mental health professionals.