Rod Robertson. Jan, 2001.Radiology of cystic fibrosis [online]. Leeds University Teaching Hospitals, Leeds, UK. Available from http://www.cysticfibrosismedicine.com

The cardinal features of this disease are those of emphysema, peribronchial thickening and bronchiectasis, lung infiltration and enlarged hila. The enlargement of the hila is due to both adenopathy and in later stages enlargement of the pulmonary arteries as pulmonary hypertension occurs. The bronchial disease often starts with peribronchial thickening and tubular bronchiectasis, but later more characteristically cystic bronchiectasis occurs. The focal infiltration may be nodular or linear, and some of the nodular change is due to mucus plugging of peripheral bronchi. This mucus plugging may cause lung atelectasis. Other lung infiltration occurs when there is super added infection and chest x-rays should be monitored for change. Two complications that occur include pneumothorax and pulmonary hemorrhage. Chest x-ray-Adult patient with cystic fibrosis and significant lung disease.

A number of scoring systems have been developed to monitor chest x-ray changes. In the UK, the Chrispin-Norman score has been used most frequently. This measures the overall chest configuration with hyperinflation, a bowed sternum and kyphosis all being measured as part of this. The chest is then split into quadrants and the quadrants are each measured for lines, nodules (mottling), rings and consolidation. For each of these features a score of 0, 1 or 2 is given for each quadrant with a maximum score of 32. Added to this is a score for each of the features of chest configuration again on a 0 to 2 scale, giving it a potential total score of 38. In the USA, the Brasfield score was used predominantly (Brasfield D; 1980). The scores have not achieved widespread acceptance partly because an individual score does not necessarily correlate with the patient's condition. Also in the scores there is a significant variability, and one study showed there was a 20% variability in the Brasfield score when repeated (Sawyer; 1994).

CT has given further detail of the lung changes. Much of this has confirmed the plain film findings. A recent study by Helbich et al (Helbich ;1999) looked at CT findings in 117 patients and split them into different age groups. They confirm that bronchiectasis was the predominant feature with peribronchial thickening also present in the majority of patients. Mosaic perfusion due to lung hyperinflation was very frequent and mucus plugging was seen in half the patients. Unsurprisingly the number and degree of CT findings increased with older age groups. They found that overall CT scores correlated with pulmonary function tests and clinical scores. Another study by Mason et al (Mason; 1999) confirmed that in adults bronchiectasis was present in virtually all lobes, but the severity of bronchial dilatation was greatest in the upper lobes. In a different study by Helbich et al (Helbich; 1995) they found little change in the morphological features in the chest if a scan was repeated within 18 months. It is fairly common practise to obtain CT scans in cystic fibrosis patients prior to lung transplantation. A study by Maron et al (Maron; 1999) questions the utility of this. They evaluated 56 patients. 7 had discrete nodules, and of those who were transplanted, all were found to be due to mucoid impaction. 5 of the patients were thought to have a possible mycetoma on CT, but none were found in those transplanted. Finally, chest x-ray was better than CT at predicting pleural disease and the overall conclusion was that HRCT was of little value in pre-transplant work up. The most interesting feature of this study is the over calling of mycetoma and the cause of the lung nodules.

Whilst the cause of death is usually related to the pulmonary problems, the features below the diaphragm should also be remembered. Cirrhosis and portal hypertension are common and can be followed with ultrasound and doppler studies as well as CT and MR. The pancreas is replaced by fat occurring most often in older patients and a degree of replacement correlates with pancreatic exocrine function but not endocrine function. This is best seen with CT.

Further radiology may be required for pulmonary complications such as haemoptysis when bronchial arteriography and embolisation can provide both diagnosis and potential cure. The haemoptysis however often recurrs after many months or years as other collaterals open up to supply the bronchial arteries and further arteriographic studies and emoblisation may be required. Post transplant, CT scanning is useful for monitoring complications. Obliterative broncholitis is the complication most commonly sought. This is manifest by areas of low attenuation in the lung with reduced vascular pattern, usually with some bronchiectasis. These features are accentuated on expiratory scanning when there is clear evidence of air trapping.

References

Brasfield D American Journal of Roengtology 134(6):1195-8 June 1980

Sawyer et al Thorax 49(9):860-2 September 1994

Helbich et al Radiology 213(2):537-544 November 1999

Mason et al Clinical Radiology 54(8):507-12 August 1999

Helbich et al American Journal of Radiology 173(1):81-88 July 1999

Maron et al Radiology 213(1): 283-288 October 1999

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