Kidney and Urinary Tract Pathology Notes

Chapter 12: Kidney and Urinary Tract Pathology

Congenital Lesions
  • High yield for exams as they tie embryology with clinical scenarios.
Horseshoe Kidney
  • Definition: A conjoined kidney typically at the lower pole; most common congenital renal anomaly.
  • Location: Abnormally positioned in the lower abdomen due to blockage during ascent by the inferior mesenteric artery (IMA).
  • Embryology: Kidneys develop in the pelvis and ascend into the abdomen, but may get "stuck" during this process.
  • Importance: Recognizing the abnormal location is crucial for diagnosis.
Renal Agenesis

  • Definition: Absence of kidney formation.

    • Unilateral Agenesis: Loss of one kidney leads to hypertrophy of the existing kidney doing the work of two, potentially leading to hyperfiltration injury and increased risk of renal failure over time.
    • Bilateral Agenesis: Absence of both kidneys; associated with oligohydramnios.

  • Oligohydramnios Consequences:

    • Lung Hypoplasia: Insufficient amniotic fluid means less lung growth due to lack of breathing movement.
    • Facial Characteristics: Develops flat face with low set ears from compression against uterine wall.
    • Extremity Defects: Developmental issues due to being pressed against maternal tissue.

  • Potter Sequence: The aggregate consequences of oligohydramnios including lung hypoplasia, flat face with low set ears, and extremity defects. Critical for exam understanding.

Dysplastic Kidney
  • Definition: A non-inherited malformation characterized by cysts with abnormal tissue (often cartilage).
  • Clinical Presentation: Typically unilateral but recognized as bilateral in exams. Not inherited, lowering risk in subsequent pregnancies.
  • Comparison to Polycystic Kidney Disease (PKD): Important to distinguish non-inherited dysplastic kidney from inherited forms of cystic kidney diseases.
Polycystic Kidney Disease (PKD)
  • Definition: An inherited defect leading to bilateral enlargement of kidneys due to cysts in both renal cortex and medulla.
  • Variants:
    • Autosomal Recessive PKD:
    • Noted in infants, may cause renal failure and hypertension early on, presenting with Potter sequence due to renal dysfunction.
    • Associated with congenital hepatic fibrosis and hepatic cysts, presenting signs of portal hypertension.
    • Autosomal Dominant PKD:
    • Presents in young adults, associated with hypertension, hematuria, and renal failure.
    • Due to mutations: ADPKD gene 1 and 2; cysts develop over time.
    • Important associations: berry aneurysms, hepatic cysts, and mitral valve prolapse. Berry aneurysms carry a risk of hemorrhagic strokes.
Medullary Cystic Kidney Disease
  • Definition: An inherited defect with cysts in the medullary collecting ducts leading to shrunken kidneys.
  • Key Features:
    • Size of Kidneys: Unlike PKD, kidneys are shrunken.
    • Clinical Presentation: Presents with worsening renal failure.
Conclusion
  • Understanding these congenital defects and their embryological connections are crucial for exam success.