**7. Evolution**

Fig 14: Chest X-ray showing a large cavity with a germinative layer in the Left Upper Lobe.

The hydatid cysts can grow more easily and faster in the lungs because of the elastic struc‐ ture of the lungs compared to the liver. For this reason, the growth rate of cysts in the lungs is estimated to be at least 5-fold higher than in the liver [12]. It has been noted that the per‐ centage of pulmonary cysts larger than 10 cm (huge cyst) is 21.9%-25% [13, 14]. We also not‐

Rarely, expectoration of the cystic fluid and germinative membrane may lead to spontane‐

**Figure 16.** CT scan of the chest showing an empty cavity with thin walls after complete evacuation of hydatid mem‐

The simultaneous involvement of the liver and lung is quite uncommon but when it occurs, the right lung is involved in 97% of the cases [15]. Transdiaphragmatic hydatid disease has

ed that huge pulmonary cysts occur more often in children than in adults.

ous healing of the residual cavity in some of the small cysts. (Fig 16)

Fig16: CT scan of the chest showing an empty cavity with thin walls after complete evacuation of

Figure 15: Mass with few air bubbles (arrows)

hydatid membrane

been very seldom reported. (Fig 17)

brane

**Figure 15.** Mass with few air bubbles

206 Principles and Practice of Cardiothoracic Surgery

During the natural course of infection, the fate of the hydatid cysts is variable. Some cysts may grow (average increase: 1–30 mm per year) and persist without noticeable change for many years. Others may spontaneously rupture or collapse and can completely disappear. Calcified cysts are not uncommon. Spillage of viable protoscoleces after spontaneous or traumatic cyst rupture, or during interventional procedures, may result in secondary echi‐ nococcosis.
