Causes of Vitamin B12 Deficiency - Cobalamin Decreased Intake Pancreas: Insufficiency Intestine: SIBO, Celiac disease, IBD, Lymphoma, Amyloidosis, Resection, D. latum Stomach: Pernicious anemia, Bypass/gastrectomy, H. pylori infection, B12 malabsorption, Gastritis Other: Medications (PPI, H2 blockers, metformin), Genetic - BWH Medicine Chiefs @BrighamChiefs #Vitamin #B12 #Deficiency #Cobalamin #differential #diagnosis #causes

Approach to Thyroid Function Tests in the Evaluation of Hyperthyroidism • Low TSH, Low normal T4 → Possibly Central Hypothyroidism. unlikely subclinical hyperthyroidism. • Low TSH, normal T4 +/- T3 → Subclinical Hyperthyroidism: Work-up similar to hyperthyroidism as below. Can repeat labs 6 weeks after the resolution of pregnancy, critical illness, and dopamine agonists/octreotide. • Low TSH, high T4 +/- T3 → Primary Hyperthyroidism → Signs of symmetrically enlarged thyroid & ophthalmopathy → Graves' Disease → Confirm with TRAb → Radioactive Iodine Uptake & Scan • High or normal TSH, high T4 +/- T3 → Central (secondary) Hyperthyroidism → MRI Pituitary - Dr. Claire Brickson @crbricks #Hyperthyroidism #algorithm #diagnosis #endocrinology #TFTs #TSH #Interpretation

Pathophysiology of The Nephron - Electrolyte and Water Exchange The nephron — electrolyte and water exchange. 180 L of water and 26000 mmol of sodium per day enter the nephrons via the afferent arterioles to the kidneys. Removal or addition of electrolytes results in the excretion of approximately I L of water and 60—180 mmol of sodium per day. #Pathophysiology #Nephrology #Nephron #Electrolytes #Reabsorption

General approach to AKI - Checklist Urine electrolytes & FENa - Previously, it was believed that urine sodium excretion and fractional excretion of sodium (FENa) could help differentiate between pre-renal and intrinsic renal failure. However, more recent research has shown that FENa performs poorly. Urine eosinophils - This has poor performance for diagnosing acute tubular interstitial nephritis. - Dr. Josh Farkas @PulmCrit #AKI #Checklist #AcuteKidneyInjury #Nephrology #CriticalCare

Colonic Thumbprint Sign on Abdominal XRay - Differential Diagnosis: • inflammatory bowel disease: UC and CD • infection (e.g. pseudomembranous colitis) • bowel ischemia • diverticulitis mucosal/submucosal • hemorrhage • lymphoma • amyloid • typhlitis #Colon #Thumbprint #Sign #Differential #Diagnosis #radiology #KUB #Abdominal #XRay