UWorld Pediatrics Practice Test 2025 – Complete Exam Prep

In hemolytic uremic syndrome (HUS), one of the hallmark laboratory findings is an elevation in lactate dehydrogenase (LDH). HUS is characterized by a triad of symptoms: hemolytic anemia, acute renal failure, and thrombocytopenia. The hemolysis that occurs in this condition leads to the release of LDH, an enzyme that is found in high concentrations in red blood cells and other tissues such as the liver and heart.

When red blood cells are destroyed, which is a central feature of hemolytic anemia in HUS, LDH enters the bloodstream, resulting in elevated serum levels. This increase serves as a marker of red blood cell destruction and is often assessed in conjunction with other parameters, such as haptoglobin levels (which may be low) and indirect bilirubin (which may be high) to assess the extent of hemolysis.

In contrast to other laboratory findings typically assessed in HUS, white blood cell count may not show a significant change specifically related to hemolysis, serum electrolytes may be affected but do not serve as a defining laboratory marker, and platelet counts are usually low due to consumption rather than elevated. Therefore, the elevation of LDH is a key