Labs and Imaging

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WBC

Anemia

Microcytic

Hypersegmented neutrophil, i.e. ≥ 5 lobes present. Pathological and histological images courtesy of Ed Uthman.

Hypersegmented neutrophil, i.e. ≥ 5 lobes present. Pathological and histological images courtesy of Ed Uthman.

Normocytic

  • Hemolytic

    • Adult: Autoimmune hemolytic disease

      • Patients age > 40 years

      • Pathophysiology: Cold-reactive antibodies formed in response to EBV or mycoplasma infections

    • Pediatric

      • DDX: Sickle cell disease, spherocytosis, G6PD deficiency

      • Obtain CBC, corrected reticulocyte index, peripheral blood smear, +/- hemoglobin electrophoresis

  • Non-Hemolytic

Macrocytic

  • Megaloblastic anemia (hypersegmented neutrophils): B12/Folate deficiency

  • Non-megaloblastic anemia (neutrophils with < 5 lobes)

Platelets

BMP/CMP

Individual Values

  • Sodium: Hyponatremia, hypernatremia

  • Potassium

    • Hypokalemia

      • Common etiologies: Vomiting, diarrhea, bulimia nervosa

      • Less common etiologies: Dialysis/plasmapheresis, VIPoma

      • Medication-induced: Diuretics, laxatives, insulin, albuterol

    • Hyperkalemia (consider if K+ > 5.5, start if > 6)

      • Calcium gluconate 1000 mg (10 mL of 10% solution)

      • Albuterol nebulizer q4-6 hours

      • Regular insulin 10 u in 500 mL 10% dextrose solution

      • Potassium binder: 8.4 g qd (onset of action = 7 hours)

      • Consider nephrology consult

  • Chloride

  • Bicarbonate

    • Low

      • Unstable: Obtain CBC, CMP, serum lactate, ABG, UDS and consider beta-hydroxybutyrate in setting of hyperglycemia

      • Stable: Obtain CBC, CMP serum albumin and calculate anion gap (Na − [Cl + HCO3]); see acid-base disturbances for further information

  • BUN and Creatinine

  • Glucose

  • Elevated serum protein: Consider serum protein electrophoresis

    • Hypogammaglobulinemia: Indicates immunodeficiency

      • Primary: Congenital (pediatric)

      • Secondary: Metabolic (renal disease, DM), loss in urine/stool, malignancy, immunosuppression (HIV, Rx)

    • Hypergammaglobulinemia

      • M-protein negative: Liver disease, autoimmune disease, chronic infection, malignancy

      • M-spike positive: MGUS (no lytic lesions), multiple myeloma (lytic lesions), Waldenström’s macroglobulinemia (monoclonal IgM, Bence-Jones protein)

  • Calcium: Hypocalcemia, hypercalcemia

  • Liver enzymes (acute elevation)

    • Review risk factors: Recent travel, alcohol use, IV drug use, sexual history, medications. Discontinue offending agents (e.g. statins).

    • Review of systems: Ischemia risk (e.g. CAD, mesenteric ischemia), coagulopathy risk (e.g. previous DVT/PE), abdominal pain, jaundice

    • Obtain: Hepatitis A Ab/IgM, HBSAg, anti-HBs, anti-HBc, albumin, bilirubin, alkaline phosphatase (+/- GGT), PT, PTT, INR

  • Vitamin deficiencies

Value Patterns

Urinalysis

Other

Imaging

Source: Colorectal Cancer Screening and Surveillance per AAFP. Memory device: Tubular adenomas &lt; 10 mm divided by 2 (or fewer) polyps = 5 years.

Source: Colorectal Cancer Screening and Surveillance per AAFP. Memory device: Tubular adenomas < 10 mm divided by 2 (or fewer) polyps = 5 years.