DIFFERENTIAL DIAGNOSIS:
Urolithiasis (Kidney Stones)
The patient presents with flank pain and hematuria, which are common in kidney stones. However, the absence of calculi on ultrasound and CT imaging, along with the presence of a renal mass, rules out urolithiasis as the primary diagnosis.
Urinary Tract Infection (UTI) or Pyelonephritis
Symptoms such as flank pain and hematuria can also be seen in UTIs or pyelonephritis. However, the lack of fever, abnormal urinalysis findings, and the presence of a solid renal mass on imaging makes this an unlikely diagnosis.