# A 3-year-old toddler is admitted to the pediatric unit with suspected hemolytic-uremic syndrome (HUS). Which assessment finding would be most indicative of this condition?

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## 문제

A 3-year-old toddler is admitted to the pediatric unit with suspected hemolytic-uremic syndrome (HUS). Which assessment finding would be most indicative of this condition?

## 보기

1. Thrombocytopenia, hemolytic anemia, and acute kidney injury **✔ 정답**
2. Hypertension, proteinuria, and gross hematuria
3. Fever, arthralgia, and petechial rash
4. Bradycardia, hypotension, and dehydration

**정답: 1**

## 해설

Hemolytic-uremic syndrome is characterized by the classic triad of thrombocytopenia, hemolytic anemia, and acute kidney injury, making this the most indicative assessment finding. Other options represent findings not specific to HUS.

## 심화 해설

Understanding the Classic Triad of HUS

The question asks for the assessment finding most indicative of hemolytic-uremic syndrome (HUS). The correct answer is thrombocytopenia, hemolytic anemia, and acute kidney injury. This combination represents the classic clinical triad of the disease, which is a form of thrombotic microangiopathy (TMA) [1][3][4].

The underlying pathophysiology explains why this triad develops. In HUS, damage to the vascular endothelium, often triggered by Shiga toxin in the typical form, initiates a cascade of events [1][4]. The injured endothelial cells promote platelet aggregation and the formation of microthrombi in small blood vessels, particularly in the kidneys. This process leads to three direct consequences:

1.  Thrombocytopenia: Circulating platelets are consumed to form these widespread microthrombi, causing a drop in the platelet count [1][4]. A value like 46 x 10⁹/L is a hallmark finding [2].

2.  Microangiopathic Hemolytic Anemia (MAHA): As red blood cells are forced through the partially occluded small vessels, they are mechanically sheared and fragmented (schistocytes), leading to hemolytic anemia [1][3][4].

3.  Acute Kidney Injury (AKI): The microthrombi occlude the renal microvasculature, reducing glomerular filtration. This is the most common organ injury in HUS and can manifest as oliguria and elevated serum creatinine, such as a level of 4.5 mg/dL [1][2][3][4].

Why the Other Options Are Incorrect

*   Option 2 (Hypertension, proteinuria, and gross hematuria): While AKI from HUS can lead to hypertension and hematuria may be present [3], this grouping describes a general nephritic syndrome picture. It misses the two critical hematologic components—thrombocytopenia and microangiopathic hemolytic anemia—that are essential for differentiating HUS from other causes of acute kidney injury [1][4]. The triad of Option 1 is far more specific.

*   Option 3 (Fever, arthralgia, and petechial rash): This constellation of findings is more suggestive of an immune-mediated vasculitis or a condition like Henoch-Schönlein purpura (IgA vasculitis). While petechiae can occur with severe thrombocytopenia, the combination with arthralgia and fever is not the defining presentation of HUS. The classic triad is centered on microangiopathic hemolysis, platelet consumption, and renal failure [1][4].

Option 4 (Bradycardia, hypotension, and dehydration): These findings are non-specific and point toward hypovolemia or a prodromal gastrointestinal illness. A child with HUS from Shiga toxin-producing E. coli* may have a history of diarrhea and dehydration, but the cardinal signs that signal the progression to HUS are the laboratory and clinical indicators of the triad: a falling platelet count, anemia from hemolysis, and rising creatinine with oliguria [1][3].References (research sources)

- [1]Hemolytic Uremic SyndromeResearch articleRout P, Daley SF. (2026)

- [2]Hemoglobinuria-associated acute kidney injury in hemolytic uremic syndrome without renal thrombotic microangiopathy.Research articleMancianti N, Jingjing L, Tripodi SA, Guarnieri A, Garosi G. (2026) · DOI: 10.1186/s12882-026-04887-0

- [3]Delayed-Onset Hemolysis in a Case of Hemolytic Uremic Syndrome: A Diagnostic Challenge.Case reportYounas M, Fatima N, Naveed Z, Nafisa S. (2026) · DOI: 10.1155/crh/2941212

- [4]Recurrent Atypical Hemolytic-Uremic Syndrome (aHUS) Associated With CD46 Genetic Mutation: A Report of a Rare Case.Research articleBiswas N, Adhikari P, Baral N. (2026) · DOI: 10.7759/cureus.103475

## 임상 시나리오

Recognizing the HUS TriadClassic Presentation in a Young Child
The most indicative assessment finding for hemolytic-uremic syndrome (HUS) is the simultaneous presence of thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. This triad defines the disease.

In a typical presentation, look for a platelet count of 46 x 10⁹/L (thrombocytopenia), fragmented red blood cells (schistocytes) on a peripheral smear (hemolytic anemia), and an elevated serum creatinine like 4.5 mg/dL with oliguria (acute kidney injury).

CautionDo not confuse HUS with acute glomerulonephritis, which presents with hypertension, proteinuria, and gross hematuria, or Henoch-Schönlein purpura, which features a palpable purpuric rash and arthralgia. The combination of hemolysis and low platelets is key.

## 핵심 개념

- **Thrombotic Microangiopathy (TMA)** — A pathologic process characterized by endothelial damage and microthrombi formation in small vessels, leading to thrombocytopenia and mechanical hemolysis; HUS and TTP are classic TMAs.
- **Microangiopathic Hemolytic Anemia (MAHA)** — Hemolysis caused by mechanical shearing of red blood cells as they pass through platelet-rich microthrombi in narrowed small vessels, resulting in schistocytes on peripheral smear.
- **Schistocytes** — Fragmented red blood cells seen on a peripheral blood smear, a hallmark laboratory finding in microangiopathic hemolytic anemias including HUS.
- **Shiga Toxin** — A bacterial exotoxin produced by Shigella dysenteriae or enterohemorrhagic E. coli (e.g., O157:H7) that causes endothelial injury, triggering the most common form of typical HUS in children.
- **Oliguria** — Reduced urine output, often defined as less than 1 mL/kg/hr in children, a common clinical manifestation of the acute kidney injury component of the HUS triad.

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