Chemical Pathology Semester 1 Clinical Cases OmpathStudy

Question 1 : SIADH / Hyponatremia (10 marks) An elderly male smoker is admitted with acute confusion. Examination reveals digital clubbing and a right-sided pleural effusion. Laboratory results show: - Serum sodium: 118 mmol/L - Serum osmolality: 236 mOsm/kg - Urine osmolality: 350 mOsm/kg - Urine sodium: 50 mmol/L - Urea and creatinine: normal Chest radiograph shows a right lower-zone mass suggestive of carcinoma. A. What is the most likely cause of his hyponatremia? (2 marks) B. State two biochemical features characteristic of SIADH. (2 marks) C. Explain why the urine osmolality is high despite hyponatremi D. (2 marks) E. Name the lung tumour most commonly associated with SIADH. (2 marks) Answer: A. What is the most likely cause of his hyponatremia? (2 marks) --- Question 2 : Thiazide + Laxative Abuse (Hypokalemic Metabolic Alkalosis) (10 marks) A 67-year-old woman presents with profound muscle weakness. She has a long history of laxative use and was recently started on a thiazide diuretic. Investigations show severe hypokalemia and metabolic alkalosis. A. What is the most likely biochemical abnormality? (2 marks) B. Briefly explain how thiazide diuretics cause hypokalemi C. (2 marks) D. Explain how chronic laxative abuse produces metabolic alkalosis. (3 marks) E. Mention one common ECG change seen in hypokalemi Answer: A. What is the most likely biochemical abnormality? (2 marks) --- Question 3 : Shock + Acute Abdomen (Severe Metabolic Acidosis) (10 marks) A 60-year-old man presents with severe abdominal pain for 24 hours. He is shocked, has a rigid distended abdomen, and absent femoral pulses. Arterial blood gases show: - pH: 7.05 - PaCO₂: 26.3 mmHg - PaO₂: 90 mmHg - HCO₃⁻: 7 mmol/L A. Identify the acid–base disturbance present. (2 marks) B. Explain the biochemical mechanism producing this metabolic acidosis. (3 marks) C. Why is the PaCO₂ low in this patient? (2 marks) D. What is the most likely underlying diagnosis? (2 marks) E. State two causes of markedly elevated lactate in acute abdomen. (1 mark) --- ### ANSWER 3: Answer: A. Identify the acid–base disturbance present. (2 marks) --- Question 4 : Head Injury (Respiratory Alkalosis) (10 marks) A young woman is admitted unconscious following head trauma. CT scan reveals extensive cerebral contusions. She is hyperventilating at 38 breaths per minute. Arterial blood gas shows: - PaCO₂: 29 mmHg - HCO₃⁻: 19 mmol/L A. What acid–base disorder is present? (2 marks) B. Explain the mechanism of respiratory alkalosis in head injury. (3 marks) C. Why is the bicarbonate level slightly reduced after 3 days? (2 marks) D. State one effect of respiratory alkalosis on cerebral blood flow. (2 marks) E. Which area of the brain regulates the respiratory drive? (1 mark) --- ### ANSWER 4: Answer: A. What acid–base disorder is present? (2 marks) --- Question 5 : Quality Control in Clinical Chemistry (10 marks) A. Define the following terms as used in quality control: (4 marks) i) Accuracyii) Precisioniii) Sensitivityiv) Specificity B. Explain the difference between internal and external quality control. (3 marks) C. List three pre-analytical factors that can affect biochemical test results. (3 marks) --- ### ANSWER 5: D. Definitions: (4 marks) i) Accuracy – The closeness of a measured value to the true or accepted reference valu E. It indicates how correct a measurement is and reflects systematic error or bias. ii) Precision – The reproducibility or… Answer: A. Define the following terms as used in quality control: (4 marks) i) Accuracyii) Precisioniii) Sensitivityiv) Specificity --- Question 6 : Acid-Base Balance (10 marks) A. Calculate the anion gap for a patient with the following results: (3 marks) - Sodium: 138 mmol/L - Chloride: 98 mmol/L -… B. Interpret the acid-base status of a patient with these blood gas results: (4 marks) - pH: 7.28 - PaCO₂: 30 mmHg - HCO₃⁻: 14 mmol/L C. List three causes of high anion gap metabolic acidosis. (3 marks) [hidden] --- ### ANSWER 6: D. Interpretation: Markedly elevated anion gap, consistent with high anion gap metabolic acidosis E. Three Causes of High Anion Gap Metabolic Acidosis (MUDPILES): (3 marks) - Diabetic Ketoacidosis (DK Answer: A. Calculate the anion gap for a patient with the following results: (3 marks) - Sodium: 138 mmol/L - Chloride: 98 mmol/L -… --- Question 7 : Lipid Profile Interpretation (10 marks) A 50-year-old male patient presents with the following lipid profile results: - Total Cholesterol: 280 mg/dL - LDL-Cholesterol: 190 mg/dL - HDL-Cholesterol: 35 mg/dL - Triglycerides: 275 mg/dL A. Interpret these results and state the lipid abnormalities present. (4 marks) B. Calculate the VLDL cholesterol level. (2 marks) C. What is the cardiovascular risk category for this patient? (2 marks) D. Outline two lifestyle modifications you would recommen E. (2 marks) --- ### ANSWER 7: Answer: A. Interpret these results and state the lipid abnormalities present. (4 marks) --- Question 8 : Liver Function Tests (10 marks) A. Diffe