Table 2.
Specific aspects of organ fibrosis
| Kidney | Liver | Heart | Lung | Skin | |
|---|---|---|---|---|---|
| Top 3 etiologies | Diabetes mellitus | Viral hepatitis | Hypertension | Idiopathic pulmonary fibrosis (IPF) | Physical injury |
| Hypertension | Alcohol-induced | Coronary artery disease | Occupational diseases | Idiopathic scleroderma | |
| Glomerulonephritis | Nonalcoholic-steatohepatitis (NASH) | Aortic stenosis | Sarcoidosis | ||
| Epidemiology | Prevalence of chronic kidney disease ≈5% of general population (US) | Prevalence of liver cirrhosis: ≈ 5–10% of general population | Prevalence of diastolic heart failure ≈ 1% of the general population | Prevalence 0.03% of general population | Prevalence of hypertrophic scars ≤75% upon physical trauma |
| Prevalence of end-stage renal disease ≈0.2% of general population | Prevalence of systemic scleroderma ≈ 0.02% of general population | ||||
| Diagnosis | Blood tests to assess excretory kidney function (serum creatinine, BUN, GFR) | Blood tests to assess global liver function | Functional assessment of diastolic dysfunction through Doppler echocardiography or invasive measurements (i.e., LVEDP ) | Imaging (HRCT scan, chest X-ray) | Location (association with prior lesion) |
| Kidney biopsy | Imaging (FibroScan, ARFI, MRI) | Spirometry (restriction and impaired gas exchange) | Appearance (i.e., pigmentation, aesthetics) | ||
| Liver biopsy | Lung biopsy | Stiffness, elasticity skin thickness (SScl) | |||
| Relevant classifications of fibrosis | Area of kidney cortex occupied by fibrotic tissue (rel. %), glomeruli viewed as separate entity (glomerulosclerosis) | Distinction between fibrosis (early) and cirrhosis | Distinction between endomyocardial and perivascular fibrosis | Radiographic location and appearance (central vs. peripheral; upper lobes vs. lower lobes) | Adequate scar vs. hypertrophic scar vs. keloid |
| Grading for inflammatory activity | Local vs. systemic scleroderma | ||||
| Clinical reports of regression of established fibrosis | Regression of fibrosis in patients with diabetic nephropathy 10 yr after pancreas transplantation (31, 32) | Liver fibrosis regresses upon removal of the pathogen (21, 30, 49, 65, 105, 106) | Sporadic reports of improved diastolic dysfunction and regression of cardiac fibrosis in patients with hypertensive heart disease upon blood pressure normalization (13) | Case reports of pulmonary fibrosis regression upon treatment or removal of underlying pathogens | Hypertrophic scars regress regularly, only sporadic reports of keloid regression |
| Sporadic reports of improved kidney function upon intensified ACE inhibitor therapy (103) | Reports of regression of cirrhosis are debated (28, 52, 90) | ||||
| Unique features | Kidney fibrosis causes anemia due to cessation of erythropoietin production when renal fibroblasts become activated | Stellate cells contribute to liver fibrosis | Because cardiac fibroblasts are required for electromechanic coupling, fibrosis can cause atrial fibrillation | Mean time of survival of patients with IPF is <6 yr | Association of skin color and keloid formation (none in albinos, highest incidence in African population) |
| Microvascular shunts are detrimental, because they cause porto-venous hypertension |
ACE, angiotensin-converting enzyme; ARFI, acoustic radiation force impulse imaging; BUN, blood urea nitrogen; GFR, glomerular filtration rate; HRCT, high-resolution computed tomography; LVEDP, left ventricular end diastolic pressure.