Exocrine pancreatic insufficiency US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Exocrine pancreatic insufficiency. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Exocrine pancreatic insufficiency US Medical PG Question 1: A 29-year-old female is hospitalized 1 day after an endoscopic retrograde cholangiopancreatography (ERCP) because of vomiting, weakness, and severe abdominal pain. Physical examination findings include abdominal tenderness and diminished bowel sounds. A CT scan demonstrates fluid around the pancreas. Serum levels of which of the following are likely to be low in this patient?
- A. Amylase
- B. Triglycerides
- C. Calcium (Correct Answer)
- D. Glucose
- E. Lipase
Exocrine pancreatic insufficiency Explanation: ***Calcium***
- In **acute pancreatitis**, systemic inflammation can lead to **saponification** of perinecrotic fat, binding calcium and causing **hypocalcemia**.
- Additionally, glucagon release and hypomagnesemia can contribute to decreased parathyroid hormone (PTH) secretion and end-organ resistance, further lowering calcium levels.
*Amylase*
- **Amylase** levels are typically **elevated** in acute pancreatitis due to the release of pancreatic enzymes into the bloodstream.
- An elevated amylase, along with lipase, is a key diagnostic marker for pancreatitis.
*Triglycerides*
- **Hypertriglyceridemia** can cause acute pancreatitis, and triglyceride levels would be expected to be **elevated** in such cases.
- Triglycerides themselves are not directly lowered by the pancreatitis process in the way calcium is.
*Glucose*
- **Glucose** levels often become **elevated** in acute pancreatitis due to impaired insulin secretion and increased glucagon release.
- Pancreatic damage can affect the endocrine function of the pancreas, leading to hyperglycemia.
*Lipase*
- **Lipase** levels are also typically **elevated** in acute pancreatitis, often staying elevated longer than amylase.
- It is a more specific marker for pancreatic injury than amylase.
Exocrine pancreatic insufficiency US Medical PG Question 2: An 82-year-old woman presents with 2 months of foul-smelling, greasy diarrhea. She says that she also has felt very tired recently and has had some associated bloating and flatus. She denies any recent abdominal pain, nausea, melena, hematochezia, or vomiting. She also denies any history of recent travel and states that her home has city water. Which of the following tests would be most appropriate to initially work up the most likely diagnosis in this patient?
- A. Fecal fat test (Correct Answer)
- B. Tissue transglutaminase antibody test
- C. Stool O&P
- D. Stool guaiac test
- E. CT of the abdomen with oral contrast
Exocrine pancreatic insufficiency Explanation: ***Fecal fat test***
- The patient's symptoms of **foul-smelling, greasy diarrhea**, along with **fatigue, bloating, and flatus**, strongly suggest **malabsorption**, specifically **steatorrhea** (excess fat in stool).
- A **fecal fat test** (e.g., Sudan stain or 72-hour quantitative stool fat collection) directly assesses fat malabsorption and would be the most appropriate initial diagnostic test.
*Tissue transglutaminase antibody test*
- This test is used to screen for **celiac disease**, which can cause malabsorption symptoms.
- While celiac disease is a possibility, a fecal fat test is a more general and appropriate initial step to confirm fat malabsorption before looking for specific causes.
*Stool O&P*
- Stands for **Stool Ova and Parasites**, used to detect parasitic infections like **Giardia** or **Cryptosporidium**, which can cause diarrhea.
- However, the absence of recent travel, city water, and the prominent greasy nature of the stool make this less likely as the primary initial investigation compared to confirming malabsorption.
*Stool guaiac test*
- This test detects **occult blood in stool**.
- The patient denies **melena or hematochezia**, and there are no signs pointing to gastrointestinal bleeding, making this test irrelevant for her presenting symptoms.
*CT of the abdomen with oral contrast*
- A CT scan with contrast might be used to investigate structural abnormalities or inflammation if other tests confirm malabsorption or point to a specific organ pathology (e.g., pancreatitis, Crohn's disease).
- It's an imaging study and generally not the most appropriate *initial* test for evaluating the described symptoms of malabsorption.
Exocrine pancreatic insufficiency US Medical PG Question 3: A 55-year-old woman presents with acute onset abdominal pain radiating to her back, nausea, and vomiting. CT scan suggests a diagnosis of acute pancreatitis. The pathogenesis of acute pancreatitis relates to inappropriate activation of trypsinogen to trypsin. Which of the following activates trypsin in normal digestion?
- A. Secretin
- B. Lipase
- C. Cholecystokinin
- D. Enterokinase (Correct Answer)
- E. Amylase
Exocrine pancreatic insufficiency Explanation: ***Enterokinase***
- **Enterokinase** (also known as enteropeptidase) is a brush border enzyme of the duodenum that specifically cleaves and activates pancreatic **trypsinogen** into its active form, **trypsin**.
- Once activated, **trypsin** then activates other pancreatic proteases (e.g., chymotrypsinogen, procarboxypeptidases, proelastase) within the intestinal lumen.
*Secretin*
- **Secretin** is a hormone released by S cells in the duodenum in response to acidic chyme and acts on the pancreas to stimulate the secretion of **bicarbonate-rich fluid**, which neutralizes gastric acid.
- It does not directly activate digestive enzymes like trypsinogen.
*Lipase*
- **Lipase** is a pancreatic enzyme secreted in its active form that breaks down **dietary fats** (triglycerides) into fatty acids and monoglycerides.
- It plays no role in the activation of trypsinogen.
*Cholecystokinin*
- **Cholecystokinin (CCK)** is a hormone released by I cells in the duodenum in response to fats and proteins, stimulating the contraction of the **gallbladder** and the secretion of **pancreatic enzymes**.
- While it promotes the release of pancreatic enzymes, it does not directly activate trypsinogen.
*Amylase*
- **Amylase** is a pancreatic enzyme secreted in its active form that breaks down **complex carbohydrates** (starches) into simpler sugars (disaccharides and oligosaccharides).
- It is not involved in the activation cascade of pancreatic proteases.
Exocrine pancreatic insufficiency US Medical PG Question 4: A 49-year-old woman comes to the physician because of difficulty walking and dizziness for the past 2 weeks. She has also had fatigue, heartburn, and diarrhea for 4 months. The stools are foul-smelling and do not flush easily. Over the past 4 months, she has had a 2.2-kg (5-lb) weight loss. Her only medication is an over-the-counter antacid. Her mother has autoimmune thyroid disease and Crohn disease. She is 150 cm (4 ft 11 in) tall and weighs 43 kg (95 lb); BMI is 19.1 kg/m2. Vital signs are within normal limits. Examination shows a wide-based gait. Muscle strength and tone are normal in all extremities. Rapid alternating movement of the hands is impaired. The abdomen is soft and there is mild tenderness to palpation in the epigastric area. Her hemoglobin concentration is 11.1 mg/dL, and levels of vitamin E and vitamin D are decreased. Upper endoscopy shows several ulcers in the gastric antrum and the descending duodenum. Which of the following is the most likely underlying mechanism of this patient's symptoms?
- A. Autoantibodies against the intestinal mucosa
- B. Intestinal inflammatory reaction to gluten
- C. T. whipplei infiltration of intestinal villi
- D. Inactivation of pancreatic enzymes (Correct Answer)
- E. Small intestine bacterial overgrowth
Exocrine pancreatic insufficiency Explanation: ***Inactivation of pancreatic enzymes***
- The constellation of **steatorrhea** (foul-smelling, difficult-to-flush stools), **weight loss**, epigastric tenderness, and **gastric/duodenal ulcers** suggests **Zollinger-Ellison syndrome (ZES)** due to a gastrinoma.
- The excessive **gastric acid production** in ZES **inactivates pancreatic enzymes** (lipases) in the duodenum, leading to **fat malabsorption**, hence the deficiency in **fat-soluble vitamins** (D and E) and steatorrhea.
- The **cerebellar signs** (wide-based gait, dizziness, impaired rapid alternating movements) are due to **vitamin E deficiency**, a direct consequence of fat malabsorption from pancreatic enzyme inactivation.
*Autoantibodies against the intestinal mucosa*
- This mechanism is characteristic of **autoimmune enteropathy**, which causes severe diarrhea and malabsorption, but is typically associated with **immune dysregulation** in infants or young children and less commonly with ulcers.
- While malabsorption is present, the specific ulcers and neurological symptoms point away from primary autoimmune enteropathy as the sole mechanism.
*T. whipplei infiltration of intestinal villi*
- This describes **Whipple disease**, which can cause malabsorption, weight loss, diarrhea, and neurological symptoms.
- However, Whipple disease typically presents with **lymphadenopathy**, **hyperpigmentation**, and **arthralgia** and does not typically cause gastric or duodenal ulcers.
*Intestinal inflammatory reaction to gluten*
- This describes **celiac disease**, which causes malabsorption, diarrhea, and weight loss due to **villous atrophy** in the small intestine, leading to deficiencies in fat-soluble vitamins.
- Celiac disease does not typically cause **gastric or duodenal ulcers** and neurological symptoms like impaired rapid alternating movements are less characteristic than in ZES or other conditions.
*Small intestine bacterial overgrowth*
- **SIBO** can cause diarrhea, malabsorption, and weight loss due to bacterial consumption of nutrients and damage to the intestinal mucosa.
- While SIBO can be a consequence of conditions like ZES due to reduced acid, it is less likely to be the primary cause of ulcers and the overall clinical picture without a predisposing anatomical reason or motility disorder.
Exocrine pancreatic insufficiency US Medical PG Question 5: A 46-year-old man is brought to the emergency department because of severe epigastric pain and vomiting for the past 4 hours. The pain is constant, radiates to his back, and is worse on lying down. He has had 3–4 episodes of greenish-colored vomit. He was treated for H. pylori infection around 2 months ago with triple-regimen therapy. He has atrial fibrillation and hypertension. He owns a distillery on the outskirts of a town. The patient drinks 4–5 alcoholic beverages daily. Current medications include dabigatran and metoprolol. He appears uncomfortable. His temperature is 37.8°C (100°F), pulse is 102/min, and blood pressure is 138/86 mm Hg. Examination shows severe epigastric tenderness to palpation with guarding but no rebound. Bowel sounds are hypoactive. Rectal examination shows no abnormalities. Laboratory studies show:
Hematocrit 53%
Leukocyte count 11,300/mm3
Serum
Na+ 133 mEq/L
Cl- 98 mEq/L
K+ 3.1 mEq/L
Calcium 7.8 mg/dL
Urea nitrogen 43 mg/dL
Glucose 271 mg/dL
Creatinine 2.0 mg/dL
Total bilirubin 0.7 mg/dL
Alkaline phosphatase 61 U/L
AST 19 U/L
ALT 17 U/L
γ-glutamyl transferase (GGT) 88 u/L (N=5–50 U/L)
Lipase 900 U/L (N=14–280 U/L)
Which of the following is the most appropriate next step in management?
- A. Crystalloid fluid infusion (Correct Answer)
- B. Fomepizole therapy
- C. Calcium gluconate therapy
- D. Endoscopic retrograde cholangio-pancreatography
- E. Laparotomy
Exocrine pancreatic insufficiency Explanation: ***Crystalloid fluid infusion***
- The patient presents with **acute pancreatitis**, indicated by severe epigastric pain radiating to the back, vomiting, epigastric tenderness, and markedly elevated **lipase** (900 U/L).
- He shows clear signs of **hypovolemia**: elevated hematocrit (53%), elevated BUN/Cr ratio (43/2.0 = 21.5), and tachycardia.
- Pancreatitis causes significant **fluid shifts** and third-spacing, requiring aggressive **intravenous fluid resuscitation** with crystalloids (preferably lactated Ringer's) to prevent hypovolemic shock, acute kidney injury, and organ dysfunction.
- Early aggressive fluid resuscitation (250–500 mL/h initially) is the **cornerstone of acute pancreatitis management** and improves outcomes.
*Fomepizole therapy*
- **Fomepizole** is an antidote for **methanol** or **ethylene glycol** poisoning, which cause a high anion gap metabolic acidosis and visual disturbances.
- While the patient owns a distillery, his symptoms and lab findings (elevated lipase, hypocalcemia, mild leukocytosis) are consistent with **alcoholic pancreatitis**, not toxic alcohol ingestion.
- No anion gap is present, and there are no visual symptoms.
*Calcium gluconate therapy*
- Although the patient has **hypocalcemia** (7.8 mg/dL), which is common in severe pancreatitis due to fat saponification and calcium sequestration, routine calcium gluconate administration is generally **not recommended unless symptomatic**.
- Symptomatic hypocalcemia includes tetany, paresthesias, seizures, or prolonged QT interval, none of which are present.
- Aggressive fluid resuscitation and management of the underlying pancreatitis are higher priorities.
*Endoscopic retrograde cholangio-pancreatography*
- **ERCP** is primarily indicated for **gallstone pancreatitis with cholangitis** or persistent biliary obstruction.
- This patient likely has **alcoholic pancreatitis** (heavy alcohol use, elevated GGT), and there's no evidence of biliary obstruction (normal bilirubin, AST, ALT, ALP).
- Routine early ERCP in acute pancreatitis without cholangitis is not beneficial and carries procedural risks.
*Laparotomy*
- **Laparotomy** (surgical exploration) is rarely indicated in the initial management of acute pancreatitis.
- It might be considered for complications such as infected necrosis, pancreatic abscess, or abdominal compartment syndrome, but there is no indication for surgical intervention in this patient at this stage.
- Initial management focuses on medical stabilization with fluid resuscitation and supportive care.
Exocrine pancreatic insufficiency US Medical PG Question 6: A 34-year-old woman comes to the emergency department because of decreased appetite, nausea, vomiting, and episodic abdominal pain for the past two months. The pain is sharp, colicky, and lasts about an hour after meals. Her stools are light in appearance and difficult to flush. Physical examination shows tenderness in the right upper quadrant. Without treatment, this patient is at greatest risk for developing which of the following?
- A. Steatohepatitis
- B. Megaloblastic anemia
- C. Delayed wound healing
- D. Low bone mineral density (Correct Answer)
- E. Glossitis
Exocrine pancreatic insufficiency Explanation: ***Low bone mineral density***
- This patient presents with symptoms highly suggestive of **gallstones** (cholelithiasis) leading to **biliary obstruction** or **cholestasis**, evidenced by episodic postprandial colicky pain, nausea, vomiting, and light-colored, difficult-to-flush stools (steatorrhea due to **fat malabsorption**).
- Chronic fat malabsorption inhibits the absorption of **fat-soluble vitamins** (A, D, E, K). A deficiency in **vitamin D** is a significant risk factor for **low bone mineral density** and **osteoporosis** over time.
*Steatohepatitis*
- **Steatohepatitis** (fatty liver inflammation) is typically associated with **metabolic syndrome**, chronic alcohol use, or rapid weight loss, which are not directly indicated here.
- While gallstones can be linked to obesity, they do not directly cause steatohepatitis in the way described by the patient's acute symptoms.
*Megaloblastic anemia*
- **Megaloblastic anemia** is primarily caused by deficiencies in **vitamin B12** or **folate**.
- While malabsorption can lead to B12 deficiency (e.g., in pancreatic insufficiency affecting intrinsic factor activity), biliary obstruction directly impacts fat-soluble vitamin absorption, not primarily B12 or folate.
*Delayed wound healing*
- **Delayed wound healing** can be a symptom of **vitamin C** or **zinc deficiency**, or overall malnutrition.
- Although chronic malabsorption can lead to general malnutrition, vitamin D deficiency and its impact on bone health are a more specific and immediate long-term risk associated with the described symptoms.
*Glossitis*
- **Glossitis** (inflammation of the tongue) is typically associated with deficiencies in **vitamin B group** vitamins (e.g., B12, folate, niacin, riboflavin) or **iron deficiency**.
- While this patient might eventually develop general nutritional deficiencies, biliary obstruction leading to fat malabsorption does not directly or primarily cause these specific B vitamin deficiencies.
Exocrine pancreatic insufficiency US Medical PG Question 7: A 62-year-old Caucasian man visits his primary care provider with recurrent episodes of moderate to severe abdominal pain, nausea, and anorexia for the past 2 years. Additional complaints include constipation, steatorrhea, weight loss, polyphagia, and polyuria. His personal history is relevant for a 2-year period of homelessness when the patient was 55 years old, cigarette smoking since the age of 20, alcohol abuse, and cocaine abuse for which is currently under the supervision of a psychiatry team. He has a pulse of 70/min, a respiratory rate of 16/min, a blood pressure of 130/70 mm Hg, and a body temperature of 36.4°C (97.5°F). His height is 178 cm (5 ft 10 in) and weight is 90 kg (198 lb). On physical examination, he is found to have telangiectasias over the anterior chest, mild epigastric tenderness, and a small nodular liver. Laboratory test results from his previous visit a month ago are shown below:
Fasting plasma glucose 160 mg/dL
HbA1c 8%
Serum triglycerides 145 mg/dL
Total cholesterol 250 mg/dL
Total bilirubin 0.8 mg/dL
Direct bilirubin 0.2 mg/dL
Amylase 180 IU/L
Lipase 50 IU/L
Stool negative for blood; low elastase
This patient’s condition is most likely secondary to which of the following conditions?
- A. Hypertriglyceridemia
- B. Alcohol abuse (Correct Answer)
- C. Cocaine abuse
- D. Hypercholesterolemia
- E. Obesity
Exocrine pancreatic insufficiency Explanation: ***Alcohol abuse***
- Chronic alcohol abuse is a major risk factor for **chronic pancreatitis**, which manifests with recurrent abdominal pain, steatorrhea, weight loss, and can lead to **diabetes mellitus** (polyphagia, polyuria, elevated fasting glucose and HbA1c).
- The elevated amylase, although not diagnostic for chronic pancreatitis on its own, along with low stool elastase (indicating **pancreatic exocrine insufficiency**), telangiectasias (suggesting liver disease often associated with alcohol), and a nodular liver (pointing to **cirrhosis**), strongly support chronic pancreatitis secondary to alcohol.
*Hypertriglyceridemia*
- While severe hypertriglyceridemia (typically >1000 mg/dL) can cause acute pancreatitis, the patient's triglyceride level (145 mg/dL) is not high enough to be the cause of his chronic pancreatic issues.
- Furthermore, chronic pancreatitis symptoms like steatorrhea and diabetes are better explained by long-term alcohol exposure.
*Cocaine abuse*
- Cocaine can cause **vasoconstriction** and ischemia, potentially leading to acute pancreatitis, but it is not a common cause of chronic pancreatitis with the constellation of symptoms observed here.
- The clinical picture strongly aligns with the chronic effects of alcohol on the pancreas and liver.
*Hypercholesterolemia*
- While hypercholesterolemia (total cholesterol 250 mg/dL) is a risk factor for cardiovascular disease, it is not directly implicated in causing pancreatitis or liver disease in the way described.
- It does not explain the recurrent abdominal pain, steatorrhea, or the development of diabetes and liver changes seen in this patient.
*Obesity*
- Obesity is a risk factor for various metabolic disorders, including type 2 diabetes and non-alcoholic fatty liver disease (NAFLD), but it is not a primary cause of chronic pancreatitis.
- The specific signs of liver damage (telangiectasias, nodular liver) and the pancreatic exocrine insufficiency point away from obesity as the primary etiology for this patient's condition.
Exocrine pancreatic insufficiency US Medical PG Question 8: A 42-year-old man comes to the physician because of severe epigastric pain for a week. The pain is constant and he describes it as 6 out of 10 in intensity. The pain radiates to his back and is worse after meals. He has had several episodes of nausea and vomiting during this period. He has taken ibuprofen for multiple similar episodes of pain during the past 6 months. He also has had a 5.4-kg (12-lb) weight loss over the past 4 months. He has a 12-year history of drinking 3 to 4 pints of rum daily. He has been hospitalized three times for severe abdominal pain in the past 3 years. He appears ill. His temperature is 37°C (98.6°F), pulse is 87/min, and blood pressure is 110/70 mm Hg. There is severe epigastric tenderness to palpation. Bowel sounds are normal. Cardiopulmonary examination shows no abnormalities. Laboratory studies show:
Hemoglobin 13.6 g/dL
Leukocyte count 7,800/mm3
Serum
Glucose 106 mg/dL
Creatinine 1.1 mg/dL
Amylase 150 U/L
A CT of the abdomen is shown. Which of the following is the most appropriate long-term management for this patient?
- A. Pancreatic enzyme therapy (Correct Answer)
- B. Whipple procedure
- C. Endoscopic stent placement
- D. Celiac ganglion block
- E. Gluten-free diet
Exocrine pancreatic insufficiency Explanation: ***Pancreatic enzyme therapy***
- This patient likely has **chronic pancreatitis** due to long-term alcohol abuse, presenting with severe epigastric pain, weight loss, and recurrent episodes. **Pancreatic enzyme replacement therapy (PERT)** helps in managing malabsorption and pain by reducing pancreatic stimulation.
- While amylase is only slightly elevated (150 U/L), this is typical in chronic pancreatitis where extensive glandular destruction prevents dramatic enzyme elevation seen in acute pancreatitis. The abdominal CT would likely show calcifications or ductal dilation, further supporting the diagnosis and the need for enzyme support due to **exocrine insufficiency.**
*Whipple procedure*
- The **Whipple procedure** (pancreaticoduodenectomy) is a complex surgical intervention primarily performed for **pancreatic head tumors** or severe, intractable chronic pancreatitis not amenable to less invasive treatments.
- This patient's symptoms, while severe, do not immediately indicate a need for such aggressive surgery, and other medical managements should be attempted first.
*Endoscopic stent placement*
- **Endoscopic stent placement** is typically used to relieve **biliary obstruction** or **pancreatic duct strictures** that cause pain or cholangitis in chronic pancreatitis.
- While it might be considered for specific ductal complications, it is not the initial long-term management for the diverse symptoms of chronic pancreatitis, especially **exocrine insufficiency**.
*Celiac ganglion block*
- A **celiac ganglion block** provides temporary pain relief for severe abdominal pain, particularly in conditions like **chronic pancreatitis** or **pancreatic cancer**, by interrupting nerve signals.
- It is a **palliative measure** for pain control and does not address the underlying **exocrine insufficiency** or disease progression, making it not a long-term comprehensive management strategy.
*Gluten-free diet*
- A **gluten-free diet** is the primary treatment for **celiac disease**, an autoimmune disorder affecting the small intestine.
- There is no clinical indication or laboratory finding in this patient's presentation (e.g., diarrhea, positive celiac serology) to suggest celiac disease as the cause of his symptoms or to warrant a gluten-free diet.
Exocrine pancreatic insufficiency US Medical PG Question 9: A 42-year-old female with a history of systemic lupus erythematosus (SLE) has a 3-year history of daily prednisone (20 mg) use. Due to long-term prednisone use, she is at increased risk for which of the following?
- A. Systolic hypertension
- B. Weight loss
- C. Pathologic fractures (Correct Answer)
- D. Hair loss
- E. Pancreatic insufficiency
Exocrine pancreatic insufficiency Explanation: ***Pathologic fractures***
- Chronic systemic **corticosteroid use**, like prednisone, can lead to **osteoporosis** by increasing bone resorption and decreasing bone formation.
- This weakens bones, making them susceptible to **pathologic fractures** even with minimal trauma.
*Systolic hypertension*
- While corticosteroids can cause **hypertension**, they typically lead to an increase in both **systolic and diastolic pressures**, not isolated systolic hypertension.
- The primary mechanism involves increased fluid retention and vasoconstriction.
*Weight loss*
- Long-term prednisone use is commonly associated with **weight gain** due to increased appetite, fluid retention, and altered fat distribution (e.g., central obesity).
- It does not typically cause weight loss.
*Hair loss*
- **Hair loss** can be a symptom of SLE itself, but it is not a direct or common side effect of prednisone therapy.
- Corticosteroids can sometimes cause hair to grow thicker or change texture.
*Pancreatic insufficiency*
- Although corticosteroids can cause **pancreatitis** in rare cases, they do not typically lead to chronic **pancreatic insufficiency**.
- Pancreatic insufficiency is more commonly associated with conditions like cystic fibrosis or chronic alcohol abuse.
Exocrine pancreatic insufficiency US Medical PG Question 10: A 2720-g (6-lb) female newborn delivered at 35 weeks’ gestation starts vomiting and becomes inconsolable 48 hours after birth. The newborn has not passed her first stool yet. Examination shows abdominal distention and high-pitched bowel sounds. A water-soluble contrast enema study shows microcolon. Serum studies show increased levels of immunoreactive trypsinogen. Which of the following is the most likely additional laboratory finding?
- A. Increased sodium concentration in sweat (Correct Answer)
- B. Decreased hydrogen ion concentration in renal collecting duct
- C. Increased chloride concentration in alveolar fluid
- D. Increased bicarbonate concentration in pancreatic secretions
- E. Increased serum calcium concentration
Exocrine pancreatic insufficiency Explanation: ***Increased sodium concentration in sweat***
- The clinical picture of **abdominal distention**, **vomiting**, failure to pass meconium, and **microcolon** in a preterm infant, combined with **elevated immunoreactive trypsinogen (IRT)**, is highly suggestive of **cystic fibrosis with meconium ileus**.
- In cystic fibrosis, the dysfunctional **cystic fibrosis transmembrane conductance regulator (CFTR) protein** impairs **chloride and sodium reabsorption** in sweat ducts, leading to **increased sodium and chloride concentration in sweat**.
- The **sweat chloride test** (which also measures sodium) is the **gold standard diagnostic test** for cystic fibrosis and is the most likely additional laboratory finding.
*Decreased hydrogen ion concentration in renal collecting duct*
- This finding is characteristic of **metabolic alkalosis** or certain forms of **renal tubular acidosis** where there is an inability to excrete hydrogen ions, which is not directly related to the pathophysiology of cystic fibrosis.
- While electrolyte imbalances can occur in cystic fibrosis due to gastrointestinal losses, this specific renal finding is not a primary or direct diagnostic feature.
*Increased chloride concentration in alveolar fluid*
- While it is true that cystic fibrosis causes **increased chloride concentration in airway surface liquid** due to defective CFTR, this is **not a routinely measurable laboratory test** used for diagnosis.
- The airway chloride concentration is a **local pathophysiologic finding** at the tissue level, not a practical diagnostic laboratory test.
- The question asks for an "additional **laboratory finding**," and the sweat chloride/sodium test is the standard diagnostic laboratory test, not measurement of alveolar fluid chloride.
*Increased bicarbonate concentration in pancreatic secretions*
- Patients with cystic fibrosis typically have **decreased bicarbonate secretion** in pancreatic secretions due to the dysfunctional CFTR channel, leading to acidic pancreatic fluid and precipitation of proteins, causing duct obstruction.
- This leads to **pancreatic insufficiency**, not increased bicarbonate concentration.
*Increased serum calcium concentration*
- **Hypercalcemia** is not a characteristic finding in cystic fibrosis; rather, patients with cystic fibrosis may be at risk for **osteopenia** or **osteoporosis** due to malabsorption of fat-soluble vitamins (including vitamin D) and chronic inflammation, potentially leading to **decreased serum calcium** in severe cases.
- This finding would suggest other conditions like hyperparathyroidism or malignancy.
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