The fibrotic form is typically characterized by irregular linear opacities/coarse reticulations, traction bronchiectasis, and honeycombing, patchy ground-glass attenuation, centrilobular nodules, and mosaic attenuation. Three-density pattern (head cheese sign) is radiological sign which shows a region of the lung with three or more different types of attenuation which can be typical for the fibrotic type. Histopathology
The acute form can be characterized by poorly formed noncaseating interstitial granulomas and mononuclear cell infiltration in a peribronchial distribution with prominent giant cells. The subacute, or intermittent, form produces more well-formed noncaseating granulomas, bronchiolitis with or without organizing pneumonia, and interstitial fibrosis. Much like the pathogenesis of idiopathic pulmonary fibrosis (IPF), chronic HP is related to increased expression of Fas antigen and Fas ligand, leading to increased epithelial apoptosis activation in the alveoli. Cholesterol clefts or asteroid bodies are present within or outside granulomas. Pulmonary Function Testing
Pulmonary function tests (PFTs) can generally reveal a restrictive pattern  however, either a restrictive or obstructive pattern (or both) may emerge on PFTs. PFTs, therefore, are less useful in making a diagnosis but rather tracking improvement or deterioration in lung function following removal or addition of suspected antigens. They may also demonstrate reduced diffusion capacity of lungs for carbon monoxide (DLCO). Bronchoscopy
Bronchoalveolar lavage (BAL) is a reliable way to detect inflammation in the lung airways. Fluid analysis from the lavage extracted from the airways on bronchoscopy often reveals a total elevation in cell count in addition to an elevation in the percentage of T lymphocytes.
Distal to the superior and extensor retinacula of the foot it becomes the dorsal artery of the foot. The posterior tibial forms a direct continuation of the popliteal artery which enters the flexor compartment of the lower leg to descend behind the medial malleolus where it divides into the medial and lateral plantar arteries, of which the posterior branch gives rise to the fibular artery.For practical reasons the lower limb is subdivided into somewhat arbitrary regions: The regions of the hip are all located in the thigh: anteriorly, the subinguinal region is bounded by the inguinal ligament, the sartorius, and the pectineus and forms part of the femoral triangle which extends distally to the adductor longus. Posteriorly, the gluteal region corresponds to the gluteus maximus. The anterior region of the thigh extends distally from the femoral triangle to the region of the knee and laterally to the tensor fasciae latae. The posterior region ends distally before the popliteal fossa. The anterior and posterior regions of the knee extend from the proximal regions down to the level of the tuberosity of the tibia. In the lower leg the anterior and posterior regions extend down to the malleoli. Behind the malleoli are the lateral and medial retromalleolar regions and behind these is the region of the heel. Finally, the foot is subdivided into a dorsal region superiorly and a plantar region inferiorly. Veins
The veins are subdivided into three systems. The deep veins return approximately 85 percent of the blood and the superficial veins approximately 15 percent.