Intra-abdominal pathology may have distant effects on the pulmonary vascular bed, the pulmonary parenchyma, or the pleural space. This chapter reviews the pulmonary complications of intra-abdominal disease, focusing on the pathology, epidemiology, clinical features, and management. Topics are organized according to the primary abdominal organ system in which the disease is centered.
PULMONARY COMPLICATIONS OF HEPATIC DISEASE
A number of respiratory complications of hepatic disease are well recognized, including portopulmonary hypertension (POPH), hepatopulmonary syndrome (HPS), hepatic hydrothorax (HH), and spontaneous bacterial empyema (SBEM). Each is discussed in the subsequent sections.
POPH is defined as pulmonary arterial hypertension (PAH) occurring in the setting of liver disease, or more specifically, in the setting of portal hypertension.
Epidemiology and Pathogenesis
Approximately 2% to 6% of patients with decompensated liver disease develop POPH.1–3 Based on multicenter, case-control studies, autoimmune hepatitis and female sex are identified risk factors for the development of POPH; therefore, the role of hormonal and immunologic influences in the pathogenesis of POPH is a focus of investigation.4,5
Patients with POPH have measurable alterations in levels of pulmonary vasoactive substances. For example, prostacyclin is a potent pulmonary vasodilator that also has antithrombotic and antiproliferative properties; levels of prostacyclin are decreased in the lungs of patients with PH. In patients with POPH, loss of endothelial prostacyclin synthase expression compared with normal controls has been demonstrated.6 Endothelin 1 (ET-1), a pro-proliferative and vasoconstrictive agent implicated in the pathophysiology of other types of PH, has also been shown to be increased in the circulation of patients with POPH.7 Bone morphogenetic protein 9 (BMP9), an endothelial quiescence factor produced in the liver, is a sensitive, specific, and prognostic biomarker of POPH. Circulating levels of BMP9 are reduced in POPH as well as HPS.8,9
Histologically, POPH appears to be very similar to other types of PH. POPH is a precapillary pulmonary arteriopathy involving multiple layers of the vessel; specifically, POPH is characterized by smooth muscle hypertrophy, adventitial proliferation, and endothelial cell proliferation. In addition, the plexiform lesions characteristic of other types of PH have been demonstrated in patients with POPH (Fig. 97-1).10
Autopsy specimen from a 55-year-old female with cryptogenic cirrhosis and portopulmonary hypertension, showing the plexiform lesion common in pulmonary arterial hypertension. The arrows show acute platelet-fibrin thrombi within the plexiform lesion. (Reproduced with permission from Krowka MJ, Edwards WD. A spectrum of pulmonary vascular pathology in portopulmonary hypertension. Liver Transpl. 2000;6(2):241–242.)
The microvascular changes in POPH result in a pulmonary circulation characterized by increased resistance and low capacitance—the antithesis of the normal pulmonary vascular physiology, which is characterized by a low-pressure and high-flow state. ...