Case study tutorials on clinical chemistry Flashcards
Case 1: - 56 M referred liver clinic - malaise and pruritis - increasingly unwell over last few weeks - past few days developed jaundice - urine has gone dark Blood tests: - Bilirubin = 97 (1-22) - ALT = 108 (<35) - AST = 97 (<31) - ALP = 396 (45-105) - Albumin = 32 (35-45) - gamma-GT = 750 (<55)
What is the best description of this pattern of results?
cholestatic
- due to the bilirubin being 97 this means the conjugated bilirubin fraction will be more than the unconjugated bilirubin
What causes cholestatic jaundice and what are the key signs?
caused by bile duct obstruction
- malignancy (cholangiocarcinoma, pancreatic carcinoma)
- gallstones
- sclerosing cholangitis
painful (galllstones, pancreatitis) vs painless (malignancy
bilirubin clinically detectable at >50
pale stools and dark urine
ALP»ALT
conjugated bilirubin>unconjugated bilirubin
When is ALT/ AST higher than ALP?
in hepatitis - ALP and gamma GT will only be slightly raised
Case 1: - 56 M referred liver clinic - malaise and pruritis - increasingly unwell over last few weeks - past few days developed jaundice - urine has gone dark Blood tests: - Bilirubin = 97 (1-22) - ALT = 108 (<35) - AST = 97 (<31) - ALP = 396 (45-105) - Albumin = 32 (35-45) - gamma-GT = 750 (<55)
Based on the Hx and exam what is the most likely cause?
carcinoma of the head of the pancreas= painless
- a pancreatic mass causing extrahepatic obstructionn and there were multiple hypoechoic lesions in the liver suspicious of metastatic deposits
referred to oncology for possible palliative chemo and ERCP with stenting
Case 2: - 68 retired secretary - tiredness and SOB - no pmhx but smoked 50 pack year history Blood test results: - free T4 = 3.2 (10-22) - free T3 = 0.2 (3.1-7.7) - TSH = 41 (0.4-4.5)
What is the biochemical abnormality?
What is the most likely cause of this biochemical abnormality?
primary hypothyroidism
- autoimmune thyroid disease - commonest cause of hypothyroidism
What is the earliest time at which repeat thyroid function testing is indicated i.e. full effects of levothyroxine treatment will be seen?
4 weeks - full time to take its affect
Case 3: - 71 F known hx of breast cancer- treated with oral anastrozole - after a wide local clearance 6 months earlier, presents with nausea, vomiting and widespread pains Blood results: - Ca2+ = 2.88 (2.2-2.6) - Albumin = 24 (35-45) - Phosphate = 0.96 (0.8-1.4) - ALP = 102 (45-105) - PTH = <1 (1.05-6.83)
What is the calculated adjusted calcium concentration ?
3.20 mmol/L = higher than the reported Ca2+
plasma Ca and albumin correction
= plasma Ca + [40-plasma albumin] x0.02
Why do you have to correct the calcium concentration based on albumin level?
calcium is present in 2 main forms:
- calcium bound to proteins (principally albumin)
- free ionised calcium
changes in plasma protein concentration alter the commonly measures plasma total calcium concentration
most labs report adjusted calcium conc
if albumin is low the Ca2+ will be high
Case 3: - 71 F known hx of breast cancer- treated with oral anastrozole - after a wide local clearance 6 months earlier, presents with nausea, vomiting and widespread pains Blood results: - Ca2+ = 2.88 (2.2-2.6) - Albumin = 24 (35-45) - Phosphate = 0.96 (0.8-1.4) - ALP = 102 (45-105) - PTH = <1 (1.05-6.83)
What is the most likely diagnosis?
hypercalcaemia of malignancy
- if you have a high calcium and a low PTH think malignancy
- high ca in blood suppresses PTH
What malignancies is hypercalcaemia associated with?
bony metastases e.g. breast, lung, prostate, kidney, thyroid
solid tumours with humoral effects
haematological tumours (multiple myeloma)
Clinically what does bony metastases look like?
hypercalcaemia associated with a rise in phosphate concentration and a rise in plasma ALP (usually due to osteoclast activity)
What is humoral hypercalcaemia of malignancy caused by?
synthesis of parathyroid hormone related peptide
- secreted in breast and certain lung tumours
- not detected by PTH assay
Which of the following clinical features is NOT associated with hypercalcaemia?
- constipation
- depression
- diabetes mellitus
- short QT interval on ECG
- thirst and polyuria
diabetes mellitus - can occur in insipidus but not mellitus
Case 4: - 15 F 10 day hx lethargy, thirst and polyuria - abdominal pain and been vomiting for last 2 days - clinically unwell, deep sighing breathing and dry mucous membrane - GCS 14/15 - BP 85/42 - 104 bpm Blood results - Na= 131 (135-145) - K = 6.3 (3.5-5.5) - Urea = 14.2 (4-8) - creatinine = 120 (75-105) - bicarbonate= 15 (22-28) - glucose = 35 (4-5)
What does the low bicarbonate prompt?
An ABG to be carried out
Case 4: - 15 F 10 day hx lethargy, thirst and polyuria - abdominal pain and been vomiting for last 2 days - clinically unwell, deep sighing breathing and dry mucous membrane - GCS 14/15 - BP 85/42 - 104 bpm Blood results - Na= 131 (135-145) - K = 6.3 (3.5-5.5) - Urea = 14.2 (4-8) - creatinine = 120 (75-105) - bicarbonate= 15 (22-28) - glucose = 35 (4-5)
Blood gas
- pH = 7.21
- pO2 = 18
- PCO2= 2.8
- HCO3= 12
What is the best description of this abnormality ?
What is the most likely diagnosis?
metabolic acidosis with partial respiratory compensation
- bringing CO2 down by deep sighing breathing = kusmal’s breathing
- only partial because although the CO2 is low the patient is still acidotic
Diabetic ketoacidosis
- resuscited with fluids and IV insulin infusion
- at risk of hypokalaemia
