Differential Diagnosis for the Student Athlete's Urinalysis Results

The urinalysis results for the student athlete show several abnormal findings, including the presence of crenated red blood cells (RBCs), trace blood, and various types of casts. These findings can be indicative of several conditions. Here's a differential diagnosis organized into categories:

• Single Most Likely Diagnosis

  • Dehydration: This is the most likely cause given the patient's history as a student athlete, which may involve intense physical activity leading to dehydration. Dehydration can cause concentrated urine, which is indicated by the high specific gravity (1.032) and dark yellow color. Dehydration can also lead to the presence of crenated RBCs due to the concentrated state of the urine.

• Other Likely Diagnoses

  • Urinary Tract Injury: The presence of RBCs and trace blood could suggest a urinary tract injury, possibly from physical activity or trauma.
  • Nephrolithiasis (Kidney Stones): Although not directly indicated, the presence of blood and RBCs could be related to kidney stones, especially if the patient has been experiencing pain or discomfort.
  • Exercise-Induced Hematuria: This condition is characterized by the presence of blood in the urine after strenuous exercise, which could fit the patient's profile as a student athlete.

• Do Not Miss Diagnoses

  • Rhabdomyolysis: This is a serious condition where muscle tissue breaks down, releasing myoglobin into the blood, which can then appear in the urine. It's crucial to consider this diagnosis, especially in athletes who may have undergone extreme physical exertion. Although the urinalysis does not directly indicate rhabdomyolysis, the clinical context (e.g., recent intense exercise) makes it a condition not to miss.
  • Kidney Disease: Early stages of kidney disease can present with similar urinalysis findings. It's essential to rule out underlying kidney issues, especially if the patient has risk factors or a family history of kidney disease.

• Rare Diagnoses

  • Sickle Cell Trait or Disease: Individuals with sickle cell trait or disease can experience hematuria due to sickling of RBCs in the kidney. This would be a rare but important consideration, especially if the patient has a known history of sickle cell disease or trait.
  • Alport Syndrome: A genetic disorder characterized by kidney disease, hearing loss, and eye abnormalities. It's a rare condition but should be considered in cases of unexplained hematuria, especially in younger patients.

Justification and Considerations

• The presence of crenated RBCs is likely due to dehydration, as these cells can become misshapen in concentrated urine.
• The trace blood detected by the reagent strip, despite the presence of 15–20 RBCs/hpf, could be because the strip is less sensitive to crenated or altered RBCs.
• RBCs that vary in size or have cellular protrusions are referred to as dysmorphic RBCs in the context of urinalysis, similar to how poikilocytes are described in hematology.
• Given the patient's history as a student athlete, dehydration or exercise-induced hematuria are probable causes of the abnormal results.
• To prevent abnormal urine results, the student should be asked to collect a midstream urine specimen after adequate hydration to help differentiate between transient and pathological conditions.