Diagnostic radiology

Chest

Views

See: Chest radiograph#Views

PA (posterior => anterior): typically performed on ambulatory adults

Least amount of magnification (and scattering) for the heart

AP (anterior => posterior) typically performed on pediatric patients OR patients who are weak, unresponsive, very sick, bed-confined, etc.

X-ray beam is scattered by the heart closer to the source and further away from the detector (enlarged cardiac silhouette)

Systematic approach: ABCDs

Airway: Trachea, mediastinal width, aortic knob (do not miss: tracheal deviation)
Breathing: Lung field outlines, (a)symmetry, pleural space (do not miss: pneumothorax)
Circulation: Heart size on PA film, heart borders, heart shape
Diaphragm: Hemidiaphragm levels, costophrenic angles, diaphragm contour lines (do not miss pneumoperitoneum)

RIPE: Rotation, Inspiration, Picture, Exposure
Soft tissues / skeleton: Breast tissue, calcification, bones

Birth defects

Radiation dosing

Abdomen

Pancreatic cancer (90% of cases are pancreatic adenocarcinoma)

Pt is often asymptomatic. Signs and symptoms show up late in the disease process:

Courvoisier's law (" a painless palpably enlarged gallbladder accompanied with mild jaundice is unlikely to be caused by gallstones")
Epigastric pain radiating to the back
Painless obstructive jaundice
recent onset of type 2 diabetes
Dilatation of pancreatic duct and intrahepatic biliary ducts (due to compressive obstruction / mass effect)
Pruritus (from bile salts entering the bloodstream causing elevated serum bilirubin)

Radiologic markers of Whipple procedure / Pancreaticoduodenectomy

Pathology and histology

Cellular pathophysiology

Cell death type (high yield)

Apoptosis
Coagulative necrosis most common
Liquefactive necrosis second most common/significant (on exams)

Systems and syndromes

Widespread necrosis in the central venule regions of the liver acinus

Mostly viable hepatocytes in the portal area (zone 1) of the liver acinus, with arrows pointing to a necrotic zone on the edge

These H&E pathology slides were taken from an acetaminophen poisoning case involving an adult with a history of alcohol abuse. Case contributed by Dr. Linda Ferrell, UCSF, Department of Pathology.

Endocrine

Adrenal crisis and adrenal cortical atrophy due to withdrawal from exogenous glucocorticoids (e.g. lecture case due to stomach virus / vomiting causing unintentional drug withdrawal)

Gross pathology: Cortex in case is much thinner than medulla cf. normal/healthy adrenal gland
Histology: Cells in the zona fasciculata lack lipid droplets, empty voids due to shrinking of cell volumes

Liver

Mallory hyaline (Mallory body) associated with alcoholic liver disease
Histology of paracetamol poisoning: coagulative necrosis around zone 3 of the liver acinus (liver lobule) around central venule

Remember to review and add Case 3, Slide 35 (Introduction to Pathology - Part 2 (Interactive Workshop) / Cellular Alterations and Circulation - Clinico-Pathological Correlation, Dr. Lto, Friday Nov 17), to class Anki deck for this lecture ; H&E slide taken from Robbins Pathology of Disease
Features of well-developed coagulative necrosis visible on pathologic specimens around 24 hour hours of death of cells
Architecture of tissue is retained (initially), cytoplasm is hypereosinophilic, cells are anucleate
Biochemistry: CYP3A4 and CYP2E1 metabolism of paracetamol to NAPQI (oxidant), antidote is N-acetylcysteine

Distinguish perisinusoidal space v. liver sinusoid on histology slides

Biochemistry

Lipid transport

PCSK9 - LDL transporter recycling

Vitamins and cofactors

Ascorbic acid (impact of deficiency => scurvy and bone defects)

Collagen biosynthesis

prolyl hydroxylase
lysyl hydroxylase (clarify ascorbic acid's role in lysyl oxidase)

Norepinephrine biosynthesis via dopamine beta-hydroxylase
Tyrosine catabolism (hydroxylation of Homogentisic acid)
Carnitine biosynthesis via lysyl hydroxylase

Post-translational modification of specific peptide hormones (hydroxylation of C-terminal glycine to amide terminus)
Iron absorption (reduction of poorly-soluble ferric ion to better-soluble ferrous ion)

(cf. anemia due to hepcidin)

Stabilizes tetrahydrobiopterin in its reduced form
Stimulates osteoblast activity over osteoclast activity
Tetrahydrobiopterin
Thiamine (B1) (deficiency => beriberi)

Carried into the mitochondria via Mitochondrial thiamine pyrophosphate carrier (SLC25A19)
Required for pyruvate dehydrogenase activity to form acetyl CoA

Impaired biosynthesis of acetylcholine (from choline and acetyl-CoA)

"What metabolites in serum and urine can be used to differentiate between a folate deficiency and a vitamin B12 deficiency? What information is revealed by the Schilling test and modified Schilling test?"

Immune markers and cytokines to memorize (please finish/organize by Dec 10)

Pathogen-associated molecular patterns

Lipopolysaccharide (LPS) on gram-negative bacteria

Clusters of differentiation (diagnostic / immunohistological)

CD3: T-cell co-receptor for the T-cell receptor (TCR), ubiquitously expressed by pro-thymocyte precursors to all T-cells, and differentiated T-cells. Required for T-cell activation

Section CD3 (immunology)#immunohistochemistry: "The pro-thymocytes differentiate into common thymocytes, and then into medullary thymocytes, and it is at this latter stage that CD3 antigen begins to migrate to the cell membrane. The antigen is found bound to the membranes of all mature T-cells, and in virtually no other cell type... The antigen remains present in almost all T-cell lymphomas and leukaemias, and can therefore be used to distinguish them from superficially similar B-cell and myeloid neoplasms." ^[1]

CD4: TCR co-receptor, required for activation of helper T-cells, specific for MHC Class II antigens
CD8: TCR co-receptor, required for activation of cytotoxic T-cells, specific for MHC Class I antigens, also found on dendritic cells and natural killer (NK) cells.
CD14: Coreceptor expressed by all macrophages, binds to LPS
CD15: Important for leukocyte tethering and rolling. Constitutively expressed by all granulocytes, but not in unactivated (resting) lymphocytes
CD19 (B-Lymphocyte Surface Antigen B4): present on all B cells
CD34: ubiquitous (but not exclusive to) marrow-bound hematopoietic stem cells
CD45 (single-pass membrane protein expressed by all differentiated hematopoetic cells (except erythrocytes and some plasma B cells)

T regulatory cells (which suppress immune response) express FOXP3, CD3, CD4, CD25 and secrete IL-10 which suppresses immune response
V(D)J recombination: pro-B cells will express CD19 and CD20