Nephrology - Electrolytes

Question 1

Hyponatraemia

Answer 1

• Addison’s disease, hypothyroidism
• burns
• liver cirrhosis, heart failure
• vomiting, diarrhoea
• SIADH
• psychogenic polydipsia

Drugs

• sodium valproate
• carbamazepine
• sulfonylureas
• loop diuretics
• thiazides

Question 2

Causes of SIADH

Answer 2

Central nervous system

• Head injury
• Cerebral neoplasm

Respiratory system

• Small cell lung carcinoma (SCLC)
• Pneumonia (Legionnaire’s is the college favourite)

Drugs

• NSAIDs,
• Tricyclic antidepressants,
• SSRI,
• Haloperidol.

Question 3

Causes of hyponatremia with low urine sodium (<10 meq/L)

Answer 3

• Dehydration
• Vomiting
• Diarrhea
• Sweating and other skin losses

Question 4

Causes of hyponatremia with high urine sodium (>10 meq/L)

Answer 4

• Diuretics
• ACE inhibitors
• Addison disease

Question 5

Hyperkalemia (drugs)

Answer 5

• amiloride
• ciclosporin
• angiotensin II receptor blockers
• spironolactone
• heparin
• Tacrolimus

Question 6

Hypokalemia with hypertension

Answer 6

• Cushing’s syndrome
• Conn’s syndrome (primary hyperaldosteronism)
• Liddle’s syndrome (similar to hyperaldosteronism)
• 11-beta hydroxylase deficiency*

Question 7

Hypokalaemia without hypertension

Answer 7

• GI loss (e.g. Diarrhoea, vomiting)
• Diuretics
• Renal tubular acidosis (type 1 and 2)
• Bartter’s syndrome
• Gitelman syndrome

Question 8

Hypomagnesaemia

Answer 8

• loop and thiazide diuretics
• cisplatin,
• aminoglycosides,
• amphotericin B,
• cyclosporine
• hungry bone syndrome following parathyroidectomy

Question 9

Hypophosphatemia

Answer 9

• Alcohol Excess
• Acute Liver Failure
• Diabetic Ketoacidosis (DKA)
• Insulin Administration for Severe Hyperglycemia
• Refeeding Syndrome
• Primary Hyperparathyroidism
• Osteomalacia
• Hungry Bone Syndrome (post-parathyroidectomy)
• Respiratory Alkalosis
• Chronic Diarrhea
• Vitamin D Deficiency

Question 10

Hyperphosphatemia

Answer 10

• Hypoparathyroidism,
• hypocalcemia,
• renal failure,
• rhabdomyolysis,
• tumor lysis

Question 11

1) Hypercalcemia
2) Hypercalcemia due to cancer

Answer 11

• thiazides
• Addison’s disease, thyrotoxicosis, primary hyperparathyroidism, acromegaly
• vitamin D intoxication
• milk-alkali syndrome
• dehydration
• sarcoidosis

Malignancies:

• Squamous cell carcinomas arising in the lung or the head and neck
• Multiple myeloma
• Breast carcinoma
• T-cell lymphoma/leukemia
• Renal cell carcinoma
• Hepatocellular carcinoma
• Bone metastasis

Question 12

Hypocalcaemia

Answer 12

• magnesium deficiency
• vitamin D deficiency
• chronic kidney disease
• rhabdomyolysis
• pseudohypoparathyroidism
• hypoparathyroidism

Note: Both hyper- and hypomagnesemia can cause hypocalcemia.

Question 13

Causes of hypernatraemia

Answer 13

• dehydration
• osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma
• diabetes insipidus
• excess IV saline

Question 14

Causes of low calcium and high phosphate

Answer 14

• Chronic renal failure
• Hypoparathyroidism
• Pseudohypoparathyroidism
• Magnesium deficiency*
• Rhabdomyolysis

* Due to end-organ resistance to the effects of PTH

Question 15

Causes of pseudohyponatremia

Answer 15

• severe hypertriglyceridemia,
• diabetic ketoacidosis,
• plasma cell dyscrasia, such as in patients with multiple myeloma
• obstructive jaundice