**Question:** Which of the following is seen in haemolytic uremic syndrome (HUS)?

A. Thrombocytopenia
B. Hemolytic anemia
C. Acute kidney injury
D. Gastrointestinal symptoms

**Core Concept:** Haemolytic Uremic Syndrome (HUS) is a rare but severe complication characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It is primarily caused by Streptococcus pneumoniae infections, Shiga toxin-producing Escherichia coli (STEC) infections, or autoimmune conditions.

**Why the Correct Answer is Right:** HUS primarily involves the small blood vessels (microvasculature) in various organs, leading to the clinical manifestations listed in the answer. Thrombocytopenia (A) and hemolytic anemia (B) are direct consequences of microvascular damage, as platelets and red blood cells are destroyed in the affected vessels. Acute kidney injury (C) is a downstream consequence of the microangiopathic damage, as the kidneys are particularly vulnerable to this kind of injury.

**Why Each Wrong Option is Incorrect:** Gastrointestinal symptoms (D) are not a primary feature of HUS. HUS primarily affects the microvasculature in various organs, not specifically the gastrointestinal tract. Although some patients may experience mild gastrointestinal symptoms, they are not the primary hallmark of the disease.

**Clinical Pearl:** Haemolytic Uremic Syndrome is a clinical entity with a triad of symptoms - microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The correct answer focuses on the primary clinical manifestations while ignoring gastrointestinal symptoms (D) that are not the primary feature of the condition.