What is the diagnosis for a patient with a computed tomography (CT) scan of the abdomen showing no hydronephrosis, no ureteral stones, fluid in the small bowel and colon suggestive of mild ileus or non-specific gastroenteritis, diverticulosis without diverticulitis, and no evidence of appendicitis, with laboratory results indicating leukocytosis with bandemia, lymphopenia, metabolic acidosis with low bicarbonate (CO2) levels, elevated C-reactive protein (CRP) levels indicative of inflammation, and urinalysis showing hematuria, proteinuria, and bacteriuria?

Differential Diagnosis

• Single most likely diagnosis
  • Pyelonephritis: The presence of moderate blood, protein, and RBCs in the urine, along with moderate bacteria, suggests a urinary tract infection. The elevated CRP indicates significant inflammation, which is consistent with pyelonephritis. The absence of hydronephrosis and ureteral stones makes a obstructive cause less likely, but the clinical presentation and lab results point towards an upper urinary tract infection.
• Other Likely diagnoses
  • Urinary tract infection (UTI) with cystitis: While the presence of bacteria and blood in the urine could suggest a lower urinary tract infection, the elevated CRP and the presence of protein in the urine suggest a more severe infection, which may involve the upper urinary tract.
  • Diverticulitis: Although the CT scan reports diverticulosis without diverticulitis, the presence of fluid in the small bowel and colon, and the elevated CRP, could suggest a mild or early diverticulitis. However, the absence of specific findings on the CT scan makes this diagnosis less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Sepsis: The elevated CRP, bands on the CBC, and the presence of bacteria in the urine suggest a significant infection. If the infection is not adequately treated, it could progress to sepsis, which is a life-threatening condition.
  • Perforated viscus: Although the CT scan does not show evidence of a perforated viscus, the presence of free fluid in the abdomen and the elevated CRP could suggest a perforation. This is a surgical emergency that requires prompt attention.
• Rare diagnoses
  • Vasculitis: The presence of protein and blood in the urine, along with the elevated CRP, could suggest a systemic vasculitis. However, this diagnosis is less likely and would require further evaluation, including autoimmune testing and biopsy.
  • Tubulointerstitial nephritis: This is a rare condition that could present with similar laboratory findings, including protein and blood in the urine. However, it is less likely and would require further evaluation, including renal biopsy.