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.