Organ-specific histology US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Organ-specific histology. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Organ-specific histology US Medical PG Question 1: An investigator is studying patients with acute decompensated congestive heart failure. He takes measurements of a hormone released from atrial myocytes, as well as serial measurements of left atrial and left ventricular pressures. The investigator observes a positive correlation between left atrial pressures and the serum level of this hormone. Which of the following is most likely the mechanism of action of this hormone?
- A. Increases potassium excretion at the collecting ducts
- B. Constricts afferent renal arteriole
- C. Decreases sodium reabsorption at the collecting tubules (Correct Answer)
- D. Decreases reabsorption of bicarbonate in the proximal convoluted tubules
- E. Increases free water reabsorption from the distal tubules
Organ-specific histology Explanation: ***Decreases sodium reabsorption at the collecting tubules***
- The hormone described, exhibiting a positive correlation with left atrial pressure and released from atrial myocytes, is **Atrial Natriuretic Peptide (ANP)**.
- ANP promotes **natriuresis** (sodium excretion) and **diuresis** by directly inhibiting sodium reabsorption in the collecting tubules, thereby reducing blood volume and cardiac preload.
*Increases potassium excretion at the collecting ducts*
- While ANP does promote fluid and electrolyte excretion, its primary effect is on sodium and water, not a direct increase in **potassium excretion**. **Aldosterone**, not ANP, primarily increases potassium secretion in the collecting ducts.
- This option describes a mechanism more consistent with **mineralocorticoid activity**, which is counteracted by ANP.
*Constricts afferent renal arteriole*
- ANP generally causes **vasodilation** of the afferent arteriole and constriction of the efferent arteriole, increasing glomerular filtration rate (GFR).
- **Angiotensin II** is a primary constrictor of the afferent and efferent renal arterioles, which is the opposite effect of ANP.
*Decreases reabsorption of bicarbonate in the proximal convoluted tubules*
- This mechanism is primarily involved in **acid-base balance** and is influenced by factors like parathyroid hormone or respiratory/metabolic acidosis/alkalosis.
- ANP's main action is on **sodium and water balance**, not directly on bicarbonate reabsorption.
*Increases free water reabsorption from the distal tubules*
- **Vasopressin (Antidiuretic Hormone, ADH)** is responsible for increasing free water reabsorption in the distal tubules and collecting ducts.
- ANP's action is to *increase* water excretion, working in opposition to ADH to reduce circulating fluid volume.
Organ-specific histology US Medical PG Question 2: A 56-year-old African American presents to the emergency department due to abdominal pain, fatigue, and weight loss over the past 3 months. He has a long-standing history of chronic hepatitis B virus infection complicated by cirrhosis. On examination, he has jaundice, leg edema, and a palpable mass in the right upper abdominal quadrant. Abdominal ultrasound shows a 3-cm liver mass with poorly defined margins and coarse, irregular internal echoes. Lab results are shown:
Aspartate aminotransferase (AST) 90 U/L
Alanine aminotransferase (ALT) 50 U/L
Total bilirubin 2 mg/dL
Albumin 3 g/dL
Alkaline phosphatase 100 U/L
Alpha-fetoprotein 600 ng/mL
Which of the following is a feature of this patient's condition?
- A. It arises from the bile duct epithelium
- B. Daughter cysts are usually present on abdominal ultrasound
- C. Liver biopsy is required for diagnosis in a majority of patients
- D. It arises from hepatocytes (Correct Answer)
- E. Doppler blood flow shows venous pattern
Organ-specific histology Explanation: ***It arises from hepatocytes***
- This patient's clinical presentation, including chronic **hepatitis B** with **cirrhosis**, an abdominal mass, and significantly elevated **alpha-fetoprotein (AFP)**, strongly indicates **hepatocellular carcinoma (HCC)**.
- HCC is a primary liver cancer that originates from the **hepatocytes**, the main functional cells of the liver.
*It arises from the bile duct epithelium*
- This describes **cholangiocarcinoma**, which arises from the **bile duct cells**.
- While cholangiocarcinoma is a primary liver cancer, its risk factors, imaging features, and tumor markers (e.g., **CA 19-9**) typically differ from those seen in this patient, and **AFP** elevation is not characteristic.
*Daughter cysts are usually present on abdominal ultrasound*
- **Daughter cysts** on ultrasound are characteristic of **hydatid cysts**, typically caused by **Echinococcus granulosus** infection.
- This parasitic condition presents differently, and the patient's elevated **AFP** and history of **cirrhosis** are not associated with hydatid disease.
*Liver biopsy is required for diagnosis in a majority of patients*
- In patients with **cirrhosis** and a lesion larger than 1 cm with characteristic imaging findings **(e.g., contrast enhancement on MRI/CT)**, along with a high **alpha-fetoprotein (AFP)** level, a biopsy is often **not required** for the diagnosis of HCC, as per standard guidelines.
- The combination of risk factors (cirrhosis, chronic HBV), elevated AFP, and imaging findings is sufficient for diagnosis in many cases, especially to avoid biopsy-related risks like bleeding or tumor seeding.
*Doppler blood flow shows venous pattern*
- **Hepatocellular carcinoma** typically exhibits a **hypervascular arterial enhancement pattern** on imaging with **early washout** in the venous phase.
- This is a key diagnostic feature, and flow showing a venous pattern would be inconsistent with HCC.
Organ-specific histology US Medical PG Question 3: A 65-year-old man with a 40-pack-year smoking history presents with hemoptysis and a persistent cough. Chest CT shows a 3.5 cm centrally located mass in the right main bronchus. Positron emission tomography confirms a malignant nodule. Bronchoscopy with transbronchial biopsy is performed and a specimen sample of the nodule is sent for frozen section analysis. The tissue sample is most likely to show which of the following tumor types?
- A. Carcinoid tumor
- B. Metastasis of colorectal cancer
- C. Small cell lung carcinoma
- D. Large cell carcinoma
- E. Squamous cell carcinoma (Correct Answer)
Organ-specific histology Explanation: ***Squamous cell carcinoma***
- This is the most likely diagnosis given the **central location** in the main bronchus, **heavy smoking history**, and presentation with **hemoptysis**.
- **Squamous cell carcinoma** accounts for 25-30% of lung cancers and characteristically arises in **central/proximal airways**, making it readily accessible by **bronchoscopy**.
- Histologically, it shows **keratin pearls** and **intercellular bridges** on biopsy.
- The **central endobronchial location** and ability to obtain tissue via transbronchial biopsy strongly favor squamous cell over peripheral tumors.
*Carcinoid tumor*
- **Carcinoid tumors** are **neuroendocrine tumors** that can present as central endobronchial masses and cause hemoptysis.
- However, they are typically **slow-growing** with more indolent presentation, and PET scans show **variable uptake** (often less intense than aggressive carcinomas).
- They represent only **1-2% of lung tumors** and occur more commonly in **younger, non-smoking patients**.
*Metastasis of colorectal cancer*
- While lung is a common site for **colorectal metastases**, these typically present as **multiple peripheral nodules** rather than a solitary central endobronchial mass.
- The clinical presentation strongly suggests **primary lung cancer** rather than metastatic disease.
- Without history of colorectal cancer, this is unlikely.
*Small cell lung carcinoma*
- **Small cell lung carcinoma** (SCLC) represents 15% of lung cancers and typically presents as a **large central mass** with early mediastinal involvement.
- However, SCLC is usually **too extensive at presentation** for transbronchial biopsy alone and often requires mediastinoscopy or CT-guided biopsy.
- Histology shows **small cells with scant cytoplasm**, **salt-and-pepper chromatin**, and **oat-cell morphology**.
- While possible, the single accessible endobronchial mass is more characteristic of squamous cell.
*Large cell carcinoma*
- **Large cell carcinoma** is a **diagnosis of exclusion** made when tumors lack features of adenocarcinoma, squamous cell, or small cell differentiation.
- It typically presents as **large peripheral masses** rather than central endobronchial lesions.
- It represents only **10% of lung cancers** and is less common than squamous cell carcinoma in this clinical scenario.
Organ-specific histology US Medical PG Question 4: A 27-year-old woman presents to the emergency department complaining of a left-sided headache and right-sided blurry vision. She states that 2 weeks ago she developed dark urine and abdominal pain. She thought it was a urinary tract infection so she took trimethoprim-sulfamethoxazole that she had left over. She planned on going to her primary care physician today but then she developed headache and blurry vision so she came to the emergency department. The patient states she is otherwise healthy. Her family history is significant for a brother with sickle cell trait. On physical examination, there is mild abdominal tenderness, and the liver edge is felt 4 cm below the right costal margin. Labs are drawn as below:
Hemoglobin: 7.0 g/dL
Platelets: 149,000/mm^3
Reticulocyte count: 5.4%
Lactate dehydrogenase: 3128 U/L
Total bilirubin: 2.1 mg/dL
Indirect bilirubin: 1.4 mg/dL
Aspartate aminotransferase: 78 U/L
Alanine aminotransferase: 64 U/L
A peripheral smear shows polychromasia. A Doppler ultrasound of the liver shows decreased flow in the right hepatic vein. Magnetic resonance imaging of the brain is pending. Which of the following tests, if performed, would most likely identify the patient’s diagnosis?
- A. Flow cytometry (Correct Answer)
- B. Glucose-6-phosphate-dehydrogenase levels
- C. Anti-histone antibodies
- D. Bone marrow biopsy
- E. Hemoglobin electrophoresis
Organ-specific histology Explanation: ***Flow cytometry***
- The patient's symptoms (headache, blurry vision, dark urine, abdominal pain, hepatomegaly) along with laboratory findings of **hemolytic anemia** (low hemoglobin, elevated reticulocyte count, high LDH, elevated indirect bilirubin) and signs of **thrombosis** (decreased hepatic vein flow, neurological symptoms) are highly suggestive of **paroxysmal nocturnal hemoglobinuria (PNH)**.
- **Flow cytometry** is the gold standard for diagnosing PNH by detecting the absence of **CD55** and **CD59** on red blood cells, granulocytes, and monocytes, indicating a deficiency in the **GPI anchor protein**.
*Glucose-6-phosphate-dehydrogenase levels*
- **G6PD deficiency** typically presents with hemolytic anemia triggered by **oxidant stressors** (like trimethoprim-sulfamethoxazole) but does not typically cause **thrombosis** or widespread organ involvement (e.g., hepatic vein thrombosis, neurological symptoms) as seen in this patient.
- Measuring G6PD levels would be appropriate if G6PD deficiency was suspected, but the clinical picture points more strongly to PNH due to the thrombotic events.
*Anti-histone antibodies*
- **Anti-histone antibodies** are primarily associated with drug-induced **lupus erythematosus**, which can manifest with various systemic symptoms, but not typically with severe hemolytic anemia and thrombotic microangiopathy in this specific pattern.
- While drug exposure is present (trimethoprim-sulfamethoxazole), the overall clinical and lab findings (especially the severe hemolytic picture and thrombosis) are not characteristic of drug-induced lupus in this context.
*Bone marrow biopsy*
- A **bone marrow biopsy** might show findings consistent with increased erythropoiesis due to hemolysis but is not a primary diagnostic test for PNH or its associated thrombotic complications.
- While it could be part of an evaluation for underlying bone marrow disorders, it would not directly confirm a diagnosis of PNH, which requires specific surface marker detection.
*Hemoglobin electrophoresis*
- **Hemoglobin electrophoresis** is used to diagnose **hemoglobinopathies** such as **sickle cell disease** or **thalassemia**. The patient's brother has sickle cell trait, but the patient's symptoms, particularly the prominent hemolytic anemia and thrombotic events, are not typical of a hemoglobinopathy in this acute presentation.
- While it could rule out a hemoglobinopathy, it wouldn't explain the full spectrum of symptoms, especially the thrombosis and the specific pattern of hemolysis (e.g., elevated LDH, indirect bilirubin).
Organ-specific histology US Medical PG Question 5: A 46-year-old man comes to the physician because of a 4-month history of progressively worsening fatigue and loss of appetite. Five years ago, he received a kidney transplant from a living family member. Current medications include sirolimus and mycophenolate. His blood pressure is 150/95 mm Hg. Laboratory studies show normocytic, normochromic anemia and a serum creatinine concentration of 3.1 mg/dL; his vital signs and laboratory studies were normal 6 months ago. Which of the following is the most likely underlying mechanism of this patient’s increase in creatinine concentration?
- A. Drug-induced tubular vacuolization
- B. CD8+ T cell-mediated parenchymal cell damage
- C. CD4+ T cell-mediated intimal smooth muscle proliferation (Correct Answer)
- D. Donor T cell-mediated epithelial cell damage
- E. Donor endothelial cell damage by preformed host antibodies
Organ-specific histology Explanation: ***CD4+ T cell-mediated intimal smooth muscle proliferation***
- The patient's history of a kidney transplant 5 years ago, worsening fatigue, loss of appetite, elevated blood pressure (150/95 mm Hg), and a significant increase in serum creatinine from normal to 3.1 mg/dL, along with normocytic, normochromic anemia, strongly suggests **chronic rejection** of the renal allograft.
- **Chronic rejection** in kidney transplantation is primarily mediated by **CD4+ T cells** which induce injury to vessel walls, leading to **intimal smooth muscle proliferation** and progressive obliteration of the vascular lumen, causing chronic ischemia and graft dysfunction.
*Drug-induced tubular vacuolization*
- **Drug-induced tubular vacuolization** can occur with medications like sirolimus, but it typically presents with **acute kidney injury** and specific biopsy findings, not the progressive, chronic decline seen here.
- While sirolimus can cause nephrotoxicity, the clinical picture of hypertension, anemia, and a gradual increase in creatinine over months, years after transplant, is more indicative of chronic rejection rather than a primary direct tubular injury.
*CD8+ T cell-mediated parenchymal cell damage*
- **CD8+ T cell-mediated parenchymal cell damage** is characteristic of **acute cellular rejection** and typically presents with a more rapid onset of graft dysfunction and specific histological features like tubulitis and interstitial inflammation.
- This patient's symptoms have developed progressively over 4 months, which is more consistent with chronic rather than acute processes.
*Donor T cell-mediated epithelial cell damage*
- **Donor T cell-mediated epithelial cell damage** is associated with **graft-versus-host disease (GVHD)**, which primarily occurs after **hematopoietic stem cell transplantation**, not solid organ transplants like a kidney.
- GVHD manifests in organs like the skin, liver, and GI tract, not typically as isolated chronic allograft nephropathy.
*Donor endothelial cell damage by preformed host antibodies*
- **Donor endothelial cell damage by preformed host antibodies** is the mechanism of **hyperacute rejection**, which occurs within minutes to hours post-transplant due to pre-existing host antibodies (e.g., ABO incompatible, preformed anti-HLA antibodies) and leads to immediate graft failure.
- The patient had a successful transplant 5 years ago and developed symptoms gradually, ruling out hyperacute rejection.
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