Which of the following clinical conditions are correctly matched with their respective anion gap status? 

A) Starvation – Increased anion gap

B) Diabetic ketoacidosis – Increased anion gap

C) Severe vomiting – Increased anion gap

1. A

   Only A is correct

2. B

   A and C are correct

3. C

   A and B are correct

4. D

   Only B is correct

Appeared in: Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Explanation

• Both starvation and diabetic ketoacidosis (DKA) involve the breakdown of fatty acids for energy due to a lack of available glucose.
• This process, known as ketogenesis, produces acidic ketone bodies (β-hydroxybutyrate and acetoacetate).
• These ketone bodies are 'unmeasured anions' in the standard electrolyte panel.
• The accumulation of these unmeasured anions consumes bicarbonate and increases the calculated anion gap, leading to High Anion Gap Metabolic Acidosis (HAGMA).

Why Other Options Were Wrong

• Option A: This option is incomplete. While statement A (Starvation) is correct, statement B (Diabetic Ketoacidosis) is also a correct cause of an increased anion gap.
• Option B: This option is incorrect because statement C (Severe vomiting) is wrong. Severe vomiting leads to the loss of gastric acid (HCl), causing metabolic alkalosis, which is typically associated with a normal anion gap.
• Option D: This option is incomplete. While statement B (Diabetic Ketoacidosis) is a classic cause of an increased anion gap, statement A (Starvation) also correctly leads to an increased anion gap through the same mechanism of ketoacidosis.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Anion gap in metabolic acid-base disorders helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• Calculating the anion gap is a critical first step in the emergency department and ICU when a patient presents with metabolic acidosis. It rapidly narrows the differential diagnosis between conditions that produce unmeasured anions (HAGMA) and those that cause bicarbonate loss (normal anion gap acidosis).
• A high anion gap is a red flag that prompts an immediate search for serious underlying conditions like DKA, lactic acidosis, or toxic ingestions, guiding urgent treatment decisions.
• What if the patient had severe diarrhea instead of vomiting? Severe diarrhea causes a loss of bicarbonate-rich fluid from the intestines. This leads to a normal anion gap metabolic acidosis (also called hyperchloremic metabolic acidosis) because the kidneys compensate for bicarbonate loss by retaining chloride to maintain electrical neutrality.

How to Approach the Question

• First, understand the core question: which conditions are correctly matched with an 'increased anion gap'.
• Recall the definition of the anion gap: the difference between measured cations (Na+) and anions (Cl- + HCO3-). An increase signifies the presence of unmeasured anions.
• Analyze the pathophysiology of each condition:
• Starvation: No glucose -> fat breakdown -> ketones (acids/unmeasured anions) -> Increased anion gap.
• Diabetic Ketoacidosis: No insulin -> no glucose uptake -> massive fat breakdown -> massive ketones -> Increased anion gap.
• Severe Vomiting: Loss of stomach acid (HCl) -> loss of H+ and Cl- -> body retains HCO3- -> metabolic alkalosis -> Normal anion gap.

Concept Tested & Keywords

• Concept Tested: Anion gap in metabolic acid-base disorders
• Stem keywords: clinical conditions, anion gap, starvation, diabetic ketoacidosis, severe vomiting
• Lead-in keywords: correctly matched

Question ID

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Copy ID

Reference Book

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 562-564

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 56-58

E6 Physiology Guyton 4SAE Part 2B p. 79-81