Differential Diagnosis
- Single most likely diagnosis
- Pyelonephritis: The patient's left flank pain, elevated white blood cell count (WBC 13.8), and elevated absolute neutrophil count (seg neut absolute 11.9) suggest a bacterial infection of the kidney, which is consistent with pyelonephritis.
- Other Likely diagnoses
- Nephrolithiasis (kidney stones): The left flank pain could be indicative of a kidney stone, which may cause an inflammatory response and subsequent elevation in WBC.
- Urinary Tract Infection (UTI): A UTI could also cause an elevated WBC and flank pain, although the location of the pain and the severity of the WBC elevation might suggest pyelonephritis over a lower urinary tract infection.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Sepsis: Although the patient's WBC is elevated, indicating an infection, it's crucial to consider sepsis, especially if the patient shows signs of systemic inflammation (e.g., fever, tachycardia, tachypnea). Sepsis can arise from any infection, including pyelonephritis or a UTI, and is life-threatening if not promptly treated.
- Appendicitis (if the pain radiates or is referred): Although less likely given the description of left flank pain, appendicitis can sometimes present with atypical pain locations, especially if the appendix is retrocecal. It's a surgical emergency.
- Renal infarction: This is a less common condition but can present with acute flank pain and might be associated with an elevated WBC due to the inflammatory response to tissue necrosis.
- Rare diagnoses
- Vasculitis (e.g., ANCA-associated vasculitis): These conditions can cause renal inflammation and damage, presenting with flank pain and elevated inflammatory markers, including WBC.
- Renal cell carcinoma: Although typically presenting with a more chronic course, a renal tumor could cause flank pain and potentially an elevated WBC if there's associated infection or necrosis.
- Infarction of a renal cyst or other renal pathology: These conditions are less common and might present with acute flank pain and could potentially cause an inflammatory response.