Differential Diagnosis for a 42-year-old Man with Low Back Pain

Single Most Likely Diagnosis

• Renal calculi: The patient's presentation of colicky low back pain radiating to the groin, microscopic hematuria, and the physical examination findings (T12 flexed, rotated right, sidebent right) are classic for a renal colic due to a kidney stone. The pain's nature and radiation pattern, along with the absence of infection signs (no bacteria or leukocytes in urinalysis), strongly support this diagnosis.

Other Likely Diagnoses

• Bladder tumor: Although less likely than renal calculi, a bladder tumor could cause hematuria. However, the acute onset of colicky pain is more suggestive of a stone. A tumor might cause more constant pain and possibly other symptoms like weight loss or more significant hematuria.
• Cystitis: This would typically present with signs of infection such as dysuria, frequency, and possibly fever, which are not mentioned. The absence of bacteria or leukocytes in the urinalysis makes this less likely.
• Urethritis: Similar to cystitis, urethritis would likely present with dysuria and possibly discharge, which are not described in the scenario.

Do Not Miss Diagnoses

• Abdominal aortic aneurysm (AAA): Although the patient's age and smoking history increase his risk for AAA, the specific pain pattern and urinalysis findings are not typical for AAA. However, any acute onset of severe back or abdominal pain, especially in a smoker, warrants consideration of AAA due to its high mortality if ruptured.
• Pyelonephritis: While the urinalysis does not show signs of infection, pyelonephritis can sometimes present with minimal findings in the urine, especially early in the course. The patient's symptoms could be consistent with an upper urinary tract infection, especially if the infection is not yet severe.

Rare Diagnoses

• Testicular torsion: This condition would more likely present with acute testicular pain rather than low back pain radiating to the groin. It's a surgical emergency but seems less likely given the description.
• Psoas abscess: Could cause low back pain and might radiate to the groin, but typically would have other signs such as fever, and the urinalysis findings would not directly suggest this diagnosis.
• Spinal or vertebral pathology: Such as a herniated disc or vertebral fracture, could cause back pain but would not typically cause hematuria or the specific radiation pattern described.