Question
A 25-year-old male visits his family doctor requesting evaluation for a hereditary illness present in his family. His father and older sibling both developed kidney-related problems, and his sibling also experienced a sudden intracranial bleed in early adulthood. He is currently asymptomatic and examination findings are normal.
Considering the most probable underlying condition, which is the best initial test for screening?
a. CT scan of abdomen and pelvis
b. MRI scan of brain
c. DNA mutation analysis
d. Renal ultrasonography
e. CT scan of brain
Answer:
Renal ultrasonography
Detailed Explanation:
The clinical scenario strongly suggests Autosomal Dominant Polycystic Kidney Disease, an inherited disorder characterized by multiple renal cysts and progressive kidney enlargement.
Key clues:
- Positive family history (father and brother affected)
- Hereditary pattern → autosomal dominant
- History of intracranial bleed → suggests association with berry aneurysms
ADPKD is commonly associated with:
- Bilateral renal cysts
- Hypertension
- Chronic kidney disease
- Intracranial aneurysms → risk of subarachnoid hemorrhage
Why ultrasound is best:
- First-line screening tool in asymptomatic relatives
- Non-invasive, safe, inexpensive
- High sensitivity in detecting cysts
- No radiation exposure
Diagnostic ultrasound criteria (with family history):
- <30 years → ≥2 cysts (uni/bilateral)
- 30–59 years → ≥2 cysts in each kidney
- ≥60 years → ≥4 cysts in each kidney
Why other options are incorrect:
- CT abdomen → used if ultrasound inconclusive (not first-line)
- MRI brain → only if screening for aneurysm (not initial test here)
- Genetic testing → reserved for equivocal imaging or special cases
- CT head → only for acute neurological symptoms
Cheat Sheet (Exam-Oriented):
- Disease: ADPKD
- Inheritance: Autosomal dominant
- Genes: PKD1 (chr 16), PKD2 (chr 4)
- Screening test: Ultrasound
- Association: Intracranial berry aneurysm
- Complications: CKD, hypertension, haematuria
- Treatment option: Tolvaptan (selected patients)
Flash Cards
Q: Most common inherited kidney disease?
A: ADPKD
Q: First-line screening test for ADPKD?
A: Renal ultrasound
Q: Gene mutation in majority of ADPKD cases?
A: PKD1
Q: Important extra-renal association of ADPKD?
A: Intracranial berry aneurysm
Q: When is genetic testing used in ADPKD?
A: When imaging is inconclusive
MCQs
- A 28-year-old with family history of cystic kidney disease requires screening. Best initial test?
a. MRI abdomen
b. Renal ultrasound
c. CT abdomen
d. Genetic testing
Answer: b
Explanation: Ultrasound is first-line screening modality due to safety and effectiveness.
- Which of the following is FALSE regarding ADPKD?
a. It is autosomal dominant
b. Associated with intracranial aneurysms
c. Ultrasound is first-line screening
d. Genetic testing is routinely required
Answer: d
Explanation: Genetic testing is not routinely required; used only if imaging unclear.
- A patient with ADPKD is at highest risk of which complication?
a. Hepatitis
b. Subarachnoid hemorrhage
c. Pulmonary fibrosis
d. Pancreatitis
Answer: b
Explanation: Berry aneurysm rupture → subarachnoid hemorrhage.
- Which gene is most commonly mutated in ADPKD?
a. PKD2
b. PKD3
c. PKD1
d. WT1
Answer: c
Explanation: PKD1 mutation accounts for ~85% cases.
- Diagnostic criteria for ADPKD in a 35-year-old with family history?
a. One cyst in one kidney
b. Two cysts total
c. Two cysts in each kidney
d. Four cysts in one kidney
Answer: c
Explanation: Age 30–59 → ≥2 cysts in each kidney.
- Which investigation is most appropriate for screening intracranial aneurysm in ADPKD?
a. CT abdomen
b. MRI brain
c. Ultrasound
d. X-ray skull
Answer: b
Explanation: MRI/MRA brain is used for aneurysm screening.
- Which drug may slow progression in selected ADPKD patients?
a. Metformin
b. Tolvaptan
c. Ramipril
d. Furosemide
Answer: b
Explanation: Tolvaptan (V2 receptor antagonist) slows cyst growth.
Summary for Quick Exam Revision
Autosomal dominant polycystic kidney disease is the most common inherited renal disorder, caused mainly by PKD1 mutations and characterized by progressive bilateral renal cyst formation. It often presents with hypertension, haematuria, and eventual chronic kidney disease. A key associated feature is intracranial berry aneurysms, which can lead to subarachnoid hemorrhage, explaining family history of early “brain bleed.” Screening in asymptomatic relatives is best done using renal ultrasound, which is safe, non-invasive, and cost-effective. Diagnostic criteria depend on age and number of cysts detected. CT and MRI are reserved for equivocal cases, while genetic testing is not routine. Management includes blood pressure control and, in selected patients, tolvaptan to slow disease progression.