Differential Diagnosis for Second Trimester Pregnancy with Dysuria, Flank Pain but Negative Culture

• Single Most Likely Diagnosis
  • Urinary tract infection (UTI) with a negative culture due to prior antibiotic use or a fastidious organism: This is a common issue in pregnancy, and symptoms can be present even with a negative culture due to various factors such as recent antibiotic use or infection with organisms that do not grow well in standard cultures.
• Other Likely Diagnoses
  • Pyelonephritis: An infection of the kidney, which can present with flank pain and dysuria, even if the urine culture is initially negative due to factors like antibiotic use or a low bacterial load.
  • Ureteral obstruction or stone: Pregnancy can increase the risk of ureteral obstruction due to the mechanical effects of the enlarged uterus, and stones can cause severe pain and dysuria without necessarily resulting in a positive urine culture.
  • Interstitial cystitis: A condition causing bladder pressure, bladder pain, and sometimes pelvic pain, which can mimic UTI symptoms without a positive culture.
• Do Not Miss Diagnoses
  • Pre-eclampsia: Although less common, severe pre-eclampsia can present with abdominal or flank pain and should be considered in any pregnant woman with new-onset symptoms, as it can be life-threatening if not promptly diagnosed and treated.
  • Placental abruption: This condition involves the placenta separating from the uterus and can cause abdominal pain, which might be confused with urinary tract issues, and is a medical emergency.
• Rare Diagnoses
  • Kidney infarction: Although rare, it can present with acute flank pain and might not initially have a positive culture, requiring imaging for diagnosis.
  • Renal vein thrombosis: More common in patients with nephrotic syndrome or dehydration, it can cause flank pain and might not have an associated positive urine culture, requiring specific diagnostic tests for identification.