Differential Diagnosis for Acute-Onset Left-Sided Flank Pain

Single Most Likely Diagnosis

• Nephrolithiasis (Kidney Stone): The patient's presentation of acute-onset flank pain, inability to sit still, and gross hematuria is highly suggestive of a kidney stone. The pain is often severe and can cause significant discomfort, leading to restlessness. The presence of blood in the urine further supports this diagnosis, as stones can cause irritation and bleeding in the urinary tract.

Other Likely Diagnoses

• Pyelonephritis: Although the patient is afebrile, pyelonephritis (infection of the kidney) can sometimes present without fever, especially in early stages. The costovertebral angle tenderness and hematuria could be consistent with this diagnosis.
• Urinary Tract Infection (UTI) with Hematuria: A UTI could cause hematuria and flank pain, though the severity of pain and restlessness might be less typical for a simple UTI.

Do Not Miss Diagnoses

• Renal Infarction: This is a serious condition where the blood supply to the kidney is interrupted, which could present with acute flank pain and hematuria. It's crucial to consider this diagnosis due to its potential for severe consequences if missed.
• AAA (Abdominal Aortic Aneurysm): Although less common in a 32-year-old woman, an AAA could potentially cause flank pain and, if ruptured, could lead to hematuria due to the proximity of the aorta to the kidneys. The severity of the condition warrants its consideration.
• Sepsis: If the patient's condition were to deteriorate, or if there were signs of infection not immediately apparent (like in the case of a urinary tract infection leading to sepsis), this would be a critical diagnosis not to miss.

Rare Diagnoses

• Renal Vein Thrombosis: This condition, which involves a blood clot in the veins that carry blood from the kidneys back to the heart, can cause acute flank pain and hematuria. It is more common in patients with nephrotic syndrome or other specific conditions but should be considered in the differential due to its potential severity.
• Vasculitis: Certain types of vasculitis, such as ANCA-associated vasculitis, can affect the kidneys and cause hematuria and flank pain. These conditions are less common but important to consider due to their potential for significant morbidity if not treated.