Episodic Flank Pain With Urinary Frequency in an HIV-Positive Man

A 46-year-old man with a history of HIV infection presents to the emergency department for left flank pain. He has had this same pain 3 times in the past year, and each time he was given a diagnosis of pyelonephritis and was treated with antibiotics. Each time he improved, but the pain gradually returned. The most recent episode was about 3 months ago.

Today the patient’s symptoms are identical to those in the previous episodes. They include 4 or 5 days of left-sided back pain, low-grade tactile fevers, and urinary frequency. He denies nausea, vomiting, abdominal pain, hematuria, and dysuria and states that he feels he can empty his bladder completely without straining. He has no lower extremity symptoms or other complaints.

On examination, the patient’s vital signs are all normal, including an oral temperature of 37.2°C (98.9°F). The results of his head and neck examination are normal, and he has no thrush. His lungs are clear, with normal oxygen saturation, and his heart rate is regular without murmurs. The results of his abdominal examination are benign, but he definitely has left costovertebral angle (CVA) tenderness as well as some midline spinal tenderness. His strength and sensation are normal in both legs and both arms. The rest of the examination findings are normal.

Laboratory data show a white blood cell (WBC) count of 9.8 x 10³/µL, with 77% neutrophils. The metabolic panel is normal. Urinalysis (UA) shows negative nitrites, 48 WBCs, and no red blood cells.

A lateral x-ray film of the patient’s lumbar spine is shown above.

• What is the differential diagnosis?
• What is the most likely diagnosis?
• What other information might be useful to make the correct diagnosis for this patient?

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