bronchi, and pleural surfaces. The bronchioles and bronchi in the areas of Þbrosis are often dilated and tortuous (traction bronchiolectasis and bronchiectasis). Parenchymal involvement is typically patchy on HRCT, with areas of normal and markedly abnormal lung often present in the same lobe. Other Þndings of UIP on HRCT include irregular thickening of interlobular septa and patchy areas of GGO. On HRCT, the overall extent of Þbrosis (reticulation and honeycombing) has been consistently shown to correlate with disease severity parameters on pulmonary function tests and prognosis [10]. Recently, the extent of honeycombing at baseline as well as its progression on sequential follow-up CT scan is demonstrated as an important prognostic determinant in patients of Þbrotic interstitial pneumonia, including UIP and Þbrotic NSIP [9].

CT–Pathology Comparisons

Histologically, UIP shows a variable degree of interstitial inßammation and Þbrosis [13]. As disease becomes more severe, alveoli are replaced by Þbrous tissue. Contraction of this tissue results in the dilatation of respiratory bronchioles and alveolar ducts, leading to the formation of honeycombing cysts. The intralobular lines reßect the presence of interstitial Þbrosis. Interlobular septal thickening reßects the presence of Þbrosis in the periphery of the secondary lobules and patchy areas of GGO reßects areas of inßammation or Þbrosis. Patchy parenchymal involvement on HRCT reßects histologic features of heterogeneous appearance in which areas of Þbrosis with scarring and honeycombing alternate with areas of less affected or normal parenchyma.

Patient Prognosis

Symptoms and Signs

Cough and dyspnea are the most common symptoms in patients with idiopathic NSIP [14]. The duration of respiratory symptoms is around 6 months, which is shorter than in IPF. Median age of NSIP is 52 years (range 26Ð73). Finger clubbing can be observed but is less frequent than in IPF.

CT Findings

The most common HRCT Þndings of NSIP consist of lower lobe, peripherally predominant, and GGO with reticular abnormality, traction bronchiectasis, and lower lobe volume loss [5]. Honeycombing and consolidation are relatively uncommon. The reported prevalence of honeycombing ranges from 0 to 44 % (Fig. 17.3). The HRCT pattern of NSIP may overlap with those of cryptogenic organizing pneumonia (COP), desquamative interstitial pneumonia, and UIP. The parenchymal abnormalities of NSIP, including reticular pattern, traction bronchiectasis, and GGO, may be reversible on follow-up exam. Although differentiation from UIP is very difÞcult, NSIP is characterized by lack of honeycombing, more GGO, and a Þner reticular pattern than UIP. Moreover, in NSIP, relative subpleural sparing [7] or distribution of reticulation along the central bronchovascular bundles is more frequently observed. On recent comparative study of NSIP and UIP at long-term follow-up, 28 % of patients with initial CT Þndings suggestive of NSIP progressed to features suggestive of IPF/UIP on follow-up CT scans [7].

CT–Pathology Comparisons

IPF is a chronic, progressive, irreversible, and usually fatal lung disease. There is no therapy proven to be effective [16]. Median survival has been reported to be 2Ð5 years. Lung transplantation remains the last therapeutic option.

Nonspecific Interstitial Pneumonia

Pathology and Pathogenesis

It is a uniform-appearing, cellular interstitial pneumonia characterized by a lymphoplasmacytic inÞltrate within the alveolar septa. Varying amounts of Þbrosis consisting predominantly of collagen are admixed with the chronic inßammation, and cases can be divided into cellular and Þbrotic variants. Patchy intra-alveolar macrophage accumulation and small foci of intraluminal Þbrosis resembling BOOP may occur but are always overshadowed by the more extensive interstitial pneumonia [17].

Areas of GGO with or without reticular abnormality or traction bronchiectasis on CT correspond histologically to the areas of interstitial thickening caused by varying degrees of interstitial inßammation or Þbrosis showing temporal uniformity [18]. The areas of consolidation are related to the areas of COP, foamy cell collections in alveolar spaces or foci of honeycombing in which the cystic spaces are Þlled with mucus.

Patient Prognosis

Prognosis of idiopathic NSIP is much better than IPF. The 5-year and 10-year survival of the patients with idiopathic NSIP has been reported to be 82.3 and 73.2 %, respectively [14]. Cellular NSIP shows a much better survival than Þbrotic NSIP. Corticosteroids with or without immunomodulatory drugs such as azathioprine and cyclophosphamide are the main drugs for the treatment.