Question

A 50-year-old man with a remote history of alcohol dependence is evaluated in the clinic for chronic diarrhea and weight loss. The patient has had bloating with daily loose stools for the past 2 years. His stool is described as greasy and malodorous. Pancreatic insufficiency is suspected despite normal abdominal imaging. The patient undergoes a test in which bicarbonate concentration is measured from duodenal aspirates as hormone A is infused intravenously. The data is plotted in the graph below

Hormone A is most likely produced by which of the following cell types?

A. Duodenal S cells

B. Gastric G cells

C.Pancreatic alpha cells

D.Pancreatic beta cells

E. Parenchymal hepatocytes

F. Renal peritubular cells

Correct Answer: A. Duodenal S Cells

• 🧠 These cells secrete secretin in response to acidic chyme.

• ⚙️ Secretin stimulates pancreatic bicarbonate secretion, protecting the duodenum

Concept

Alcohol Dependence History 🧠
⬇
Chronic alcohol consumption damages pancreatic parenchyma
⬇
Loss of pancreatic acinar cells ⬇ Pancreatic enzyme secretion (lipase, protease, amylase) 🧠
⬇
Impaired digestion of fats, proteins, and carbohydrates ⬇ Steatorrhea (greasy, malodorous stools)
⬇
Chronic nutrient malabsorption ⬇ Weight loss

Acidic Chyme in Duodenum 🧠
⬇
Duodenal S cells detect low pH and secrete secretin
⬇
Secretin acts on pancreatic ducts ⬆ Bicarbonate secretion 🧠
⬇
Neutralization of acidic chyme protects duodenal mucosa

Patient's Findings: Chronic diarrhea + steatorrhea
⬇
Points to pancreatic exocrine insufficiency 🧠
⬇
Test Interpretation: Infusion of hormone A (secretin) stimulates bicarbonate secretion, confirming normal ductal response but impaired acinar enzyme function

Think of digestion as a kitchen:

🧼 Bicarbonate is like the soap that neutralizes the acid spills (chyme).

🧪 Secretin is the call (signal) to the soap dispenser (pancreatic ducts) to release it.

Without enzymes (from damaged acinar cells), the kitchen remains greasy (steatorrhea).

Clues in the Question

🔍 Clue #1: Understanding the Symptoms

🧠 Key Insight: Chronic diarrhea + greasy stool → Think malabsorption

⚙️ Mechanism:

• Steatorrhea suggests impaired fat digestion (think “oil spills in digestion 🚤🛢️”).

• Possible causes:

  • 🔑 Pancreatic insufficiency (enzymes ↓ → fat breakdown ↓).

  • Small bowel or bile acid dysfunction.

🔍 Clue #2: History of Alcohol Dependence

🧠 Key Insight: Chronic alcohol use is toxic to pancreatic cells ⚙️

• Acinar cell damage → Enzyme production ↓ → Malabsorption symptoms.

• This history tilts the scales ⚖️ towards pancreatic insufficiency.

🔍 Clue #3: Diagnostic Test – Role of Hormone A

• 🧠 Key Insight: Hormone A triggers bicarbonate secretion from the pancreas.

• ⚙️ Mechanism:

  • Duodenal S cells secrete secretin when exposed to acidic chyme.

  • Secretin ↑ bicarbonate production from pancreatic ducts, neutralizing acid.

• If bicarbonate secretion is normal in the test, the ducts are functional but the enzymes (produced by acinar cells) are impaired.

🔍 Step 4: Linking the Graph to the Diagnosis

• 🧠 Key Insight: Bicarbonate secretion ↑ with higher levels of hormone A → Consistent with secretin function.

• The test confirms pancreatic insufficiency due to acinar damage, not ductal dysfunction.

Explanation of Other Answers

B. Gastric G cells

• 🧠 G cells secrete gastrin, which ↑ stomach acid (think “fire 🔥 in the stomach”).

• ⚖️ Gastrin plays no role in bicarbonate secretion.

C. Pancreatic Alpha Cells

• 🧠 Alpha cells secrete glucagon (think “sugar thermostat 🧭”), regulating blood sugar, not digestion.

D. Pancreatic Beta Cells

• 🧠 Beta cells secrete insulin, controlling glucose, unrelated to bicarbonate.

E. Parenchymal Hepatocytes

• 🧠 Hepatocytes produce bile, which emulsifies fats (think “dish soap 🍽️🧼”), but this process is independent of bicarbonate secretion.

F. Renal Peritubular Cells

• 🧠 These cells produce erythropoietin, stimulating red blood cell production. They do not interact with digestive processes.

Flashcards 🃏

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Dr. Shoaib Ahmad