Source / episode info

• **Episode:**532
• **Title:**Divine Intervention Episode 532: USMLE Step 2CK/3 Rapid Review Series 114
• **Published:**2024-04-16
• Source:Episode page

One-liner

This episode provides rapid review of high-yield topics including the prognosis of hemangiomas, congenital urinary tract obstruction leading to oligohydramnios/pulmonary hypoplasia, achalasia workup (manometry/barium swallow), microangiopathic hemolytic anemia (MAHA) from prosthetic valves or HUS, and differentiating atherosclerotic renal artery stenosis from fibromuscular dysplasia.

High-yield summary

• Strawberry Hemangioma: These are capillary hemangiomas/vasculotomes that typically grow rapidly via angiogenesis but have a benign prognosis; management is usually reassurance, though blockers can be used for symptomatic control.
• Oligohydramnios: The most common cause of fetal oligohydramnios on USMLEs is obstruction at the Ureteropelvic Junction (UPJ), followed by Vesicoureteral Reflux (VUR) or Posterior Urethral Valves (PUV). Severe, prolonged oligohydramnios leads to pulmonary hypoplasia due to lack of amniotic fluid for lung development.
• Achalasia: Pathophysiology involves the loss/damage of inhibitory ganglion cells in the myenteric plexus, leading to decreased relaxation of the Lower Esophageal Sphincter (LES) and impaired esophageal peristalsis. Diagnosis requires Barium Swallow (Bird-beak sign) and Manometry (High LES pressure, absent mid-esophageal peristalsis).
• MAHA: Characterized by schistocytes/helmet cells/fragmented erythrocytes due to mechanical shearing of RBCs. Associated conditions include prosthetic cardiac valves, DIC, HUS (E. coli O157:H7), TTP, and severe sepsis. Labs show low haptoglobin, high indirect bilirubin, and elevated LDH.
• Renal Artery Stenosis vs. FMD: Renal artery stenosis is an intimal problem due to atherosclerosis; FMD is a medial wall defect. Both can cause hypertension and secondary hyperaldosteronism (leading to hypokalemia/metabolic alkalosis). The "string of beads" pattern suggests FMD, but it can also be seen in Polyarteritis Nodosa or Primary Sclerosing Cholangitis (PSC).

Learning objectives

• Differentiate the pathophysiology and clinical presentation of various causes of congenital urinary tract obstruction (UPJ, VUR, PUV).
• Interpret findings from esophageal manometry and barium swallow in motility disorders like achalasia.
• Recognize the characteristic laboratory triad (low haptoglobin, high indirect bilirubin, schistocytes) associated with microangiopathic hemolytic anemia.
• Distinguish between intimal (atherosclerosis) and medial (FMD) causes of renal artery stenosis.
• Understand the consequences of chronic oligohydramnios on fetal development, particularly pulmonary hypoplasia.

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